Signs of these costs are showing up everywhere, because ecosystem services are beginning to fail. After several record-breaking drought years, the Amazon is approaching a tipping point when its “rain machine” may malfunction, putting South American agriculture in peril. Australia’s rice and wheat crops are failing due to drought, sending worldwide wheat prices to a ten-year high. Emerging diseases are being unleashed as forests are cut. Honeybee colonies are vanishing, leaving commercial crops from avocados to oranges unpollinated. Water shortages, food riots, failed crops, the worldwide collapse of pollinators: this is only the beginning. Welcome to the demographic winter, the new hot season in hell.
But what if we had a choice? What if we could slow or even stop the Sixth Great Extinction? What if conservation could save us from the demographic winter?
It can. Conservation biologists have developed a number of methods for restoring the balance between ourselves and nature, for saving biodiversity. The most exciting and promising of these methods is rewilding. Proposing conservation and ecological restoration on a scale previously unimagined, rewilding has become a principal method for designing, connecting, and restoring protected areas—the ultimate weapon in the fight against fragmentation.
Michael Soulé and a colleague, Reed Noss, formulated the essence of the new discipline in a 1998 paper, “Rewilding and Biodiversity: Complementary Goals for Continental Conservation.” In it, they boiled the requirements down to three words: “Cores, Corridors, and Carnivores.” Core protected areas had long been a feature of conservation design, but Soulé and Noss described national parks and wildlife refuges as only the beginning, the kernels from which larger, mightier protected areas must grow. Cores, they argued, must be continental in scale, preserving entire ecosystems: mountain forests, grasslands, tundra, savannah. Corridors were necessary to reestablish links between cores, because isolation and fragmentation of wilderness areas erode biodiversity: They enabled wildlife to migrate and disperse. And carnivores were crucial to maintaining the regulatory mechanisms keeping ecosystems healthy, harking back to those chaparral canyons. Because large carnivores regulate other predators and prey, exercising an influence on the ecosystem far out of proportion to their numbers, their protection and reintroduction is crucial. Because predators need large areas to survive, “they justify bigness.”
Over time, the definition has been broadened and refined by a host of experts. Cores are to be expanded and strictly protected, and their natural fire and flood regimes restored, wherever possible. Corridors are only one type of connectivity, which may take forms other than simple linear strips of land, including patches, or stepping stones, of habitat. Both cores and corridors may require restoration of degraded habitat to achieve large-scale connectivity; carnivores may need to be reintroduced. The category of carnivores has now been joined by “keystone species,” creatures that interact so strongly with the environment that they wield an outsized influence. The damming of beavers—altering the course of streams, opening meadows within forests, and creating pond ecosystems—elevates them to a keystone species. The grazing and browsing of elephants, who act as forest engineers, pushing over trees and keeping vast grasslands like the Serengeti open, makes them keystones.
The original proponents of rewilding were careful to propose it as a “complementary” method to those being implemented by nongovernmental organizations like the World Wildlife Fund. Some of those methods are similar to rewilding in their focus on large-scale conservation. “Representation,” for example, is one large-scale strategy, focused on preserving representative areas of every identifiable ecosystem, such as savannah, tropical moist forest, tundra, desert, coral reef. The WWF’s “eco regions” program favors representation. Another model, “hotspots,” is designed to save unique areas of high endemism, places like the Galápagos Islands, where many species of plants and animals found nowhere else in the world have evolved. The large-scale continental reserves envisioned by rewilding might neglect island hot-spots like Madagascar or Java. Likewise, a single-minded focus on hotspots might shortchange areas like the African savannah, which is low in endemic species but enables mass migration.