How Rainforests Make Their Own Rain

A rainforest is a place of heavy rain, but the forest is not simply on the receiving end. Large forests also help to produce the rain that falls on them.

Trees as water pumps

A tree takes up water from the soil through its roots and draws it up to its leaves. Tiny openings in the leaves let some of that water escape as water vapour. This process is called transpiration. When thousands of trees do this at the same time, a great deal of moisture is released into the air above the forest. Water also evaporates directly from wet leaves and soil.

From vapour to cloud

Warm, moist air rises. As it climbs, it cools, and the water vapour condenses into tiny droplets that form clouds. When the droplets grow large enough, they fall as rain. Some of that rain soaks into the ground, is taken up by trees, and begins the journey again. In large forest regions, a notable share of the rain comes from moisture that the forest itself released.

Helping clouds to form

Forests also release tiny particles and natural chemicals into the air. Some of these can act as seeds around which cloud droplets form, which may further help clouds to develop above forests.

Why it matters

Because the forest is part of the water cycle, clearing large areas of it can change the local climate. With fewer trees, less water is returned to the air, and in some regions this can mean less rain. Forests also shade the ground and hold the soil in place, which helps rainfall to soak in slowly rather than run straight off.

Rainforests in India

India has tropical rainforests too, in the Western Ghats and in the north-east. These forests are home to a huge variety of plants and animals, and they play an important part in the rainfall of their regions.

Key points

• Trees release water vapour from their leaves, a process called transpiration.
• Moist air rises, cools and forms clouds that produce rain.
• In large forests, much of the rain is moisture the forest has recycled.
• Clearing forest can reduce local rainfall.