Thriving on Our Changing Planet A Decadal Strategy for Earth Observation from Space (2018) / Chapter Skim
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8 Marine and Terrestrial Ecosystems and Natural Resources Management
8 Marine and Terrestrial Ecosystems and Natural Resources Management
Pages 348-420
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Moderate resolution (250 m to ~1 km) , multispectral imaging systems have enabled the first consistent, global determinations of primary production for land and ocean ecosystems and its variations on seasonal to interannual time scales.
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) can extend measurements of phytoplankton carbon biomass (and Net Primary Production [NPP]
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Key fluxes within ecosystems are mediated by the composition and functional traits of the organisms present. Imaging spectroscopy is a tool for determining global terrestrial and marine plant functional traits and functional types and, in some cases, provides taxonomic composition.
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The high-fidelity imaging spectrometer instrument would be the first of its kind to routinely measure the entire global landmass and coastal waters at high spatial resolution. Another challenge is to determine the vertical distribution of the ocean primary producers that is not possible from passive Ocean Color Radiometry (OCR)
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Priority Targeted Observables Science and Applications Objectives Aerosol Properties E-2a Atmospheric Winds E-2a Greenhouse Gases E-2a, E-3a Surface Biology and Geology E-1a, E-1b, E-1c, E-2a, E-3a Terrestrial Ecosystem Structure E-1b, E-3a Ocean Ecosystem Structure E-1b Aquatic-Coastal Biogeochemistry E-1a, E-1b, E-1c, E-2a, E-3a Soil Moisture E-1c, E-3a Ocean Surface Winds and Currents E-1b, E-2a Vegetation, Snow, and Surface Energy Balance E-1c, E-3a Surface Topography and Vegetation E-1b, E-3a coastal environments, and open-ocean ecosystems. Example applications include sustainable forest management for greenhouse gas accounting and precision agriculture.
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Together, climate and ecology help to determine biodiversity. This coupling, through biogeochemistry and the carbon cycle, affects greenhouse gas concentrations in the atmosphere, which in turn control ocean and land temperatures and affect essential vertical mixing in the ocean.
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Units are in billion metric tons for carbon stocks and billion metric tons/year for fluxes. The Carbon Dioxide Information Analysis Center advises that 1 ppm of atmospheric CO2 is equivalent to 2.13 gigatons of carbon.
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Only satellite-borne sensors can provide simultaneous global carbon cycle observations needed for quantifying large-scale carbon cycle processes that control the land's forest and vegetation biomass stocks, and only satellite-borne sensors provide the necessary spatial and temporal observations to understand the role of the oceans in carbon fluxes and storage. Using data from these sensors with models now enables researchers to track carbon through the land, ocean, and atmosphere.
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. The current global land carbon sink is 2.9 Pg C/year with a land cover change flux of 0.9 Pg/C year.
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These data could be enhanced by the addition of hyperspectral data that can provide additional information on ecosystem functioning. Transitioning Mature Airborne Technology to Space Following the 2007 Earth Science Decadal Survey, NASA made substantial technology investments in airborne hyperspectral imaging of vegetation and ocean color, and lidar observations of vegetation structure, greenhouse gases, and ocean profiles of particulate carbon.
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. Quantifying primary production for both terrestrial and marine ecosystems has been a central concern of carbon cycle research and is now integrated into earth system models.
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. Landsat-5 imagery was used to construct a 30+ year time series of giant kelp canopy biomass on a 30 m basis over the entire California coastal waters and was used to diagnose the controls on kelp canopy changes in space and time (e.g., Bell et al., 2015a)
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. Hyperspectral data allow various band combinations to be used to optimize the imagery compared to multispectral sensors.
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Motivation Characterization of the functional traits, functional types, and composition of terrestrial vegetation was identified by the Ecosystems Panel as a Very Important measurement based on the need to better understand the relationships between the composition of the biosphere and other Earth system processes, including climate. Multiple properties of plants (biochemistry, structure, phenology, reproduction)
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imaging spectrometer for coastal and inland waters will determine signatures of phytoplankton taxonomic diversity and particle size distributions, enabling us for the first time to quantify global ocean ecosystem structure and biodiversity metrics from space. Space-based high-resolution imaging spectroscopy will also enable for the first time global characterization of the nearshore coastal zone and shallow aquatic ecosystems.
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While imaging spectroscopy is the only technology that can provide the detailed spectral data to allow identification and quantification of major biochemical and structural components of plant canopies, the combination of hyperspectral imagery with multispectral time series data will achieve improved understanding of ecosystem function and early detection of changes in these processes. In support of such a mission, NASA has invested in numerous pre-HyspIRI airborne, modeling, and field program activities, with numerous publications and government documentation, to further advance and mature the coupled science and technology for a future orbital spaceborne imaging spectrometer mission.
