The number of people living in Africa has grown enormously.
Some 90 per cent of Kenya's original forests have gone
This means there are more mouths to feed and less land on which to grow the food.
In Ethiopia, Eritrea, Somalia and Sudan, the population has risen from 60 million in the 1960s to 190 million in 2000.
People have resorted to cutting down forests to make way for farming land.
In 1900, 40 per cent of Ethiopia was forested. Today this has been reduced to 4 per cent.