Road Kill And Habitat Fragmentation: A Problem Deserving Attention
I recently drove from Portland, Oregon to Los Angeles, California. Almost the entire drive I was on Interstate 5, a highway that runs along the west coast of United States, parallel to the Pacific Ocean. The highway is 1,381 miles long, stretching from the U.S.-Canada boarder all the way to the U.S.-Mexico border. Driving down the 5 is a journey that exposes travelers to the horrors of humanity’s abuse and carnage of other species.
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Throughout California, there are stretches of the drive in which you are immersed in the stench of factory farming. In plain sight, thousands of cows stand in their own waste and huge toxic pools of this waste are also visible. The stench, sounds and sights are nearly unbearable. Just as notable, but seemingly less discussed among animal advocates, is the carnage on the side of the road. According to a report compiled by Merritt Clifton in 2000, among other animals, about 1.2 million dogs, 5.4 million cats, and 8.3 million opossums were killed on U.S. roadways. The consequences that man-made structures have for the earth and other animals with whom we share the earth is obvious on Interstate 5.
From the regular splat of bugs dying against the windshield, to the frequent sightings of animals dead on the side of the highway, it became clear that I-5 is a deadly barrier preventing the passage of animals for over 1,000 miles. If any animal needs to move east or west to follow migration patterns, flee from disaster such as storms or fires, or go in search of food, they face the possibly deadly challenge of crossing the I-5.
And I-5 is only one of many highways. The map below details all the U.S. routes as of 2006, painting a stark picture of many of the prevalent roadways in one country. When you imagine all of the highways, roadways, buildings, damns, parking lots, and other man-made structures, the fragmented nature of the environment is astounding. This leads to what is known as “habitat fragmentation.”
Habitat fragmentation occurs when land that was once connected becomes spatially separated. While this type of fragmentation can be due to natural causes such as volcanoes, it is increasingly due to man-made structures and manipulations of the environment, including roadways. Man-made causes are perhaps the most deleterious:
“…[H]umans have produced dramatic and swift transformation of landscapes throughout the world, resulting in a level of habitat fragmentation that has induced worldwide reduction in biodiversity and interruption of sustainable yields of natural resources.” –Encyclopedia of the Earth
Habitat fragmentation becomes a problem for individual animals as they may be hit by cars or get trapped in an urban area without a food source. It can also have negative consequences for biodiversity more broadly. If animals cannot travel and plants cannot spread, biodiversity within an area can decrease. Further, diversity within a single species can also decrease if animals cannot seek out mates in other groups, which leads to an increase in inbreeding.
One potential solution for managing the effects of fragmentation due to roadways is to develop habitat and wildlife corridors. Wildlife corridors are pathways that connect segments of land that have been fragmented by roadways or other man-made structures.
For all of the efforts of the animal protection community to help wildlife, the discussion of highways seems missing. Making the case for effective wildlife corridors should become more important. Not only is the death toll of individual animals high and the consequences for certain species as a whole even greater, it is something that is winnable. Arguments can be made about the obvious benefits to human safety that come from fewer animals on the road, and these corridors can be built into the plans of many ongoing public works and roads projects. One reason that corridors are often not built is that funders argue that there is not solid research showing that they work.
In my next post on this topic I will discuss research that investigates the effectiveness of wildlife corridors, as well as describe the various types of wildlife corridors that have so far been implemented or imagined. Continue Reading…