SciDev.net: Most climate models suggest that increasing atmospheric carbon dioxide levels should drive tree growth in tropical forests such as the Amazon. To better understand the health of the Amazon forest, Roel Brienen of the UK's University of Leeds and his colleagues examined 200 000 trees from 321 plots distributed across South America. They found that the forest currently absorbs just 1 billion tons of CO2 each year, compared with the 2 billion tons it absorbed in the 1990s. The researchers suggest that the drop in CO2 absorption may be partly associated with the increase in the tree death rate, which has risen by one-third since the 1980s. If rising CO2 levels are in fact killing trees rather than driving growth, significant changes to climate models may be necessary.
