The relationships between human population dynamics and natural resources have been of interest at least as far back as Malthus, who argued that human population growth could outstrip the ability of the Earth to provide food. More recent scholars have noted that population-environment relationships are much more complex and are influenced by many more human activities than just procreation. About a decade ago, the National Institute of Child Health and Human Development, the William and Flora Hewlett Foundation, and other research sponsors began providing concerted support of research to understand connections between human population and environmental quality that are mediated by changes in land use. This volume focuses on research in which land use or land cover change is a key mediator of human-environment interactions, in which demographic variables figure prominently among the driving forces investigated, and in which efforts are made to investigate the causal mechanisms by which human population changes affect land use and environmental outcomes. It takes stock of the progress that has been made in such research to see what has been learned, to identify gaps and problems that remain, and to develop a set of recommendations about future research directions.
The main areas of research progress have been refining the broad concepts of population, land use, and environment into more specific and illuminating concepts; developing sustained research on the relationships among these factors over time at specific sites; identifying ways in which population–land use–environment relationships depend on the scale at which observations are made and in which relationships at one scale affect processes at others; and developing some effectively functioning interdisci-
plinary research teams. Recent research has clarified how population effects depend not only on total numbers, but also on migration, household size, and other demographic variables. It has shown how the causes of change in forest cover look different depending on how secondary forest is treated in the analysis. Current research challenges include linking social with environmental data, collecting data at the appropriate levels of resolution, achieving comparability of data across sites and time, and moving from descriptive studies to ones that can reasonably be used for causal inference. Interdisciplinary collaboration remains a challenge despite the progress that has been made.
The Panel on New Research on Population and the Environment makes the following recommendations:
1. Research should be increasingly coordinated to promote creation of a body of integrated knowledge that links demographic, land use, and environmental variables and seeks to move beyond site-based observations toward the development of general knowledge. To accomplish such coordination,
Organizations that support population–land use–environment research should work with researchers to develop minimum reporting standards for data collected and analyzed in site-based studies.
Individual projects should provide an inventory of important contextual variables for their study sites.
Efforts should be made to coordinate definitions of variables measured and research designs chosen in different site-specific studies to enhance the creation of a body of integrated knowledge in the field.
Research should be pursued at this time in two substantive areas that hold promise for building knowledge of generic processes—the study of new settlement (“frontier”) areas and of regions of rapid urban (including suburban) development.
2. Research should continue to decompose or “unpack” the complex, general phenomena of population, land use, and environment and examine causal relationships among their more specific component factors. Such refined analyses will improve understanding of the mechanisms and feedbacks that connect population, land use, and environment, clarify assumptions and theoretical structures, and facilitate interdisciplinary communication and integration. Population–environment research on land use should include research with a substantive focus on water because of the special importance of coastal and riparian regions to marine productivity, storm and flood impacts, and the transformation of wetland habitats.
3. Research should investigate the dynamic interactions involving population and land use and environmental variables, coupling all three classes
of variables and remaining attentive to contextual factors that may influence these relationships.
4. Research should increasingly explore scale dependencies and cross-scale interactions. In particular:
Researchers focused on population–environment relationships should pay explicit attention to spatial, temporal, and social scale in framing their studies and offering explanations. They should be explicit about the scales at which they are working. Research funders should use their influence to develop gridded approaches that can place local studies within spatial matrices and to encourage levels of temporal resolution (including of remotely sensed images) adequate to understanding dynamic processes.
Researchers should be encouraged to address explicitly the extent to which the population–land use–environment relationships they study vary by scale of analysis, how these scale dependencies may vary by place or time, and how relationships at one scale may influence those at another scale, for example, by using appropriate modeling techniques.
5. Organizations that support population–land use–environment research should support and encourage continued development of linked data sets that include information about population, land use, and environmental variables and that are spatially explicit, multilevel, and longitudinal.
Continued investment should be made in existing linked longitudinal data sets and in developing similar datasets at new sites in understudied regions and in places that offer unique research opportunities.
Continued investment is warranted in developing methods for data and process integration.
Guidelines must be developed for use of linked data sets and for making data available to researchers beyond the original research team.
6. Increased effort should be devoted to modeling and quantifying causal relationships among population, land use, and environment using a variety of approaches, as well as to analyzing uncertainties in models of these complex systems. Mathematical models have considerable value for addressing dynamic relationships of population, land use, and environment; for structuring discussion across disciplines; for identifying open questions; and for providing forecasts for policy analysis.
7. A research effort should be made to identify highly effective mechanisms to facilitate interdisciplinary research. Specifically, organizations that support population-environment research should support a systematic assessment of which approaches seem to result in the best and most rigorously trained young scholars in this field and the most productive research collaborations.