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. Owing to the complexity of light interactions in these environments, high to moderate spatial resolution imaging spectroscopy has been demonstrated to provide greater retrieval accuracy than multispectral sensors (e.g., Botha et al., 2013; Phinn et al., 2013)
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While the spectral resolution is limited (based on the legacy SeaWiFS sensor) , the SeaHawk concept provides an important opportunity to evaluate the improved spatial coverage for coastal and inland waters.
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Unlike satellite ocean color imagers, active remote sensing with lidars can operate during darkness and can penetrate through moderate cloud and aerosol layers. This is critical for very high latitude oceans where the complete annual coverage of phytoplankton biomass is poorly known (Behrenfeld et al., 2017)
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Vertical profiles of particle backscatter and vertical lidar path attenuation are created and are related to the total seawater absorption coefficient. To first order, passive ocean color observations provide measurement of
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Synergy with a new imaging spectrometer would also confer significant advances in assessments of the carbon cycle (Schimel et al., 2015) and biodiversity conservation (Asner et al., 2017)
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A key to understanding the biogeochemical cycles and fluxes discussed in Questions E-2 and E-3, their sensitivity to climate change, and their feedbacks to climate are predictions of future conditions of the biosphere and the climate system. The biochemical properties of terrestrial vegetation, aquatic biomass, and soils provide quantitative or qualitative measurements that are used to determine the physiological dynamics of primary producers and soil processes.
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optical constituents such as sediments and colored dissolved organic matter. Fluorescence has also been used effectively to directly assess physiological status, and, in combination with estimates of particulate organic carbon, can be used to quantify changes in photosynthetic capacity independent of biomass (e.g., Behrenfeld et al., 2009)
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Measurements of soil moisture in the root zone would contribute to more accurate estimates of evapotranspiration if radar systems could provide greater penetration into the soil root volume (González-Zamora et al., 2016)
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a moderate- spatial, moderate-hyperspectral-resolution imaging spectrometer to assess biochemistry and composition of t errestrial, aquatic, and coastal ecosystems; (2) a global hyperspectral ocean color imaging spectrometer to quantify open ocean planktonic ecosystems (similar to the PACE mission in the POR)
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A substantial contribution of soil moisture to NASA Earth Science Objectives (ESOs) requires a level of performance for L-band data not less than the current SMAP mission (2-3 day return frequency, 40 km spatial resolution, 0.04 m3/m3 accuracy)
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The advantages of P-band are that it theoretically samples the soil profile to a greater depth than L-band observations. The disadvantages are reduced spatial resolution and more sensitivity to vertical discontinuities unrelated to soil moisture such as clay lenses.
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. Imaging spectroscopy from satellites and aircrafts provides observations at spatial, temporal, and spectral resolutions that facilitate these measurements and are complemented by expanding computational capacity and in situ monitoring systems.
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Similarly, invasive plant species or harmful algal blooms are often found in large patches, which makes their detection and mapping possible. New measurement technologies, especially imaging spectroscopy and imaging lidar, in combination with SLI multitemporal and multispectral 30 m data, provide opportunities to monitor species and biodiversity from space and allow assessment of efficacy of conservation and land and coastal management actions and goals.
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Further, both the profiling ocean lidar and the vegetation canopy imaging lidar detailed in Objective E-1b, will help to provide species identification and mapping as well. Connections to Other Panels Quantifying the composition of terrestrial vegetation and marine biomass and the physiological dynamics of Earth's primary producers are important to aspects of other decadal survey panel's science objectives, and their solutions require the measurement approaches that are identified here.
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Objective E-2a Objective E-2a. Quantify the fluxes of CO2 and CH4 globally at spatial scales of 100 to 500 km and monthly temporal resolution with uncertainty <25 percent between land ecosystems and atmosphere and between ocean ecosystems and atmosphere.
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measurements, which can support attribution of emissions to combustion and noncombustion sources, are recommended. Measurements used to estimate ocean and land primary production, biomass burning, and respiration are also critically needed to interpret net carbon fluxes and attribute to ecosystem processes.
