"What Is Wilderness?" asks what wilderness actually is. We learn that the greatest biodiversity occurs where large grazing animals are part of the habitat, yet the species-rich megafauna that once existed disappeared from Europe with the arrival of modern humans. Domestic animals, too, can provide the same “ecosystem engineering services” when they graze in the right numbers as substitutes for the large herbivores that have been driven to extinction. This offers an opportunity for our future, not only because wild pastures have been shown to store more carbon than forests. Wherever many natural processes are allowed to take place, we can achieve a state that resembles wilderness. Perhaps it is a new kind of wilderness, but one that is beneficial and important for biodiversity, animal welfare, and the climate.