The Amazon River in the Sky

High in the Andes Mountains, the mighty Amazon River begins. It trickles from glaciers and oozes from mountain wetlands. It gains momentum and volume and feeds into clear streams and muddy rivers that pass through high cloud forests and lowland valleys. The torrents of the waters carry nutrients through the vast Amazon River basin, some 4,000 miles across the rest of the South American continent.

At the same time, in the rainforest and delta estuaries, another, more ethereal—but no less essential—river is forming.

A single large tree in the Amazon rainforest can transpire about 264 gallons of water per day.

Across the Amazon rainforest, water is being sucked up by plant roots, transported through their bodies, and emitted or “transpired” from their leaves. In the air, this vapor rises and cools, condensing into clouds. Thus suspended, it becomes a sort of “flying river” of water vapor, flowing west, back toward the Andes. Along its own winding journey, its contents will fall as precipitation, forming upland rivers, wetlands, and mountain snow and icepack to feed, once again, the Amazon.

Thisinterconnected cycle has been a sustaining force for some