Two recent articles about the drought in Brazil. Worst since 1930 made worse (probably much worse) by deforestation. Go humans.
“The Amazon works as a giant pump, channeling moisture inland via aerial rivers and rainclouds that form over the forest more dramatically than over the sea … It also provides a buffer against extreme weather events, such as tornados and hurricanes.”
“Natural forests act like giant sponges soaking up rain and gradually releasing it into streams,”
“Long-standing assumption: rain forests are a consequence of heavy rainfall. New hypothesis: some forested regions may produce conditions that lead to heavy rainfall. This “biotic pump” model contends that a vast forest such as the Amazon draws in large amounts of water vapor. Evaporation and condensation of the acquired water lead to a local atmospheric pressure drop. That decrease causes rain and attracts more water vapor to the forest, in a continuous positive feedback loop. “This theory could explain why continental interiors with huge rain forests remain so moist,” says Wildlife Conservation Society researcher Douglas Sheil, who in an April Bioscience paper revived the biotic pump model, originally proposed in 2006 by Anastassia Makarieva and Victor Gorshkov, both at the Petersburg Nuclear Physics Institute in Russia. “It could also underline the dangers of widespread deforestation.” Though promising, the model needs more data regarding air circulation patterns and vegetation types to support it, Sheil notes. —Steve Mirsky