Read here. Increased atmospheric CO2 levels have done wonders for old tropical rain forests, such as the Amazon, and newer ones growing on former cleared lands. Based on the findings of their research,
"Consequently, it would appear that the historical increase in the atmosphere's CO2 concentration, driven by the burning of fossil fuels, has been good for the Amazon's trees, and (very likely) for the rest of the region's plants and animals, even in the face of the local warming of 0.26°C per decade that they report for the region since the mid-1970s."
