(I).. tried to answer the question of how many tree species there are in the Amazon (about 16,000) and how abundant each of those species are (anywhere from dozens to billions of individual trees). Our estimates were respectable enough to be published in Science, but in retrospect one of our main findings seems almost preposterous. What the models tell us is that several thousand of the tree species that grow in the Amazon are so rare that scientists will never find them.
The math is straightforward. If you are one of the species that the models estimate has a population of fewer than 1,000 individual trees in the Amazon, then the probability of finding you among all 390 billion trees in the basin is so infinitesimal that it’s hardly worth calculating. For a boots-on-the-ground example, a couple of months ago I was in a remote area of Peru where I spent practically every daylight hour surveying trees. In two weeks I looked at about 2,000 trees. According to the numbers in our paper, the chance that I encountered one of the rarest species is about one chance in 200,000.
A colleague of mine calls this our “dark biodiversity” problem. Just as the astrophysicists’ models tell them that half of all the matter in the universe is invisible to science, so our models seem to be telling us that a large portion of Amazonian biodiversity is invisible to science—that is, lives and dies at densities below our capacity to see it. The numbers are pretty unforgiving. If instead of two weeks in Peru I had stayed on for 20 years—no weekends, no holidays, no sick days, just tree after tree after tree—my odds would have improved to about 1 in 4,000. Where does it all leave us? Back in a dark wood, apparently.
