A new report is warning that the Earth is in the midst of a mass extinction of animals. 

The study by a team of scientists in Mexico and the US said nearly one-third of the species they looked at are in decline and three-quarters of the planets species could be gone within a hundred years.

At the California Academy of Sciences in San Francisco, people of all ages marvel at the massive collections – living and non-living – that showcase life on earth. It’s not hard to find endangered species like these African penguins, which are here as part of an international captive-breeding program to save it from extinction.

It may not be enough. Conservationists said African penguins have been “sliding towards extinction.” And they have plenty of company, a new study said the earth is witnessing a “biological annihilation.”

“It was surprising and eye-opening to me in that it’s really highlighting this point that this is all happening faster than we expected,” Michelle Trautwein, an evolutionary biologist at the California Academy of Sciences said.

“What makes the planet Earth unique in the universe is that we have this incredible diversity of life and it shows us we are doing a pretty poor job of being caretakers of the species all around us.”

Analyzing nearly half of all known vertebrate species, the study found nearly a third are decreasing in population size and range.

The study also conducted detailed analysis documenting 177 mammal species from 1900 to 2015.  Scientists discovered that all of them have lost at least 30% of their geographic ranges and that at least 40% experienced severe population decline.

“The plants, other animals and microorganisms of the planet are our life support systems,” said evolutionary biologist Paul Ehrlich at Stanford University. “Humanity absolutely depends on them to maintain its civilization. So when we wipe them out, what we are basically doing is sawing off the branch that we are sitting on.”

Ehrlich is one of the professors who conducted the research. He cites overpopulation, overconsumption and climate change as key drivers of this decline.

“Organisms did not evolve to live in strip malls, sewers, houses, farm fields and so on,” Ehrlich said. “And what we are basically doing, as the human population grows and our consumption patterns grow, is destroying the habitats that our life support systems need to persist. So the basic problem is really economic and political, that is–how do you move from a world where most politicians ignorantly think you can grow forever, and move toward shrinking the human population and reducing consumption.”

Ehrlich points to severe population declines in bats and polar bears in North America. 

His message can be an unpopular one. Ehrlich faced criticism in the ‘70’s over past predictions that overpopulation would lead to disaster.

“If people accuse me of being a doomsayer, I am a doomsayer,” said Ehrlich. “We’re in desperate condition. There’s a lot of controversy about how long the past extinctions took, but for example the biggest of all, the Permian – the one at the end of the Permian – may have taken millions of years. We’re going to get the job done in a century or so.”

Instead of focusing on endangered species lists, Ehrlich said wildlife population declines paint a more accurate picture of where the Earth is headed.