COULD LEAD TO ENVIRONMENTALLY FRIENDLY HIGHWAYS
Now, stopping to check interesting roadkills would be both illegal and dangerous. But that was immaterial on this last trip, because I saw no dead animals for almost fifty miles. One reason for this was that I was traveling at midday when crows and buzzards would have already picked the highway clean of small snakes or frogs killed the previous night. But another reason for the lack of larger animals is that Alligator Alley has 36 culverts, called "panther crossings," that allow endangered Florida panthers, as well as other wildlife, to travel beneath the highway instead of across the deadly surface. A 10-foot-high chain-link fence paralleling the road on each side runs from culvert to culvert. If a nonflying animal that is too big to get through the mesh of the fence wants to get to the other side, the culverts are the only way to go.
Under-the-road crossings, or ecopassages, for wildlife are positive ecological steps that counter the proven negative environmental impacts of highways. Millions of animals are killed annually on North American highways, which fragment the habitat into compartments that may be too small for some species, which then try to cross the road in search of more suitable habitat. Over the past few years, wildlife have benefited from hundreds of successfully constructed ecopassages, including those originally designed for spotted salamanders in Connecticut, toads in England, and desert tortoises in California.
A situation at Lake Jackson near Tallahassee, Florida, serves as a dramatic example of the effectiveness of using barriers to redirect the travel pattern of animals to avoid highway mortality. Matthew Aresco of Florida State University constructed a guide fence to lead turtles and other animals to a culvert beneath a highway that bisects the lake. Prior to the fence's construction, highway deaths of more than 9,000 individual animals comprising more than 50 different species were documented over a 3-year period on a half mile of highway. By making the local community aware that an average of more than 50 animals die each week on the highway, Aresco has inspired action. The Lake Jackson Ecopassage Alliance comprises a group of environmentally concerned citizens intent on developing a permanent ecopassage to connect the two parts of the lake.
A permanent ecopassage has already been constructed along the two miles where Highway 441 crosses Payne's Prairie, a large wetland south of Gainesville, Florida. Concrete guide walls prevent or at least discourage animals from entering the highway from the road shoulder, and culverts beneath the road give animals the option of moving safely from one side of the wetland to another. The number of road-killed animals has unquestionably numbered in the millions since the highway was built in the 1920s, and a study conducted by Ken Dodd and Lora Smith through the University of Florida confirmed that mortality remained high in the late 1990s. They identified and counted roadkills on the Payne's Prairie highway three days each week for a year and documented that more than 17 animals were killed each day and night. During the year of the study, they recorded 29 dead alligators on the highway.
Highways, which in one sense are ecopassages for humans, can be highly
disruptive to wildlife populations. When a highway bisects wildlife
corridors, historical migration routes can be cut off. For example,
adult amphibians living in a terrestrial habitat must be able to reach
wetland breeding sites that may be located several hundred yards away.
Guide fences and underpasses to protect wildlife from the human-created
threat of a highway are simple solutions to a major environmental problem.
Road-kill impact assessments should be required before any new highway
is built and conducted for many established roads as well. Ecopassages
should then be constructed in ecologically appropriate sections. Doing
so will make highways safer for wildlife--and where Florida panthers
and large alligators live, safer for drivers.