The biodiversity crisis is a math problem. Unlike most math problems, however, this is one where getting hung up on the precise numbers can lead you astray. Maybe 1 million species are at risk of extinction. Or if you’re going by species that scientists have specifically identified as threatened, it’s 42,100. But neither of these is exactly right. At least we can agree that extinction rates are 1,000 times higher than historical averages. Or is it 100 times higher?
Here’s the thing: Whichever numbers you plug into the calculation, you get the same result. The planet is in a dire state. There are many, many more species faced with extinction than we can realistically save. We’re in an emergency, and in emergency situations we need to triage our victims.
Picking which species to protect and which to sideline is right at the heart of conservation, but we don’t talk enough about how these decisions are made. Do we pick species that are culturally significant, like the bald eagle? Or maybe we should focus on medicinally useful plants? What about species that are critical parts of their ecosystem? Or the ones that are most under threat? Then there are creatures that grab our attention because they are cute, charismatic, or—in the case of meerkats—the cheery, anthropomorphized face of a long-running British ad campaign to sell car insurance. Simples.
There is another way of thinking about animals that can help us decide which species to protect. Rikki Gumbs, a conservationist at the Zoological Society of London, argues that we should be focusing more on species that are both evolutionarily distinct and endangered. This approach can lead us toward all kinds of strange and wonderful creatures. Take solenodons, for example. This shrew-like animal is one of the very few venomous mammals that exist today. The two living solenodon species diverged from other mammals around 76 million years ago. That is a lot of evolutionary history on those very small, very hairy, shoulders.
Luckily, scientists have a way of measuring just how unique and at-risk certain species are. In 2007, conservationists devised a metric called EDGE. It stands for “evolutionarily distinct and globally endangered,” and it was developed as a way to prioritize species for conservation that represented a large chunk of evolutionary history. To rank highly in terms of EDGE scores, a species has to be evolutionarily distinct, have very few close living ancestors, and be extremely endangered.
Gumbs calls these species “weird and wonderful”—they diverged so long ago from their ancestors and have so few living relatives that they stick out to us as unusual. Species like this are—to use Gumbs’ word—edgy. Another edgy animal is the Madagascar blind snake, a bright pink burrowing reptile that diverged from its closest living relative around 65 million years ago.