A cosmic collision with a rock more than 6 miles wide triggered Earth’s last mass extinction, wiping out the dinosaurs along with three quarters of all species that lived on the planet 66 million years ago.

This time around, we are the meteor.

Human-caused climate change could drive close to a third of all plant and animal species worldwide to extinction in the next 50 years, according to a new study by researchers at the University of Arizona.

Without a concerted effort to curb global warming, roughly 3 million species could be lost by 2070, warned UA professor John Wiens, who co-authored the study published last week in the Proceedings of the National Academy of Sciences.

“What happens is up to us,” Wiens said. “If we do nothing, there’s going to be a massive loss of species. If we take action … we can cut that in half.”

The startling findings are based on analysis of historical data from 538 plant and animal species at 581 sites around the world, close to half of which had already vanished from some local areas where they were once found.