Construction of new roads and rehabilitation of old unused roads significantly changes the area where the road is situated, often leading to the loss of valuable habitats. Scientists are aware that plant and animal species are becoming extinct at an unusually rapid rate all over the world; right now the earth is experiencing a rate of species extinction that is on a par with the massive extinctions that occurred 65 million years ago when the dinosaurs disappeared. Since habitat destruction is the most important cause of extinction, environmental conservation is now one of the major approaches recommended to slow down species loss. Reducing the number of roads we build and keeping them completely out of some areas will help to slow down species loss. As we learn more about the environmental impacts of roads, especially when we realize how roads contribute to the major losses of species now occurring throughout the world, we will fight to keep them out of important habitat areas.

The Roadless Rule

Several years ago President Clinton directed protection of nearly 60 million acres of National Forest from most commercial logging and road building with the Roadless Area Conservation Rule of 2000. Upon taking office in 2001, President Bush questioned the value of protecting national forest lands from further road development and placed an injunction upon the Rule. The 9th Circuit Court lifted the Bush injunction in spring of 2003; the decision was based on the environmental protection gained from keeping large areas roadless. In order to further strengthen the roadless rule, U.S. Representatives Sherwood Boehlen (R-NY) and Jay Inslee (D-WA) along with 150 co-sponsors introduced H.R. 2369 in June 2003 "To protect inventoried roadless areas in the National Forests." California co-sponsors include Susan Davis (CA-53) and Bob Filner (CA-51).

In an action to stimulate rural road building, in February 2003 the Bush Administration reactivated the Civil War-era rule, RS 2477, which says that any road or trail used for transportation after 1866 and before 1976 can be reopened for public use, if desired. The reopening of this rule could lead to extreme degradation of many currently unused areas if the many old roads that exist in these areas are opened again in areas where they will be used by recreational vehicles.

The Effects of Roads

Obviously roads have value to us as avenues for the easy transport of goods and movement of people, but can we reduce the number of roads while retaining the economic and social values they provide? From an environmental point of view, the addition of a road to an ecosystem has several effects. First, it leads to immediate environmental damage to the land that is changed from natural habitat to a roadway. Second, a road creates a barrier that divides ecosystems, creating habitat fragments that are reduced in size from the original habitat. And third, the built road that is traveled upon has widely extended effects on both sides of the road where human activities are increased and changes occur in water flow, air quality, and numbers of exotic species.

The Immediate Effects

Road construction itself kills many individual plants and animals during the preparation of the road surface, including scraping, grading, and filling, plus the impacts due to the noise and dust created by the machinery and work crews. The hard surface of the completed road changes water flow in the area, leading to altered habitats and increasing the possibility of erosion alongside the road. The changes in water flow and distribution caused by the introduction of the hard, impermeable surfaces of roads reduce the capability of land to infiltrate rainwater into the ground. Water velocity is increased across the hard surfaces leading to erosion and production of sediment when the more rapidly running water reaches the softer ground at the edge of the hard surface. Rainwater running across these hard surfaces picks up pollutants such as petroleum byproducts from motorized vehicles and introduces them into the groundwater. Because of impaction of the earth, even an unpaved road has effects on the vegetation and water behavior in the roadway. Thus the introduction of roads changes the capabilities of the entire watershed in which they are located.

Plants and animals that are not directly destroyed by the introduction of a road into their habitat, or by changes in water flow or the presence of petroleum byproducts, can be negatively affected by the fragmentation of their habitat. Roads create a barrier that reduces the habitat size for the species that cannot successfully cross the road. Connections to food and water sources may be lost or reduced, as may sources of replacement individuals needed after catastrophic events such as fire and flood. Habitat loss may lead to a reduction in mating possibilities with non-related individuals. Plants may lose exposure to their pollinating species if the roadway is too wide for the appropriate pollinators to cross. Small animals may not want to cross the open roadway with its absence of protective vegetation to hide in, or when they do attempt to cross, they may be killed. Snakes like to rest on the warm surface of roads and are thus often run over. Our roads heavily victimize large mammals such as mountain lions. The Los Angeles Times reported on a study by wildlife biologist Paul Beier in which he electronically tracked 32 mountain lions in Southern California over a period of five years. Only seven of the original 32 animals survived over the five years. One third of the deaths were the result of automobile accidents (James, 2000).

Edge Effects

Beyond the direct effects of construction, changes in water flow, the introduction of pollutants, the creation of barriers to species movement, and death and maiming by vehicles, there are road effects on wildlife that extend for some distance on either side of the road. When roads fragment ecosystems, the adjacent, undeveloped land, which may appear to retain an intact habitat, will be altered by so-called edge effects. These edge effects are the consequences of the changes that roads and their uses bring to the native ecosystem. Even if native plants are retained in the neighboring lands, they may be exposed to more or less sunlight, more or less water and other nutrients than previously was the case as well as fumes from automobile exhausts and runoff of petroleum products and pesticides and fertilizers from landscaping practices along the road margins. These changes often reduce the ability of the original plants and animals to survive.

