President Barack Obama last month designated three new national monuments in the California desert: Mojave Trails, Sand to Snow and Castle Mountains. All in all, the new monuments protect nearly two million acres of sand dunes, lava flows, snow-capped peaks and Native American trading routes. Player utilities PopoutShare 00:0000:00 download Listen to the Story. But if you add it all up, the tally of protected land in the US is still only about 14 percent; worldwide, it’s about the same. And that, argues Harvard biologist Edward O. Wilson, isn’t nearly enough to stave off another mass extinction of the world’s biodiversity. If we want to preserve our wildlife, Wilson says, we need to set aside at least half of the world’s lands and seas. “At one half,” Wilson says, “we are now very roughly in a position of moving the extinction rate … down to 10-20 percent over what’s going to happen if we leave it alone.” Wilson argues that setting aside half of the Earth for preservation is not as difficult as it sounds.