Life on Earth is hurtling toward extinction levels comparable with those after the dinosaur-deleting asteroid impact of 65 million years ago, propelled forward by human activities, according to scientists from UC Berkeley.
This week, scientists announced that if current extinction rates continue unabated, and vulnerable species disappear, Earth could lose three-quarters of its species as soon as three centuries from now.
“That’s a geological eyeblink,” said Nicholas Matzke, a graduate student at UC Berkeley and author of a paper describing the doom-and-gloom scenario. “Once you lose species, you don’t get them back. It takes millions of years to rebound from a mass extinction event.”
This means that not too far in the future, backyards might not be buzzing with bees, bombarded by seagulls or shaded by redwood trees. And while that might seem far off, species already are disappearing on a global scale. In recent history, we’ve lost the dodo bird and the passenger pigeon, the Javan tiger and the Japanese sea lion, and now, maybe the eastern cougar — declared extinct by the U.S. Fish and Wildlife Service on Wednesday. Amphibians, mammals, plants, fish — none are immune to going the way of the dinosaurs, courtesy of the human impact on fragile ecosystems.
Such enormous losses have only occurred five times in the past half-billion years, during events known as “mass extinctions.” The best-known of these events occurred 65 million years ago — a “really bad day,” according to paleontologists — when an asteroid collided with Earth, sending fiery dust into the atmosphere and rapidly cooling the planet. These “Big Five” events set the extinction bar high: to reach mass-wipeout status, 75 percent of all species need to disappear within a geologically short time frame, meaning that Earth is currently on the brink of the sixth mass extinction. (more…)
