State of Roraima, Brazil, 2018

One of the most extraordinary - and perhaps least known - features of the Amazon rainforest is a phenomenon variously known as "flying rivers" or "aerial rivers." It may seem like a contradiction to talk of a "river" that cannot be seen, yet these "flying rivers" carry more water than the Amazon River itself and affect a larger area of South America and beyond. Scientists have estimated that, while 17 billion tons of water enter the Atlantic from the Amazon River each day, over a similar period 20 billion tons of water rise into the atmosphere from the jungle, earning it the nickname of the "Green Ocean", and then leave the Amazon region. What is remarkable, though, is the scale on which this takes place. A large tree can suck water from as much as 60 meters below the ground and produce as many as 1,000 liters of water per day. And since this is repeated by between 400 and 600 billion trees, it is easy to see how the Amazon forest generates an important proportion of the water that it later receives. In fact, even the water that reaches the mainland through evaporation of sea-water is itself quickly recycled by the jungle in a process known technically as "evapotranspiration." But if the "flying rivers" are vital to the economic welfare of tens of millions of people, mainly in Brazil, they also impact weather patterns across the globe and are themselves vulnerable to the effects of deforestation and global warming.