Tropical forests are not only vital carbon sinks and biodiversity strongholds they are also powerful “rain machines” generating billions of dollars’ worth of rainfall every year, according to new research led by the University of Leeds.
The study, published in Communications Earth & Environment, calculates that each hectare of tropical forest produces around 2.4 million litres of rainfall annually roughly enough to fill an Olympic-sized swimming pool. Researchers say putting a monetary value on this overlooked ecosystem service could strengthen global efforts to halt deforestation.
Amazon’s Rainfall Service Valued at $20 Billion Annually
To measure forest-driven rainfall, scientists combined satellite observations with next-generation climate model simulations, helping to reduce long-standing uncertainty around how much rain forests help generate through evapotranspiration the process by which moisture from leaves enters the atmosphere and later returns as precipitation.
Using a simplified economic model, the team estimated that rainfall generated by the Amazon Rainforest alone is worth approximately $20 billion per year to Brazilian agriculture. That figure far exceeds the financial incentives currently allocated toward protecting or restoring the Amazon.
Across tropical regions, each square metre of forest contributes about 240 litres of rainfall annually, rising to nearly 300 litres in the Amazon basin.
Lead author Dr. Jess Baker described the findings as the most comprehensive evidence to date of the economic value of tropical forests’ rainfall provision. She noted that deforestation continues despite international pledges to halt forest loss by 2030, underscoring the urgency of recognizing forests as critical water-generating systems.
Deforestation Undermining Crops and Water Security
The study also highlights how deeply modern agriculture depends on forest-generated moisture. Cotton cultivation, for example, requires 607 litres of moisture per square metre equivalent to the rainfall produced by two square metres of intact forest. Soybeans need 501 litres, or roughly 1.7 square metres of forest.
Deforestation in the Amazon estimated at around 80 million hectares over recent decades may already have reduced rainfall-generation benefits by nearly $5 billion annually, the researchers found. The consequences extend beyond agriculture, affecting hydropower production, drinking water supplies and river transport in remote regions.
Brazil’s economy is particularly exposed, with about 85% of its agriculture relying on rainfall rather than irrigation. Reduced precipitation and delayed wet seasons have already impacted soy and maize yields in heavily deforested areas.
Beyond economic losses, declining rainfall linked to forest destruction could weaken the remaining forests’ carbon-storage capacity, potentially intensifying climate change in a dangerous feedback loop.
Co-author Dr. Callum Smith argued that rainfall generation has been largely absent from legal and economic debates on forest protection. Recognising forests as essential drivers of regional water cycles, he said, could help bridge divides between agricultural and conservation interests.
As climate pressures and water insecurity mount worldwide, the study suggests that acknowledging the true economic value of tropical forests may be crucial to securing their future and the rainfall systems millions depend on.