Wildlands Network published For the Wild in 2017 to celebrate 25 years of reconnecting nature in North America. Every couple of weeks, we’ll be posting a new excerpt from this inspiring collection of prose, poetry, and photographs as a special feature on our website. Please join the Rewilding Society or our Wildlands Stewards giving circle to receive a bound copy of For the Wild. Visit our Donate page to learn more.
Rewilding and Biodiversity: Complementary Goals for Continental Conservation
by Michael Soulé and Reed Noss
THE FOURTH CURRENT—along with Monumentalism, Biodiversity Conservation (including representation of ecosystems), and Island Biogeography—in the modern conservation movement is the idea of rewilding—the scientific argument for restoring big wilderness based on the regulatory roles of large predators. Until the mid-1980s, the justification for big wilderness was mostly aesthetic and moral. The scientific foundation for wilderness protection was yet to be established.
We recognize three independent features that characterize contemporary rewilding: large, strictly protected, core reserves; connectivity; and keystone species. In simplified shorthand, these have been referred to as the three Cs: Cores, Corridors, and Carnivores.
Keystone species enrich ecosystem function in unique and significant ways. Although all species interact, the interactions of some species are more profound and far-reaching than others, such that their elimination from an ecosystem often triggers cascades of direct and indirect changes on more than a single trophic level, leading eventually to losses of habitats and extirpation of other species in the food web. Top carnivores are often keystones, but so are species that provide critical resources or that transform landscapes or waterscapes, such as sea otters, beavers, prairie dogs, elephants, gopher tortoises, and cavity-excavating birds. In North America, it is most often large carnivores that are missing or severely depleted.
Three major scientific arguments constitute the rewilding argument and justify the emphasis on large predators. First, the structure, resilience, and diversity of ecosystems are often maintained by “topdown” ecological (trophic) interactions that are initiated by top predators. Second, wide-ranging predators usually require large cores of protected landscape for secure foraging, seasonal movement, and other needs; they justify bigness. Third, core reserves are typically not large enough in most regions; they must be linked to ensure long-term viability of wide-ranging species. In addition to large predators, migratory species such as caribou and anadromous fishes also justify connectivity in a system of nature reserves. In short, the rewilding argument posits that large predators are often instrumental in maintaining the integrity of ecosystems. In turn, large predators require extensive space and connectivity.
The ecological argument for rewilding is buttressed by research on the roles of large animals, particularly top carnivores and other keystone species, in many continental and marine systems. Studies are demonstrating that the disappearance of large carnivores often causes these ecosystems to undergo dramatic changes, many of which lead to biotic simplification and species loss. On land, these changes are often triggered by exploding ungulate populations. For example, deer, in the absence of wolves and cougars, have become extraordinarily abundant and emboldened in many rural and suburban areas throughout the United States, causing both ecological and economic havoc.