There are three broad types of forests in the world: boreal, temperate and tropical. Each forest type has its own kind of trees, which are best suited to the local climate. The animals in each type of forest are also adapted to their surroundings.

We all rely on forests. They recycle rainfall and store vast amounts of carbon dioxide, which they draw in from the atmosphere. Tree roots stabilise soil, preventing erosion, flooding and landslides. Many forest species provide cures for illnesses such as malaria, and forests are home to more than a million indigenous people who depend on them for their survival. They also provide the world with timber for building and wood for heating and cooking.

Forests contain as much as 90 per cent of the world's terrestrial biodiversity: animals such as great apes, tigers and giant pandas, and millions of species of plants. We cannot conserve these species without conserving their forest habitat.

Tropical forest | Temperate forest | Boreal forest

Tropical forests
Tropical forests grow in the warm regions around the Earth's equator, between the Tropics of Cancer and Capricorn. They cover about 14 per cent of the Earth's land surface.

There are three main types of tropical forest: rainforests, which thrive in hot, humid conditions all year round and contain an incredible range of plant and animal species; cloud forests, which are found at high altitudes; and dry forests, where the trees are more scattered.

Many tropical rainforests seem like very fertile places, due to the number of plants growing there. However, most of the nutrients are found in the plants, not the soil. If an area of rainforest is cleared, the nutrients are lost along with the trees - all that is left is poor quality soil, which soon turns to desert.

Rainforest trees grow very tall and have dense canopies that let through little light. When a tree falls, sunlight floods through the canopy and saplings race to grow up and fill the gap. Some rainforest plants, such as lianas, 'cheat' and use the trunks of other trees to climb up to the light. Epiphytes, which include orchids, can grow on the branches of large trees up near the sunlit canopy. They have no contact with the ground and take their nutrients from rainwater.

What do chocolate, vanilla, rice, coffee and tomatoes all have in common? They all originated from wild plants growing in rainforests. Medicine has also benefited from rainforests. Scientists have identified more than 2,000 tropical forest plants with anti-cancer properties.

Most species living in tropical forests haven't yet been formally described and named by science. We will never know many of them as forests are being cleared at an alarming rate. Since 1980, an area of tropical forest greater than the size of India has been cleared for plantations, agriculture, pasture, mining and urban development.

Temperate forests
In the UK we live in the temperate zone, sandwiched between the cold north and the warm tropics. There is also a temperate zone in the southern hemisphere. Trees in temperate forests are mainly broad-leaved and deciduous, such as oak and beech, but there are also conifers, such as pine and spruce. The UK has 29 native broad-leaved trees and three native conifers.

In this zone there are four distinct seasons - spring, summer, autumn and winter - and, as the seasons change, so do many of the trees. In autumn, deciduous trees change the colour of their leaves, and by winter they have fallen off, only to grow back in the spring. Lack of leaves in the cold part of the year saves the trees from dehydration - wide, flat leaves lose water quickly and, when the ground is frozen, trees can't absorb much water. Spring is relatively mild, so tender new leaves can start growing ready for the warm summer when the trees do most of their growing.

Temperate forests usually have three layers of plants. The canopy of the trees forms the top layer. Under the canopy there is enough light for a middle layer of shrubs and, on the forest floor, small plants such as mosses and wildflowers grow.

The animals that live in temperate forests must be able to adapt to the changing seasons. Winter is the hardest season. Some animals, such as hedgehogs, hibernate. Others, like the song thrush, migrate to warmer areas. Squirrels and foxes store food for when times are hard.

Along the temperate west coast of North America, the soils are rich and the rainfall is even. It is home to some of the largest trees on Earth - up to 90 metres tall and 5 metres across. These trees are worth thousands of dollars to the timber corporations, hence the forests are gradually being destroyed.


Boreal forests
Boreal forests lie in the far north, where winters are harsh and summers short. They cover vast tracts of land, forming an almost continuous belt, just below the Arctic Circle, across Northern America, Europe and Russia.

The trees in these forests are tough - they have to be. In winter, temperatures can drop to below -60ºC and in summer they can exceed 30°C. Added to these temperature extremes, there is little rain, meaning conditions are dry. However, one group of trees grows very well here, due to a number of adaptations to the environment. These are conifer trees, which include spruces, larches, pine and fir trees.

Their conical shape allows snow to slide off without causing damage, while their needle-like leaves reduce the surface area through which water is lost, preventing dehydration. Almost all conifers are evergreen, keeping their foliage all year round, and so waste no time growing leaves when the short summer growing season begins. Another adaptation is the dark colour of spruce and fir, which helps the trees to absorb more heat from the sun.

The animals that live in the boreal forests are also suited to their environment. The North American crossbill has a specially adapted beak for extracting seeds from pine cones. Larger animals also roam these forests - in Europe and Russia there are reindeer, brown bears and wolves, and in the Russian Far East, where the boreal forests are known as the 'taiga', lives the largest cat in the world - the Amur tiger.

In many parts of the world, boreal forests have been little affected by human activity. But, as we use more and more timber, these vast areas of wilderness are beginning to be exploited by logging companies. Unless logging is very carefully managed to be sustainable, huge areas of forest could be lost, along with the animals that live there.


Current threats & problems

We abuse trees relentlessly. Forests are cut down, burned and cleared for agriculture, cattle raising, housing and profit. In numerous cases they are never replaced, so land and people are exposed to serious danger from flash flooding on the one hand and dustbowl conditions on the other.

For decades, the destruction of the world's forests has been one of our biggest environmental problems. Almost half the planet's original forests have disappeared - and, of those remaining, only around 10 per cent are protected. UK forests enjoy a high level of protection, but we import around 85 per cent of our timber from 70 other countries, so we also have a great impact on forests around the world.

The problem is that we all want timber and timber products such as paper. Many forests, such as those in Indonesia, are not managed sustainably, and are falling prey to the multi-million dollar illegal logging industry, which takes no account of environmental considerations.

Another threat facing forests is their clearance for agriculture. The palm oil and soy production industries are expanding rapidly, and many forests are being converted into plantations. This process destroys habitat for the forest species, including many that are rare.


What WWF is doing

In response to the global forest crisis, WWF is working with governments throughout the world to: establish a network of protected areas; start more forest restoration programmes; and launch good forest management schemes. WWF is also helping many communities to use forest goods and services at levels that damage neither the environment nor the forests themselves.

WWF has also played a leading role in establishing the Forest Stewardship Council (FSC), which lays down strict international standards for forest management. Products that come from well-managed forests, wherever they might be, carry the "tick-tree" trademark that was launched in 1996. Look out for it on thousands of timber products in superstores and DIY shops.
If the forests of the world are to thrive, it is up to all of us to insist that they are preserved, and to ensure that we treat them with respect by purchasing timber that is labelled as coming from well-managed forests.