in the central Amazon around Manaus, Brazil, I showed that 83% of the beetle species in the samples were found in only the samples of one of the types of forest, 14% of the species were shared between two, and only 1% of the species of beetles was found in all four forest types (Erwin, 1983a). This added fuel to the “numbers” controversy, because of the numerous types of forest known to exist in the Amazon Basin alone and the fact that the analysis was based on more than 1,000 species of beetles, a fairly substantial data base. At this point, I turned my attention to the now well-refined sampling techniques of insecticidal fogging of forest canopies at the Tambopata Reserved Zone in the southeast corner of Amazonian Peru. I developed these techniques for the purpose of testing the main hypothesis regarding biological diversity in tropical forests and the subhypothesis that host specificity is a main feature of the lifestyle of tropical canopy insects. The following paragraphs provide some glimpses of the Tambopata Canopy Project, some preliminary observations on the fauna itself, and what I believe to be the status of the 30 million species hypothesis. With a data base of a million specimens (we’ll get to the number of species later), it will take a long time to complete the data analysis from just 1 year of collecting.

THE PROBLEM

It has been predicted that in 25 to 30 years, much of the humid tropical forest could be gone or severely converted (see Raven, this volume, Chapter 12). Between 25 and 40% has already been lost to misguided human exploitation. The best estimate is that an area the size of Honduras is being lost or converted each year, and by the year 2000 some popular accounts have predicted that a million species will become extinct. Although I regard such guesses as a bit low, a point discussed later in this chapter, they mean that in our generation we, the only species on Earth with the mental capacity to reason, will see the virtual disappearance of contiguous tropical forests and probably the extermination of more than 20% of the diversity of life on Earth, and we humans will have caused it.

THE HISTORY

The Amazon basin (Figure 13–1) has the richest biota on Earth. There are several factors involved, not the least of which is the sheer size of the basin. We must start the historical analysis with the Amazon basin as it was on the western portion of the megacontinent Gonwanaland some 100 million years ago. The biota of today is a result of many events that occurred after two supercontinents, South America and Africa, rifted, and South America drifted in a westerly direction. As this occurred, the uplift of the Andes began. This wonderful mountain chain, extending from Venezuela down into Chile, became a dike that reversed the western flow of all the rivers of Gonwana, turning them around and beginning their flow to the east. In the last 40 million years, this event has caused a mosaic of habitats, the fine-grained resolution of which we have no comprehension at this time. As I am discovering in some of my work in Peru, the fine-grainness of habitats is far, far greater than what the botanical classifications have led us to believe. We need



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement