Carbon sinks only a short-term fix
The findings — published in the scientific journal Nature — could have implications for ministers meeting for international climate change talks, where the importance of carbon sinks and ‘emissions trading’ are still major points of controversy.
Land and ocean sinks currently absorb about half of the carbon dioxide created by burning fossil fuels, and at present this uptake is limiting the impact of carbon emissions from human activity on climate change.
But the land sink is not a constant phenomenon, the researchers warn, and its effect in the future is uncertain. In the 1980s, for example, the world’s land mass had a neutral effect — absorbing roughly the same amount of carbon dioxide that it gave out — but in the 1990s it became a net carbon sink.
These variations are largely the result of changes in land use, such as fire prevention and regrowth on abandoned agricultural land, as well as environmental changes, such as longer growing seasons, and fertilisation by carbon dioxide and nitrogen.
The net land sink might disappear altogether in the future, the researchers say, when these processes reach saturation and cease to take effect.
Reference: Nature 414, 169 (2001)
Link to Nature article