Animals are dying off in the wild at a pace as great as the extinction that wiped out the dinosaurs about 65 million years ago because of human activity and climate change.

Current extinction rates are at least 12 times faster than normal because people kill them for food, money or destroy their habitat, said Anthony Barnosky, a biology professor at the University of California-Berkeley.

“If that rate continues unchanged, the Earth’s sixth mass extinction is a certainty,” Barnosky said. “Within about 200 to 300 years, three out of every four species we’re familiar with would be gone.”

The findings, aired in a documentary on the Smithsonian Channel on Nov. 30, add to pressure on envoys from some 190 countries now gathering at a United Nations conference in Peru to discuss limits on the greenhouse gases blamed for global warming.

“We might do as much damage in 400 years as an asteroid did to the dinosaurs,” said Sean Carroll, a biologist who leads the Department of Science Education at Howard Hughes Medical Institute in Bethesda, Maryland. He was also interviewed for the documentary.

Temperatures already have increased by 0.85 of a degree since 1880 and the current trajectory puts humanity on course for a warming of at least 3.7 degrees Celsius, the U.N. estimates. That’s quicker than the shift in the climate when the last ice age ended about 10,000 years ago.

“We would have an extinction crisis without climate change simply through how we use land and water and population growth,” Carroll said. “But now you add to that this global force of climate change and that changes relationships between species and ecosystems in unpredictable ways.”

Warmer temperatures are having a perverse impact on some animals. Grizzly bears and red foxes move north and come in contact with polar bears and arctic foxes, said Elizabeth Hadly, a biology professor at Stanford University who specializes in animal diversity, another subject of the documentary.

The arctic fox is now in decline because red foxes are more aggressive, Hadly said. Grizzly bears and polar bears sometimes mate, and that produces offspring with neither camouflage for the snow nor the ability to hunt in the woods.

The number of animals in the wild has about halved in the past 40 years mainly because humans have moved into habitats, competing for space and water supplies, according to a report by the environmental group WWF and the Zoological Society of London released in September.

“The hybrids aren’t really adapted for either environment,” Hadly said. “Climate change will cause more of those unpleasant surprises.”

The impact isn’t confined to land. The amount of ocean acidification projected by scientists by 2100 is “very similar” to levels about 252 million years ago at the end of the Permian epoch, Earth’s most severe extinction event to date, Hadly said. The planet took millions of years to recover from that shock, which wiped out about 95 percent of marine species and 70 percent of land organisms.

“We are approaching the conditions where all shelled creatures have trouble making shells,” Carroll said. “Extinction in the oceans will directly impact humans as we rely on them for food.”

Species can be brought back from the brink. In the U.K., red kites, a bird of prey, has gone from almost extinct in the wild to about 2,000 breeding pairs because of a successful reintroduction program, said Robin Freeman, head of the indicators and assessments unit at the Zoological Society of London.

“If we can bring together the political will, the business pressure and reduce our personal footprints, we can move toward a place where these declines aren’t inevitable,” Freeman said in a video message on the conservation’s group’s website.

So far, Earth has lost only about 1 percent or less of species that have been on the planet for the past 12,000 years, according to Carroll and Barnosky. Humans can in the short term clamp down on poaching and invasive species, reduce over- harvesting and expand marine and land preserves where species can recover, Carroll said. Longer term, human consumption needs to become more sustainable and carbon output reduced, he said.

“We still have a chance to save almost all the species,” Barnosky said. “It’s not too late but the window of opportunity is closing fast.”

In a time of both misinformation and too much information, quality journalism is more crucial than ever.
By subscribing, you can help us get the story right.