Road ecology

Roads are known to cause significant damage to forests, prairies, streams and wetlands. Besides the direct habitat loss due to the road itself, and the roadkill of animal species, roads alter water-flow patterns, increase noise, water, and air pollution, create disturbance that alters the species composition of nearby vegetation thereby reducing habitat for local native animals, and act as barriers to animal movements.

Hydrology

See also: Stormwater

De-icing chemicals

The chemicals applied to roads along with grit for de-icing are primarily Salt and calcium chloride. Other chemicals such as urea are also used. These chemicals leave the road surface either in water runoff or in water spray. Vegetation can be damaged by salt as far as 100 m (110 yd) from the road. An increased level of chloride in water due to salt application to roads can be widespread in waterways, rather than a local phenomenon of the road edge itself.

Noise

Noise pollution is a factor of environmental degradation that is often overlooked and typically seen as not having a significant impact, though traffic noise can contribute to numerous disturbances for wildlife. Few studies have been done on road ecology, and even fewer on the effects of noise on wildlife, though one study revealed that noise can have a negative impact, particularly on birds. Noise from major roads can interrupt the calls of song birds, and their instinctive calls associated with mating, communication, migration, and other purposes are hindered by noise from roads. This did not necessarily directly provide a fatal effect for the tested birds, but the study showed that species abundance declined around major roads due to noise.

Effects on wildlife

Amphibians and reptiles

Snapping turtle (Chelydra serpentina) crossing a road

Roads can be particularly hazardous to populations of amphibians and reptiles that migrate to vernal pools, or to the gravel on road verges that several species try to use as nest sites. Reptiles’ instinctive activities can lead them towards roads and lead to an increase in mortality rates: snakes, for example, may use roads as a source of heat for thermoregulation. Also some turtles have been noted to lay their eggs on road shoulders. Migratory patterns from season to season can also bring frogs and snakes into contact with roads and lead to an increase in their mortality rates.

Mitigation efforts

Road permeability

Wildlife crossings that allow animals to safely cross human-made barriers such as roads, are intended not only to reduce roadkill, but ideally to provide connectivity of habitat areas, combating habitat fragmentation. Wildlife crossings may include: underpass tunnels, viaducts, and overpasses.

Habitat construction and planting

In Washington County, North Carolina, along Highway 64, a study was conducted to analyze the effects of wildlife underpasses on the local wildlife. Three wildlife underpasses were built with fencing around the highway in the study zones. The study showed that deer used the underpasses the most and made up 93% of all crossings. Mortality rates were calculated and showed that the numbers of deaths were lower near underpasses. This cannot be said about all animals. Some have smaller home ranges so they were not inclined to travel to underpasses to cross the road. Underpass would most likely benefit larger mammals such as bears, deer, and cougars. Underpasses were seen to lower mortality rates and increase local species ability to adapt to a habitat along a major road.

See also

• Acoustic ecology
• Anthropocene
• Environmental impact of transport
• Habitat fragmentation
• Population fragmentation
• Railroad ecology
• Rubberized asphalt, a technology that reduces road noise from tires
• Synanthrope