ECOSYSTEMS
Working Group Participation
David S. Schimel, Chairman
Otis B. Brown
William E. Easterling
Diana M. Liverman
James J. McCarthy
Harold A. Mooney
Piers J. Sellers
Herman H. Shugart
Peter Vitousek
Designated Federal Liaison: Robert Harriss
Rapporteur: William Westermeyer
WORKING GROUP SUMMARY
David S. Schimel,
Chairman
Large-scale ecosystem studies are a rapidly maturing field of science, which under the impetus of global change research has had major successes over the past decade. Improvements in fundamental understanding of marine and terrestrial ecosystems and hydrology have already led to practical applications in weather and climate modeling, air quality, and improved water resources; forest, fisheries, and rangeland management; and natural hazards responses.
The principal questions in large-scale ecosystem science involve understanding the effects of changing land cover on land- atmosphere exchanges of carbon dioxide (CO2), water, and energy, and consequent effects on climate and the carbon cycle. The synergistic instrument complement of the Earth Observing System (EOS) AM-1 and PM-1 platforms, combined with data from Landsat and other ocean-sensing satellites to document the roles of marine ecosystems in the carbon cycle, will satisfy in large measure the satellite data needs of the ecosystems community and will result in a massive improvement in the quality of remote observations.
Assessment and Future Requirements of the U.S. Global Change Research Program and the Mission to Planet Earth Overall, the U.S. Global Change Research Program (USGCRP) has been successful in advancing the science and tools required for space-based assessment of ecosystem change. The ground- and ocean-based components of the program have had varying degrees of success. Elements linked to atmospheric science (biophysics and trace gases) have had the strongest programs. The more ecological (vegetation and land cover) and integrative (ecosystem manipulation experiments) components have been supported on an ad hoc basis. Extension of local understanding from process studies to regional and global scales requires modeling. This work has made major advances but is less well-developed than in situ or remote sensing aspects of the program. Fulfilling the goals of the USGCRP requires enhancement of integrative modeling and close coordination of modeling with ground-, ocean-, and space-based studies.
Areas of Success
- Field and theoretical studies have been carried out that have laid the foundation for understanding the role of vegetation and soils in weather and climate, and have advanced our methods for interpreting satellite data. Execution of the field experiments planned for the Mississippi and Amazon basins would complete this series of studies.
- Satellite observation techniques, ground-based observations, and models, have been developed that can determine changes in land cover type, as well as spatial and seasonal changes of vegetation.
- The role of nutrients in the large-scale interactions of ecosystems with the atmosphere has been elucidated. The effects of nutrients such as nitrogen and phosphorus now must be systematically incorporated into global models of land-atmosphere interactions.
- An ambitious program has been implemented to measure and model the sources and sinks of CO2 and trace gases from biological and biomass-burning sources. This program will allow the development of an observing system to determine trends and patterns of emissions and uptake on continental scales.
- Oceanic time-series observations have revealed previously unknown year-to-year variations in coupled ocean biology, chemistry, and physics that are, linked to climate variability.
- Regional ocean carbon studies have quantified seasonal marine ecosystem effects on atmosphere-ocean CO2 exchange and El Niñ o-related variations in the equatorial Pacific sources and sinks of CO2.
- Impacts of climate change and variability on agricultural and forest ecosystems have been modeled.
Critical Work in Progress That Should Be Continued or Enhanced
- Experiments to determine the long-term ecosystem-level effects of rising CO2 in forests and agricultural crops and grasslands have just begun; these experiments must be sustained and effectively linked to global change modeling efforts.
- Observations of atmospheric CO2, its isotopes, and oxygen are crucial for quantifying processes within the carbon cycle, these measurements are at a minimal density for success and must be expanded over the continents.
- The ocean CO2 survey must be completed, and associated modeling efforts enhanced, in order to fully assimilate this information into global climate models.
- The ability to determine land cover changes from space has been demonstrated in regional studies. Global implementation, including the expansion of international partnerships, is required.
- Regional case studies of human land cover change have begun. Efforts to understand how changes in population, technology, and development affect land cover must be developed and linked to global-scale models.
Several Areas Requiring Special Emphasis
- Great opportunity for understanding the role of ocean ecosystems in the global carbon cycle has been lost with the nearly decade-long hiatus in ocean color data. Launch of the SeaWiFS instrument must be given high priority.
- Data sets must be developed for the use, intercomparison, and testing of models of terrestrial vegetation and productivity.
- Preliminary exploration is necessary of the potential for emerging and possibly commercial satellite measurement technologies, especially for managed ecosystems such as agriculture and forests.
- Implementation of vegetation analysis transects, utilizing existing and new field studies, is required to characterize the large scale relationships among climate, vegetation, and human activity.