FLORA & FAUNA OF THE AMAZON

The Amazon Basin is famous as the largest rainforest on earth. The Amazon is important not just for its size, however, but also for its high biodiversity, or the numbers of plant and animal species that can be found in the Amazon. The western edge of the Amazon, where the lowland forest meets the lower slopes of the Andes mountains, is the most diverse area of all. Here, there is a long geological history of expansion and contraction of rainforest habitat, resulting in periods of isolated forest "refugia", followed by periods of contiguous forest, allowing for the diversification of many groups of organisms. Sea-water intrusion into the western Amazon lowlands, and the rise of the Andes mountains contributed further to the creation of a diversity of habitats, permitting a greater diversity of species. Today, although this portion of the Amazon may appear quite uniform at a casual glance, the soils, geography, water chemistry, and hydrology combine to produce great variation in plant and animal communities. The great rivers themselves are barriers for many animal species, with sister species being found on opposite banks.

What exactly is "BIODIVERSITY"? It is more than a simple listing of species that can be found in an area. Alpha-diversity is the number of species encountered in a set area, say an acre or hectare of rainforest. The more species present, the higher the Alpha-diversity. Beta-diversity is the change in species that might be found as you move from one acre to the adjoining acre. If completely different species are found in the two adjacent areas, then Beta-diversity would be very very high. The western Amazon area has high Alpha- and Beta-diversity! But biodiversity is still more than either Alpha- or Beta-diversity. It is also the the sum of the interactions between species, with the number of potential interactions increasing exponentially with increasing numbers of species. If an area has only 5 species, for instance, there is the potential for 10 different 2-way species interactions. With 10 species, however, the potential number of 2-species interactions increases to 45, and with 15 species, to 105 interactions. When potential 3-way (or higher level) potential interactions are added in, the numbers become larger even faster. Imagine the potential numbers of all interactions in an ecosystem with millions of species!

HOW MANY SPECIES ARE THERE IN THE AMAZON?

We don't know. We don't even have a clue, really. Scientists have described less than two million species on the entire planet, but estimates of the total number of species present range from about 10 million (the very low end of the estimate scale) to over 100 million species. A majority of these undescribed and unknown species are in the tropics, and a sizeable proportion are certainly in the Amazon. Most of the species yet to be discovered and described are small or inconspicuous insects, fungi, protozoans, algae, mites, bacteria, and the like. These organisms play crucial roles in the functioning of ecosystems, and in the recycling of nutrients, fixing of nitrogen, creation of soil, and as the base of the food chain for larger organisms. The Amazon can survive (albeit diminished) without Jaguars, but it is doomed without fungi. Not all undescribed species are small. At the Project Amazonas field sites alone, several new species of fish have been discovered over the past years, and in May 2002, a distinctive new species of tree over 100' tall was discovered by a visiting botanist. This Podocarpus tree species is still known to science only from a single individual -- lucky it wasn't logged out before the place where it grows became part of the Madre Selva Biological Station!

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