The precise ecosystem study of the reaction of a Texas grassland to a range of carbon dioxide levels has shown that soil nitrogen availability may limit the capacity of ecosystems to absorb expected increases in atmospheric CO2. The researchers said their study emphasizes the urgency with which the U.S. and other nations should adopt stringent limitations on CO2 emissions, as outlined in the international Kyoto accord on climate change.

The researchers, led by Duke University ecologist Robert Jackson and USDA Agricultural Research Service researchers Wayne Polley, and Hyrum Johnson, published their findings in the May 16, 2002, Nature. First author of the study is Richard Gill, a former Duke postdoctoral associate, now a faculty member at Washington State University. The research was supported by the Department of Energy and the U.S. Department of Agriculture.

"Based on fossil fuel emissions, the carbon dioxide concentration in the atmosphere should be going up twice as fast as it currently is," said Jackson. "However, natural systems such as the regrowing Eastern forests are currently taking up that extra carbon dioxide, so we're really getting a free ride now.

"Many of us, myself included, believe that this free ride won't continue to the same extent that it has, because the incremental benefits of the extra CO2 get smaller and smaller relative to other nutrient constraints," he said. The policy implications of their findings are apparent, said Jackson.

"Considering the expected population increase, greater resource use per capita and the inability of natural systems to take up CO2, we may well be looking at increases per year that are double what they are now, with atmospheric CO2 concentrations as high as 8
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Contact: Dennis Meredith
dennis.meredith@duke.edu
919-681-8054
Duke University
15-May-2002