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Grand Challenges in Environmental Sciences (2001)

Chapter: The Grand Challenges

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Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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2

The Grand Challenges

For each grand challenge described in this chapter, the committee judges that major scientific and/or practical payoff is likely to result if there is a significant infusion of research support over the next decade or two. We begin the discussion of each challenge by identifying the scientific payoffs that appear most likely and practical payoffs that the expected scientific advances would make possible. We then identify recent scientific progress that makes major advances in the area of the challenge possible now. Next we list focused research areas within each challenge that are especially deserving of intensive development. These lists are not intended to be comprehensive; rather, they include only those areas we judge most exciting and likely to yield major break-throughs in the near future.

GRAND CHALLENGE 1: BIOGEOCHEMICAL CYCLES

The challenge is to understand how the Earth's major biogeochemical cycles are being perturbed by human activities; to be able to predict the impact of these perturbations on local, regional, and global scales; and to determine how these cycles may be restored to more natural states should such restoration be deemed desirable.

Practical Importance

Six nutrient elements—carbon, oxygen, hydrogen, nitrogen, sulfur, and phosphorus—make up 95 percent of the biospheric mass on the Earth and form the biochemical foundation for life (Schlesinger 1997). The cycling of these

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

elements through the Earth system in their biological, geological, and chemical forms constitutes the biogeochemical cycles. Also included under the rubric of biogeochemical cycling can be elements such as potassium, calcium, molybdenum, iron, and zinc, which are needed as physiological regulators or cofactors for enzymes. Imbalance in the availability or utilization of these elements has both direct and indirect influences on the distribution and viability of many organisms.

Research during the last several decades has provided many insights into the importance of biogeochemical cycles. It is now recognized that the evolution of photosynthetic organisms more than 2 billion years ago transformed the Earth's atmosphere from strongly reducing to its current oxygen-rich state. The interrelationship between greenhouse gases and climate was identified more than a century ago (Arrhenius 1896). Today we understand that carbon dioxide (CO2)-induced ocean warming was sufficient to trigger the large-scale destabilization of methane hydrates (Norris and Rohl 1999). This positive feedback with global effects occurred at the Paleocene/Eocene transition, and was associated with high-latitude warming and changes in terrestrial and marine biota. The concentrations of many greenhouse gases (e.g., CO2, nitrous oxide [N2O], and methane [CH4]) have risen over the last 100 years at rates unprecedented in the geologic record. It is clear that these rapid rises in concentrations are being driven by global changes in the Earth's biogeochemical cycles. What is less clear is how long these changes in biogeochemical cycles will continue, what effects they are having on the climate system, how these effects will reverberate throughout the Earth system, and how positive and negative feedbacks within the system will interact to accelerate or ameliorate these effects.

Human actions strongly influence changes in the Earth's biogeochemical cycles, with potentially devastating effects. Combustion of fossil fuels and conversion of forested land to agriculture have redistributed carbon from plant, soil, and mineral pools into the atmosphere, where greatly increased CO2 has the potential to alter climate, affect the photosynthetic efficiency of vegetation, and change large-scale ecosystem dynamics (Amthor 1995). The combustion of fossil fuels and the manufacture and use of nitrogen fertilizers have approximately doubled the annual supply of fixed nitrogen to the soil relative to preindustrial times, a circumstance that has the potential to alleviate nitrogen limitation of productivity in terrestrial ecosystems and may thus contribute to enhanced terrestrial carbon uptake (Holland et al. 1997). Similarly, ore smelting and coal combustion have roughly doubled annual emissions of sulfur gases to the atmosphere, with implications for both acid rain and global climate change (Galloway 1995). Anthropogenic perturbation of the cycle of phosphorus, a limiting nutrient for many plants, has been less studied, but is thought to be significant at least at a regional scale.

It is clear that these human-induced stresses to the biosphere interact, but the net effect of the multiple perturbations remains uncertain. Increased tropospher

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

ic CO2 and widespread nitrogen deposition both act to fertilize plant growth, but other factors—such as soil acidification, high tropospheric ozone levels, loss of soil fertility through base cation loss, and their interactions with plant diseases and pests—all reduce plant productivity and have other effects on the biosphere. The net effect of these factors on crop productivity and the biosphere's ability to consume the carbon emitted through fossil fuel combustion needs to be understood. This is but a single example. We also know, for instance, that the current changes to the nitrogen cycle have had profound impacts on freshwater and perhaps oceanic resources and fisheries.

Human influences on the biogeochemical cycles are not all increasing so dramatically. Recent restrictions on sulfur dioxide (SO2) emissions in some countries have resulted in reduced inputs of acid rain to surface waters and ecosystems. The production and emissions of chlorofluorocarbons (CFCs) have also been reduced. Despite these scientifically informed policies, however, the abundance of N2O, CH4, and sulfate aerosols, all biogeochemically important compounds, will interact with the changing climate to influence the rate of recovery of the ozone layer. Yet while the biogeochemical cycles of the nutrient elements constitute crucial constraints on the Earth 's physiology, they remain poorly understood. This lack of understanding strongly limits our perspective on the many facets of global change. During the next century, continuing expansion of the influence of urbanization, industry, and agriculture on already perturbed biogeochemical cycles is likely. Increased scientific understanding of these cycles and the activities that are perturbing them is vital to formulating plausible political and social solutions to these important environmental perturbations.

Scientific Importance

The goal of biogeochemistry is to quantify the rates of transfer of relevant compounds and their accumulation or depletion in storage reservoirs. Knowing the residence time of compounds in each type of reservoir is central to predicting their changes over time. For example, during the last decade, research on the global carbon cycle has established that fossil fuel combustion has released an average of 5.5 (+/−0.5) gigatons (Gt) of carbon in CO2 into the atmosphere each year, and land-use changes have contributed an additional 1.6 (+/−1.0) Gt, for a total of 7.1 (+/−1.1) Gt (Schimel et al. 1995). Only 3.3 Gt of carbon is actually stored in the atmosphere. Ocean uptake of 2.0 (+/−0.8) Gt leaves an additional 1.8 Gt to be accounted—for the so-called “missing sink” of carbon. The remaining carbon is probably stored on land, and the locations and mechanisms of this carbon storage continue to be the subject of discussion and research (Tans et al. 1990, Nabuurs et al. 1997, Fan et al. 1998, National Research Council 2000a, Schimel et al. 2000). The likely mechanisms are CO2 or nitrogen fertilization of

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

the biosphere; reforestration, resulting in carbon storage in wood; and interactions with climate and its interannual variability. Yet the lack of a complete understanding of the current carbon budget hampers efforts to understand past geologic changes and to predict future changes in CO2 concentrations. The magnitude, global scale, and potential destructiveness of some cycle perturbations make research on these cycles particularly urgent and timely.

As indicated by its very name, biogeochemistry links scientific specialties. New discoveries have emerged as specialists in any number of areas have recognized that they must collaborate with scientists from other disciplines to solve their problems. Limnologists and oceanographers recognize that atmospheric chemists and ecosystem ecologists may be their best sources of information on future rates of nitrogen fixation. Researchers around the world are using the output of climate models to understand the internal dynamics of the ecosystems they study. Modelers, foresters, and botanists are beginning to appreciate how increases in nitrogen deposition may enhance carbon storage, for example, or how carbon uptake may be limited in other areas that are nitrogen-saturated (Townsend et al. 1996). Bringing these different perspectives together is important, but it poses a challenge for scientists and managers seeking to build workable structures that can support the needed science.

The ecosystem implications of the biogeochemical cycles come into focus most sharply when variations in space and time are taken into account. Ecosystems vary widely from place to place and over time for many reasons, and globally averaged cycle information relates only weakly to those unique situations. As the broad outlines of the biogeochemical cycles become better delineated, spatial distributions and temporal trends in the parameters of interest will link the cycles in increasingly useful ways to topics of interest within other grand challenges.

Scientific Readiness

The growth of the field of biogeochemistry during the past 10 to 15 years has led to significant theoretical and experimental developments that can serve as the base for future research, and the study of carbon and nitrogen cycles has greatly benefited from recent technological advances. Of particular note are analytical techniques for isotope analysis of 13C, 18O, 15N, deuterium, and 14C, as well as the measurement of an increasing array of atmospheric trace gases, including reactive oxides of nitrogen, sulfur gases, OH, and O2. Direct flux measurements of energy, momentum, and CO2 and H2O vapor exchanges, not possible a decade ago, today have become a cornerstone of both the U.S. and European field experiment programs (Brasseur et al. 1996). Remote measurements of ocean and land surfaces and the atmosphere made possible by recent satellite launches (such as the National Aeronautics and Space Administration's [NASA]

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

TOMS instrument and Terra satellites) have and will continue to enable great advances in understanding. They will also fill gaps in the global information database, including the understanding of land-cover change argued for under Grand Challenge 7. Models have progressed dramatically, and are beginning to provide realistic simulations of the complex interactions among atmospheric, oceanic, and terrestrial systems (American Meteorological Society 1998).

The existence of long-term measurements made possible by funding from a number of federal agencies has been essential to progress in the field. These datasets include the global trace gas measurements made by the Climate Monitoting and Diagnostics Laboratory (1996-1997), funded by the National Oceanic and Atmospheric Administration, which have provided insights into the carbon cycle and carbon cycle models. NASA's archiving of Landsat satellite images has enabled quantification of large-scale land-use change (Skole and Tucker 1993). The Environmental Protection Agency's surface observations of pollutants and the development of emission inventories have helped test our understanding of atmospheric chemistry (Guenther et al. 1994, Benkovitz et al. 1996). The National Atmospheric Deposition Program/National Trends Network Program and the National Dry Deposition Network have provided long-term measurements (1978-present and 1990-present, respectively) of wet and dry deposition that enable regional and national evaluations of acid rain inputs, nitrogen deposition (Holland et al. 1997), base cations inputs (Driscoll et al. 1998), and surface water resources. The Department of Energy 's funding of the Carbon Dioxide Information and Analysis Center has provided a much-needed synthesis of CO2 data at a critical time. Maintaining these long-term data programs is seldom easy, but is crucial to deriving increased insight. The above are but a few key examples of successes in the field.

We are now poised to place our understanding of biogeochemical cycles on a much firmer theoretical and empirical base than now exists. In the coming decade, it will be possible to gain a solid quantitative understanding of the cycles and budgets of the key biogeochemical constituents. In fact, a well-developed strategy (the U.S. Carbon Cycle Science Plan) already exists for understanding the cycling of CO2. Continuing major commitments of financial and human resources by multiple agencies are needed to bring this plan to fruition. An ultimate goal is to make reliable predictions of future changes in these cycles and the resulting effects on planetary functioning. Progress toward this goal will depend on continued research on biogeochemical processes and on human activities that drive these processes. (The extent to which this approach spans disciplinary areas is indicated by the fact that the use of the nutrient elements and of land, water, and various natural materials is addressed in Grand Challenge 7, Grand Challenge 4, and Grand Challenge 8, respectively.) In a policy context, predictive biogeochemical models could help guide decisions about such matters as fossil fuel use, energy production, agricultural and industrial practices, and mitigation of climate change.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×
Important Areas for Research
  1. Improve the quantification of sources and sinks of the nutrient elements, and gain a better understanding of the biological, chemical, and physical factors regulating transformations of nutrient reservoirs. Greatly improved estimates of the sizes of nutrient reservoirs on regional and global scales and their rates and causes of transformation are essential for identifying those reservoirs and transformations most influenced by human activity and predicting the impact of the transformations on ecosystem health; global climate; and human needs, such as food supplies and clean air. Studies of the Earth's history can reveal the significance of biogeochemical cycles in altering climate and the distribution, abundance, and diversity of organisms, and aid in understanding positive and negative feedbacks within the global system.

  2. Improve understanding of the interactions among the various biogeochemical cycles. Nitrogen, phosphorus, and essential trace nutrients such as iron alter the productivity of terrestrial and oceanic plants and the transfer of carbon from the atmosphere to living organisms. Likewise, decomposition and remineralization of organic matter transform nutrients captured by organisms back into inorganic form. All of the cycles of essential nutrients interact with each other, and the positive and negative feedbacks among them are at present poorly quantified and understood. In addition, the biogeochemical cycles are strongly influenced by the terrestrial hydrologic cycle. An understanding of these synergisms and their impacts is necessary if changes in any one cycle are to be predicted.

