planned for the Mississippi and Amazon River basins will complete this series of studies.

  • Development of satellite observation techniques, ground-based observations, and models to determine changes in land cover type and spatial and seasonal changes of vegetation.

  • Clarifying the role of nutrients in large-scale interactions of ecosystems with the atmosphere. The effects of nutrients such as nitrogen and phosphorus must now be systematically incorporated into global models of land-atmosphere interactions.

  • Implementation of an ambitious program to measure and model the sources and sinks of CO2 and trace gases from biological and biomass burning sources. This new information will facilitate the development of an observing system to determine trends and patterns of emissions and uptake at continental scales.

  • Oceanic time series observations that have revealed previously unknown year-to-year variations in coupled ocean biology, chemistry, and physics, linked to climate variability.

  • Regional ocean carbon studies that have quantified seasonal marine ecosystem effects on atmosphere-ocean CO2 exchange, and El Niño-related variations in equatorial Pacific sources and sinks of CO 2.

  • Modeling the impacts of climate change and variability on agricultural and forest ecosystems.

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 synergistic instrument complement consisting of the Earth Observing System (EOS) AM-1 and PM-1 platforms, combined with data from other ocean-sensing satellites, will largely satisfy the satellite data needs of the ecosystems community and will result in a massive improvement in the quality of remote observations. The ground- and ocean-based components of the program have had varying degrees of success. Atmospheric science components (biophysics and trace gases) have had the strongest programs. The more ecological components (vegetation and land cover) and integrative components (ecosystem manipulation experiments) have been supported on a rather ad hoc basis.

The Research Imperatives for the future are as follows:

  • Land surface and climate. Understand the relationships between land surface processes and weather prediction and changing land cover and climate change.

  • Biogeochemistry. Understand the changing global biogeochemical cycles of carbon and nitrogen.

  • Multiple stresses. Understand the responses of ecosystems to multiple stresses.

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