Science has long informed the environmental movement. Now it must take the lead, because we are forced to enter an era of large-scale ecosystem engineering, and we have to know what the hell we're doing. That sermon gets a chapter. Beavers are benevolent ecosystem engineers; so are soil-enriching earthworms; so were American Indians, who terraformed a continent; so are all of us who work on restoring natural infrastructure. A chapter on that subject leads straight to the book's conclusion: our obligation to learn planet craft, to be as life-enhancing as any earthworm, in the big yard.