  3. Assess the impacts of anthropogenic perturbations of biogeochemical cycles on ecosystem functioning and atmospheric and oceanic chemistry, and develop a scientific basis for societal decisions about managing these cycles. Greatly improved projections of future concentrations of CO2, CH4, nitrous oxides, and aqueous and atmospheric pollutants, as well as understanding of the responses of natural and managed ecosystems to these and other atmospheric components, are required to make wise management decisions regarding human activities. Better projections will depend on research to improve understanding of the drivers of human actions that perturb the cycles and to enhance models of biogeochemical processes and their ecological effects. An understanding of the impacts of past and current land-use and agricultural, industrial, and domestic practices and policies on nutrient cycles would facilitate the development of models for fully assessing those impacts. In addition, the cycles of non-nutrient elements, addressed in Grand Challenge 8, Reinventing the Use of Materials, are important to ecosystem functioning. Thus a longer-term goal is to integrate the environmental implications of the nutrient and non-nutrient elements. Research on the effects of changes in biogeochemical cycles on human societies and economic activities is also an essential part of the scientific basis for societal decisions.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×
  1. Explore prospects for mitigating these perturbations. There is a need for extensive research regarding the feasibility and effectiveness of a variety of both technical approaches (e.g., precision agriculture, creation of carbon sinks, technologies for more efficient uses of nutrient elements) and institutional approaches (e.g., financial incentives for resource conservation, creation of emissions markets) for achieving sustainability of the essential nutrient cycles. This research priority has obvious overlap with Grand Challenge 6 on institutions and resource use.

The research priorities for biogeochemistry are clearly related to those for a number of the other grand challenges in addition to the overlaps noted above. Significant changes in biogeochemical cycles are often driven by extreme weather events, such as those outlined in Grand Challenge 3 on climate variability. Moreover, it is clear that interannual variation in climate drives interannual changes in carbon and possibly nitrogen cycling (Braswell et al. 1997, Erickson 1999). Understanding the linkages between micronutrient and nutrient cycles, as well as transforming that understanding into meaningful policy, will also require information and insights gleaned from Grand Challenge 3. Vitousek et al. (1997b) have shown how acceleration of the nitrogen cycle can affect biodiversity and species composition in terrestrial and aquatic ecosystems, effects that have obvious overlap with Grand Challenge 2 on biological diversity and ecosystem functioning. In addition, acceleration of the nitrogen cycle is implicated in the widespread hypoxia in the Gulf of Mexico, in freshwater pollution following the North Carolina floods of 1998 and 1999, and in the Pfiesteria outbreaks along the Eastern Coast of the United States, addressed by Grand Challenge 5 and Grand Challenge 6 on infectious disease and institutions, respectively. And changes in land-use dynamics (Grand Challenge 7) have driven large-scale changes in the carbon and nitrogen cycles.

GRAND CHALLENGE 2: BIOLOGICAL DIVERSITY AND ECOSYSTEM FUNCTIONING

The challenge is to understand the regulation and functional consequences of biological diversity, and to develop approaches for sustaining this diversity and the ecosystem functioning that depends on it.

Practical Importance

Human impacts on the land and oceans are pervasive and profound. The human enterprise has appropriated nearly half of the Earth's primary productivity, more than doubting the global cycling of nitrogen (Vitousek et al. 1997a,b). Humans harvest much of the oceans' production as well, drill petroleum from continental shelves, and are poised to begin using the deeper ocean floors for both mining and waste disposal and petroleum recovery.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

Human use of an area has generally meant its severe degradation as a natural habitat. Ecosystems and their functioning are threatened. As a result, the rate of species extinction is higher now than at almost any time in the Earth's history (National Research Council 1995). Today, indeed, we face the risk of a great mass extinction, one of only a handful in the history of the Earth.

The permanence of extinction makes it qualitatively different from other kinds of environmental change. Many societies around the world support the protection of species diversity, often explicitly, on ethical, moral, cultural, and aesthetic grounds. Many U.S. federal and state laws support the maintenance of species diversity. For example, the U.S. Endangered Species Act of 1973 states that it is “the policy of Congress that all Federal departments and agencies shall seek to conserve endangered species and threatened species. . . .” (Section 2 {b[c]}). Thus an anthropogenically driven mass extinction would be a great societal as well as biological loss.

Such a loss would also be risky. Humans depend crucially on nature for many things, from food, fiber, and medicines to recycling of nutrients and regulation of air quality, water quality, and climate (Daily 1997, National Research Council 1999f). Environmental scientists do not yet fully understand the sensitivity of these things to changes in the diversity of organisms and ecosystems. At present, we have a limited appreciation of what is really at risk, of the time scale for losses, and of the environmental consequences of simplifying and mixing the Earth's biota. Nonetheless, a major loss of biological diversity clearly threatens the capacity of the Earth to support human societies.

To predict the impacts of human activities on the diversity of genotypes, species, and ecosystems, we need a thorough understanding of the fundamental natural controls on biological diversity. We also need to make a major investment in discovering to what extent ecosystems with altered diversity can provide the services humanity depends on. Further, progress made in understanding the genesis and regulation of biological diversity needs to be applied in developing the capacity for preserving that diversity. Given the already pervasive impacts of human activity, high priority must be placed on the formulation of strategies for integrating conservation with human uses.

Threats to biological diversity on the land and in the oceans are generally unintended consequences of the development of human societies, growth in human populations, and efforts to improve standards of living. Practical efforts to protect species and ecosystems must reconcile ecological objectives with human needs.

Scientific Importance

Throughout its history, the field of ecology has focused on understanding the factors that produce and control biological diversity (e.g., von Humboldt 1807, Preston 1948, Hutchinson 1959, Rosenzweig 1999). Success would be a

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

substantial intellectual prize. It would represent a pinnacle of knowledge of the Earth's riving systems—comparable to the goal of cosmology to discover the events and processes that determine and guide the development of the physical universe. The practical value of such understanding would appear to be inestimable.

Since the early 19th century, observers have noted striking variations in patterns of species diversity with latitude, productivity, climate, and area (e.g., von Humboldt 1807). Area and isolation are fundamentally important, reflecting control of local and regional diversity on shorter time scales by the balance between migration and local extinction. Understanding of the relationship between species diversity and area —known as a species-area curve—is a powerful tool. At longer time scales, speciation also becomes important as the factor generating species diversity.

Although considerable understanding of the processes that lead to new species and those that destroy established ones has been achieved (e.g., National Research Council 1995), we do not yet know how to fuse that understanding into a quantitative theory capable of predicting changes in continent-scale or even local species-area patterns. It is not yet known whether a local extinction in one group will cause extinctions in others or whether species introductions, which are such an important part of the modern biological landscape, always lead to compensating or amplified losses in the diversity of native species. Without quantitative theories, we have only limited ability to predict rates of change or specific losses and gains that will follow a perturbation in the environment. However, current theories can be applied successfully to rank species diversities both within and among scales (MacArthur and Wilson 1967, Rosenzweig and Ziv 1999). Thus, a concerted effort during the coming decade could bring substantial advances.

Meanwhile, recent deep-sea research has taught us that the planet 's deep ocean floor—most of the Earth's surface—harbors many more species than was previously believed. Thus, many of the species of the deep sea and their patterns of diversity remain to be discovered. At present, we do not know even the major features of the biogeography of the deep sea. The technology needed to obtain this information now exists. But the vastness and severe habitat of both the abyss and the edges of the continental shelves make sampling expensive and have restricted such activities. At present, deep-sea habitats remain wildernesses, and as such they allow the study of diversity in an environment relatively unaffected by human activities. Soon they may be affected by petroleum drilling, mining, waste disposal, and fishing. An infusion of major support is therefore needed to take advantage of the current window of opportunity.

Diversity in terrestrial soils is poorly characterized as well. Although soils are easier to study in many ways than the deep sea, what their diversity means for microbes is not well understood. Because microbes are such an old and large fraction of the Earth's biota, improving this understanding is of great scientific and practical interest.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

It is also important to understand diversity at scales larger and smaller than that of the species. Past changes in the number and distribution of the major terrestrial biotic communities, or biomes, are important keys to understanding the history of the Earth. Understanding the limits on the number and distribution of biomes becomes more critical as human-caused climate change creates pressures for biome shifts and perhaps for the disappearance of some biomes and the emergence of others. Dynamic global vegetation models (International Geosphere-Biosphere Programme 1997) are a recent attempt to simulate the number, diversity, and distribution of biomes, based on competition among plants representing the major functional types. Unfortunately, our understanding of the factors that control this competition is still limited, and the results of these models are therefore tentative.

The study of the relationship between biological diversity and ecosystem structure and functioning is in its infancy. Early studies have produced many examples but few general principles (Tilman 1999, Wardle et al. 2000, Naeem 2000). Obviously, at the lower limit (only one or very few species), loss of species diversity must affect ecosystem functioning, but there is no general principle concerning the impact of decreasing biological diversity on the risk of widespread loss of ecosystem functioning. It is clear that not all species are equally important, but little is known about the general extent to which ecologically similar species can substitute for each other in providing ecosystem services. A dedicated effort combining experiments with long-term studies, opportunistic observations, and synthesis would greatly advance understanding of the relationships between diversity and functioning. Although we cannot predict the results of these studies, almost any result would be of great value. Whether there is a general relationship, no relationship, or—most likely—different relationships under various circumstances, the knowledge will be essential for understanding and preserving biological diversity and ecosystem services.

For much of the 20th century, researchers in population genetics and population biology sought to understand the factors that regulate a third scale of biological diversity—the genetic diversity within species and populations. Biologists succeeded in many particular cases. But they lack a comprehensive theory linking genetic diversity with other factors, including environmental stresses and diversity at the level of species or ecosystems. While it is clear that genetic diversity is a powerful influence on ecological success and hence on the persistence of species, we cannot yet quantify this relationship, although many examples illustrate the vulnerability of low-diversity agricultural systems to attack by pests.

Even total understanding of the laws of diversity would be inadequate by itself to conserve diversity in the face of the changes humans make in the environment. Research is also necessary on the needs of specific species and ecosystems that have been truncated by human activities. Moreover, as noted above, practical efforts to protect species and ecosystems must be based on a balance

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

between conservation needs and human needs. Achieving such a balance will entail answering many scientific questions related to three major strategies for protecting biological diversity—reservation, restoration, and reconciliation:

  • Reservation is the setting aside of natural and near-natural areas for non-human biota. This strategy, exemplified by the establishment of national parks, has grown into a U.S. and worldwide program. It has reduced species losses, but it has not and cannot by itself eliminate them because so much natural habitat has been altered by human activities. Nonetheless, research is important to improve the design and implementation of biological reserves.

  • Restoration ecology—only now beginning to see large-scale scientific application—attempts to return degraded sites to some degree of natural structure and functioning (see, e.g., National Research Council 1992). Restoration has much to offer for protecting biological diversity but is challenging, largely because of incomplete knowledge of which aspects of an ecosystem must be restored to protect an endangered species and to what degree of functioning. For example, Zedler (1996) describes how an apparently successful restoration of the vegetation in a coastal wetland did not support endangered clapper rails because the cordgrass was not tall enough to support their nesting. Similarly, red-cockaded woodpeckers do not depend simply on the presence of long-leaf pines, but require nest-holes in living trees (McWhite et al. 1993). And natterjack toads need more than early successional stages of sandy heathlands; they must have ponds warm enough to support early breeding so their tadpoles can escape predation by tadpoles of the common toad (Denton et al. 1997).

  • Reconciliation ecology is beginning to emerge as a scientific discipline. Reconciliation is based on the premise that there are ways to design and manage habitats for productive human use and the maintenance of natural biota.

Given continued human dominance of most terrestrial ecosystems, successful conservation of biological resources will depend on continued advances in our understanding of reservation, restoration, and especially the relatively new field of reconciliation ecology.

Scientific Readiness

The following conditions make a scientific initiative on biological diversity and ecosystem functioning particularly timely.

Advances in understanding biogeography, speciation, and extinction. Species-area patterns are now known to exist at four scales, each of which has been associated with a set of processes ranging from sampling artifacts, to co-evolution, to speciation-extinction dynamics. Many details of these relationships and of their mechanisms of action are beginning to emerge, creating the

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

opportunity for a concerted effort to combine the understanding of these processes into a quantitative theory of species diversity.

Progress in understanding the interaction of biodiversity and ecosystem functioning. Many recent studies have explored aspects of the relationship between the diversity of species (and in some cases the diversity of genotypes or ecosystems) and ecosystem functioning (e.g., Chapin et al. 1997, Tilman 1999). The focus of these studies ranges from primary production, to resistance to biological invasion, to leakiness for nutrients. Given the support of extensive experimental and observational work, the next decade or two could see the emergence of a general theory. Even if it were discovered that there is no general relationship, that information would be of enormous scientific and practical value, so this work is certain to produce important results.

