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Peru Rainforest Amazon Pachitea Llullapichis Panguana Species Diversity : Diversität

It is extremely difficult to make even a somewhat reliable estimate on the number of plant and animal species living in the tropical rainforest. Despite the growing interest on the diversity in the rainforest, there have been very few attempts to count the species in a certain area. As was mentioned at the beginning, tropical rainforests only encompass six percent of the continental earth's surface. They contain over half of all living organisms on earth, however. How accurate are these estimates, which are shared by most experts? The keyword here is latitudinal or global diversity gradient, which is a general principle in biology stating that the most plant and animal species are 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 counties 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).

                      Trees Flowering plants Amphibians Reptiles  Birds Mammals Insects

Germany       30          2.400                 19             12          255           94        30.000 

 6 km2 Amazon 750         1.500                  70            100         400         100            ?

The number of different insect species cannot even be estimated. From research in much smaller areas, we know that over 40,000 species can exist in an area the size of a soccer field.

Based on the numbers given up to now, it is clear the terrestrial biodiversity is mainly spread out over the tropical rainforests. The insects, which could represent several ten millions of species in the rainforest according to entomologist Edward O. Wilson, are the best proof that the number of organisms living on land increases at the equator (with a few exceptions such as the salamander) and that at least half all species exist in this area.

Before we look at possible reasons for the enormous diversity, we should agree on a definition of the term biodiversity. The term has been highly overused recently and used as a synonym for the number of species. Biodiversity covers a much larger spectrum of parameters as just the number of species. Genetic variation of the same type, large groups of species, large groups of a genus, families and even higher taxa are all a part of it. Biodiversity also includes variety in ecosystems, which includes organism communities within a certain living space as well as the physical conditions. It is also the "variety of organisms that is to be found across all biological levels of organization" (Wilson, 1997).

In any comparison of species diversity of different rainforest areas, the standard that is used must be taken into consideration. It is thus reasonable to compare the species diversity of a certain vegetation unit, for example. The number of tree species over 0.1 hectares offers information on so-called alpha diversity. A landscape is generally comprised of different vegetation. The total number of different species taken together is called the gamma diversity. If terra firma is compared with terra firma and flood forests with flood forests we see that from location to location within these formations the species replace each other. This so-called beta diversity is another example of form diversity.


Text und Fotos © Andreas Schlüter 2003-2004