Biologists say the sixth mass extinction episode on Earth is already happening. But researchers say if we only look at species extinctions, we miss a big part of the story.
Paul Ehrlich is a professor emeritus of biology at Stanford University, and an author of a new study about this published in Proceedings of the National Academy of Sciences.
He and his colleagues write in the paper that two vertebrate species go extinct every year on average. But not a lot of people notice, because they tend to be obscure creatures, such as the Catarina pupfish (a little fish from Mexico) or the Christmas Island pipistrelle (a bat on a Pacific island).
“And although that rate of extinction is maybe 100 times the background rate that’s persisted for the last millions of years, it’s indicative that we’re moving into another mass extinction event," Ehrlich says.
“And what our new paper shows is that we’re right in the middle of it. That is in fact, although we’re not losing species, the loss of individuals and populations is horrendous, and of course that’s what makes a big difference to human beings because we’re utterly dependent on the populations of other organisms, other plants and animals on the planet, for the persistence of our civilization.”
Ehrlich says although it's crucial to pay attention to species extinction events, we also need to be aware of population declines, because those are the preludes to extinction.
“For example, let’s suppose that all the bees in North America, the honey bees, were wiped out. The honey bee species would not be gone; we would have had no loss of species, but we lose something on the order of $18 billion worth of pollination services and the quality of our diets would plunge.”
He says estimates show that in the last 40 or 50 years, we’ve lost about half of the wildlife on the planet, even though we haven’t lost half of the earth’s species.
“It means we've lost half of the individuals, and of the populations. We’re sawing off the limb that we’re sitting on. It’s largely a political and economic problem,” says Ehrlich.
“That is, everybody realizes that the basic cause of the extinction crisis as well as the climate crisis, which is tightly tied to it because climate change tends to wipe out populations as well, is due to the fact that we’re vastly overpopulated as people and that we consume - the rich - consume much too much, and it’s very difficult to see this happening in a world where people believe in the fairyland tale that you can grow forever on a finite planet.”