Study: World is undergoing mass extinction

SANTA BARBARA, Calif., Oct. 21 (UPI) -- U.S. scientists say the Earth is in the midst of its sixth mass extinction of plants and animals, with nearly 50 percent of all species disappearing.

Biologists at the University of California-Santa Barbara say they are working to determine which species must be saved.

"The current extinction event is due to human activity, paving the planet, creating pollution, many of the things that we are doing today," said study co-author Assistant Professor Bradley Cardinale. "The Earth might well lose half of its species in our lifetime. We want to know which ones deserve the highest priority for conservation."

Cardinale said the last mass extinction near the current level, the Cretaceous Tertiary extinction, occurred about 65 million years ago when a meteor struck the Earth. It's best known for causing the extinction of non-avian dinosaurs, as well as numerous plant species.

"Given that we are losing species from ecosystems around the world, we need to know which species matter the most and which we should pour our resources into protecting," said first author Marc Cadotte.

Cadotte, Cardinale and co-author Associate Professor Todd Oakley report their findings in the Proceedings of the National Academy of Sciences.