Imagine that all over America, people were to start planting trees in their backyards suited for the ecology that will be arriving in their areas half a century from now. Imagine that some of them looked up what the climate in their neighborhood was like 6000 years ago during the Hypsithermal, others simply looked at what grows in climates a few hundred miles further south, and still others used whatever other guidance that appealed to them. Imagine that fifty years from now, some of those trees will have grown to maturity, and will then provide food and habitat for birds, insects, and other living things that have relocated with the changing climate. That’s the same strategy the Ice Age hunters used to make the glacial tundras more habitable in another era of climate change. One essential principle in making it work is that it should not be organized; above all, there should be no officially promulgated list of approved plants. Dissensus—the deliberate avoidance of consensus—is essential in uncertain times. When nobody can know in advance what the right choice will be, encouraging people to make as many different choices as possible maximizes the chance that some of the choices will work.