Amazon trees release billions of tonnes of water, seeding their own rain

The Amazon rainforest is often called the planet's largest river, but its most important waterway may be invisible. Through a process called transpiration, trees pull water from the soil and release it as vapor through tiny pores in their leaves. This vapor rises, condenses, and falls back as rain, making the forest a major driver of its own wet climate. ^[1][2]

A Flying River

A single large Amazonian tree can release hundreds of liters of water into the air each day. When multiplied across billions of trees, the result is an atmospheric flow of moisture—sometimes called a "flying river"—that carries more water than the Amazon River itself. This moisture travels across the continent and can fall as rain thousands of kilometers away. ^[2][3]

How the Forest Makes Its Own Rain

The recycling process depends on a tight loop between trees and rainfall. Moisture evaporated from the Atlantic Ocean falls as rain over the eastern Amazon. Trees absorb it, transpire it back into the air, and the wind carries it further west. By the time air masses reach the Andes, much of the rain has been recycled several times over. ^[1][3]

• Transpiration: water moves from soil to leaves and exits as vapor through stomata. ^[1]
• Evapotranspiration: combines transpiration from plants with evaporation from soil and water surfaces. ^[1]
• Atmospheric recycling: the fraction of rainfall that comes from local evapotranspiration rather than distant oceans. ^[3]

Why It Matters

This self-generated rain keeps the Amazon humid and resilient, supporting the forest's extraordinary biodiversity. It also influences rainfall far beyond the basin, including agricultural regions in South America. When deforestation removes trees, transpiration drops, and rainfall can decline—potentially pushing parts of the forest toward a drier, savanna-like state. ^[2][4]

1. 1970s

   Large-scale Amazon deforestation begins, raising concerns about rainfall recycling.

2. 1990s–2000s

   Studies quantify the "flying rivers" and atmospheric moisture transport from the Amazon.

3. 2010s–present

   Research warns that continued deforestation could weaken the forest's water cycle and cause dieback.

The Amazon's rain machine is not just a curiosity—it is a critical part of the region's climate stability. Protecting the forest means protecting the rain that sustains it. ^[4]