The idea that diversity itself causes evolution (Cody 1975) has led to the investigation of several crucial issues, including the evolution of specialists (Brown and Pavlovic 1992) and the factors that influence how rapidly and strongly evolution occurs in response to diversity (Holt and Gomulkewiecz 1997). Incorporation of such coevolutionary theories into experimental work on ecosystems and diversity and into ecological models will improve understanding and the accuracy of predictions.

New and improved tools. Several tools with direct relevance to the study of diversity have substantially improved the pace and quality of diversity research:

  • Satellite remote sensing yields global maps of ecosystem distribution at a spatial scale of 1 km, and even higher resolution will be available soon. Satellite sensing reveals the distribution and diversity of ecosystem types, information critical for testing and improving models of ecosystem diversity.

  • Deep-sea sampling routinely produces cores from both medium and abyssal depths using remotely controlled submersibles, providing new methods of assessing and understanding patterns of species diversity.

  • Genomics using polymerase chain reaction (PCR) and microarrays can now be used for rapidly and efficiently assessing genotypic diversity and variation in gene expression. Molecular tools for characterizing microbial diversity reveal vast stores of hidden diversity in oceans, sediments, and soils, including environments at extremes of temperature and pressure. These methods will lead to new insights into the significance and consequences of diversity below the species level, as well as better understanding of species diversity.

  • Dynamic global vegetation models integrate the results of research on plant ecology, soil, water, and atmospheric conditions. They attempt to forecast changes in plant cover in response to environmental variations.

  • Bias-reduction software, based on work by Burnham and Overton (1979) and Chao and Lee (1992), reduces by an order of magnitude the sample-size biases associated with diversity estimation (Chazdon et al. 1998, Turner et al.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

2000). Thus it dramatically advances our ability to perform fast, reliable assessments of species diversity and measure the dynamic responses of diversity to environmental changes.

Progress in conservation science. There is a large and growing store of experience with restoration of relatively small habitat patches and with the design of terrestrial and marine reserves (National Research Council 2001). Meanwhile, conservation science has increasingly turned its attention to the land humans continue to use. Various investigations have shown that human use of an area does not have to preclude its use by other species. Habitats for human use—if exploited with care—can harbor large numbers of native species (Daily 1999). Conservation ecologists are learning how to modify land-use techniques to favor diversity. They are also discovering that—for surprisingly small investments—they can adapt human landscapes to sustain target species that may be imperiled (e.g., Yosef and Grubb 1994).

Integration of ecology with economics, psychology, and sociology. Cultural, economic, and psychological factors drive human actions, mediate human preferences for environmental conditions, and thus help shape the configuration of landscapes in which diversity must survive. The relationship between the disciplines that study these factors and ecology is not well developed, but it is an increasing area of focus, with new programs, journals, and paradigms emerging. Many challenges remain before these disciplines are effectively integrated, but the right conversations are now under way, and future progress should be rapid.

Important Areas for Research
  1. Improve tools for rapid assessment of diversity at all scales—species, population, and ecosystem. New technologies—such as molecular techniques and remote sensing—should be incorporated in such tools as they are required and become available. Continuing work is also needed on the development of techniques for assessing diversity from incomplete sampling and on the use of remotely sensed data to examine ecosystem characteristics.

  2. Produce a quantitative, process-based theory of biological diversity at the largest possible variety of spatial and temporal scales. The goal should be to predict the diversity of biomes, growth forms, and functional types, as well as species and genotypes. To attain that goal, it will be necessary to continue to investigate and interrelate species-abundance and range-size distributions, population structures and densities, and productivity patterns, as well as mechanisms of speciation and the relationship of population size to evolutionary change. In addition, theories of coevolution need to be extended and matured.

  3. Elucidate the relationship between diversity and ecosystem functioning. Much evidence suggests that biological diversity affects ecosystem functioning

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

mainly through sampling: a high level of diversity increases the probability of including a species or functional type that fills a particular role. It is not known whether this is true in general, or other principles become more important under some conditions. In short, there is no theory for the role of diversity in ecosystems. A series of experiments is needed to test explicit hypotheses about the mechanistic controls on biological diversity at all scales, and about the relationship between biological diversity and ecosystem functioning, including persistence. Some of these experiments would involve manipulated diversity and landscape complexity. Others would involve the consequences for diversity of a range of patterns of human activity.

  1. Develop and test techniques for modifying, creating, and managing habitats that can sustain biological diversity, as well as people and their activities. Such work would depend on having an understanding of the design of the habitats in which people live and work, as well as the factors that influence human choices and preferences for different habitat types. Much of the science required would reveal the habitat requirements of imperiled species and the degree to which their continued existence is required for the adequate functioning of an ecosystem. It would also involve identifying species whose loss would likely lead to a cascade of further extinctions. As part of this effort, it would be necessary to develop management techniques that could be used to keep spatially diminished ecosystems at work.

GRAND CHALLENGE 3: CLIMATE VARIABILITY

The challenge is to increase our ability to predict climate variability, from extreme events to decadal time scales; to understand how this variability may change in the future; and to assess its impact on natural and human systems.

Practical Importance

Although climatic changes have occurred throughout the Earth's history, the accumulation of greenhouse gases in the atmosphere is perturbing the climate system with unknown effects on climate extremes and variability. The increase in greenhouse gases may be affecting the frequency and magnitude of severe events (e.g., episodes of heavy rainfall) (Intergovernmental Panel on Climate Change 1996) and may also be changing seasonal weather patterns (e.g., length of growing season, number of snow days, duration of ice cover on lakes). Because human land use has altered the resiliency of natural ecosystems, changes in weather extremes and in interannual variability may have a larger impact on ecosystems than the increases in average temperatures projected for the next century. Indeed, even if the spectrum of extreme events and climate variability were to remain unchanged, the impact of droughts, floods, and severe storms would probably increase as a result of extensive human alteration of landscapes

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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through removal of forests, drainage of wetlands, channelization of rivers, construction of cities on floodplains, and growth of human populations in high-risk coastal areas. Mortality and morbidity associated with temperature extremes, loss of livestock confined in feedlots or barns under extreme conditions, extensive property damage due to hurricanes such as Andrew and Floyd, and significant agriculture losses and water supply problems during drought have substantially increased public awareness of the safety issues and economic impacts of extreme weather events. Yet despite the importance of these issues, understanding of how climate variability is likely to change in response to global warming and large-scale land-use changes remains poor.

Scientific Importance

Several factors underlie the scientific importance of this research challenge. First, although we are far from a comprehensive theory of climate variability, substantial progress has been made in understanding some of its aspects, in particular El Niño-Southern Oscillation (ENSO) events, a major source of climate variability on seasonal to interannual time scales. Observations recorded in ice, corals, and tree rings are extending the historical record of ENSO, and new observational and modeling capabilities have greatly improved our ability to predict the evolution of ENSO events. However, comprehensive predictions that capture the extent of ENSO and its impacts in different regions of the Earth are not yet possible. As a consequence, our ability to assess changes in ENSO over the next century is highly limited. Research on other modes of climate variability is in its infancy, and characterizing those modes is necessary if we are to unambiguously discern long-term climate trends caused by human activities, as well as understand natural variations in the global carbon cycle.

Second, many investigators believe the intensity and frequency of extreme events, including hurricanes, ice and snow events, floods, and droughts, change significantly in concert with longer-term climate changes. Investigators have found recent changes in the character, frequency, and seasonal patterns of extreme weather events (Intergovernmental Panel on Climate Change 1996), raising concern that these patterns are due to anthropogenically driven climate change. Yet the mechanisms controlling these variations are still largely unknown, and extreme events remain among the most uncertain of all climate projections.

Third, fine-resolution sampling of paleorecords reveals sudden shifts of climate occurring within years or decades at many different times in the past, suggesting that the climate system can shift from one mode to another as certain thresholds are crossed. There is concern that the rapid changes in climate in the coming century could trigger such a shift. Yet our understanding of the mechanisms of abrupt climate transitions is extraordinarily limited.

Fourth, extreme events and climate variability have dramatic potential to

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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alter coastal and terrestrial ecosystems through direct temperature, precipitation, and physical (e.g., wind) impacts; through changes in freshwater inputs; and through indirect changes to air and water quality. The potential impacts extend from habitat disruption to changes in species composition and diversity. Yet we understand very little of how changes in the frequency and character of events or in interannual variability may influence ecosystems.

Finally, human societies and economic systems have adapted to historic patterns of climate variability, but may be disrupted to various degrees, depending on their coping capacities, if these patterns change. In addition, human alterations of the landscape may have changed the vulnerability of social systems to climate variations within historic ranges. Understanding the potential impact on humans of changes in patterns of climate variation depends on improved fundamental understanding of such human-climate interactions.

Scientific Readiness

Comprehensive models incorporating the atmosphere, oceans, vegetation cover, ice, and biogeochemistry are required to assess the nature of the climate changes associated with various factors, most of which are themselves rapidly undergoing change due to human activities. Newer, faster computers are driving the development of comprehensive interactive models with coupled atmosphere and oceans. However, because of limited access to powerful supercomputers, U.S. modeling centers have found it difficult to perform high-resolution studies of coupled ocean-atmosphere climate change, and this in turn has hampered scientific progress in understanding fundamental climate processes (National Research Council 1999b). Vegetation has large effects on climate. Although incorporating these effects into climate models introduces significant challenges, important work has begun. Since human land use may alter vegetation more rapidly than natural processes, collaborations between social and natural scientists become essential so that reasonable predictions of human behavior can be incorporated into the models. Such collaborative modeling studies have shown great potential, although examples are still few.

The finer spatial scale of recent models increases their potential for simulating weather events and patterns of variability on short time scales that can be verified through comparison with the rapidly expanding observational record. Remote sensing of vegetation and a variety of key climatic variables, combined with weather and deep-ocean observations, provide a much greater capability to study climate and climate change. Paleorecords from many parts of the globe are beginning to provide a strong foundation for comprehensive models of the Earth system. Fine-resolution records from ocean sediments, ice cores, and lakes are making it possible to describe levels of climate variability on annual and decadal scales and to recognize extreme events. All of these new records enable testing of climate models to assess their ability to predict climate varia

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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tions under changed boundary conditions. Finally, multidisciplinary investigations are beginning to allow ecologists to interact with social scientists in examining both ecological and human responses to climate change and variability.

Important Areas for Research
  1. Improve observational capability. As noted by the National Research Council (1999a), our instrumental capacity to observe the Earth's climate system is deteriorating worldwide, greatly limiting the ability to adequately document climate variations. It is crucial to strengthen and revitalize these observational systems, originally designed to monitor weather, so we can better understand the spatial and temporal attributes of climate variations. Long-term, consistent, and accurate observations are needed, along with enhanced observations of climate-related ecosystem and social phenomena and the ability to take advantage of technological advances, such as new satellites and ocean monitoring systems.

  2. Extend the record of observations. Historical observations of climate represent only a small segment of time and are inadequate for assessing the nature of climate variability. Paleorecords are being dated more precisely, and high-resolution data are being compiled for a variety of indices. Enhancing the quality of these observations and extending the records spatially and temporally are critical to a full understanding of climate variability. Where possible, paleorecords should overlap with the instrumental record, enabling the development of integrated historical and proxy datasets. Paleorecords of climate should be linked with paleoecological, archaeological, and historical data to build a basis for improved understanding of climate interactions with ecosystems and social systems. Doing so would also improve our capability for hydrologic forecasting (Grand Challenge 4).

  3. Conduct diagnostic process studies. Uncertainties in our understanding of climate variations and interactions among climate, ocean circulation, carbon cycling, atmospheric chemistry, vegetation, hydrology, and human systems should guide focused field and model studies. These studies should be directed at the controls of climate variability; they must include an emphasis on boundary layer processes, linkages among the ocean-atmosphere-land surface, more explicit representation of climate-vegetation interactions, evaluation of ecosystem implications, and process studies of human coping mechanisms. Portions of this research overlap strongly with Grand Challenge 1 (Biogeochemical Cycles), Grand Challenge 2 (Biological Diversity and Ecosystem Functioning), and Grand Challenge 7 (Land-Use Dynamics).

  4. Develop increasingly comprehensive models. Neither a predictive understanding of climate variability nor an assessment of the interactions between climate and other critical elements of the Earth system is possible without the development of increasingly comprehensive coupled models. Greater attention should be given to (a) model-data and model-model comparisons, with an em

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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phasis on testing these models against known geologic evidence and observed climate variations; (b) elimination of major uncertainties in model parameterizations; and (c) the development of predictions at spatial and temporal scales as appropriate for the examination of biologic, hydrologic, and socioeconomic systems. Portions of this research overlap with Grand Challenge 4 (Hydrologic Forecasting).

