Wildlife crossing
They also assist in avoiding collisions between vehicles and animals, which in addition to killing or injuring wildlife may cause injury or death to humans and property damage.
Road mortality has significantly affected a number of prominent species in the United States, including white-tailed deer (Odocoileus virginianus), Florida panthers (Puma concolor coryi), and black bears (Ursus americanus).
[10] Finally, species that are unable to migrate across roads to reach resources such as food, shelter and mates will experience reduced reproductive and survival rates, which can compromise population viability.
These small populations are particularly vulnerable to extinction due to demographic, genetic, and environmental stochasticity because they do not contain enough alleles to adapt to new selective pressures such as changes in temperature, habitat, and food availability.
[13] Research in the 1990s estimated the number of collisions with ungulates in traffic in Europe at 507,000 per year, resulting in 300 people killed, 30,000 injured,[14][15] and property damage exceeding $1 billion.
In parallel, 1.5 million traffic accidents involving deer in the United States cause an estimated $1.1 billion in vehicle damage each year.
Of the currently available options, structures known as wildlife crossings have been the most successful at reducing both habitat fragmentation and wildlife-vehicle collisions caused by roads.
[21] Written reports of rough fish ladders date to 17th-century France, where bundles of branches were used to create steps in steep channels to bypass obstructions.
A version was patented in 1837 by Richard McFarlan of Bathurst, New Brunswick, Canada, who designed a fishway to bypass a dam at his water-powered lumber mill.
As the Industrial Age advanced, dams and other river obstructions became larger and more common, leading to the need for effective fish by-passes.
[25][26] The Humane Society of the United States reported in 2007 that the more than 600 tunnels installed under major and minor roads in the Netherlands have helped to substantially increase population levels of the endangered European badger.
[26] The longest "ecoduct" overpass, Natuurbrug Zanderij Crailoo, in the Netherlands, runs 800 meters (2,600 ft) and spans a highway, railway and golf course.
Recognizable wildlife crossings are found in Banff National Park in Alberta, where vegetated overpasses provide safe passage over the Trans-Canada Highway for bears, moose, deer, wolves, elk, and many other species.
To reduce the effects of the four-lane TCH, 24 wildlife crossings (22 underpasses and two overpasses) were built to ensure habitat connectivity and protect motorists (Clevenger 2007).
Clevenger et al. (2001) reported that the use of wildlife crossings and fencing reduced traffic-induced mortality of large ungulates on the TCH by more than 80 percent.
Parks Canada is currently planning to build 17 additional crossing structures across the TCH to increase driver safety near the hamlet of Lake Louise.
These crossings are specifically designed to target and protect the endangered Florida panther, a subspecies of cougar found in the Southeastern United States.
Scientists estimate that there are only 80–100 Florida panthers alive in the wild, which makes them one of the most endangered large mammals in North America (Foster & Humphrey 1995).
In San Bernardino County, biologists have erected fences along State Route 58 to complement underpasses (culverts) that are being used by the threatened desert tortoise.
Studies by Haas (2000) and Lyren (2001) report that underpasses in Orange, Riverside, and Los Angeles Counties have drawn significant use from a variety of species including bobcats, coyotes, gray fox, mule deer, and long-tailed weasels.
The Netherlands also boasts the world's longest ecoduct-wildlife overpass called the Natuurbrug Zanderij Crailoo (sand quarry nature bridge at Crailo) (Danby 2004).
In 1997, the Victorian Government Roads Corporation built Slaty Creek wildlife underpass at a cost of $3 million (Abson & Lawrence 2003).
The results indicate that the underpass could be useful to a wide array of species but the authors suggest that Slaty Creek could be improved by enhanced design and maintenance of fencing to minimise road kill along the Calder Freeway and by attempting to exclude introduced predators such as cats and foxes from the area.
[40][41] The design features a single 100 m (328 ft) concrete span across the highway that is planted with a variety of vegetation types, including a pine-tree forest and meadow grasses, to attract different species to cross.
