The “Sixth Extinction” Adds Urgency to Habitat and Climate Protection

The Northern Mexican gartnersnake (Thamnophis eques) lives in wetland areas alongside rivers.  Over 90 percent of its riverside habitat has disappeared in the last century due to overgrazing, water diversions, wildfires and drought.  A proposed diversion of the Gila River in New Mexico poses a new threat. Photo by Doug Hotle/ABQ BioPark
The Northern Mexican gartnersnake (Thamnophis eques) lives in wetland areas alongside rivers. Over 90 percent of its riverside habitat has disappeared in the last century due to overgrazing, water diversions, wildfires and drought. A proposed diversion of the Gila River in New Mexico poses a new threat. Photo by Doug Hotle/ABQ BioPark

It’s now unequivocal: the sixth great spasm of species extinctions has begun. We – homo sapiens – are its cause. And only we can slow it down.

Over the last century, the average rate of loss of vertebrate species — fish, amphibians, reptiles, birds and mammals – has been up to 100 times higher than the background extinction rate, according to a new study published last week in the journal Science Advances.

In order to help settle the question of whether a sixth extinction episode has indeed begun, the scientific team chose assumptions that would tend to minimize evidence that it has. As a result, their calculations almost certainly underestimate the severity of the extinction crisis under way.

“[W]e can confidently conclude that modern extinction rates are exceptionally high, that they are increasing, and that they suggest a mass extinction under way – the sixth of its kind in Earth’s 4.5 billion years of history,” the researchers write.

The study team included scientists from Princeton, Stanford, the University of California-Berkeley, the Universidad Nacional Autónoma de México, and the University of Florida.

The last episode of mass extinction occurred about 65 million years ago, when the dinosaurs and about half of all species living on Earth at the time were wiped out.

A huge crater off Mexico’s Yucatán Peninsula dated to the time of this event suggests an extraterrestrial impact as a leading cause.

But, in a first, the current mass extinction is driven by human activities – deforestation, dam-building, over-harvesting, wetland-draining, —> Read More

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