RAINFOREST ECOLOGY

Viewed from the air, Manu�s rainforest looks like an endless sea of lumpy green sponges stretching in all directions as far as the horizon. It is this thick umbrella of trees - the jungle's equivalent of an enormous housing project - that creates the millions of homes in which animals and specialized plants live below the canopy. If you were able to slowly float down through the canopy you would soon discover that the first layer is virtually a desert of sorts.

The crowns of the trees are exposed both to the fierce tropical sun and to winds that frequently snap and topple the tallest of trees. To reduce evaporation, the leaves at this level are quite small. Many of the epiphytes here - plants that live on other plants - actually take on the form of cacti to reduce water loss.

As you descend through the upper canopy however, you immediately begin to enter a different world of reduced light. Protected from direct sun and wind, the leaves here are larger in size and the struggle for available light begins.

Traveling further down towards the jungle floor, leafy plants are much less abundant as there is less and less light. Although the first explorers traveling by river often reported thick and impenetrable jungles, under the canopy away from the rivers one can move quite easily through the forest as most branches and leaves are well off the ground. Like conditions beneath the sea, even in strong storms all is calm and still.

The sound of insects is overwhelming, as millions of tiny creatures call to one another unseen. At the lowest level, most leaves are either very large or else have other adaptations to cope with low levels of light, for less than 5 % of the sun's rays ever reach the jungle floor.

It is this enormous variation of light, wind and temperature which creates the specialized homes of millions of different species of animals and plants. Whole communities of insects, birds and other animals are adapted to life at different levels of the rainforest., which not surprisingly contains the highest species diversity in the world. Here in Manu, for example, an area of roughly 100 by 50 miles (160 by 80 Kms), are found:

200 species of mammal (the U.S�s Yellowstone National Park has just 28)

1000 bird species (there are 800 bird species in all of North America)

10% of all the plant species found in the world (20% of South America's total)

More than 1200 species of butterflies (Europe has 400)

A single rainforest tree may host as many as 43 different species of ants - more than the entire number of ant species found in England.