It’s been 65 million years since the last mass extinction on Earth, when the dinosaurs died off. In other words, mass extinctions are rare and catastrophic events–not ideas to be taken lightly. A new study concludes that the planet is entering the next mass extinction, and this time the cause isn’t asteroids or toxic volcanoes, but us.
“Usually mass extinctions have occurred in periods of thousands or even millions of years,” says the study’s lead author, Gerardo Caballos of the National Autonomous University of Mexico, who worked with researchers from Stanford University, Princeton University, and the University of California-Berkeley. “The current extinction rate is wiping out hundreds of species in 100 years. And it is the tip of the iceberg; many species are critically endangered.”
Extinctions are notoriously hard to track; scientists estimate that there may be around 8.7 million species on Earth, and we don’t know about the vast majority of them yet, let alone whether they’ve disappeared. When researchers think that a species is extinct, it can take years to verify that fact, especially if it lives in remote locations. It’s also hard to track what the “normal” rate of extinction has been in the past.
So the researchers used only the most conservative estimates, looking at the highest rate of past extinctions in the fossil record, and the recent extinctions that have been verified. They found that under normal rates, there would have been nine extinctions in the 20th century. Instead, there were 468, from the Bali tiger to the Western black rhino.
“We wanted to evaluate if even under the most constrained conditions we could detect that we are entering a mass extinction,” says Caballos. “So there is no doubt we are in a sixth mass extinction.”
The study doesn’t even factor in the pressures of climate change or ocean acidification–just the extinctions that have happened as a result of other human activity, such as overfishing and deforestation. It’s the first time in the planet’s history that a single species has commandeered so much of the world for itself; humans make up a third of the vertebrates on land, and the animals we raise for food make up most of the rest. Wild animals are now less than 5% of the total population.
This isn’t just bad news for bears or birds. In many situations, humans rely species, like crop-pollinating honeybees, that are rapidly dwindling. Within three human lifetimes, the study says, our ecological life support system could be destroyed. Still, the researchers argue that it’s not too late to turn things around.
“We need to get our act together understanding that the current extinction rate and other environmental problems threatens us,” says Caballo. “We do not have a choice. Unless we act fast, really fast, we may face catastrophic scenarios. But I am optimistic. We humans have the capability to do it.”