Designing Wildlife Corridors

For most of human history, nobody was in a position to know or understand what was happening in other parts of the planet—or even to have a notion of being on a planet. There was less widespread awareness of the wider ramifications of wildlife trends in their part of their world, such as the disappearance of saber-toothed tigers or the North American bison being hunted to near-extinction.  

Now, thanks to researchers, technology, and popular nature documentaries, there’s global awareness of not just individual species but how species fit together in complex webs of ecology. According to scientists the world is currently losing species at a rate between 100 and 1,000 times faster than happened before humans became a major presence on Planet Earth. 

The Issue of Animal Conservation in Urban Societies 

It’s not just the rapid decline and even complete disappearance of some species that’s an issue. It is notable that there’s also a major issue with the decline of biodiversity— the variety of life that makes it possible for species to adapt and for ecosystems to be resilient to stress. It stands to reason that with the planet’s population verging to nearly 7.8 billion, species of all sizes are squeezed into ever smaller ranges when their habitats are taken over, degraded or destroyed by the activities of the planet’s human inhabitants. On land, the uninterrupted natural spaces of the world have been fragmented by cities, roads, railway lines, farmland, fences and other human demands. This has left wildlife marooned in small groupings on isolated patches of habitat with limited genetic diversity.   

How Wildlife Corridor Design Has Helped Wildlife Conservation 

One solution that’s been refined over the years by ecologists is to join up isolated patches by creating wildlife corridors—strips of habitat that provide a way for wildlife to move unhindered across man-made obstacles to migrate, breed, and feed. In some cases, such corridors enable a number of different species to move freely between patches of habitat. And to do that takes a lot of specialist design—these wildlife corridors must take into account the needs, behaviors and interactions of multiple species, including humans.  

Experts divide wildlife corridor users into “passage users” and “dwellers”. “Passage users” are transient and are in the corridor only when moving between habitats. They’re typically large herbivores and medium to large carnivores—the sort of animals that migrate and others that prey on the migrating animals. “Dwellers” move into the corridor and stay longer—even indefinitely. They’re typically trees, plants, amphibians, reptiles, small mammals, and insects.  

Wildlife corridor design has to take account of the presence, or absence, of natural features that can enable the safe transit of wildlife.  

The Importance of Wildlife Corridors Around the World 

On one end of the scale are massive corridors spanning land that’s still relatively uninhabited. The Yellowstone-to-Yukon nature corridor, initiated in 1993, stretches sparsely-populated 2,000 miles (3,200 kilometers) from the Greater Yellowstone Ecosystem to Canada’s Yukon. Spanning five American states, two Canadian provinces, two Canadian territories, and the traditional territories of at least 75 Indigenous groups, the Y2Y gives wide-ranging animals such grizzly bears, wolves, elk, bison and mountain lions the space needed to maintain healthy populations. In India, the Balpakram-Baghmara and Siju-Rewak corridors enable endangered elephant populations to roam the Garo Hills region of Meghalaya state. In Tanzania, researchers are using tracking collars on wildlife to identify naturally-occurring structural corridors that could be maintained at lowest cost. 

At the other end of the scale are man-made bridges and underpasses. Along the busy Trans-Canada Highway, animals are kept off the road by fencing but they can cross between their wild habits using tree-covered bridges and shadowy tunnels. Black bears and mountain lions prefer the tunnels while grizzly bears and big ungulates (e.g. moose) prefer the bridges.  

Singapore’s 140-metres long Mandai Lake Bridge passes over a busy road to join two small patches of forest. On Christmas Island, Australia, rangers created a purpose-built crab-friendly bridge over a busy highway to give some of the island’s 40 million crabs a safer route on their annual migration from the forest to the sea and back. 

Designing wildlife corridors may not have the cachet of designing new technology or buildings. On the other hand, it does bring together diverse disciplines (life sciences, technology, and construction) to create custom-designed answers to one of the most pressing issues of our age: how can humans live with less destructive impact on the natural world?