A new study led by the University of Leeds has calculated the economic value of one of nature’s least recognised services: tropical forests’ ability to generate rainfall for surrounding regions.
Published today in Communications Earth & Environment, the research estimates that rainfall generated by the Brazilian Amazon alone is worth roughly US$20 billion (£16 billion) to the region’s agriculture each year.
“This is the most comprehensive and robust evidence to date of the value of tropical forests’ rainfall provision,” said lead author Dr Jess Baker, from the University of Leeds’ School of Earth, Environment and Sustainability.
The rain machine
Using satellite data and climate models, the researchers found that each hectare of tropical forest generates 2.4 million litres of rain annually — enough to fill an Olympic-sized swimming pool.
This process, known as evapotranspiration, sees the sun’s energy transfer moisture from leaves into the atmosphere, eventually falling as rain. Across the tropics, each square metre of forest contributes about 240 litres of rainfall per year, rising to 300 litres in the Amazon.
This moisture is vital for crops. For instance, the study found that producing enough rain to sustain a square metre of soybean crops requires the moisture output of 1.7 square metres of intact forest.
Economic consequences
The findings highlight a stark economic reality for countries like Brazil, where 85 per cent of agriculture is rain-fed.
The researchers estimate that decades of deforestation in the Amazon — amounting to around 80 million hectares — may have already slashed rainfall-generation benefits by almost US$5 billion annually.
“Tropical deforestation is increasing, despite international efforts to halt forest loss,” said Dr Baker. “Demonstrating the financial benefits that tropical forests provide will unlock investment and strengthen arguments for forest protection.”
Beyond agriculture, the decline in forest-driven rainfall threatens hydropower generation, drinking water supplies, and river transport.
