Mezrich: ...This is the cool is the cool part of the story. Yeah, the tundra has a permafrost that’s like a ticking time bomb that if it went off would be worse than if we burned all the forests on Earth three times, and this permafrost is always getting close to melting ( Editor’s Note: Mezrich is talking about the potential for a catastrophic methane release from melting Arctic permafrost ) . These scientists, the Zimoffs, have been running this experiment since the 80s where they rope off a part of the tundra and repopulate it with Pleistocene type herbivores. They’ve put bison in, reindeer reindeer, horses, a WWII-era tank that they drive to mimic a mammoth, knocking down trees. And they’ve discovered they can lower the temperature by as much as fifteen degrees, which is an incredible thought (Editor’s Note: This is a speculative idea that Mezrich describes in more detail in the book, in which Pleistocene herbivores might help transition forests and shrub lands into grasslands, which absorb less heat.) The idea is to repopulate the area with mammoths. Church’s goal is 80,000 mammoths, and [he hopes that] you could lower the temperature of the permafrost for generations.