Rain From Amazon's Tropical Forests Is Worth Billions

Each patch of tropical forest is doing more than sheltering wildlife—it's also quietly manufacturing rain on a massive scale, a new study finds. University of Leeds researchers estimate that every hectare of tropical forest helps generate about 634,000 gallons of rainfall annually, roughly enough to fill an Olympic pool, per Phys.org. Using satellite data and advanced climate models, the scientists then put a price on that water: about $20 billion a year in rainfall that could be used for agriculture in the Brazilian Amazon alone.

That number dwarfs current financial incentives to protect or restore the region's forests, the authors say. The study, published in Communications Earth & Environment, links forest moisture production to key crops. It finds, for instance, that sustaining cotton and soybeans can require more forest area for rainfall generation needed to keep the crops going than the cropland itself occupies.

Deforestation in the Amazon—about 80 million hectares in recent decades—may already have erased nearly $5 billion per year in rainfall-related benefits, with ripple effects on food production, drinking water, and hydropower. The researchers argue that by leaving the importance of such rainfall out of law and economic policy, governments are undervaluing one of the most concrete reasons to keep forests standing and agriculture churning. The UK's Natural History Museum in London has more on the science behind how forests produce rain.