Context of Rewilding

Rewilding is a relatively new notion: it only appeared at the end of the twentieth century. However, it deals with a topic that societies have confronted throughout the ages: the reality that people and wildlife share resources, including space. Urban planning and development practice addressed this reality largely by excluding wild animals from cities. And yet, it is estimated that eighty percent of the total population living in urban settings coexist with a large range of wildlife species. 

The importance of mobility and human activities made policymakers adopt a very pragmatic and technical approach. Highway and roads, sewage systems or other infrastructures were the main focus in urban planning. Design was human-centered, exclusively considering the needs and interaction of people. Furthermore, concerns for biodiversity and habitat protection focused almost exclusively on wildlands, with cities considered ‘human habitat’ despite the large numbers of animals residing there. As such, most rewilding has been seen as a continental or regional process, aiming to develop connected spaces for big mammals. Strategies focused on the need to provide large-scale wildlife bridges or corridors allowing animals to move, barrier-free, from one large wildland habitat to another. Many projects advocate a wildlife preservation approach in order to regulate species movement and mitigate the species endangerment crisis.

Some of the most famous examples are outlined below. These large-scale approaches have informed our understanding of corridor and crossing options.

CASE STUDIES OF LARGE-SCALE rewilding visions & projects

Southern California's U.S Highway 101 Bridge

In comparison with Buffalo Commons, that aims for rewilding an entire geographic region, rewilding has also been pursued at the metropolitan and urban scale, to connect large habitat patches separated by human settlement. 

Agoura Hills, a suburban community in Southern California's Western San Fernando Valley, is surrounded by mountains that are home to mountain lions. These large, solitary carnivores, who require large home ranges, are especially vulnerable to habitat fragmentation, as they require large territories. Major infrastructure features, such as U.S. Highway 101 running through the San Fernando Valley in Los Angeles County, create major barriers for mountain lion movement. Fragmented habitat makes it difficult for young lions to establish their own home ranges, find food and mates, and may lead to local extirpation.  

In order to help lions and other wildlife avoid collisions with cars, and to increase their mobility and access to habitat space, the Wallis Annenberg Wildlife Crossing will connect mountain lion habitat north and south of US Highway 101. At a cost of $90 million, this project is mainly financed by private philanthropy and private donations (up to 60%). The project has captured the public's interest in implementing these features to protect wildlife and encourage their preservation.

The design (see renderings below) consists of a bridge spanning the 10-lane highway and connecting the mountainous areas adjacent to the highway. It is planned to be “invisible” in the natural landscape setting. Fences will be erected to guide animals onto the bridge, and prevent them from crossing the roadway. The soil and vegetation used on this wildlife crossing draws from surrounding vegetation along the edges of the bridge and upland. In this way, the bridge itself can be used as habitat for some wildlife species. Finally, acoustic and visual protections will block sound and light from the highway stressful to the animals crossing the bridge.

Wildlife Underpass I-4 - Reedy Creek, Florida 

A new wildlife underpass is being built on Interstate 4, located to the west of Haines City in Polk County, Florida. The construction of this underpass is part of a larger project - the 18 million acre Florida Wildlife Corridor, 10 million acres of which are protected conservation lands - that aims to create a series of passages to enable wild animals to freely follow their natural migration patterns.

The underpass will help to reconnect a green corridor between two parts of a wildlife management area. This area has been separated by I-4 since the 1970s, and the underpass will help to restore the continuity of habitat and reduce the risk of crossing a large freeway.

Key Takeaways

The broad definition of rewilding and the various considerations it entails create a very diverse portfolio of large-scale infrastructure and regional planning options, as depicted in these examples. Though they may attract attention, strategies for large swaths of wilderness cannot easily be translated to fine-grained urban contexts. 

In our research, we offer suggestions for small-scale interventions as opportunities to support ecological health and the preservation of diverse species in complex urban settings. These interventions represent an underutilized resource. In creating a network of patches, habitat can be enhanced and connected to support both wildlife and people within the greater urban ecology. Wildlife species continually evolve and many find ways to adapt and live in urban areas, often using urban infrastructure to establish new habitats, provide new migration routes, or food opportunities. Many smaller animals do not need large-scale features to migrate or thrive in an urban ecosystem. This means that focusing on a neighborhood-scale approach to wildlife habitat preservation is often more accessible and effective in urban settings. Small-scle strategies includes creating stepping stone habitats and corridors through revegetation strategies, as well as creating autonomous patches with small-scale movement corridors between them to avoid lethal barriers such as roads. As policymakers have started to embrace urban ecology and the need for multispecies coexistence, neighborhood-scale urban rewilding efforts have gained momentum. 

Along with providing habitat, these strategies develop methods for adaptation in the face of climate change. Using nature-based solutions has become increasingly necessary. These methods are gaining traction in larger scale adaptation efforts and in the planning of cities. With this, rewilding strategies may provide mutually beneficial spaces for both people and wildlife, helping protect of our cities from sea level rise and flooding. Thus, our project focuses on how smaller-scale urban rewilding projects can enhance the ability for urban wildlife to persist while also providing additional green spaces for people.