What a difference a leaf makes! Well, not one leaf. We have 3.1 trillion trees on our planet—that’s 422 trees per person. If we count all the leaves on all those trees and take a look at what they do collectively to the air around us, the effect—and I do not exaggerate—is stunning. I’ve got a video from NASA. When you see it, I think your jaw is going to drop—just a little.

It tracks the flow of carbon dioxide across the planet over 12 months, starting in January. Most of the action takes place in the Northern Hemisphere because that’s where most of the land is, and so that’s where most of the trees are. The biggest temperate