Recently, one of my colleagues, Brian Brown, found thirty new species of flies in urban Los Angeles. Species not yet named. Species not yet studied. Species that could be of great value to society (or, less likely, great cost) but that had just gone missed, flying among highways and movie stars.
The discovery made by Brown and his team is wondrous, revelatory, awesome, and makes me want to look for new species of flies in my own backyard. But, in a broad sense, it is not a surprise, for one simple reason, two hundred million species live on Earth and just two million of which are named. That is to say, 99 out of 100 species on Earth are not yet named.
Where did I get the number two hundred million from? I just made it up. Though, there is a little more history than that.
When I first started as a faculty member at North Carolina State University I wrote a book called Every Living Thing in which I tell the stories of, among other things, the quest to find and name all of the species on Earth; every, living, thing. This quest has several features that have recurred throughout history. First, in each generation people find it easiest to believe that most of life is discovered. In the 1700s, Linnaeus thought that he, personally, would find all the species on Earth, about, he thought, 12,000 species. In the 1800s, as more and more scientists explored the tropics, it became clear that Linnaeus was very wrong. The number of species on Earth moved up (individual scientists named thousands of new species) as enthusiastic field biologists came back from rain forests with boats full of new life.
When I was born, in 1975, to the extent that anyone talked about it at all, the sense was that there might be a couple of million species on Earth, with more than half of those probably already named (though no one had a tally at the time).
Then, in 1982, everything changed. For the first time someone tried to formally estimate the number of species on Earth, sort of. Terry Erwin, a beetle biologist used his knowledge of the number of arthropod species found in an average tropical tree (and specific to that kind of tree) to estimate the number of arthropod species on Earth. Actually, his estimate was more modest than that. He estimated the number of tropical arthropod species on Earth. His approach yielded the estimate that, as he puts it in the original two-page paper, “there are perhaps as many as 30,000,000 species of tropical arthropods, not 1.5 million! ” Erwin would later go on, informally, to suggest there might be as many as a hundred million species (of all life) on Earth.
Two things followed these estimates. The first was a series of passive aggressive responses from other scientists. Critics honed in both on Erwin’s equations and on the field measurements they depended on. The second was a series of spectacular attempts to actually try to find all of the species in particular places, a park in Costa Rica, a park in the Great Smoky Mountains, and Sweden.
At the time that I was writing Every Living Thing, the efforts to find all of the species anywhere had slowed. The leaders of these projects were valiant, emperors of biodiversity and yet ferociously underfunded ones. The attempts to estimate the number of species on Earth stalled too. Debate continued, but focused mostly on the potential number of species of tropical arthropods, not life in general. To the extent that a consensus emerged, it was a conservative one, namely that there were probably, at least, another six million arthropods to be named (which is to say, even by conservative estimates, something like six out of every seven arthropod species are NOT named). This was a smaller number than Erwin’s estimate and yet a number filled with caveats, a number that depended among other things on the assumption that in the unexplored parts of the world life more or less obeyed the rules discerned in the few sort of well-explored places. Even fewer studies commented on the rest of life, the bacteria, diverse worms, fungi, protists, viruses and the like (of note, in questions of biodiversity vertebrates are so unimportant as to disappear in the rounding error).