  1. Conduct integrated impact assessments, and study human responses to climate change. A key challenge is to understand how climate variability interacts with terrestrial, freshwater, and marine ecosystems; water and food supplies; and the quality of human life. Improved prediction of climate variability is insufficient without careful assessment of the impacts of climate variability and a much greater understanding of the linkages between climate variability and natural ecosystems. Also needed is improved knowledge of human responses to a changing climate (e.g., changes in land use), which themselves can have major environmental effects.

GRAND CHALLENGE 4: HYDROLOGIC FORECASTING

The challenge is to predict changes in freshwater resources and the environment caused by floods, droughts, sedimentation, and contamination in a context of growing demand on water resources.

Practical Importance

Water is an essential natural resource that shapes regional landscapes and is vital for ecosystem functioning and human well-being. Human use and contamination of freshwater are stressing the resource, and alterations in the hydrologic regime have serious consequences for people and the environment. This grand challenge addresses the need to forecast both the hydrologic regime and the environmental consequences of changing that regime.

Human use of fresh water. In the next two decades, water use is expected to triple in the world (L'vovich and White 1990, Postel 1998), leading to corresponding increases in pollution, erosion, runoff, dewatering, and salinization. Although per capita domestic water use in the United States is 500-600 liters per day, total daily per capita water use in urban areas is about 5,000 liters (Solley et al. 1998). To satisfy the growing demand for water, the United States has built more than 75,000 dams (Graf 1999) and has exploited groundwater resources to the extent that major aquifers are being mined and the resource consumed (Graf 1993, Bredehoeft 1984). During the last few decades, depletion of aquifers has also become a widespread problem in parts of China, India, North Africa, and the Arabian peninsula, leading to critical water shortages, especially among poor, rural communities (Postel 1999).

Threats to freshwater ecosystems. Human demands on water resources have

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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strong effects on the integrity of freshwater ecosystems (Naiman et al. 1995, Naiman and Turner 2000). In the United States, only about 2 percent of the 5 million km of streams is in good condition, and more than half of the animal species listed federally as threatened or endangered are aquatic. Nationally, 39 percent of native fish species are rare to extinct, and many others have a high to moderate risk of extinction in the near future (Stein and Flack 1997). This situation is due mainly to hydrologic alterations of freshwater habitats and to the presence of introduced, nonnative species. Similar ecological stresses are occurring in many other parts of the world, where major river systems, such as the Nile in northeast Africa and the Ganges and Indus in southeast Asia, have been heavily altered by dams, reservoirs, and diversions (Postel 1999).

Social and environmental impacts of floods and droughts. From 1990 through 1997, floods were responsible for more than $34 billion in damage in the United States alone (National Drought Mitigation Center 1999). In poor countries whose populations are highly vulnerable to weather disasters, the impacts of floods can be enormous. When record flooding occurred in the Yangtze River basin in China in 1998, more than 2,000 people drowned, and millions were driven from their homes. Prodigious floods occurring in Southern Africa in February 2000 displaced several hundred thousand people in Mozambique, Botswana, South Africa, and Zimbabwe. Damage due to drought is more difficult to quantify, but agricultural losses (and in poor countries, resulting problems of malnutrition) can be severe. The magnitude of the impacts of floods and droughts is a function of both hydrologic processes and human interaction with the environment.

Consequences of water contamination. Point- and non-point-source surface water and groundwater contamination threatens human health and natural ecosystems. Cleanup cost is one measure of the magnitude of the problem. The Environmental Protection Agency (1998) has estimated that there are 217,000 point-source sites in the United States, most of which affect groundwater, and that it will cost about $187 billion (in 1996 dollars) to clean them up. The use of pesticides and herbicides has led to widespread soil and groundwater contamination. For example, of 45,000 wells around the United States tested for pesticides, 5,500 had harmful levels of at least one.

Scientific Importance

Currently, our understanding and predictive ability with regard to hydrologic forecasting are limited by theory, method, and the scope of available models, as well as by data. Recent and evolving developments in remote sensing of parameters such as precipitation, soil moisture, snowpack, river discharge, vegetation cover, and surface topography are beginning to yield spatial and temporal data that are driving a revolution in hydrologic science, making it possible to measure hydrologic phenomena never before seen and thus poorly understood.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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Yet the hydrologic and ecological theory, methods, and facilities needed to take advantage of this high-resolution information do not exist. Theoretical and methodological advances in hydrologic science are therefore needed to use and interpret field measurements and the abundant remote sensing data that soon will become available. A sustained research effort is likely to result in major advances in interpreting the behavior of hydrologic systems across different spatial and temporal scales; forecasting changes in water quantity and quality; and determining the impacts of these changes on surface and subsurface water resources, landscape dynamics, ecological communities, and human systems. These points are elaborated below in the discussion of important areas for research.

In meeting this challenge, science would draw on new high-resolution atmospheric, surface, and subsurface data obtained as a result of rapid advances in remote sensing and geophysical technology. Multidisciplinary collaboration, field measurements and experiments, and data integration would enable the development of a new body of hydrologic science, linking traditional hydrology, geomorphology, and aquatic/riparian ecology.

Scientific Readiness

The primary obstacles to advances in hydrologic research have been limited, sparse, spatially distributed data and broad disconnects between the scales of data generated. Recent and projected technological advances in remote data collection, coupled with field experiments, can supply abundant information about vast regions of the Earth at increasingly finer spatial and temporal scales. These data—including high-resolution visual, radar, and infrared satellite-based maps of the land, water, and atmosphere; precise surface topographic maps; new geophysical images of the shallow subsurface; and real-time, integrative environmental information—have never before been available. (For details on specific sensors and monitoring techniques, see National Aeronautics and Space Administration 1999a,b; National Research Council 2000b.) When linked with data on human consumptive use of water, contaminant emissions, and land-use patterns, this new information will provide the basis for greatly improved understanding and prediction of hydrologic and related environmental processes.

For the past three decades, hydrologists have built quantitative process-imitating models of water flow, sediment transport, channel dynamics, and contaminant migration. However, their ability to make hydrologic and ecological forecasts has been limited by the lack of understanding of interactions across multiple spatial and temporal scales. The new data from remote sensing, together with new methods such as geophysical tomography, will enable the development of a new generation of hydrologic/ecological theory and methods, thereby providing predictive capabilities that do not exist today. Such developments will require the integration of field measurements and experiments with atmospheric, surface, and subsurface satellite imagery. This information can be incorporated into

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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predictive models being developed for land-use change (see Grand Challenge 7 on land-use dynamics) to increase the models' accuracy and usefulness for decision making.

Important Areas for Research
  1. Improve understanding of hydrologic and geomorphic responses to pre-cipitation. New biophysical theories and models needed to utilize the new high-resolution radar data are not yet in place. Comprehensive theories of flooding and new methods of flood forecasting would soon become possible if scientific advances enabled hydrologists and geomorphologists to take advantage of satellite images of the atmosphere and the Earth 's surface. For example, the sparse network of modern semiautomated rain gauges does not capture such essential features of storms as their spatial extent and patterns of temporal intensity. With large-scale, high-resolution radar coverage and experimentally determined relationships of radar data to local precipitation, new models of the hydrologic response to precipitation could be developed to enhance forecasts of floods and their potential impacts on human settlements. Advances in understanding rainfall-runoff processes at climatic extremes would also be possible with remotely sensed data. These data could be used in combination with field measurements to construct improved maps of land cover and surface topography, and to make better estimates of soil hydraulic properties and channel dynamics.

  2. Improve understanding of surface water generation and transport. Research is required to extract critical environmental-sensitivity information from satellite imagery and field instrumentation. New methods are needed to develop standard environmental indicators for surface water that can take advantage of the high resolution of precipitation forecasts. Such indicators could be used to inform and constrain process-based models of river flow and lake circulation. For example, satellite data could be used to detect contamination events and changes in water temperature, and to develop quantitative descriptions of hydrologic transport processes in rivers and lakes. Forecasting based on hydrologic and geomorphic simulations and real-time data analysis could also provide an early warning of waterborne disease outbreaks, of impending fish kills (as high water temperature indicates low dissolved oxygen content), and environmental disasters resulting from hot-water or contaminant discharges. Spatially explicit models of water and sediment distribution and movement would provide the foundation for predicting effects on aquatic organisms, including riparian species.

  3. Examine environmental stresses on aquatic ecosystems. Future remote sensing capability will enable ecologists to quantify the effects of altered hydrologic regimes (for instance, from irrigation and dams) and of environmental stresses (such as pollution, erosion, and salination) on the fundamental ecological properties of aquatic systems such as biodiversity, community dynamics,

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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primary and secondary productivity, elemental cycling, and resistance/resilience to disturbance. Such increased understanding would allow the development of creative strategies for assessing the tradeoffs between preservation and restoration of aquatic resources and demand for water.

  1. Explain the relationships between landscape change and sediment fluxes. Future hydrologic research should be aimed at developing new concepts and quantitative physical models of sediment transport, erosion, and deposition that are based on precise topographic data of entire watersheds and high-resolution radar imagery. With improved theories of landscape evolution over a range of time scales, quantitative hydrologic and mass-transport models could become tools for anticipating environmental hazards that are the consequence of active surficial processes. Such research could help provide improved real-time warnings of land-slides and mudslides; estimates of the long-term impacts of sedimentation and erosion on river morphology and consequently on navigability and flooding potential; and, when combined with analysis of land-use dynamics (Grand Challenge 7), estimates of the cumulative impacts of forest clearcutting, urban development, and other land-cover changes on water quality and on habitat as a result of changes in flooding patterns and frequencies. In addition, satellite radar data could be used to detect small changes in land-surface elevation and monitor land subsidence over vast regions due to groundwater extraction.

  2. Improve understanding of subsurface transport. New high-resolution geophysical techniques will enable scientists to “see through” the Earth and develop a clearer understanding of the structure and behavior of subsurface water-bearing and -transmitting reservoirs (National Research Council 2000b). This understanding is beyond the reach of traditional invasive measurement methods involving well drilling and trenching. Subsurface reservoirs supply much of the nation's public water supplies, and yet many are threatened by overuse and by contamination with industrial solvents, metals, fertilizers, pesticides, and herbicides. Zones of contamination are of undetermined extent, and the migration path is often unknown. The rapidly advancing field of geophysical tomography could, for the first time, make it possible for geological scientists to observe the shallow subsurface. This type of data, combined with hydraulic information, could yield a new understanding of subsurface properties and the distribution of relative flow paths and flow barriers. The resulting hydrogeological theories and models could be used to assess declining water levels, locate subsurface contaminants, track contaminant migration, and improve the knowledge base for decisions on managing aquifers.

  3. Map groundwater recharge and discharge vulnerability. New remote mapping capability using radar and infrared satellite data could be coupled with field measurements and new theories in hydrologic science to understand the signature of recharge areas and estimate evapotranspiration rates over vast regions. There are two critical environmental problems to be addressed. First, maintaining groundwater supplies depends on identifying groundwater recharge

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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areas and assessing which of these areas are threatened by depletion or contamination resulting from human activities. Second, identifying regions experiencing environmental stress due to a lack of soil moisture is key to managing agricultural production potential and assessing vulnerable aquatic habitats. New hydrologic models would make it possible to interpret high-resolution radar and infrared satellite imagery collected over time to identify and quantitatively assess impacts to recharge and discharge areas.

The hydrologic cycle is a ubiquitous part of the Earth's environmental system, so it is not surprising that this grand challenge overlaps in substantive ways with several others identified in this report. As noted earlier, land-use changes can have significant hydrologic impacts, and thus the observations and modeling efforts described here must be closely linked with those related to land use (Grand Challenge 7). The ability to predict climate variability and extreme weather events (Grand Challenge 3) is obviously a central facet of hydrologic forecasting. Biogeochemical cycles (Grand Challenge 1) are related as well, because one must understand the hydrologic characteristics of a region to estimate such phenomena as the transport of nutrients through agricultural runoff, river discharge rates, and sediment flows. Finally, the social science research discussed under Grand Challenge 6, Institutions and Resource Use, is highly relevant because of the need to strengthen institutions for water resource management, to understand the factors that drive human appropriation of water resources, and to determine how hydrologic forecasts can be used most effectively.

GRAND CHALLENGE 5: INFECTIOUS DISEASE AND THE ENVIRONMENT

The challenge is to understand the ecological and evolutionary aspects of infectious diseases; to develop an understanding of the interactions among pathogens, hosts/receptors, and the environment; and thus to make it possible to prevent changes in the infectivity and virulence of organisms that threaten plant, animal, and human health at the population level.