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. Information from the O2 A-band can also be used to estimate SIF, a quantity related to terrestrial gross primary production (Frankenberg et al., 2011; Joiner et al., 2011)
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(sw) from remotely sensed SST and ocean color (e.g., Olsen et al., 2004; Hales et al., 2012)
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Land use and climate changes are altering land ecosystems throughout the planet, and these changes propagate through rivers to marine ecosystems. For example, high nutrient loadings carried by rivers can increase marine primary production locally (e.g., Körtzinger, 2003; Regnier et al., 2013)
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Measurement Approaches Sustained land imaging from Landsat-8, Sentinel-2a, and Sentinel-2b, combined with in situ data, provides data needed to address carbon, nutrient, and particulate fluxes from land ecosystems to aquatic and marine ecosystems. Because the objective (transport in rivers to coastal waters)
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To further close the information gap on carbon fluxes in aquatic ecosystems, remote sensing approaches are needed for monitoring dissolved organic carbon (DOC)
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Use of the Operational Land Imager (OLI) aboard Landsat-8 has demonstrated the ability to detect colored dissolved organic carbon (DOC)
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Sustained land imaging will thus continue at least through 2025 as it is now constituted. The panel also advocates for Landsat-10 and Landsat-11 to continue the 30 m multispectral high-revisit frequency time series as needed in 2025 to 2030.
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For example, geostationary satellites like GOES-16 provide LST at ~4 km resolution hourly, MODIS provides near-daily global data at a 1 km resolution, and Landsat-8 provides biweekly LST data at 30 m spatial resolution using sharpening techniques that combine information from multiple bands. To advance our knowledge of the central role of heterotrophic respiration in the carbon cycle and hence climate, 30-60 m TIR observations in the 10.5-11.5 µm and 11.5-12.5 µm spectral region are needed with a 2-4 day revisit frequency for consistency with the sustained land imaging revisit frequency (currently 3.7 days)
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. Measurement Approaches Estimates of biomass burning can be improved by using sustained land imaging 30 m data instead of using MODIS 500 m imagery to provide higher resolution information about burned area and plant productivity.
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The combination of Sustained Land Imaging, imaging spectroscopy, and lidar measurements of terrestrial vegetation structure (Objective E-1b) will substantially improve understanding of ecosystem disturbance and vegetation regrowth.
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Satellite data are likely to contribute by providing information on variations in temperature and moisture, similar to the measurement approaches included in the discussion of respiration earlier. Imaging spectroscopy (hyperspectral imaging)
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Together with the PACE capabilities for assessing size and some taxa of global ocean phytoplankton, researchers will be able to better quantify the links between ocean ecology and the biological pump, a key unknown in the global carbon cycle. Measurement Approaches PACE is a critical mission for quantifying the role of the ocean ecosystem in the global carbon cycle.
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. Measurement Objectives Currently, monitoring of LMRs in marine ecosystems is hampered by the low temporal resolution of ocean color satellites and the relatively crude biological information provided by chlorophyll, which by itself does not provide functional trait information.
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may also be appropriate. As mentioned earlier, hyperspectral observations, such as those made by PACE for the open ocean and a higher spatial resolution imaging spectrometer for coastal waters, are necessary to characterize phytoplankton functional types.
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Observation of vegetation dynamics over time also provide information on GPP and NPP that, when combined with estimates of heterotrophic and autotropic respiration, provide data on carbon storage and stocks in biomass. Landsat- and Sentinel-class observations provide the main basis for measuring land cover over space and time, and can be combined with other measures, including ground-based inventories and lidar-derived canopy structure metrics, to estimate carbon stocks and carbon densities over time that can be enhanced by the addition of imaging spectroscopy-measured vegetation traits over time.
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Sustained land imaging from Landsat-8, Sentinel-2a, and Sentinel-2b provide 30 m spatial mapping of forests that, when combined with forest vertical structure, provide forest biomass to be determined from space. Imaging spectroscopy with lidar can produce maps of forest species.
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Connections to Other Panels There is a strong connection between this panel and the Climate Panel (Questions C-3 and C-8) on carbon cycle feedbacks on land, for the land carbon sink, for carbon in forests and soils, for biomass burning, for permafrost as the Arctic warms, and for better quantification of the ocean waters and ocean ecosystems' future capacities to absorb atmospheric CO2.
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An example of how ecological threshold effects can be estimated from satellite observation is shown in Figure 8.6. Here, time series of giant kelp forest canopy biomass from a 28-year time series of Landsat-5 FIGURE 8.6 Left panel: Additive effects of surface wave significant wave height (from swell propagation wave model)
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Similar threshold detection analyses can be conducted for other ecosystems. Better estimation of carbon emissions of terrestrial ecosystems from disturbance, particularly fire severity related to thresholds of warming and drying, have the potential to dramatically increase our ability to model combustion of forest biomass as well as soil organic matter, particularly in high-latitude ecosystems.
