CHAPTER 12
OUR DIMINISHING TROPICAL FORESTS

PETER H.RAVEN

Director, Missouri Botanical Garden, St. Louis, Missouri

In any discussion of biological diversity, tropical forests must occupy center stage. Broadly defined, these forests are home to at least two-thirds of the world’s organisms, a number that amounts to no fewer than 3 million species, and could be 10 or more times greater than that amount. Striking, however, is the fact that only about 500,000 species from the tropical and subtropical regions of the world have been given names and been cataloged in the scientific literature. This means, very simply, that where one might expect to identify the great majority of any collection of insects or other arthropods made within the boundaries of Europe or temperate North America, only a very few of those in any reasonably diverse sample of tropical organisms—at least among relatively small and inconspicuous groups—could be located in the world’s collections, or are mentioned in the world’s literature.

Even among those very few, only a tiny fraction would be known from more than one or several specimens, a few short lines of technical description, and a locality. In short, identifying them would not provide much help concerning their ecology, their evolutionary relationships, their behavior—or any of the components that might have been involved in their history, or that might contribute to their chances of survival. Such matters must be considered seriously as we learn more about the diversity of organisms itself.

Regardless of whether there are 2.5 million more tropical organisms to be named or 25 million, the task facing us is enormous. All the activities of all those concerned with cataloging organisms over the past centuries in all types of ecosystems throughout the world have resulted in the naming of only about 1.5 million of them, and a task at least twice, and perhaps many times, that large confronts us now. All the scientific and societal gains that depend on an increased knowledge of these



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