Practical Importance

There is a critical imperative to understand and prevent outbreaks of infectious disease in valued species, including our own. Toxic organisms and pathogens, including protists, algae, microbes, parasites, and viruses, are responsible for a major burden of disease and premature mortality among plant, animal, and human populations. The impact of natural toxins and pathogens on host populations is governed largely by factors regulating the growth of these organisms and their vectors, as well as their distribution, mechanisms of transmission/exposure (how hosts encounter pathogens), infectivity (how pathogens colonize hosts), virulence and toxicity (severity of disease), and host resistance (both host re

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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sponse and communicability to other hosts). These factors involve fundamental ecological and evolutionary processes, and are attributes of relationships between disease organisms and their environments, including the internal environment of their hosts. Pursuing this grand challenge would bring ecological and evolutionary understanding to bear on the problems of disease prevention and control.

Despite recognition of the importance of environmental conditions to microbial and pathogen ecology, a holistic understanding of the role of the environment in the distribution, infectivity, and virulence of pathogens remains in its infancy. There has recently been a great deal of interest in evaluating the effects of local and global climate conditions on distributions of vectors (Lindsay and Birley 1996, Martens et al. 1995, Doggett et al. 1999); however, other regional and local-scale factors may be equally important. The unanticipated effect of the Aswan High Dam on the distribution of the schistosomiasis vector is one well-known example (Abdel-Wahab et al. 1979). Uncontrolled dispersal of animal wastes can lead to harmful algal blooms in estuarine environments (Harvell et al. 1999, Fleming et al. 1999, National Research Council 2000a). Changes in the production of livestock feed may have contributed to the transfer of neurodegenerative diseases, such as mad cow disease, across species (Scott et al. 1999). And overuse of antibiotics (including use in factory farming of chickens and hogs in the United States, as well as medical practices and consumer misuse) results in the selective growth of antibiotic-resistant microorganisms (Tollefson et al. 1997, Wegener et al. 1999). The widespread use of genetically engineered crops has the potential to have a similar effect on pathogens (i.e., to select for resistance to the anti-infective agents in the crops).

Little attention has been given to the potentially important effects of environmental modification on host response. For example, exposure to ultraviolet light B (UVB) is known to inhibit immune function in humans (Morison 1989), while exposure to immunotoxic chemicals, such as polychlorinated biphenyls (PCBs) and dioxins, has been suggested as a contributing factor in the deaths of marine mammals in the north Atlantic (Ross et al. 1996). Understanding of such ecological factors in pathogen-host relationships is likely to lead to new insights about the causes of disease and new possibilities for prevention.

In meeting this challenge, a community of currently disparate disciplines must come together with the common goal of understanding the interactions between the environment and disease-causing organisms. Such research would lead to a more complete mechanistic understanding of the environmental factors altering the evolution of hosts and disease organisms, thus improving understanding of the mechanisms of infectious disease at the molecular and population levels. This improved understanding would in turn assist in the development of biological, social, and environmental controls for containing the spread of pathogens and toxic organisms; lead to guidelines for avoiding actions that encourage the development of resistance in pathogens; and help identify possible trigger

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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events, conditions, or underlying processes that foster changes in the population dynamics and biology of pathogens and toxic organisms.

Scientific Importance

During the past several decades, it was commonly believed that, at least in the developed countries, disease pathogens had been permanently surpassed in public health importance by noninfectious chronic diseases of aging. During this period, research on the role of pathogen/toxin exposures in human disease suffered relative neglect. Recently, however, the issue has attracted renewed scientific concern for several reasons. First, pathogens are now recognized to play a causal role in many chronic diseases and conditions, including cardiovascular disease, neuropsychiatric disorders, infertility, and ulcers. In addition, infections such as tuberculosis, malaria, and pneumonia have reemerged, and newly recognized pathogens—HIV, Nipah virus, West Nile virus, Lyme disease, transmissible spongiform encephalopathies, the hepatitis viruses—have grown in medical importance. We do not fully understand how or why these pathogens episodically present public health threats to humans, birds, and other animals. Disease-related pathogens such as Epstein-Barr virus and the tuberculosis bacillus are found in large numbers of clinically healthy individuals, suggesting that established models linking exposure and transmission to illness need amplification to incorporate virulence and changes in host susceptibility (Morris and Potter 1997).

Both human and other populations are affected by changes in pathogen distribution and virulence, but the mechanisms by which this occurs are not yet well understood. Often, as is the case with Pfiesteria-associated fish kills on the East Coast of the United States (Silbergeld et al. 2000a), domoic-acid-induced deaths of sea lions in California (Scholin et al. 2000), and Nipah virus in Malaysia (Chua et al. 1999), nonhuman species are the first sentinels of change. Deaths of crows and other birds provided the key to identifying West Nile Virus in New York in 1999 (Lanciotti et al. 1999). Similarly, understanding of the zoonotic (i.e., animal-related) aspects of immunodeficiency virus infection has importance for human health (Hahn et al. 2000). Given these linkages, recent reports of the role of parasitic infections and environmental stressors in causing amphibian deformities may reflect a sentinel event that will eventually be detected in other species (Burkhart et al. 2000).

If campaigns to reduce or eliminate major diseases such as tuberculosis and malaria are to be successful, the research community will need to design global interventions and monitor the efficacy of these investments. The phenomenon of chemotherapeutic and antibiotic resistance in many pathogens suggests that ecological approaches to disease control may be a necessary supplement to new drugs and vaccines (Morse 1993). As part of these efforts, it is important to anticipate the impacts of environmental change on disease prevalence. At

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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present, however, little is being done to evaluate the impacts of small- and large-scale environmental perturbations on host-pathogen-toxin relationships. Projections of future global change indicate that we may see the migration of new insect vectors capable of transmitting diseases such as malaria into previously uninhabitable geographic regions (Martens et al. 1995). Such changes in ecological dynamics will require both anticipation and adaptive responses by societies living in affected regions.

Because of their rapid growth rate and large populations, microbial pathogens can evolve very quickly, and these evolutionary mechanisms allow them to adapt to new hosts, produce new toxins, and bypass immune responses. Many of the weapons used against microbes (drugs, vaccines, pesticides) can inadvertently contribute to the selection of adaptations that enable pathogens to proliferate or nonpathogens to acquire virulence. This evolutionary perspective, sometimes referred to as “Darwinian medicine” (Ewald 1996, Williams and Nesse 1991), can greatly improve our understanding of pathogen behavior and host response, as well as our ability to design appropriate intervention and disease treatment strategies.

While the focus of this challenge is on the biological and ecological understanding of infectious diseases, it is important to recognize that social, behavioral, and economic factors also play a role in transmission, infection, and disease among both human and animal populations (Kiesecker et al. 1999). Changing patterns of housing in the United States have facilitated the transmission of Lyme disease via ticks to humans. Likewise, cultural change and lifestyle choices are involved in the transmission of the HIV virus and the pathogens responsible for other sexually transmitted diseases. Economic choices in animal husbandry have driven the increasing use of antibiotics to promote rapid growth, and alterations in meat processing led to the emergence of mad cow disease (DuPont and Steele 1987). These examples illustrate the range of social issues that need to be considered to fully address the population health impact of infectious diseases.

To make progress in understanding emerging infections, 1 it is necessary to develop an ecological understanding of disease. Developing such an understanding requires in turn the integration of research concepts from theoretical ecology, immunology, genetics, evolution, population biology, and the environmental and social sciences. To quote from Wilson (1999, pp. 308-309):

1  

We define emerging infections as those whose incidence has increased within the past two decades or whose incidence threatens to increase in the near future as a result of the spread of a new agent, the recognition of a previously undetected infection in a population, the realization that an established disease has an infectious origin, or the appearance of a known infection after a decline in incidence (National Research Council 1992).

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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Studies of emerging infections typically rely on disease, organismic or syndromic approaches. By contrast, understanding the process of disease emergence involves studying the origins and ecology of emerging infections. . . . Tools used to study and understand disease emergence include mathematical modeling, geographic information systems, remote sensing, molecular methods to study the genetic relatedness of organisms, and molecular phylogeny. Paleobiology, paleoecology, and studies that allow the reconstruction of past events may help inform future research and policy. The study of disease emergence must be at the systems level and must look at ecosystems, evolutionary biology, and populations of parasites and hosts, whatever their species.

Scientific Readiness

Four advances make this challenge appropriate for strategic investment at this time.

The ability to sequence the genomes of pathogens, parasites, and vectors. The technology needed to sequence the entire genomes of selected pathogenic organisms and vectors now exists. As the sequences become publicly available, it will become possible to test hypotheses related to resistance, virulence, and adaptation.

Improved understanding of gene-environment interactions in host immune response. Enhanced understanding and improved methods for acquiring further knowledge of the molecular determinants of host immune response (including but not limited to genetics) allow for more sophisticated epidemiological and zoonotic surveillance of host resistance at the molecular level than was previously possible.

Increased computing power and developments in theoretical population biology. New techniques and capacity for nonlinear dynamic modeling allow for the development and testing of more complex models that integrate information from the genome to the ecosystem. These models incorporate new insights from theoretical population genetics, evolutionary biology, and population ecology.

Data acquisition systems for ecosystem monitoring. As discussed in relation to Grand Challenge 4, Hydrologic Forecasting, and Grand Challenge 7, Land-Use Dynamics, new systems for monitoring (including satellite remote sensing) and for recording data (e.g., geographic information systems) have the potential to provide ecosystem-level information that can be incorporated into the above models (Lobitz et al. 2000, Hay et al. 1998). These remote systems can now be linked to molecular biomonitoring systems to anticipate changes in pathogens or toxin distribution (Rhodes et al. 1998). These methods and the associated predictive models are ready to be validated by epidemiological surveillance.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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Important Areas for Research
  1. Examine the effects of environmental changes as selection agents on pathogen virulence and host resistance. Pathogens, vectors, and hosts are affected by local and global changes in the environment, including physical, chemical, and climatic alterations, as well as direct human influence. Vectors and pathogens tend to adapt to environmental change through exploitation of advantageous ecosystems and through evolutionary selection that favors survival in an altered environment, which can be accompanied by the exchange of favorable genes within and across species. Antibiotics are part of the chemical environment of pathogenic organisms, and microbial resistance to antibiotics is a growing problem in managing disease (National Research Council 1999g). The ecology and molecular biology of drug resistance is understudied, and there is a need for more accurate and complex models that incorporate the mechanisms by which organisms acquire and shed resistance, the phenomenon of polyresistence, and gene transfer across organisms and populations. The ecology of pathogens is also affected by human settlement patterns, as well as agricultural, sanitation, and development practices. Research is needed to improve understanding of how pathogens adapt to all of these selection agents.

    Chemicals can also act as environmental stressors that affect pathogen virulence and immune response. Examples are the demonstrated loss of immunity to malaria brought on by low-level exposures to mercury (Silbergeld et al. 2000b) and the increased susceptibility to bacterial respiratory infections caused by exposure to air pollutants such as ozone. In general, these relationships are poorly understood, and they represent an avenue of research ripe for important discovery and offering opportunities to test existing models.

  2. Explore the impacts of environmental change and variability on disease etiology, vectors, and toxic organisms. Changes in climate, land use, water quality, natural species distribution, and species introduction brought on by human activity have the potential to alter the spread and impact of pathogens, parasites, and toxic organisms. Scientists have limited knowledge of the ecological variables that promote or deter the rapid growth of toxic organisms, such as algal blooms, or the environmental conditions that may elicit the production of natural toxins. Likewise, we have little specific understanding of how predicted widespread climate and land-use changes, changes in water and waste management, alterations in the biogeochemical cycles of nutrient compounds, or changes in food production systems may affect the ecology and spread of disease organisms on small or medium scales. Diseases such as malaria, dengue, and cholera may be especially sensitive to environmental and climate change (Lindsay and Birley 1996, Patz et al. 1998, Colwell 1996). The introduction of bioengineered organisms may also alter the ecology of pathogens, vectors, and hosts by disturbing the ecosystems of pathogen-transmitting and predatory organisms. New experimental and modeling approaches are needed to help in

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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predicting how environmental changes will interact with pathogens and toxic organisms and in developing a sufficient understanding of the mechanisms of these interactions to allow the mitigation of potential harmful effects.

