How diverse is biodiversity? The answer is as uncertain as the question is compelling. Without knowing what’s out there, it’s hard to save it. Yet after centuries of discovering, naming and classifying living things, scientists have only scratched the surface.
To date, some 1.7 million species have been formally described. But intensive spot sampling of insects—by far the most populous taxon—combined with sophisticated extrapolation exercises suggests we’re only just beginning to understand the extent of life on Earth. Current best guesses are on the order of 12.5 million distinct species, give or take 5 million.
Around the world, biologists continue to discover new creatures at the tops of trees or bottoms of seas. Even as they do, others debate what, exactly, “species” means—or whether it has any useful meaning at all. Regardless of the outcome of that argument, it’s becoming increasingly clear that we need to consider all forms of biodiversity—genetic and ecosystem as well as taxonomic—in deciding how to best sustain the systems that sustain us.
As myrmecologist E.O. Wilson observed: “Since we depend on an abundance of functioning ecosystems to cleanse our water and manufacture the very air we breathe, biodiversity is clearly not an inheritance to be discarded carelessly.”