The Amazon rainforest has a very strong metabolism for absorbing carbon dioxide, says Paolo Artaxo of the Department of Applied Physics at the University of São Paulo, Brazil, but it is being impacted by deforestation, which releases carbon stored in the trees. It’s difficult to tell whether the forest acts as a net sink or source of carbon, due to its size and complexity, but Artaxo is planning to begin long-term monitoring projects in the Amazon rainforest to try to answer that question.

Clearing rainforest changes the evaporation and transpiration patterns, since the rainforest’s vegetation is an important source of moisture in the atmosphere in that region. Pasture or cropland created by removing rainforest trees usually gets less rain, says Marcus Longo, a doctoral student in the Department of Earth and Planetary Science at Harvard University in Cambridge, Massachusetts.