A stream of traffic flows along Picture Rocks Road, past two roadside culverts where Natasha Kline is checking for animal tracks. The tunnels, intended to drain a sandy wash, are serving instead as life-saving byways for wildlife along this busy commuter route through Saguaro National Park.
As a park biologist, Ms. Kline knows such crossings can be crucial. A recent study counted as many as 53,000 animals killed on Saguaro's roads each year. "It's a huge problem," she says, "and our issue will be every park's issue in 10 years or so."
Efforts to solve the problem have spawned a new discipline called road ecology. The practice brings together transportation planners, scientists, and wildlife activists who plan new road projects to minimize impacts on animals. By using a variety of strategies - from lowered speed limits in wildlife areas to high-tech, vegetated overpasses where cameras monitor animal use - they hope to reduce the number of animals killed and improve road safety for drivers.
Increased roadkill in national parks and on America's roads is a serious issue. About 275,000 animal-related crashes occur each year in the US, according to the National Highway Traffic Safety Administration. An estimated 1 million animals are killed on America's roads each day.
Scientists and transportation planners are seeking to reverse the trend. For instance, the Western Transportation Institute at Montana State University is a leader in road ecology. Tony Clevenger, who is a biologist there, recently helped design 24 vegetated wildlife crossings over 30 miles on the Transcanada Highway, which bisects Alaska's Banff National Park. Those structures helped to cut wildlife mortality by 95 percent since the mid-1980s. In the past, he says, state wildlife officials often were the last to know about pending transportation projects.
But today, government agencies "are implementing more wildlife fencing and crossing structures right into highway planning and design, instead of waiting to the last minute to include them."
Florida leads the way in reducing roadkill, thanks to its Efficient Transportation Decision Making process. Implemented five years ago, the process requires that environmental resource and transportation agencies link up and undertake detailed scientific studies before breaking ground on new projects.
Indeed, road ecology has increased cooperation "between people who were never together in a room before," says Dr. Clevenger.
Recently, Congress has also become involved. A transportation bill signed into law this summer requires state wildlife officials to collaborate with planners on federally funded roadways.
Some see cutting costs as a huge incentive to curb roadkill. "It is much more efficient to know what kind of technical studies and research we need to do up front, before getting to the permitting stage," says Vicki Sharpe, state ecologist with Florida's Department of Transportation. Early research also helps avoid time-consuming lawsuits from environmental groups if wildlife reviews are not adequate.
"The first step is understanding where the wildlife passages and corridors are," says Alison Berry, director of the Road Ecology Center at the University of California at Davis. "Then you can go on to [developing] structural barriers, various kinds of underpasses or culverts, and wildlife crossing structures."
Others question whether those efforts go far enough. "Wildlife crossings and retrofitting roads are extremely important," says Laurie Macdonald, Florida director for Defenders of Wildlife. "But these structures should not be considered substitutes for making proper road decisions in the first place. Roads should not be put into intact wildlife habitat, and where wildlife needs to have free flow."
Despite the concerns, heavily traveled Saguaro National Park is revising its general management plan, which is expected to include strategies to reduce roadkill like those used in Banff and in Florida. Until that happens, Kline will keep monitoring ad hoc crossing areas, such as these precious culverts.