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Toadless Tunnel Exemplifies Nature's Unpredictability

Jun 18, 2007
The toads of Davis have never figured out how to use the tunnel built a dozen years ago just for them.

Or they can't find it. Or they've died out. Or they just don't want to.

In any event, city officials in the college town of Davis, California, recently told the Sacramento Bee that not a single toad has ever hopped through the 220-foot-long "toad tunnel" built underneath Pole Line Road as part of construction of an overpass above Interstate 80. The toad tunnel got national publicity at the time and even prompted a local author to write a book called The Toads of Davis, apparently a touching story about how the community pulled together to save the toads.

Over the past 20 years, California has been at the forefront of balancing urban development with the protection and restoration of natural areas. But as wildlife biologists and land-use planners alike are finding, you can lead a toad to a tunnel, but you can't make him hop.

Urban and suburban development patterns operate in a very fixed set of spaces. Even in the age of mixed-use projects, we tend to think of land as either developed or undeveloped, residential or commercial, public or private. Planners in particular usually see a landscape as a series of colors on a map, all depicting different land uses.

So when planners, developers, and even many biologists begin to think about how to work nature into this equation, they use the same prism. We find a particular portion of the landscape where we think wildlife or water or wetlands should go and we set that territory aside. Or we conduct research to see where these natural assets are now, and we assume that this is where they'll stay.

But natural systems are volatile by nature. They may follow general patterns, but they don't operate in a fixed space the way urban land uses do. Rivers meander and flood. Wetlands dry up sometimes. Birds and rodents and toads don't always turn up in the same place.

Back in the '90s, when developers and government officials were creating a large set of preserves in Southern California for endangered birds such as the California gnatcatcher and the cactus wren, I was struck by what one wildlife biologist told me when I described the whole effort.

"They're just creating a gnatcatcher theme park," he said. "Just because they set aside the land, there's no guarantee that the birds will show up." His bottom line one confirmed for me by many scientists since is that all we can do is set aside the land and pray.

Davis officials have provided all kinds of hypotheses as to why the toads never used the tunnel. It's too long. It's too small. It's too dark. It's too hot. Any or all of these might be true. But it may also be that the toads simply didn't bother to read Davis's circulation element and therefore didn't realize they were supposed to use the tunnel. After all, it remains to be seen whether the gnatcatchers and the cactus wrens will read the multi-species habitat conservation plan and figure out where they're supposed to nest.

A little cynical, I know. But you get the point: There's a difference between the way nature operates and the way planners, developers, and engineers think. Just because an area is set aside for birds doesn't mean the birds will go there. And just because an area nearby is developed doesn't mean the birds won't go there. By setting aside land for nature, we don't necessarily preserve; and by constructing buildings we don't necessarily eradicate nature.

While dealing with strict stormwater runoff regulations, many planners are getting a rapid introduction to the difference between urban land use ideas and nature's ways. When you think about stormwater where it goes, what it picks up, how it percolates you find that there's more to a community than only colors on a map depicting different land uses. As any dope who can use Google Earth has learned, there's all kinds of textures within each color parking lots and buildings and trees and sidewalks and gravel driveways and so forth. Nature interacts with the human landscape in a dozen different ways inside every color that planners put on a map.

So maybe instead of learning how to divide the world into our land and nature's land, it's time to learn how to share the land so that even the most urban place still allows natural systems function well. Maybe then the Toads of Davis will finally show up.

- Bill Fulton