  1. Develop approaches to surveillance and monitoring. There is an urgent need to develop new integrative approaches for monitoring sensitive indicators of change that will enable anticipation and mitigation of infectious diseases in humans and other species. Current methods for tracking changes in host-pathogen ecology depend on the detection of infections in target populations. Recent studies associating short-term climate change events with outbreaks of Rift Valley fever in Africa (Shimshony 1999, Linthicum et al. 1999), cholera in Peru (Franco et al. 1997), malaria in Kenya (Hay et al. 1998), and Hanta virus in the United States (Morse 1993), are highly informative in this respect. This type of monitoring can be improved by establishing disease registries that permit molecular identification of new diseases or new variants of existing diseases. Recent experience in New York City, where, as noted, West Nile virus went undetected until bird deaths were discovered, points to the importance of sophisticated methods of surveillance in multiple populations (Lanciotti et al. 1999) and to the urgent need for disease registries at the international level, given the opportunities for transboundary movement of pathogens and infected hosts (Roeder et al. 1999). Currently, it is very difficult to obtain a comprehensive picture of global infectious disease trends since in many parts of the world, basic epidemiological data are not collected or are not shared for political reasons.

    Existing programs must be expanded to include surveillance of the population ecology of zoonotic hosts, pathogens, vectors, and toxic organisms. Conducting such surveillance will necessitate developing and monitoring molecular and genetic markers of change in disease organisms, and on using geographic information systems to incorporate ecological data from remote and in situ observations with geographically explicit data on the populations of pathogens and toxic organisms. New methods developed to forecast blooms of toxic algae, incorporating both remote and on-site monitoring of population dynamics and toxin production (Rhodes et al. 1998), can be applied to other surveillance systems and theoretical models of outbreak.

  2. Improve theoretical models of host-pathogen ecology. The contributions of theoretical ecology and population biology must be incorporated into biomedical research on the prediction of infection and disease through the development of complex models of host-pathogen ecology capable of predicting infection, transmission, and disease incidence. The capacity for such cross-disciplinary endeavors needs strengthening, beginning with enhanced and redesigned training and research. In addition, complex, interdisciplinary prospective experiments must be explicitly designed to test hypotheses derived from the models. The funding of this research will require an unprecedented level of cooperation among granting agencies across the relevant basic and clinical disciplines, as well as increased support for international collaboration in research and surveillance.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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GRAND CHALLENGE 6: INSTITUTIONS AND RESOURCE USE

The challenge is to develop a systematic understanding of the role of institutions—markets, hierarchies, legal structures, regulatory arrangements, international conventions, and other formal and informal sets of rules—in shaping systems for natural resource use, extraction, waste disposal, and other environmentally important activities.

Practical Importance

Most human uses of natural resources and impacts on environments are mediated by rules and regulations—from village-based land tenure systems to international accords to regulate the release of CFCs to the atmosphere—related to the resources' provision, access, and use. These sets of rules and regulations are called institutions. For most of history, such institutions evolved locally in accordance with intimate associations between resources or environments and their human uses. Recently, however, such institutions have increasingly been designed by state or extra-state entities to address large-scale, even global, problems of open-access resources or environments (e.g., those with no enforceable rules regarding their use, such as many open-ocean fisheries). Institutions may act to limit demands on resources or to generate additional demands. In either case, understanding the character and role of institutions is pivotal to understanding human-environment interactions and to assessing the potential consequences of the many institutions emerging at multiple scales to deal with environmental change.

The range of institutions regulating access to and use of land, water, minerals, the atmosphere, forests, fisheries, and other natural resources is as broad as the range of their impacts. For example, many thousands of water management institutions—some 20,000 governing units in the United States alone—provide rules for water rights, each having different impacts on entitlements to water and on water resources. These institutions also establish a variety of rules for paying for water use. The water-use rules established by institutions can have widely varying effects:

  • Property institutions that give individuals the right to pump the Ogallala aquifer of the High Great Plains of the United States have led to dramatic declines in this source of fossil water while increasing grain production for America and much of the world.

  • In contrast, communally based regulation of irrigation systems in the Philippines has limited water withdrawals and provided for crop requirements over long periods (Siy 1982); however, they produce little beyond immediate consumption needs.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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  • A diffuse system with multiple institutional controls led to significant ecological change in Lake Erie.

  • The largest catastrophe to any major water ecosystem, the destruction of the Aral Sea ecosystem in central Asia due to the sea's drying up, followed from the actions of command-and-control water institutions that fostered excessive water withdrawal and contamination (Glazovsky 1995).

  • A polycentric system involving private associations, multiple city and county governments, the state-level court system, and special districts facilitated the reversal of a severe overdraft of coastal groundwater basins in Southern California that supported a growing urban economy (Blomquist 1992).

Management of water resources can benefit from improvements in hydrologic forecasting outlined under Grand Challenge 4 Better hydrologic forecasts alone, however, are not sufficient to inform the design of effective water management institutions.

Scientific Importance

The above examples illustrate that resource use is mediated or determined by institutions and is affected, often in major ways, by the structure and efficacy of the institutions. They also illustrate that no single institutional form is best for all resources or all situations. What we do not yet know is the conditions under which each institutional type works well or the factors that determine the environmental and social consequences of different institutional forms. The full range of institutions controlling critical resources and environments worldwide is not well documented. The fundamental characteristics and attributes of these institutions have not been examined comparatively and with the aim of clarifying how different institutions work under differing sets of human-environment conditions (e.g., rapid technological change, climatic variation, increases in resource demand).

The general lessons that can be gleaned are illustrated by various work conducted during the past decade. For instance, open-access resource systems that face increased demand are subject to rapid extraction that threatens ecosystem functioning and human welfare (see, e.g., Bromley 1992, Kasperson et al. 1995). This pattern tends to be reproduced when local institutions that enforce rules for resource use are challenged, corrupted, or destroyed and are either not replaced or replaced by externally constructed institutions, as has often happened when colonial powers or central governments have assumed responsibility for resource management. Examples include deforestation in southeastern Asia (Agrawal 1999) and wildlife management in Africa (Gibson 1999). There has been considerable relevant theoretical work on the design of markets (e.g., Baumol and Oates 1988, Loehman and Kilgour 1998), and there is a growing body of empirical work on common-pool resource institutions (e.g., Ostrom 1990);

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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however, understanding of the inner workings of various classes of institutions is still in its infancy.

Although resource institutions may need to change in response to rapidly changing environmental conditions, little is known about the characteristics of institutions that predispose some of them to adapt successfully. Some private-ownership systems (e.g., those associated with technologically vital metals) or open-access systems (e.g., some fisheries) do not provide effective incentives for the conservation of environmental goods (e.g., National Research Council 1999d,e). Others fail to provide the accurate information about biological and economic processes that is needed to adjust to change (Moxness 1998). The overarching scientific challenge is to develop a sufficient understanding of different institutions and their responses to change so that institutional design choices can be based on empirically grounded knowledge, not just intuition. For example, are institutions more adaptive and their resource bases better protected if they encourage small-scale experimentation, collect accurate performance data, and seek to monitor biophysical feedbacks and surprises?

Scientific Readiness

During the past several decades, theoretical and empirical advances in social science have significantly increased the capacity to address resource and environmental management institutions in a systematic fashion and to understand the environmental and social consequences of different institutional forms. The field stands at the threshold of substantial progress as a result of new multidisciplinary empirical studies of resource institutions; advances in institutional design theory in economics and political science; and developments in institutional, environmental, and resource economics.

An interdisciplinary research community has matured. A shared set of analytical concepts has been developed and applied by researchers in several relevant disciplines. Communication among researchers occurs in an international scientific society and through a new international research project under the International Human Dimensions Programme (IHDP) on Global Environmental Change. This project has established research foci on the role of institutions in causing and confronting global environmental changes, the factors that distinguish successful from unsuccessful institutions, and the prospects for redesigning institutions to confront environmental challenges (Young 1999).

A large body of case material has been gathered and organized around key concepts (Hess 1999). Systematic research enables scholars to identify who is eligible to use and harvest a resource at what quantity, location, and temporal order; the technology that can be used for harvesting; how provision and maintenance activities are organized; how decisions about resource management are made; what kinds of information are provided; and what outcomes are achieved in terms of economic returns, accountability, and sustainability. Further, at

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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tributes of resources and their users that affect the costs and benefits of organizing resource regimes have been identified. Ongoing field research is now beginning to test the hypotheses derived from this growing body of theory (Gibson et al. 2000).

Studies drawing on the theory of markets have identified and analyzed several promising new institutional approaches for dealing with resources that normally have no market value and are consequently subject to overexploitation. A prominent example is the construction of a market for pollution credits, first proposed in the late 1960s on the basis of economic analysis (e.g., Crocker 1966, Dales 1968) and implemented in the United States in the 1980s by creating a tradable property right to emit sulfur dioxide into the atmosphere. The experiment succeeded beyond expectations (Stavins 1998), and further applications to CO 2 emissions is being considered. Similarly, individual transferable quotas (ITQs) have sometimes been implemented successfully to control fishing (National Research Council 1999d,e). Enough practical experience is now being gained to permit systematic evaluation of the empirical performance of these new institutions. Adaptive management systems have been shown to increase the resilience of complex environmental systems (Berkes and Folke 1998). Other promising institutional innovations involve local-national comanagement of resources (Keohane and Ostrom 1995). Although science has not yet specified the range of conditions that favor successful implementation of each such institutional form, it is now possible to state clear hypotheses and evaluate them empirically.

Research on institutions is incorporating the biological and physical sciences of environmental systems. Social scientists are beginning to work with natural scientists to develop more effective models of how human actions and institutions interact with the environment (National Research Council 1998, Ostrom et al. 1999). On the technological front, recent advances in remote sensing are making it possible to monitor many resources in standard ways across space and time, providing new ways to measure the effects of different resource management practices (National Research Council 1998).

Important Areas for Research
  1. Document the institutions governing critical lands, resources, and environments. Various environmental studies, especially those requiring models to project the impacts of change, need information on the key institutions governing the land, resource, or environmental problem of concern. Thus, research on topics ranging from land-use change, to fishing stocks, to freshwater resources, to atmospheric dynamics ultimately requires consideration of the controlling institutions, especially for regional and global models. These institutions encompass national laws and regulations; market structures; property rights systems; and informal practices governing resource access, use, and exchange. Likewise,

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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research intended to be useful for planning and design purposes requires an understanding of existing resource institutions and the incentives they create for resource users.

  1. Identify the performance attributes of the full range of institutions governing resources and environments worldwide, from local to global levels. Institutions, whether they evolved over the long run to govern a specific, local resource or were recently designed to reduce damage to a global system (e.g., ozone depletion), have certain attributes that function to achieve the goals of the systems they govern. These attributes have not been addressed systematically for all forms of institutions, and their performance under different sets of conditions has not been assessed. For example, various common property systems have served well to conserve resources or environments over long periods during which demands on the systems were relatively low and static in quality (e.g., Netting 1981, Ruttan 1998). While some of these systems have adapted well to major changes, others have not served well under conditions of high resource demand, major changes in resource-extracting technology, or rapid changes in social and political conditions. In contrast, privately owned institutions may serve the economic interests of the individual user and afford an opportunity for adjustments in resource use as conditions change, but they may be poorly suited to handling environmental problems arising from landscape-level functions, such as loss of biodiversity following from landscape fragmentation.

    Research on performance attributes should address both traditional institutional forms and new forms, such as those that attempt to manage resources by creating markets for emission or extraction rights. The research should also address both the intended purposes of institutions and their unintended consequences, including effects on resources other than those they are intended to manage. An important performance attribute of resource management institutions is the way they incorporate information about resources from both local observers and organized science. Especially where resources are under threat, successful resource management is likely to depend on institutions' ability to entrain decision-relevant science and to use its outputs in a timely manner.

  2. Improve understanding of change in resource institutions. Most resource institutions evolve over the long-run in response to changes in their resource bases and their social and economic contexts. For example, broad shifts of power between national and local governments and of influence between governments and transnational organizations (e.g., corporations, intergovernmental and nongovernmental organizations) can create a change in resource institutions. Although external forces in the environment or in government may press local institutions to change, institutional changes are usually contested by interested and vested parties. In some cases, institutions are predisposed to making some kinds of changes but not others. A major scientific need is to understand the conditions both within and external to institutions that affect their patterns of adaptive change.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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  1. Conceptualize and assess the effects of institutions for managing global commons. Much attention is now being given to the design of new institutional forms for controlling previously unregulated global common-pool resources and environmental conditions, such as stratospheric ozone depletion, atmospheric CO2, and oceanic dumping of waste materials. Both global agreements and national implementation are required. Research on this topic should focus on the effects on resource use of different combinations of policy instruments and monitoring activities, and on the effects of differences and conflicts among the incentive structures of local, national, and global institutional arrangements.

GRAND CHALLENGE 7: LAND-USE DYNAMICS

The challenge is to develop a systematic understanding of changes in land uses and land covers that are critical to biogeochemical cycling, ecosystem functioning and services, and human welfare.

