one of them for this is professor tom crowther from the swiss federal institute of technology in zurich welcome to day w didn't we already know that trees absorb carbon dioxide and there are lots of tree planting schemes already out there to offset environmental damage. yes you're exactly right we've known that trees are an amazing carbon trap from the last well over the last century and there are projects out there trying to promote restoration but what this new study shows is actually we've got the 1st quantitative understanding of how much that can achieve and it's actually 10 times more than we previously expected placing restoration far far higher than the next best climate change solution so it's really about figuring out the best ways to allocate our resources and now we know that restoration is a powerful way a trillion trees sounds like an awful lot how much space is that going to take why would they go. so that's what we've modeled as way trees can exist on the planet and when you subtract away existing urban land and agricultural land we're left with the world's degraded land