Narrator: This is Science Today. With many populations of animal species classified as endangered, scientists have warned that the Earth is on the brink of a mass extinction like those that occurred five times before during the past 540 million years. Paleobiologist Anthony Barnosky of the University of California, Berkeley, compared the current extinction crisis with the "Big Five" mass extinctions of the past.
Barnosky: And to some extent, determine how far we've come towards a real mass extinction and how long it would take us to get to a magnitude of extinction that is characteristic of these very dramatic events in Earth's history.
Narrator: They found that a sixth mass extinction could arrive within as little as three to 22 centuries, but Barnosky stresses that it's not too late — especially since, unlike previous extinctions, this time humans are causing it.
Barnosky: We can set aside places to protect other species and putting a lot of energy and resources towards doing that, we can turn around this problem and avert the sixth mass extinction.
Narrator: For Science Today, I'm Larissa Branin.