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Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems


Knowledge of carbon exchange between the atmosphere, land and the oceans is important, given that the terrestrial and marine environments are currently absorbing about half of the carbon dioxide that is emitted by fossil-fuel combustion. This carbon uptake is therefore limiting the extent of atmospheric and climatic change, but its long-term nature remains uncertain. Here we provide an overview of the current state of knowledge of global and regional patterns of carbon exchange by terrestrial ecosystems. Atmospheric carbon dioxide and oxygen data confirm that the terrestrial biosphere was largely neutral with respect to net carbon exchange during the 1980s, but became a net carbon sink in the 1990s. This recent sink can be largely attributed to northern extratropical areas, and is roughly split between North America and Eurasia. Tropical land areas, however, were approximately in balance with respect to carbon exchange, implying a carbon sink that offset emissions due to tropical deforestation. The evolution of the terrestrial carbon sink is largely the result of changes in land use over time, such as regrowth on abandoned agricultural land and fire prevention, in addition to responses to environmental changes, such as longer growing seasons, and fertilization by carbon dioxide and nitrogen. Nevertheless, there remain considerable uncertainties as to the magnitude of the sink in different regions and the contribution of different processes.

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Figure 1: Zonal distribution of terrestrial and oceanic carbon fluxes.
Figure 2: An illustrative plot of the interannual variability of global terrestrial carbon exchange, as deduced using inverse modelling10.


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This Progress Article arose from the International Workshop on Integrated Carbon Research and Observations, held on 16–20 October 2000. This workshop was organized under the auspices of the International Geosphere–Biosphere Programme (IGBP) and the Global Terrestrial Observing System (GTOS), and was co-funded by NOAA, the NSF, NASA, the US Department of Energy, the US Department of Interior/US Geological Survey, the US Department of Agriculture and the International Geosphere Biosphere Programme. D.S.S. was also supported by the European Commission, NASA, and the Bundesministerium für Bildung und Forschung.

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Schimel, D., House, J., Hibbard, K. et al. Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems. Nature 414, 169–172 (2001).

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