10 million years might be needed to recover massive extinctions

If humans cause the sixth mass extinction on Earth – something that may already be happening – how long will it take for life to regenerate on the planet? CO2 stays in the atmosphere for thousands of years, but a new study suggests that it will take a lot, a lot more time than restoring biodiversity.

"We believe we are approaching a massive extinction due to the loss of our habitat and a host of factors, including climate change," said Andrew Fraass, a paleobiologist at Bristol University and author of the study. published in Nature Ecology and Evolution. "This work, and the work on which it is based, basically suggests that we will have to wait millions of years for the biosphere to recover."

The researchers studied the fossil record after the last mass extinction, when an asteroid crashed into the Yucatan Peninsula, causing a tsunami, spilling vaporized debris into the atmosphere, warming the air. 39 atmosphere and destroying the dinosaurs and about 75% of the species present on Earth. . "It's the only thing that's happening faster than modern climate change, because it's happening in one day, then pieces of North America are igniting and all these deaths and destruction are happening," says -he.

Tiny plankton called foraminifers appear in detail in the fossil record, which allowed the researchers to see how they got out of it. After the massive extinction of the Cretaceous, the number of plankton species has increased from tens to a handful. It took about 10 million years for diversity to return, as species became more and more specialized. How long can it be expected to take again if we experience a similar level of species loss?

Fraass says it's hard to determine if the world is already experiencing another massive extinction now – or just about to be – partly because scientists have little information about species in past eras, so it is difficult to compare them. (The plankton fossil is much stronger than other species.) But there are many signs of precipitous decline. A recent study found that 40% of insect species are threatened with extinction. A 2015 study of mammals, amphibians, birds and reptiles found that the average extinction rate was now up to 100 times higher than normal. As coral reefs die, marine species also die. On land, 1,700 species are at risk of extinction within 50 years due to the only loss of habitat. Another study found that humans can cause the disappearance of so many mammals in 50 years that it will take at least 3 million years for biodiversity to recover. But it can take even longer.