The Amazon region of South America, impregnated with hundreds of inches of rain a year, is home to some of the wettest land on the planet. So, how can it burn? And why did the forest fires – the flames that spit so much smoke this week – turn the day of Sao Paulo into night?
Scientists report three main causes – each resulting from human activity. The first is deforestation, largely illegal. The Amazon is losing an astonishing amount of forest cover – and its rate is increasing. An area twice as small as Rhode Island was lost in July alone. The easiest way to dispose of fallen trees and foliage is to let it dry in the sun for months, then burn it.
“This is what prevails,” said Carlos Nobre, one of the leading Brazilian scientists studying the Amazon.
The last main cause is drought. These occur naturally, but scientists say that climate change and deforestation make them more frequent and more serious. This creates a self-reinforcing loop: less dry water or even kills trees, providing more fuel for more fires.
All these factors – deforestation, agricultural practices and drought – are transmitted to each other. “The result: noncombustible rainforests normally become flammable,” researchers wrote this year in conversation.
The implications are global. The Amazon is one of the best defenses against climate change: it represents a quarter of the carbon dioxide absorbed by the world’s forests. Researchers warn that the mutually reinforcing cycle of deforestation and fire will make it very difficult, if not impossible, to keep global warming below destabilizing levels.