In 2019, a study led by Zurich's Crowther lab analyzed satellite imagery of the world's existing tree cover. By combining it with climate and soil data and excluding areas necessary for human use, they determined Earth could support nearly one billion hectares of additional forest. That's roughly 1.2 trillion trees. This staggering number surprised the scientific community, prompting additional research. Scientists now cite a more conservative but still remarkable figure. By their revised estimates, these restored ecosystems could capture anywhere from 100 to 200 billion tons of carbon, accounting for over one-sixth of humanity's carbon emissions. More than half of the potential forest canopy for new restoration efforts can be found in just six countries. And the study can also provide insight into existing restoration projects, like The Bonn Challenge, which aims to restore 350 million hectares of forest by 2030. But this is where it gets complicated. Ecosystems are incredibly complex, and it's unclear whether they're best restored by human intervention. It's possible the right thing to do for certain areas is to simply leave them alone.