What does research on tree memory have to do with humans? In episode four, we answer this question by discussing the carbon cycle and how both trees and humans fit into it. Carbon is a key building block of both trees and humans—it’s also in our food, clothing, and energy systems, and it touches all of human society. We talk about trees’ role in humanity’s future as we rearrange Earth’s carbon, and we talk about what tree memory has to do with it all.