Extinctions During the Human Era are 1000 Times More Frequent Now Than Before

It turns out the current global extinction rate is far more devastating than first thought. Scientists have found out that species die off as much as 1,000 times more frequently today than they used to. That's 10 times worse than the previous estimate of 100 times.

About 60 million years ago, humans first arrived on the scene. Understanding how this impacted species at the time and afterward is an important part of learning how humans can influence their environment. In order to learn exactly what occurred, the scientists examined the fossil record, and also looked at evidence from the evolutionary family trees of numerous plant and animal species. Called phylogenies, these family trees are constructed by studying DNA and trace how groups of species have changed over time, adding new genetic lineages and losing unsuccessful ones. This revealed information about how species have diversified over time.

"The diversification rate is the speciation rate minus the extinction rate," said Lucas Joppa, co-author of the new study, in a news release. "The total number of species on Earth has not been declining in recent geological history. It is either constant or increasing. Therefore, the average rate at which groups grew in their numbers of species must have been similar to or higher than the rate at which other groups lost species through extinction."

The scientists honed their models by testing them with simulated data for which they knew an actual extinction rate. In the end, they found that there was a normal background extinction rate of .1 extinctions per million species per year.

"We've known for 20 years that current rates of species extinctions are exceptionally high," said Stuart Pimm, senior author of the study. "This new study comes up with a better estimate of the normal background rate-how fast species would go extinct were it not for human actions. It's lower than we thought, meaning that the current extinction crisis is much worse by comparison."

The findings are published in the journal Conservation Biology.