Carbon sinks — land or ocean areas that lock up carbon dioxide — have been heralded as a way of managing increases in carbon dioxide emissions, and thereby mitigating climate change. Changes in land use could therefore have an important influence on global carbon levels.
Last year, a study found that 220 million hectares in the western part of the United States provided up to a third of the country's land-based carbon sink. This sink was attributed to the expansion of trees and woody shrubs into grasslands — a process that was thought to take up large amounts of carbon dioxide from the atmosphere.
But a study published in this week’s journal Nature suggests that the conversion of grassland into shrub-land only incorporates a small amount of carbon. The researchers found that in some cases the amount of carbon stored in the soil actually decreased.
The results suggest that the US carbon sink has been significantly overestimated, and could have serious implications on the use of new forest plantations to combat climate change.
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