Editor’s note: Welcome to Grist’s presentation of Alex Steffen’s new book Carbon Zero. We’ll be posting a new chapter every day till we’re done — here’s the full table of contents. And this post will tell you a little more about the project. If you like what you read, you can order Carbon Zero from Amazon.

Sustenance: Bringing cities and nature together

Everything in the human world originates in nature: Everything around us is made of parts that are either mined or grown. Most of our attention, when it comes to climate, is on the mined — particularly on the effects of burning mined fossil fuels, like coal, oil, and gas. And these fossil-fuel emissions are by far the biggest danger we face, and so focusing on them makes sense.