Tropical forests make rain worth billions of pounds

Rain generated by the Amazon rainforest could be worth up to £15 billion every year.

The natural world provides countless ecosystem services that make life possible, from pollinating crops to cleaning the air. These services are driven by Earth’s biodiversity as plants, animals and many other organisms interact in a vast multitude of ways.

However, these services are so ubiquitous that they’ve been taken for granted. As humans have destroyed habitats and transformed the landscape, it’s pushed biodiversity and ecosystem services into decline.

New research, published in the journal Communications Earth & Environment, hopes to change this by putting a value on these services. It’s focused on the rainfall provided by tropical forests, looking at how they boost the economy through supporting farming, water supplies and energy production.

The study estimates that for each 1.5 football pitches of tropical forest, 2.4 million litres of rain is generated per year – enough to fill an Olympic-sized swimming pool. Dr Jess Baker, the lead author, says that the research provides “the most comprehensive and robust evidence to date of the value of tropical forests’ rainfall provision.”

“Tropical deforestation is increasing, despite international efforts to halt forest loss,” Jess says. “Our work highlights the vital role of tropical forests in producing rain. We estimate that the Amazon alone produces rainfall worth US$20 billion each year.”

“Demonstrating the financial benefits that tropical forests provide will unlock investment and strengthen arguments for forest protection."

How do rainforests make rain?

When plants first evolved for life on land, they were limited by how far water could spread through their tissue. Over time, they developed complex vascular systems that allowed them to move water and nutrients around their bodies. Eventually, this led to trees that towered over their surroundings and the origins of rainforests such as the Amazon.

One of the key processes that makes this possible is transpiration. Water in the leaves evaporates into the air, drawing more water up through the plant in the process. This means that trees act a bit like a giant pump, gradually moving water up their trunks and releasing it into their surroundings.

If one tree is a pump, then tropical forests are vast pumping stations. Water vapour rising into the air drives cloud formation, causing rain that returns the water to the Earth. Just over half of this water will eventually end up back in these plants to begin the cycle again, while the rest ends up in lakes, rivers and underground.

On average, the team estimate that a square metre of tropical forest generates about 240 litres of rainfall annually. This process is even more efficient in the Amazon, where it’s around 300 litres of rainfall instead – about enough to completely fill two baths.

Protecting the Amazon

The Amazon, however, is under threat. While rates of deforestation have fallen in recent years, an area of rainforest twice the size of Luxembourg was cut down in 2025. This ongoing loss has immediate effects on wildlife, from raising the risk of disease to pushing species towards extinction.

It also has wider impacts on the climate, with deforestation linked to rising temperatures and an increasing risk of wildfires. But is also harms the water cycle, with the study estimating that the loss of 800,000 square kilometres of rainforest in recent decades cost the Brazilian economy £3.5 billion a year in lost rainfall.

With 85% of the country’s agriculture relies on rain, this is a massive issue. Certain crops, such as cotton and soybean, are particularly vulnerable as a square metre of these plants needs around twice as much forest to provide the rain needed for them to grow.

Dr Callum Smith, a co-author of the research, says that they hope the research will help to convince the agricultural industry of the benefits of preserving the Amazon and many other rainforests.

“Tropical forests make it rain, supplying water that is essential for agriculture,” Callum adds. “Recognising that crucial connection could ease tensions between agricultural and conservation interests whilst building broader support for protecting forests overall.”

The report builds on growing interest in new conservation schemes that aim to attract billions of pounds to protect rainforests around the world. Brazil is leading the Tropical Forest Forever Facility, for example, which aims to provide payments to governments and Indigenous People for looking after and restoring rainforest across the globe.

If these prove successful, they’ll go some way towards ensuring that tropical forests are as right as rain.