Rainforests are billion dollar rain-making machines

Rainforests are often described as biodiversity hotspots or carbon stores. But new research published in Communications Earth & Environment reveals something even more fundamental: tropical forests actively generate rainfall at a scale that supports agriculture, water security and regional climate stability.

This research, synthesised in Quantifying tropical forest rainfall generation (Baker, J.C.A., Smith, C., Veiga, J.A.P. et al. 2025), combines satellite observations, climate modelling and empirical deforestation–rainfall data to measure how much rainfall tropical forests produce and what that rainfall is worth.

Forests create rainfall

Forests contribute to rainfall through evapotranspiration. Water drawn from the soil moves through plant tissues and is released as water vapour from leaves. This moisture enters the atmosphere, helping to form clouds and precipitation both locally and downwind. In large forest systems, this recycling of moisture plays a central role in sustaining regional rainfall patterns.

Rainshower in the Daintree rainforest.

The study estimates that across the tropics, each square metre of intact forest contributes approximately 240 litres of rainfall per year. In the Amazon Basin, this rises to around 300 litres per square metre annually. At the landscape scale, this represents an enormous volume of atmospheric water cycling that would not occur without intact forest cover.

The economic value of rainfall generation

To better understand the societal importance of this rainfall, the researchers applied agricultural water pricing to estimate its economic value. They found that rainfall generated by the Brazilian Amazon alone is worth approximately US $20 ± 7 billion per year to agriculture.

This valuation does not represent the total worth of forests; it only captures the rainfall benefit to farming. It excludes additional services such as carbon storage, biodiversity support, freshwater regulation and cultural values. Even so, the estimated value of rainfall generation alone exceeds current financial investments in forest protection.

Implications for agriculture and water security

Many tropical and subtropical agricultural systems depend heavily on rainfall rather than irrigation. When forests are cleared, evapotranspiration declines, atmospheric moisture decreases and regional rainfall patterns can weaken or shift. This can result in longer dry seasons and reduced water availability.

The study also compares forest-generated rainfall with crop water requirements. Major crops such as cotton and soybeans require several hundred litres of water per square metre over a growing season, comparable to the magnitude of rainfall that intact forest helps sustain. In other words, forests function as part of the hydrological infrastructure supporting food production.

Deforestation, therefore, carries hidden economic risks. As forest cover declines, so too does the atmospheric moisture recycling that stabilises rainfall. Recent large-scale forest loss in the Amazon is estimated to have already reduced rainfall generation substantially, with corresponding economic impacts.

Beyond agriculture

Rainforest-driven rainfall underpins more than farming. It supports river flows, freshwater ecosystems, hydropower generation and drinking water supplies. In large tropical basins, rainfall recycling influences regional climate systems that extend across national borders.

At the same time, forests regulate climate through carbon storage and energy exchange with the atmosphere. The rain-making function of forests operates alongside these processes, reinforcing the idea that intact forest landscapes are essential climate infrastructure.

What this means for conservation

For organisations working to protect and restore tropical rainforest, this research strengthens the need for action. Rainforests are not passive recipients of rainfall; they are active drivers of the hydrological cycle. Protecting intact forests maintains atmospheric moisture recycling, stabilises regional rainfall and safeguards water security.

In the Wet Tropics of Queensland and across other Gondwanan rainforest systems, maintaining large, connected forest landscapes helps sustain local and regional hydrology. As climate variability increases, preserving these ecological processes becomes even more critical.

Rainforests are living climate systems. They regulate carbon, sustain biodiversity, and, as this research demonstrates, generate rainfall worth billions of dollars each year. Protecting them is not only an environmental priority, but it is a long-term investment in water, food, climate stability and in our future.