Best Management Practices for Wildlife Corridors


Best Management Practices for Wildlife Corridors

Paul Beier, Dan Majka, Shawn Newell, Emily Garding - 2008

Organization: Northern Arizona University



I. Practices for roads, canals, and railroads that cross corridors
Impacts of Roads on Wildlife
While the physical footprint of the nearly 4 million miles of roads in the United States is
relatively small, the ecological footprint of the road network extends much farther. Direct effects
of roads include road mortality, habitat fragmentation and loss, and reduced connectivity. The
severity of these effects depends on the ecological characteristics of a given species (Table).
Direct roadkill affects most species, with severe documented impacts on wide-ranging predators
such as the cougar in southern California, the Florida panther, the ocelot, the wolf, and the
Iberian lynx (Forman et al. 2003). In a 4-year study of 15,000 km of road observations in Organ
Pipe Cactus National Monument, Rosen and Lowe (1994) found an average of at least 22.5
snakes per km per year killed due to vehicle collisions. Although we may not often think of roads
as causing habitat loss, a single freeway (typical width = 50 m, including median and shoulder)
crossing diagonally across a 1-mile section of land results in the loss of 4.4% of habitat area for
any species that cannot live in the right-of-way. Roads cause habitat fragmentation because
they break large habitat areas into small, isolated habit patches which support few individuals;
these small populations lose genetic diversity and are at risk of local extinction.
In addition to these obvious effects, roads create noise and vibration that interfere with ability of
reptiles, birds, and mammals to communicate, detect prey, or avoid predators. Roads also
increase the spread of exotic plants, promote erosion, create barriers to fish, and pollute water
sources with roadway chemicals (Forman et al. 2003). Recent studies demonstrate that vehicles
deposit 300 to 800 exotic seeds per square meter per year to roadside areas, often from several
kilometers away (von der Lippe and Kowarik 2007). Highway lighting also has important
impacts on animals (Rich and Longcore 2006).


Document Type: BMP mitigation design
Project Type: fencing habitat creation/restoration overpass routine maintenance guidelines signage traffic calming underpass
Infrastructure Asset: existing roadway large underpass medium underpass new roadway small underpass
Fauna: small mammals medium mammals large mammals reptiles amphibians fish/aquatic organisms