Some 65 million years ago, when the dinosaurs went extinct, approximately 75 percent of the planet's species went with them.

Earth might be on the cusp of a sixth mass extinction, according to a study released on July 25.

"Human impacts on animal biodiversity are an under-recognized form of global environmental change," the team of ecologists and biologists said in Science. "Among terrestrial vertebrates, 322 species have become extinct since 1500, and populations of the remaining species show 25% average decline in abundance." 

A third of all vertebrates "are threatened or endangered," according to the scientists.

The study points to "overexploitation, habitat destruction, and impacts from invasive species" as continuing threats, but mentioned that soon, human-caused climate change will be the top driver of defaunation.

Diseases that come from pathogens introduced by humans are another threat to worry about.

"To avoid the sixth mass extinction we will probably have to employ more aggressive conservation, such as moving species to help them cope with a changing climate," said David Biello in Scientific America. "Think re-wilding: reintroducing species like wolves or beavers that were once present in a given ecosystem but have since disappeared. Aggressive conservation might also mean killing off newcomer species to preserve or make room for local flora and fauna."

Researchers said that we've already made headway in saving some animals from extinction but more needs to be done.

Over the last 500 years, 322 species have become extinct.

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