Practical Importance

Humans have dramatically altered the Earth's surface. These changes in land cover—the land surface and immediate subsurface, including biota, topography, surface water and groundwater, and human structures—are so large and rapid that they constitute an abrupt shift in the human-environment condition, surpassing the impacts of all past epoch-level events (e.g., the domestication of biota, the industrial revolution) since the rise of the human species. Indeed, they approach in magnitude the land-cover transformations that have occurred at transitions from glacial to interglacial climate (Meyer and Turner 1994, Ramankutty and Foley 1999).

Human-induced land-cover change to date, especially tropical deforestation, has been a primary influence on global atmospheric circulation patterns and a major contributor to observed increases in atmospheric concentrations of CO2 (e.g., Houghton 1994, International Geosphere-Biosphere Programme 1999). The annual rate of tropical deforestation remains high, hovering near 1.0 percent during the 1980s (Tolba and El-Kholy 1992). Human use of land, that is, what people do to exploit the land cover, has been the primary culprit in the estimated 2.95 million km2 of soils whose biotic function has been significantly disrupted by chemical and physical degradation—including 1.13 million km2 disrupted by deforestation and 0.75 million km2 by grazing. In addition, agriculture currently consumes 70 percent of total freshwater used by humankind, much of which is accounted for by the rapid expansion of irrigation, which annually withdraws some 2,000-2,500 km3 of water.

These and other human-induced changes are major contributors to global climate change, to the loss of global biotic diversity, and to the reduced functioning of ecosystems and the essential services they provide to humans. Land-use

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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change continues to contribute significantly to anthropogenic releases of CO2 to the atmosphere, changes in hydrologic dynamics and nitrogen cycling, and alterations in habitat for almost all terrestrial species. Land-use changes can also interfere with the migration of some species and facilitate the spread of disease vectors (Meyer and Turner 1992). And through their impacts on ecological services, land-use and land-cover changes affect the ability of biological systems to yield enough food, fiber, and fuel to meet human needs (Vitousek et al. 1997a).

Thus, land-use and land-cover dynamics and their spatial patterns play a significant role not only as drivers of environmental change, but also as factors increasing the vulnerability of places and people to environmental perturbations of all kinds. Improved information on and understanding of land-use and land-cover dynamics are therefore essential for society to respond effectively to environmental changes and to manage human impacts on environmental systems.

Scientific Importance

The basis for a science of land-use dynamics is beginning to emerge (e.g., Skole and Tucker 1993). However, regional and global-level stocks of most land covers and uses, including such essential categories as forest and grassland cover, agricultural uses, and urban and suburban settlement, are still poorly documented and monitored. Theory and assessment models used to address land dynamics are mainly static, economic sector-based, and nonspatial, and do not account for neighboring uses; the roles of institutions that manage land and resources; or biophysical changes and feedbacks in land use and cover, including climate change and anthropogenic changes in terrestrial ecosystems. Such inadequacies must be redressed if we are to achieve a robust understanding of these phenomena and provide the kinds of projections required to conduct environmental planning and to ensure the sustainability of critical ecosystem functions. In particular, it is necessary to improve understanding of which land units change, how, where, and why.

A growing interdisciplinary research community stands poised to document, develop theory, and provide robust regional models of land-use/cover change. Research efforts are under way worldwide to address almost all land covers and uses. Certain types of changes have been identified as especially critical and should be the focus of immediate concern: deforestation and its opposite, afforestation; pasture creation; grassland degradation; intensification of agriculture; and urban-industrial spread, including suburbanization. Of the first four, three types of change focus on the spatial magnitude of terrestrial land covers, while the intensification of agriculture deals primarily with increased water and chemical inputs to cultivation. Urban-industrial spread is important even though it involves only a small percentage of the total land surface under human management; for example, from 1982 to 1992, a relatively modest 25,800 km2 of agricultural land in the United States was converted to urban or built-up uses (Vester

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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by et al. 1997). The changed parcels, however, often constitute prime lands for cultivation with concomitant cropping infrastructures, as in the case of the spread of megacity complexes worldwide. Urban development affects hydrologic processes as well (e.g., effects of paving on runoff and of urban heat islands on storms).

Close inspection by the research community has begun to illuminate the nuances of land-cover dynamics and to challenge the conventional wisdom on a number of fronts. For example, studies of deforestation in Amazonia reveal that as much as 31 percent of formerly cut forest is in various stages of regrowth (Alves and Skole 1996), with significant implications for estimates of carbon emissions and of annual rates of change in the forested areas of the tropical world. Similarly, studies of land changes in the humid savannas of West Africa indicate that woody biomass has been increasing and continues to do so in areas claimed by some observers to be experiencing desertification (Bassett and Koli 2000). Inventories of ecosystems in the United States during the 1980s demonstrate an accumulation of carbon, largely through afforestation, equivalent to between 10 and 30 percent of U.S. fossil fuel emissions (Houghton et al. 1999). And changes in land use and cover affect local and regional climates; in South Florida, for instance, a drier, warmer interior during the months of July and August has followed the expansion of agriculture (Pielke et al. 1999).

Documentation and monitoring of these and other trends provide an observational base for efforts to improve understanding of the dynamics of land change, projections of climate change (by better specifying the contribution of land cover), and estimates of the full range of impacts of various land-cover “swaps” intended to reduce CO2 emissions (e.g., trading energy units from power plants in temperate industrialized countries for afforestation in the tropics). The international, interdisciplinary research community has begun to address the explanatory power of relative location (the effects of surrounding land uses on the potential for a unit of land to change), path dependency (the role of previous conditions and trajectories of change in constraining options for future change), biophysical feedbacks (e.g., effects of nutrient depletion with cropping), land and resource institutions (e.g., land tenure), and induced innovation (the capacity of agents and society to innovate internally as conditions change). Understanding the interrelations among these factors is often key to explaining land-use change and its environmental and social effects. For example, the highest recorded emissions of the greenhouse gas nitrous oxide and the ozone-affecting gas nitric oxide from soils have been linked to policy-influenced cropping procedures in northern Mexico's irrigated “wheatbasket” (Matson et al. 1988). Likewise, different tenure institutions controlling land uses and stocking strategies in Rajasthan, India, have led to significant differences in grassland quality and presence of trees (Robbins 1998).

Researchers are also beginning to demonstrate the value of spatially explicit analytical approaches as compared with nonspatial measures of the magnitude of change (Lambin 1994, Turner 1990). For example, by including the spatial

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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heterogeneity of the landscape and modeling interactions between land users and other decision makers, recent economic models of suburbanization in the Patuxent watershed of Maryland have improved the explanation of land use and its change over what could be achieved with traditional nonspatial and noninteractive models (Bockstael 1996).

As a result of such advances, the research community is now poised to develop at least four types of spatially explicit, integrative, explanatory land-change models: (a) those based on behavioral and/or structural theory linked to specific geographic locations, (b) those drawn from changes registered in remotely sensed imagery, (c) hybrids of these two types, and (d) dynamic spatial simulations (DSSs) that offer projections under different sets of assumptions (Frederick and Rosenberg 1994, Liverman et al. 1998). Theory- and imagery-based models are used to explore explanations of change and to provide near-term (5-10 years) projections under differing sets of assumptions. They permit tests of the applicability of various theories for different areas and conditions and the coupling of local-, regional-, and global-scale models by land cover or use type. An example is the fit of the Yucatan Peninsula to local versus pantropical models of tropical deforestation. DSSs, on the other hand, address scenarios over the longer term (more than 10 years) by making the agents, structures, and environment interactive and dynamic. For example, a DSS can examine how changes in the structures governing land access change agents' decisions about use, and in turn, the environmental qualities of the land feed back to agents and institutions governing land access.

Scientific Readiness

In addressing this challenge, new research would characterize regional variations in the pace, spatial scale, and magnitude of change in critical land uses and covers. It would identify the ways in which individual, household, and institutional actors and structures affect these changes and, in turn, respond to their biophysical consequences. The research would also develop increasingly robust models for addressing these dynamics in spatially explicit ways at different spatial scales and in relation to multiple sectors of human activity. Several recent developments make the area ripe for further advances, promising to transform land-use/cover change science.

Improved databases on land cover and land use. Key organizations and agencies are improving their databases on land in a manner consistent with the needs of global change science. For example, the Food and Agriculture Organization is leading an effort to create an international land-use typology and to employ this typology in its country-wide compilations of land conditions. The new Landsat 7 satellite will provide frequent worldwide imagery of land cover from the Thematic Mapper system at costs affordable to the community of land researchers.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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Advances in imagery analysis and geographic information science. These developments are providing the tools and analytical capacity needed to address land-use/cover dynamics spatially and to link social science and biophysical data. These capabilities and the emergence of other kinds of spatially explicit data have triggered interest in land use among new communities of researchers, such as demographers and economists (National Research Council 1998), and have inspired researchers to develop various modes of spatially explicit, multisectoral land-change models that begin to integrate statistical, diagnostic, and prognostic approaches at the regional level.

Advances in the analysis of spatial data. Advances are being made toward solving some major methodological problems involved in the analysis of spatial data. For example, spatial autocorrelation, the tendency for two points in close proximity on the Earth's surface to have similar properties, invalidates the use of statistical tests that assume independence among observations. Methods are being developed to account for spatial autocorrelation and explore its properties (e.g., Bailey and Gatrell 1995) and to analyze variables as functions of spatial location (e.g., Goovaerts 1997). Progress is also being made in finding ways to improve the drawing of inferences from large-area data—often the only data available —to small-scale processes (e.g., King 1997) and in understanding how the results of spatially aggregated data analysis depend on the basis of aggregation (Openshaw 1983).

Increased inter- and multidisciplinary interest in the science of land-use/ cover change. Stimulated by various international and national research programs, formerly diverse sets of researchers worldwide are engaged in collaborative ventures to create integrative approaches to the study of land-use/cover change. In the United States alone, 25 such teams have been formed by NASA's Land-Cover and Land Use Change program, with strong linkages to several of the centers of excellence sponsored by NSF. This figure is substantially larger at the international level. Additionally, the U.S. Geological Survey, working with the Environmental Protection Agency, is supporting research projects on land-cover trends and on urban dynamics, and NSF sponsors a small Human-Environment Regional Observatory project. These federal initiatives are an important beginning, but still lack the coordination, scope, and focus on integrated land-change models called for under this challenge.

Important Areas for Research
  1. Develop long-term, regional databases for land uses, land covers, and related social information. These databases should emphasize the critical land uses/covers of forest, grasslands, agriculture, and urban-industrial settlement and should include complementary demographic, economic, and institutional information. Work on developing useful land-cover data must include efforts to

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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improve the accuracy and reduce the uncertainty of vegetation classification from remote observation platforms.

The research community has identified regional data observatories and archives as essential. They are, however, extremely difficult to establish and sustain, and few if any interdisciplinary exemplars exist. Increased temporal resolution of high-spatial-resolution, space-based imagery is needed, along with reduced costs of such data for individual researchers. The issue of the confidentiality of social data also requires attention.

  1. Formulate spatially explicit and multisectoral land-change theory. Research in this area should address the causal roles in land dynamics of relative location, past uses (path dependency), land and resource institutions, and biophysical changes and feedbacks (e.g., climate change, nutrient depletion), and should determine the significance of regional variations in these relationships. Until now, land-change theory has been crafted in relatively simple terms and focused on specific economic or land sectors or products (e.g., agriculture or timber production). Understanding the causes and implications of land-use/cover change requires the development of theory that can account simultaneously for changes in multiple uses and covers by accounting better for the complexity of interactions that stimulate these changes. To achieve this aim, improved understanding of how agents and social structures behave or operate over space is required, along with better statistical methods that permit hypothesis testing and model validation. It is also important to understand the ecological consequences of land-use change and how ecological changes can influence land use.

  2. Link land-change theory to space-based imagery. Space-based imagery offers one of the few ways to scale analysis up spatially beyond the local level. Research in this area would push the boundaries of land-cover change detection from space and develop and test imagery-led models of change that could be coupled or merged with models based on theory (actors and/or structures). The research would also press imagery analysis to detect variables or develop proxy measures important to the human science of land change. The potential of this line of research will expand as new remote platforms offer observations at increasingly finer scales, suitable for detecting human activities not previously observable from space.

