Great rainforests stretch around the Equator, covering large parts of Central and South America, Central Africa, South-east Asia and northern Australia. These forests are the most complex ecosystems in the world and contain a wealth of resources. Despite their importance, though, they are being destroyed at an alarming rate.
Rainforests grow in areas where rainfall and temperatures are both high and constant. Over millions of years they have developed into the earth’s richest wildlife habitats. They cover less than 10% of the planet’s land surface, but they contain between 50% and 70% of all plant and animal species. The greatest of all the forests is Amazonia in Brazil.
Layering. All rain forests have a similar structure, with five main layers, each with its own specific plant and animal life. These layers often merge together, or sometimes one or more are absent.
Emergent layer – made up of a few of the tallest trees which rise 10 to 15m above the mass of greenery below. From here, Harpy eagles and other birds of prey watch alertly for the animals on which they feed.
Canopy– 30 to 40m above the ground, and some 10m thick, this is a continuous green roof formed by the interlinking leaves and branches of the tree tops. Most of the forest’s many plants and animals are found here, taking advantage of the abundant sunshine.
Understorey– made up of the tops of smaller trees that receive less light, like palms, and of younger trees struggling to reach upwards. Much sparser that the canopy, it has its own community of plant and animal life.
Shrub layer – consisting of shrubs and small trees, this layer depends on sunlight penetrating the upper layers. If none reaches here, both this and the herb layer will be sparse. When a gap appears in the canopy, sunlight reaches the lower regions, causing the shrub and herb layers to grow rapidly.
Herb layer – ferns and herbs making up a layer of undergrowth. Elusive ground dwellers, like the tapir, live down here, along with many insects.
The forest floor is covered by several centimetres of fallen leaves. Here, organic matter is rapidly recycled by the decomposers, and minerals are transferred directly to shallow plant roots. This process is so efficient that the lower layer of soil has little mineral content and most of the forest’s mineral wealth is stored in the vegetation. When the forest is cleared and burned, the minerals stored in vegetation are turned to ashes. The root systems are destroyed, allowing rain to wash away the ashes and topsoil. The remaining soil soon becomes infertile, turning areas once rich in life into wasteland. It takes centuries for the forest to return, if ever.
The importance of rainforests. Tropical rainforests play a vital role in regulating the world’s climate, through their position in the oxygen, carbon and water cycles. They are the most important source of raw materials for new medicines and area a vital source of new foods (at least 1,650 rainforest plants could be used as vegetables).
People of the forest. The rainforest is home to many native peoples, who live in harmony with its environment. Their knowledge of the forest is very important to us, if we are to understand its workings and resources. But every day these people are being forced from their own lands with no regard to their wishes or basic human rights. Both they and their knowledge are being destroyed, along with the forests in which they live.
Destruction of the rainforests. Almost 50% of the world’s rainforests have already been destroyed, and the destruction continues. The underlying causes of this are the growing populations, poverty and unequal land distribution in countries with rainforests. This is made worse by the rich nations’ demand for timber, and large. Badly-planned aid programmes. A long-term solution will only be found when these underlying causes are properly dealt with.
It’s important! It is estimated that one square kilometre of forest is destroyed every two and a half minutes – over one million acres per week.
2.13. Fill in the gaps with the word(s) from the box. Use the word(s) only once.
emergent / green / community / to grow / ground / alarming / land / fallen / to wash away
1. an …….. rate
4. …….. roof
7. …….. dwellers
2. …….. surface
8. …….. the ashes and topsoil
3. …….. layer
6. …….. rapidly
9. …….. of plant and animal life
2.14. Correspond the facts with the following numbers from the text: