Sixty-five million years ago, the dinosaurs disappeared in what’s known as the Earth’s fifth mass extinction. Today, a sixth mass extinction could be well underway and humans are the likely culprit.
The past five mass extinctions on Earth were caused by large-scale natural disasters like meteors or enormous chains of volcanic eruptions, wiping out between half and 96% of all living species.
We’ve long known that human actions—cutting down forests, building cities and using up natural resources—puts animals in danger, and can even drive them out of existence. Now, a new study has found that vertebrates—or creatures with a backbone—are dying much, much faster than they should be.
Researches from Mexico and the US wanted to compare the rate of extinctions in the last century to what is known as the “background rate”—the rate at which species have died off in previous centuries. They found that vertebrates, or animals with a backbone, were dying at a rate 114 times faster than the overall background rate for vertebrates, based on a conservative estimate.
The new study, published today in Science Advances, explains that we are suffering extremely elevated levels of species losses. It’s not an issue of a snowy owl there or a tree frog there. We’re talking about thousands upon thousands of species going extinct, which will lead to a loss of biodiversity. Without that much-needed diversity in an ecosystem, indicating that a sixth mass extinction is already under way. The risk is that food sources will dwindle — one frog going extinct can mean that the birds who feed on it go extinct, which means the cats that eat those birds go extinct, and so on. Before you know it, the food web has collapsed and rates of extinction go sky-high.
Using the background rate as a guide, researchers said that only nine vertebrate extinctions should have occurred since 1900. In fact, 477 vertebrates became extinct during that time period, including 69 mammal species, 80 bird species, 24 reptiles, 146 amphibians, and 158 fish.
Ehrlich said parrots, raptors and penguins, large mammals and small insects, including the honey bee, are now in danger. The coral reefs could be gone by 2070, he said, a disaster that could precipitate the loss of as much as a quarter of the ocean’s species.
“There are examples of species all over the world that are essentially the walking dead,” Ehrlich said.
The report concludes that people are at fault for this “global spasm of biodiversity loss.”
“If it is allowed to continue,” said co-author Gerardo Ceballos, a scientist in Mexico, “life would take many millions of years to recover, and our species itself would likely disappear early on.”
[read the full scientific paper in Science Advances]