Deforestation and Its Effects

What is deforestation?

Deforestation is the large-scale, permanent removal of forests so the land can be used for something else. It is different from a forest naturally losing some trees; deforestation means the forest is gone and replaced by farmland, pasture, mines, roads or cities. Around the world, an area of forest roughly the size of a football pitch is cleared every few seconds.

To understand what is being lost, it helps to know what a forest does. Explore how trees grow and the rich life of rainforests of the world for background.

Why forests are cleared

Most deforestation is driven by human demand for land and resources:

• Agriculture is the biggest cause. Forests are cleared to graze cattle and to grow crops such as soy (much of it fed to livestock), palm oil and coffee.
• Logging removes timber for furniture, paper and construction. Illegal logging is a serious problem in many regions.
• Mining for metals, gold and minerals clears land and pollutes rivers.
• Infrastructure — roads, dams and settlements — opens up forests and makes further clearing easier.

These pressures are strongest in tropical regions, where the Amazon in South America, the Congo Basin in Africa, and the forests of Southeast Asia are being cleared fastest.

The effects of deforestation

Forests do far more than provide wood. Removing them sets off a chain of harmful effects.

1. More greenhouse gases

Trees are carbon sinks: through photosynthesis they pull carbon dioxide out of the air and lock it in wood, leaves and soil. When forests are cut down — and especially when they are burned to clear land — that stored carbon is released back into the atmosphere. Deforestation is responsible for around a tenth of human-caused CO2 emissions, worsening the greenhouse effect.

2. Soil erosion and flooding

Tree roots act like nets that hold soil together, and the leafy canopy shields the ground from heavy rain. Strip the trees away and rain washes the fertile topsoil off the land. The bare ground can no longer absorb water well, so rivers flood more easily and the lost soil clogs waterways downstream. Why soil matters is explored in soil and why it matters.

3. A disrupted water cycle

Forests recycle huge amounts of water. Trees draw moisture from the soil and release it as vapour through their leaves — a process called transpiration — which forms clouds and rain. The Amazon effectively makes much of its own rainfall this way. Clear the forest and the region can become drier, sometimes turning toward grassland or even desert.

4. Loss of biodiversity

Tropical forests hold more than half of all land species, many found nowhere else on Earth. When their habitat is destroyed, plants and animals lose their homes and some are pushed to extinction before scientists have even named them. This is one of the main drivers of the wider biodiversity crisis covered in biodiversity and conservation.

5. Harm to people

Millions of Indigenous and local people depend on forests for food, medicine, shelter and culture. Deforestation can destroy their way of life and force them from their land.

Can deforestation be reversed?

There is real hope. Solutions that work include:

• Reforestation and afforestation — replanting cleared land and growing new forests, ideally with native species.
• Protected areas that legally safeguard forests, often managed alongside Indigenous communities who are highly effective forest guardians.
• Sustainable farming and forestry, getting more from existing farmland so less forest is cleared, and harvesting timber slowly enough that the forest recovers.
• Consumer choices and laws, such as products certified as deforestation-free and rules banning imports linked to forest destruction.

Costa Rica is a famous success story: after losing much of its forest, it reversed the trend through conservation and now has more than half its land forested again.

Try it yourself: model soil erosion

You can see the effect of tree roots with a simple test.

1. Fill two shallow trays with soil and tilt each at a slight slope, propped on a book.
2. In one tray, press a clump of grass or small leafy plants into the soil so the roots are embedded. Leave the other tray bare.
3. Slowly pour the same amount of water over the top of each slope, as if it were rain.
4. Watch how much soil washes down into a container at the bottom of each tray.

The bare tray loses far more soil. This shows how forests protect the ground — and what happens to the land when they are removed.