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Sustained land imaging from Landsat-8, Sentinel-2a, and Sentinel-2b provide 30 m spatial mapping of forests that, when combined with forest vertical structure, enables forest biomass to be determined from space. Identification of community composition and comparisons between the prefire forest composition and density and the postfire observations provides the type and degree of how much the vegetation in question was consumed in the fire.
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Specifically, fires contribute to increasing atmospheric carbon, which impacts the climate system. But importantly, fires also substantially impact nutrient cycling and affect carbon uptake by the biosphere and impose constraints on how the carbon cycle responds to variations in climate (Thornton et al., 2007)
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. Vegetation functional types, gross primary productivity, and fire severity need continued coverage through recovery from imaging spectrometer data.
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. Connections to other panels include synergies with the Climate Panel's objectives for quantifying variations in the global carbon cycle and associated climate and ecosystem impacts in the context of past and projected anthropogenic carbon emissions, and assessing uncertainty in total climate forcing that arises from aerosol changes and their interactions with clouds (Questions C-2, C-3, and C-5)
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. Landsat data that have been widely used to document forest disturbance and recovery at the 30 m scale globally for carbon cycle research have also been used to manage forest resources for countries at the national level (Hansen et al., 2013)
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REDD+ goes beyond deforestation and forest degradation, and includes the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks. Outside the diplomatic policy process associated with the conventions, other multilateral REDD+ initiatives are being implemented to provide private capital and large financial investments in low-carbon forest management.
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The recent development and use of small imagers on Unmanned Aerial Vehicles and on tractors, both linked to global positioning systems, provides an alternative platform with greater flexibility for digital image data collection with improved spatial resolution, very frequent data collection, and a significantly lower cost. The within-field collection of remotely sensed multispectral imagery has enabled what is now known as "precision agriculture." These precision technologies developed for agriculture include accurate identification of within-field fertilizer application rates, "smart irrigation systems" that work along with remotely sensed images to maximize water use efficiency based on plant needs, evaporation rates, soil texture, and soil structure.
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This can be used to guide further field operations in future years and establishes a permanent farm record. For example, this means that remotely sensed data would complement the yield data collected by the farmer's harvesting equipment and identify specific locations of yield variations within a crop field for diagnostic postharvest analysis (Johannsen and Carter, 2002)
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should enhance the benefits that already exist, as well as lead to novel ones, as in the following examples: • Creation of cost-effective ecological indicators, which can be applied to ecosystem-based manage ment and characterization of change due to natural and anthropogenic perturbations or disturbances; • Monitoring of the onset, expansion, and fate of harmful algal blooms, aiding the tourism and aqua culture industries; • Monitoring of coastal water quality as a tool in coastal zone management; • elineation of marine protected areas and identification of habitats for threatened/endangered D species; • Sustainable management of fisheries and more cost effective harvesting; • Measurement of phytoplankton photosynthesis, which is essential information for ocean ecosystem models, as well as for understanding the role of the ocean in climate change and global carbon cycles; • Creation of outstanding material for education at all levels, both in formal classroom environments and in informal education, developing public awareness of ocean processes; and • International governance on the high seas. The coastal zone, especially shallow waters <30 m depth, represent a very small proportion of the global ocean area, yet coastal ecosystems are among the most productive in the world.
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2015. Spatiotemporal patterns of terrestrial gross primary production: A review.
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2006. A comparison of global estimates of marine primary production from ocean color.
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2007. Plumbing the global carbon cycle: Integrating inland waters into the terrestrial carbon budget.
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2011. New global observations of the terrestrial carbon cycle from GOSAT: Patterns of plant fluorescence with gross primary productivity.
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2013. The impact of global warming on seasonality of ocean primary production.
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2007. Ecological fingerprinting of eco system succession: Estimating secondary tropical dry forest structure and diversity using imaging spectroscopy.
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2011. Effect of reduced spatial resolution on mineral mapping using imaging spectrometry -- Examples using hyperspectral infrared imager (HyspIRI)
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2015. Temperature acclimation of photosynthesis and respiration: A key uncertainty in the carbon cycle‐climate feedback.
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2005. Net primary production and canopy nitrogen in a temperate forest landscape: An analysis using imaging spectroscopy, modeling and field data.
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2015b. The impact of spatial resolution on the classification of plant species and functional types within imaging spectrometer data.
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2008. Vulnerability of permafrost carbon to climate change: Implications for the global carbon cycle.
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2007. The impact of agricultural soil erosion on the global carbon cycle.
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2016. Precipitation and carbon-water coupling jointly control the interannual variability of global land gross primary production.
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