| Chambers Wildlife Rainforest Lodges |  |
|
High diversity in the tropical rainforests Tropical rainforests are of course well known for their high diversity of species. However, a real appreciation of the diversity of the tropics, the real number crunching of species diversity didn't occur until halfway through last century. With such huge areas as the Amazon and such a bewildering array of unidentified species, scientists couldn't just run off through the jungle counting species. So they sampled in quite small plots of a particular group of life forms. For example, scientists measured the species of trees found in a hectare. (A hectare is a square plot of area that is 100 meters by 100 meters. It's roughly 2 and a half times the size of an acre.) In this size plot, they were finding an average of between 60 to 150 species of trees in a lowland tropical rain forest. This didn't include bushes, shrubs, epiphytes, vines; it's just the trees. In very rich rain forest regions, such as western South America, or south east Asia, they might find over 200 or even over 300 species of tree per hectare (Richards 1996). But then scientists looked even closer. And they started to identify and count the life that was even more numerous in the forest than the trees, the invertebrates that lived amongst those trees. Again, it wasn't feasible to count everything, so they had to sample in small plots. But, instead of sampling a hectare, they'd sample a single tree. In 1982, (that's only 20 years ago), a scientist named Erwin, sampled 19 trees of one particular species over three seasons, and he found almost a thousand different beetle species alone. From these sample numbers, they extrapolated the figures. And Erwin himself did calculations from his own studies. And that's exactly what that guy Erwin did with his beetle count. Some say the results have been exaggerated, some say the results are too conservative. Estimates vary from 2 or 3 million species in the world, to Erwin's 30 million (Whitmore 199) to other estimates that run into hundreds of millions. And this was the pattern that began to emerge in studies of the distribution of organisms in the tropics. The graph below displays this popularity of the tropics with organisms. It is a classic pattern well known to biologists. This particular example is for swallowtail butterflies, but it is a trend that has been found in many organisms. For the larger animal, such as mammal and birds, there is roughly twice as many species in the tropics as in the temperate regions (Whitmore 1998). With the smaller critters, such as these guys, its probably even more. In one tree in Peru, scientists found 43 ant species; so in a single tree in the rain forest, there is more ant species than live in all of Canada (Whitmore 1998).
|
|
