'Sixth Extinction' May Have Begun on Earth: Humans and Other Species at Risk

First Posted: Jun 19, 2015 05:31 PM EDT

A sixth mass extinction may have begun. Scientists have used highly conservative estimates to prove that species are disappearing faster than at any time since the time of the dinosaurs.

There is general agreement among scientists that extinction rates have reached levels unparalleled since the dinosaurs died out about 66 million years ago. However, some have challenged this theory, believing that earlier estimates rested on assumptions that overestimated the crisis.

In this latest study, though, the researchers found that even with extremely conservative estimates, species are disappearing up to about 100 times faster than the normal rate between mass extinctions, known as the background rate.

"If it is allowed to continue, life would take many millions of years to recover, and our species itself would likely disappear early on," said Gerardo Ceballos, the lead author of the new study, in a news release.

In this latest study, the researchers used fossil records and extinction counts from a range of records. They compared a highly conservative estimate of current extinctions with a background rate estimate twice as high as those widely used in previous analyses. This way, they brought the two estimates-current extinction rate and average background or going-on-all-the-time extinction rate-as close to each other as possible.

The researchers focused on vertebrates and found that at the lowest estimates, the difference between background and contemporary extinction rates justify the claim that a "global spasm of biodiversity loss" is occurring. In fact, the possibility of extinction hangs over about 41 percent of all amphibian species and 26 percent of all mammals.

As species disappear, so do crucial ecosystem services, such as honeybees' crop pollination and wetlands' water purification. At the current rate of species loss, people may lose many biodiversity benefits within three generations.

With that said, there are ways to help prevent this kind of mass extinction.

"Avoid a true sixth mass extinction will require rapid, greatly intensified efforts to conserve already threatened species, and to alleviate pressures on their populations-notably habitat loss, over-exploitation for economic gain, and climate change," write the study authors.

The findings are published in the journal Science Advances.