  3. Develop innovative applications of dynamic spatial simulation tech niques. Research in this area would exploit recent gains in computing resources and techniques. It would (a) extend dynamic spatial simulation techniques to model the distinct temporal and spatial patterns of land-use and land-cover change; (b) connect these models to extant and pending theoretical frameworks that accommodate the complexity of, and relationships among, socioeconomic and environmental factors (see research area 2 above); (c) establish common validation and replication protocols necessary for determining the robustness of model outcomes under different assessment scenarios; (d) consider the value of

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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information and the role of uncertainty in determining model outputs; and (e) examine the utility of dynamic spatial simulation models for land managers and government decision makers.

GRAND CHALLENGE 8: REINVENTING THE USE OF MATERIALS

The challenge is to develop a quantitative understanding of the global budgets and cycles of key materials 2 used by humanity and of how the life cycles of these materials may be modified. Among the materials of particular interest for this grand challenge are those with documented or potential environmental impacts, those whose long-term availability is in some question, and those with a high potential for recycling and reuse. Examples include copper, silver, and zinc (reusable metals); cadmium, mercury, and lead (hazardous metals); plastics and alloys (reusable substances); and CFCs, pesticides, and many organic solvents (environmentally hazardous substances).

Practical Importance

The extraction, use, and dissipation of technology-related materials affect humans and natural ecosystems in a myriad of important ways. First, toxic elements such as cadmium, mercury, and lead accumulating in the environment can have important negative impacts on human health (see, e.g., Thomas and Spiro 1994). An understanding of the flows of these elements and of the technological and cultural factors that drive those flows is required to mitigate these harmful effects and reduce exposure levels over the long term. Second, recovery and recycling of valuable elements such as platinum or copper can be accomplished at only 10-20 percent of the energy cost of refining these elements from natural sources (Schuckert 1997). Finally, understanding where these elements are lost during manufacturing processes and where in the environment they ultimately come to reside is necessary in considering whether to recover them.

With the changes brought about by population growth, rapidly evolving technology, more intensive agriculture, and increasing energy usage, global use of technological materials is expected to grow by as much as a factor of four

2  

“Materials” includes elements, compounds, alloys, and other substances created or mobilized by human activities, except it specifically excludes the elements that constitute the grand nutrient cycles—carbon, nitrogen, sulfur, and phosphorus. (The cycles of these elements have historically been dominated by natural processes, though human activities are now important perturbers; these cycles are the subject of Grand Challenge 1, Biogeochemical Cycles. Because of their association with human uses, the discussion that follows often refers to the materials of interest as “technological” or “technology-related.”)

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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during the next several decades. The cycles of many important materials are in rapid fluctuation, with existing reservoirs changing in size and new ones being added, and timely analysis is needed to understand some of these changes. For example, we are approaching local toxicity thresholds for some materials (Environmental Protection Agency 1998), and the availability (at reasonable cost) of certain materials essential to manufacturing is becoming threatened (Kesler 1994). New compounds and other substances are constantly being incorporated into modern technology and hence into the environment, with insufficient thought being given to the implications of these actions. All of these issues assume added importance in urban areas, which concentrate flows of resources, generation of residues, and environmental impacts within spatially constrained areas. From a policy standpoint, reliable predictive models of material cycles could be invaluable in guiding decisions about issues related to fossil fuel use, energy production, agricultural practices, and a wide range of other topics relating to human-environment interactions (Allenby 1999).

This grand challenge centrally encompasses questions about societal-level consumption patterns, since consumption is the primary force driving human perturbations of material cycles. Social scientists are exploring many questions about consumption patterns that are relevant to the issue of material cycles, such as the reasons for the large variations in consumption of resources among different cultures (National Research Council 1997); the factors that drive changes in consumption patterns over time (Organization for Economic Cooperation and Development 1997); whether policy initiatives influence these patterns; and if so, which policies are most effective for any given situation. These questions relate also to Grand Challenge 6, Institutions and Resource Use.

Scientific Importance

The basic framework for understanding the flows of materials is the “budget,” in which short- and long-term reservoirs are identified, and the flows between the reservoirs are quantified (e.g., Graedel and Allenby 1995). No overall pictures of generation, use, and fate have yet been produced for materials whose cycles are dominated by technology; our understanding of the budgets and cycles of nutrient compounds of carbon, nitrogen, sulfur, and phosphorus (addressed by Grand Challenge 1, Biogeochemical Cycles) is far more advanced. The construction of budgets for technological materials would be a natural outgrowth of the interaction of environmental science and the emerging discipline of industrial ecology, and would follow directly from the theoretical and analytic approaches developed for the major biogeochemical cycles (e.g., Bolin and Cook 1983). In fact, part of the scientific excitement generated by these questions is that they can be adequately addressed only through close collaboration among specialists in the natural sciences, the social sciences, and a variety of engineering disciplines to achieve the following:

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×
  • Understanding the operation of the natural cycle of an element, compound, or other material (if it occurs in nature)

  • Identifying the ways in which human activities define, perturb, or dominate material cycles (and establishing the magnitudes, trends, and causes of resource flows within an anthropogenically dominated system)

  • Determining the environmental and resource supply implications of these perturbations

Once this information is in hand, focused, practical implications can be addressed: to mitigate undesirable environmental consequences related to human activities, we must have an accurate understanding of those activities and of how they might be changed. One form of change is largely technological, and involves the redesign of products and processes such that the use of materials is optimized; the environmental implications of manufacture, delivery, and customer use are minimized; and the eventual recovery and reuse of resources are enhanced. A second form of change is behavioral, and involves economic producers and consumers and the forces that determine their adoption of technologies that alter the use of materials.

A useful perspective on the intellectual challenges presented by technological material cycles is provided by activities related to the biogeochemical cycles of Grand Challenge 1. For those cycles, natural and perturbed, the research activities are centered on identifying the complete suite of sources, sinks, and feedback loops; assessing how these variables have evolved over time; and predicting how they are likely to evolve in the future. Complicating factors include missing or poorly quantified information, incomplete understanding of human activities that shape the budgets, substantial spatial variation, and uncertainty about the behavior of the sources and sinks under altered physical and chemical conditions.

Many of these difficulties are present as well for the budgets controlled largely by anthropogenic activity. While sources are often rather well established, both in kind and magnitude, sinks and feedback loops are not, and the forms and magnitudes of storage in various reservoirs (formal and informal stockpiles, landfills, environmental receptor basins) are generally quite uncertain. In addition, the human activities that shape the budgets are not well documented or understood. In many cases, proxy data, inference, and archeomaterials research will be necessary to complete the picture. In this connection, the most ambitious portion of this grand challenge activity is likely to be the acquisition, comprehension, and integration of data sets and other information from the environmental, economic, and social spheres, and the development of robust ways of utilizing those results in predictive exercises. The achievement of data harmony, consistency, and rigor across this interdisciplinary landscape will be a major effort and will provide the necessary basis for a scientific understanding of material cycles.

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
×

An understanding of the use of materials and its implications is a prerequisite for many of the predictive exercises encompassed by the other grand challenges. As one example, Grand Challenge 5, Infectious Disease and the Environment, identifies chemical selection pressure from the environment on pathogens as a priority research area. This area could make use of data on contemporaneous rates of heavy metal and pesticide loss to ecosystems of interest, as well as informed projections of how those flows might be expected to change over space and time. A second example relates to Grand Challenge 4, Hydrologic Forecasting. Informed projections derived from analysis of material use would be directly applicable to predictions of water availability and quality.

Scientific Readiness

This grand challenge is timely for both scientific and policy reasons. From a scientific standpoint, work has begun on devising regional and global budgets for several of the toxic trace metals (e.g., Jolly 1992, Jasinski 1995). These and related studies have started identifying data sources related to extraction, processing, use, and disposal, and provide a framework for more general research related to the budgets of key materials used by humanity. Moreover, the sophisticated techniques and considerable scientific expertise developed to investigate nutrient cycles are directly applicable to questions about material cycles, and thus can be used to initiate research efforts in this area. In addition, as part of the Industrial Transformations project of the International Human Dimensions Programme (1999), social science and policy research has begun to address changes in production and consumption patterns. This effort is developing an international and interdisciplinary research community that is addressing fundamental questions about consumption trends and their causes that must be addressed to predict future trends in material cycles and the environmental effects of these changes.

Historical changes in material mobilization, use, and dissipation are beginning to be understood, for example, by constructing histories of fossil fuel consumption or trace metal deposition on polar ice or lake sediments. In addition to providing historical information on material utilization and dispersal, these data contribute to understanding of the historical intensity of interactions between human activities and the environment. Such efforts need to be expanded to include a wide range of materials and locales, with the ultimate goal of constructing gridded budgets integrated over the time period since the Industrial Revolution. International collaborative efforts should be encouraged, since material cycles do not respect national boundaries.

In a more practical vein, engineers in industry and academia are beginning to devote significant effort to “design for environment, ” in which the selection, processing, and use of materials play central roles. This technology-oriented research is key to the implementation of insights gained from an understanding

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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of reservoir contents and flows, and could lead to reinvention of the ways in which materials are acquired and used by modern technology. One could envision, for example, that the results would stimulate the development of policy instruments designed to encourage the recovery, reprocessing, and reuse of a variety of selected materials, along with the development of technologies that would make these policy instruments implementable in efficient and effective ways. Such new approaches to material utilization would be informed by research in the environmental sciences in general and materials-environment interactions in particular, and enabled by modern engineering tools such as life-cycle assessment, computer-aided design and manufacturing, and performance analysis.

Important Areas for Research
  1. Develop spatially explicit budgets for selected key materials. This research would involve quantifying reservoir contents and flows for the materials in question; constructing spatially resolved maps of these stocks and flows; and combining these results with other environmental, economic, and social data sets to learn more about the causes and consequences of changes in material cycles. As has been demonstrated by budgets for naturally cycling compounds of carbon and nitrogen, budgets constructed with a high degree of spatial resolution are much more useful than those that provide only aggregate, global information. The budgets thus developed would include analyses of anthropogenic flows by type of activity (e.g., mining, manufacturing, household use) and by technology, as well as by spatial location. They would require as well comprehensive integration with data on natural flows of the same materials. The generation of location-specific information would provide links between anthropogenic material cycles and their human causes and potential environmental impacts.

  2. Develop methods for more complete cycling of technological materials. Addressing this topic would involve pursuing life-cycle design of products; lengthening the useful life of products by modular design; and advancing research on the utilization of residue streams, the recovery of discarded materials, and the transformation of patterns of consumption. The work might also involve the use of more easily recycled and reused materials, perhaps including benign new materials such as biological products and composites. This is largely an engineering activity, but one whose priorities are established by contemporary budgets and future budget scenarios.

  3. Determine how best to utilize materials that have uniquely useful industrial applications but are potentially deleterious to the environment. This research would include describing the spectrum of uses for these materials, identifying points of loss of the materials to the environment and methods by which such loss might be reduced, developing substitutes for these materials, and investigating reengineering activities that could be used to cycle the materials

Suggested Citation:"The Grand Challenges." National Research Council. 2001. Grand Challenges in Environmental Sciences. Washington, DC: The National Academies Press. doi: 10.17226/9975.
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more completely. As with other types of material use, but especially in this case, dematerialization (accomplishing a given design goal with a substantially smaller amount of material) could contribute substantially.

  1. Develop an understanding of the patterns and driving forces of human consumption of resources. This research would involve studying material consumption patterns across time, in different countries, and at different levels of economic activity, with the aim of understanding how differences develop, why the patterns change, and what changes might be anticipated in the next several decades. The results would aid in understanding current patterns of material flows and provide a basis for anticipating societal drivers of those flows in the future.

  2. Formulate models for possible global scenarios of future industrial development and associated environmental implications. This research would draw on contemporary material budgets, predictions of technological developments, studies of consumption patterns, and assessments of industry structure and environmental law and policy to predict how specific circumstances or policy options might strongly influence industry-environment interactions in the next several decades. Thus, this research constitutes the equivalent for impacts of resource and material use of scenario exercises such as those of the Intergovernmental Panel on Climate Change (1996).

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Scientists have long sought to unravel the fundamental mysteries of the land, life, water, and air that surround us. But as the consequences of humanity’s impact on the planet become increasingly evident, governments are realizing the critical importance of understanding these environmental systems—and investing billions of dollars in research to do so. To identify high-priority environmental science projects, Grand Challenges in Environmental Sciences explores the most important areas of research for the next generation. The book’s goal is not to list the world’s biggest environmental problems. Rather it is to determine areas of opportunity that—with a concerted investment—could yield significant new findings. Nominations for environmental science’s “grand” challenges were solicited from thousands of scientists worldwide.

Based on their responses, eight major areas of focus were identified—areas that offer the potential for a major scientific breakthrough of practical importance to humankind, and that are feasible if given major new funding. The book further pinpoints four areas for immediate action and investment.

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