Scientists say the cause may lie high above the rainforest, where invisible “flying rivers” carry rain from the Atlantic Ocean across South America. New analysis warns that relentless deforestation is disrupting that water flow and suggests that continuing tree loss will worsen droughts in the southwestern Amazon and could eventually trigger those regions to shift from rainforest to drier savanna – grassland with far fewer trees.

“These are the forces that actually create and sustain the Amazon rainforest,” said Matt Finer, a senior researcher with Amazon Conservation’s Monitoring of the Andean Amazon Project (MAAP), which tracks deforestation and climate threats across the basin and carried out the analysis. “If you break that pump by cutting down too much forest, the rains stop reaching where they need to go.”

Most of the Amazon’s rainfall starts over the Atlantic Ocean. Moist air is pushed inland by steady winds that blow west along the equator, known as the trade winds. The forest then acts like a pump, effectively relaying the water thousands of miles westward as the trees absorb water, then release it back into the air.

Brazilian climate scientist Carlos Nobre was among the early researchers who calculated how much of the water vapor from the Atlantic would move through and eventually out of the Amazon basin. He and colleagues coined the “flying rivers” term at a 2006 scientific meeting, and interest grew as scientists warned that a weakening of the rivers could push the Amazon into a tipping point where rainforest would turn to savanna.

That’s important because the Amazon rainforest is a vast storehouse for the carbon dioxide that largely drives the world’s warming. Such a shift would devastate wildlife and Indigenous communities and threaten farming, water supplies and weather stability far beyond the region. (Jamaica Gleaner)