Do Wildlife Corridors Really Work?

When human urban habitat runs into the terrain of other species, the results can be traumatic for many of the parties involved.

Take coastal southern California, which has seen a big population boom in the past couple of decades. As people built skyscrapers and condos and highways to accommodate their growing numbers, they inadvertently split up the natural habitats of lizards and birds, bobcats and coyotes, and loads of other species. Isolated to much smaller patches of habitat (not to mention surrounded by metal, concrete and plastic), the animals wind up with a much smaller gene pool, making them more susceptible to disease, climate change and natural disaster.

Since the 1960s, a solution often trumpeted by conservationists is to build a “wildlife corridor”: a green pathway that connects one patch of habitat to another, allowing species to move across wider areas despite human developments. These corridors exist or are being built all over the world, from jaguar habitat in the Americas to hardwood forests in Bhutan to tropical rainforests in Australia.

But two active corridor builders are now questioning whether the approach is a good one.

In a commentary published last month in PLoS Biology, conservationists Paul Beier and Andrew Gregory from Northern Arizona University pointed out that there’s actually scant evidence that wildlife corridors work in large, human-dominated landscapes. Almost all research has been done on corridors less than 150 meters long, whereas most implemented corridors are many times larger. What’s more, these studies generally measure only whether animals move from patch A to patch B, rather than explicitly testing genetic diversity or long-term occupancy.

Hoping for better data, the duo has launched a crowd-sourcing project of sorts to identify corridor-like landscapes that would be useful for research. Ideally, they’d like to find spots that meet eight criteria, such as being at least 500 meters long, near urban or industrial activity and stable for at least 20 years after human development. So far, they’re learned of 15 promising sites, but hope to find at least 100. If you can think of one, let them know.