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(c) Andtreas Schlüter

Laubfrosch Hyla cf. fasciata

    Leguan Plica umbra      ochrocollaris

(c) Andreas Schlüter

Peru Rainforest Amazon  Pachitea Llullapichis Panguana Species Diversity : Regenwald

Peru - Species Diversity in Tropical Rainforests

Tropical rain forests are the most complex and rich land ecosystems in the world, containing the highest concentration of plant, fungus and animal species. Just 1000 years ago they covered around 13 percent of the earth's surface, but they have been reduced to just six percent by logging and slash-and-burn farming, which encompasses 200,000 square kilometers annually; an area that corresponds to the combined area of England, Wales and Scotland.

A dark green belt around the equator that spreads out under the clouds can be discerned on satellite photos. This seemingly homogeneous belt is in fact made up of various forest formations. Similar environmental conditions create similar adaptations however, which means that the organisms living in the American, African and Indo-Malaysian rain forests have developed similar features. The term for this phenomenon is convergent evolution. The American hummingbirds have their counterpart in the nectar birds of Africa and Asia.

The tropical rain forest is the richest in species of all land ecosystems on earth. Millions of animal and plant species within these habitats are connected with each other in an extremely complex community (biocenosis). It is estimated that the tropical rain forests shelter more than half of all organism species found on the globe. How accurate is this calculation, which is shared by most experts? The keyword here is latitudinal or global diversity gradient, which is a general principle in biology stating that the greatest number of plant and animal species are to be found in the equatorial regions. Of the 250,000 known vascular plant species 170,000, or almost 70 percent, grow in the tropical rain forests. The highest plant diversity, over 40,000 species, is concentrated in just two percent of the earth's surface. This "hot spot" is comprised of the countries Colombia, Ecuador and Peru. The concentration of species in the equatorial region is especially clear when research results from various predetermined areas are compared. In the species-rich rain forests every other tree is a different species. Alwyn Gentry was able to establish that there were 300 species of tree in a 300 hectare piece of rain forest near the Peruvian city Iquitos (there are just 30 species in all of Germany). Especially notable is the insect diversity. There may be 40,000 species in an area the size of a soccer field. The Peruvian zoologist Gerardo Lamas discovered over 1200 species of butterflies in the 55 square kilometer Tambopata Reserve in the drainage of the Río Madre de Dios. The insect group that leaves all others far behind in diversity are the beetles. There have been over 300,000 species described globally. A comparison with the species-richness in the tropics again shows the concentration; in the United States and Canada there are 24,000 known species of beetle, whereas scientists estimate around 20,000 species in one hectare.

When looking at these numbers it is difficult to comprehend that in fact this species-rich and fertile biocenosis has grown mostly out of infertile sand. The motor behind all growth is the sun. Sunlight gives the forest the energy that allows plants to create large amounts of carbohydrates through photosynthesis. Organic waste such as leaves, wood or animal carcasses are immediately reprocessed by fungi, ants, termites and other organisms, rapidly providing nutrients to the forest. The steady tropical climate makes activity and uninterrupted growth possible all year round. This direct recycling prevents a layer of topsoil from forming.

Besides the nutrient cycle, the climactic activity has a nearly closed circulation. The water pumped up into the trees evaporates above the surface of the leaves and condenses above the forest into rain clouds. The green blanket of the rain forest reduces the danger of erosion through heavy precipitation and thus regulates the water circulation

Text und Fotos Andreas Schlüter © 2003-2004