It sounds like an oxymoron—urban rewilding—and perhaps it is. When “rewilding” entered conservationists’ vocabulary in the early 1990s, modern cities were its antithesis.
The rewilding movement originated as a push for “big wilderness”: for the restoration of large, interconnected swaths of land and the reintroduction of “keystone species” to it. Keystone species are animals and plants whose presence is highly beneficial to their ecosystem, and whose absence triggers a cascade of destabilizing changes. Though keystone species in North America range from beavers to chestnut trees, rewilding emphasizes the need for large predators—wolves, cougars, bears and the like—whose need for large territories in turn justifies “big wilderness.”
Rewilding is organized around the “Three C’s,” Cores, Corridors, and Carnivores, where the cores are protected wilderness areas, and the corridors are strips of land or water connecting them. Cities hardly fit in as a fourth “C” in this vision. So why are the words “urban rewilding” increasingly cropping up together? There are a number of reasons for conservationists’ newfound interest in integrating rewilding principles into urban environments, some more fruitful than others.
There is no doubt that “rewilding” a city looks substantially different from rewilding efforts in Yosemite, Nam Phouy or the Scottish Highlands. Big wilderness and apex predators are impossibilities. People can’t be prohibited entry to urban green spaces. Urban rewilding looks more like transforming a former shopping center into a wetland park in Nottingham; like de-concretizing miles of the Kallang River in Singapore; like the hanging gardens of a new skyscraper in Sydney. Unnecessarily gray spaces are restored to green, and green spaces are incorporated into new development. There is no purity to urban rewilding: the balance of gray and green is subject to constant, organic change.
One crucial principle of rewilding that succumbs to the challenges of cities is restoring native flora and fauna. Biologist Mark Davis emphasizes the difference between non-native species—which can benefit the biodiversity of their new homes—and invasive species, which harm biodiversity. He argues that it is “time to focus much more on the functions of species, and much less on where they originated.” Davis’ logic is particularly applicable for the constraints of urban environments, dominated by “urban adapters” and “urban exploiters”: species dependent to varying degrees on human resources. Many native species struggle to thrive in the altered conditions of cities, while others can and will return with changes in urban landscaping practices.
Biodiversity may be a more feasible aim for cities than pure native species restoration. There are many justifications for increasing biodiversity in cities, ecosystem health and resilience being the most obvious, along with preserving migration routes and homes for rare species. Manhattan, for instance, a stop along the endangered monarch butterfly’s migration route, recently designed a new Central Park meadow with dozens of wildflower species to provide for them and other pollinators. Recent research has also found that the psychological benefits of spending time in urban green spaces increase with greater biodiversity. The benefits of biodiversity, however, are more obvious than the means of securing them. To increase biodiversity in cities, research suggests that small habitat patches throughout must be interconnected.
Corridors, rewilding’s second “C,” are actually an essential tool of cities. These corridors can take a number of forms, from waterways and strips of parkland to hedgerows and even walls themselves. And corridors don’t have to be unbroken: new research shows that “steppingstones” are effective in expanding the range of possible habitats for urban species to live in and move through. The High Line park along an abandoned railway in New York City is a wildlife corridor; so is the River Thames in London. Gardens, parks and playgrounds can function as steppingstones.
Corridors aren’t the only healthy challenge that rewilding principles pose to cities. Another is minimizing humans’ role in managing ecosystems. Given that an estimated 40 million acres of the United States is lawn—high-maintenance and ecologically sterile—we can imagine how transformative it would be to replace lawns with pollinator-friendly plants, to have yards and roadsides humming with birds and butterflies and bees. Cities with a long-term outlook may also consider how the financial benefits of establishing lower-maintenance landscapes can offset the start-up costs of habitat restoration. Of course, some human intervention in urban landscapes may remain both necessary and beneficial.
Perhaps the greatest challenge urban rewilding provokes is rethinking the divide between built and natural landscapes, and the human role in each. Biologist Tim Flannery reminds us that the “primeval wilderness” encountered by early American colonists only looked untouched; Native Americans were actually the most important actors in maintaining its ecological balance. Today, growing interest in “urban rewilding” reveals a new willingness to reconsider how and with whom we share our built environments. The gardeners of Manhattan’s High Line, for example, consider themselves “editors” rather than authors of the landscape, whose work is to “keep it wild.” While “wild” in the bustling neighborhood of Chelsea means self-seeding asters, not roaming wolves, it still represents a profound shift in urban landscaping practices.
What most distinguishes the conversation around “urban rewilding” from the push for native plants or greater biodiversity may be how it captures the imagination. “Rewilding” has incited strong emotional reactions since its inception, from the enthusiasm of those who take pride in the unique beauty of their local ecosystems to anger from those who fear predators’ reintroduction. Urban rewilding doesn’t involve large animals, but it still requires a shift in thinking about “ownership” of urban spaces. A 2020 study of “auto-rewilding” cormorants who took over an urban reservoir in England, upsetting local fishers, notes that most rewilding efforts have concrete goals in mind, like the reintroduction of specific species. In contrast, handing over the reins to nature means making room for “ecological surprises,” like a sudden cormorant colony. While urban residents are accustomed to living amidst a great diversity of human behavior, it may be that “ecological surprises” in cities prove especially unsettling. Managing the boundaries between people and rewilded habitats will be crucial to protect wildlife and mitigate people’s concerns. Most of the creatures using urban streets as corridors would be small and winged—insects, birds—and the majority of new animal species would inhabit rewilded parks.
Urban rewilding may be the more fruitful for its contradictions: the leap from manicured lawns to restored wetlands is even greater than the reintroduction of bears and wolves to the European continent. And if it asks more of urban residents, it also may deliver more. Urban rewilding is touted as a solution to everything from increased resilience against viruses to improved respiratory and mental health. There is no one model for a rewilded city—“wild” means something different everywhere. What rewilding promises cities is a chance to more fully realize their local character.
Image courtesy of Flickr. Originally published by S&S on May 19, 2021.