Changes in wetlands, streams, plants, mammals, amphibians and forest and grassland birds caused by road effects were shown to extend for an average width of nearly 2000 feet along 15 miles of a four-lane suburban highway in Massachusetts (Forman and Deblinger, 2000). By extending this type of analysis to the entire road system of the United States, and allowing for differences in urban and rural roads, primary and secondary roads, the researchers estimated that approximately 20% of the total area of land in the United States is directly affected ecologically by the system of public roads (Forman, 2000).

Spreading the Effects

Because of the disturbances of the land at the edges of the habitat, it will be more susceptible to invasion by exotic species (Gelbard & Belnap, 2003). The addition of new species and the probable loss of species due to the changed characteristics of the habitat will change its capacity to support other species. In the desert environment, exotic annual grasses are introduced along roadways. These grasses promote fires across an otherwise fire resistant landscape, fires which are detrimental to desert species including the desert tortoise and its habitat (Brooks, Esque & Schwalbe, 1999).

(Photo by William Boarman)

Effects of habitat fragmentation by roads can be attenuated by the use of underpasses and overpasses to provide safe movement of animals. Such linkages, which provide connectivity between the habitats divided by a road, help to maintain the biodiversity of a productive habitat. Connectivity is increasingly recognized as a critical component to the sustainability of healthy wildlife populations. Especially important is the ability of top predators, such as lions, bears, and coyotes here in California, and grazing ungulates, such as deer and bighorn sheep, to move through large landscapes. Top predators help to keep an ecosystem healthy by controlling the populations of midsize predators, such as foxes, skunks, raccoons, and opossums that eat birds and their eggs, thus depleting bird populations. The movement of grazing animals to different pastures reduces overgrazing and allows recovery of vegetation.

This photo (Boarman, 2002a) shows an underpass created specially for the threatened desert tortoise, (Gopherus agassizii) which is susceptible to damage by road traffic. Boarman and Sazaki reported finding 115 tortoise carcasses along 28.8 km of highway in the Mojave Desert in one year (Boarman, 2002b). In an effort to reduce mortality Boarman studied the ability of the tortoise to use an underpass using a computerized tracking system. The study showed five tortoises used the underpass 75 times over a period of two years indicating the value of this system for reducing tortoise deaths (Boarman, 2002a).

Spreading Roads in the Desert

Desert ecosystems are especially sensitive to the effects of constructed roads and off-highway vehicles (OHV) that form single tracks across an open area. Because of the sparse vegetation there are few signals to indicate to an OHV driver where the road goes and frequently they prefer to create new roadways, thus increasing the area over which the destructive actions of the OHV on the desert habitats take place (Jennings, 1997). Desert surfaces are quickly damaged by vehicle tracks; the thin crust that is found over most desert soil will be destroyed by only one pass of an OHV. Restoration of this crust which contains fungi, plant roots, mosses and lichens that aid in water retention, nitrogen fixation and uptake of other nutrients require at least one rainfall to be restored and may take several years (Stebbins 1995).

Not only do OHV riders increase the damage they cause to habitat by not following trails, but the desert areas in which they prefer to drive, such as washes, canyon bottoms, and hilly country, are the areas where desert tortoises are most frequently found. The tortoises are highly vulnerable to being struck by OHVs as they use the desert washes for their burrows and for travel; the plants they most prefer to eat are found in desert hills, washes and washlets. (Jennings 1997).

The Effects of Conservation Efforts

Protection of desert ecosystems can best be accomplished by refusing to build new roads through desert areas, and by removing those old roads no longer needed to access a mine or a ranch not actively used. Environmental groups have been successful in protecting threatened and endangered species by reducing road uses through legal action. In this way, they have achieved the closure of over 500,000 acres of the California Desert Conservation Area to OHVs to protect the Coachella Valley fringe-toed lizard, Pierson's milkvetch, and the desert tortoise, as well as seasonal closures of lambing areas of the Peninsular bighorn sheep (CBD, 2003).

As desert lovers, we must be aware that opening new roads, and reopening old roads, will lead to destruction of valuable, and fragile, desert ecosystems and thus hasten the loss of threatened and endangered desert species. Driving through the desert should not be a way to get there faster, it should allow us a slow look at unique and unusual ecosystems and landforms, and take us to a place where we can get out and hike through the heart of the desert, getting to know the special plants and animals that are specially equipped to survive in this unique environment.

References

Boarman, WI. "Tortoise Underpasses." Critter Crossings,
2002a. Http://www.fhwa.dot.gov////////environment/wildlifecrossings/tortoise.htm

Boarman, WI. "Threats to Desert Tortoise Populations: A
Critical Review of the Literature." p. 54, 2002b. http://www.dmg.gov/documents/DT-Threats.pdf

Brooks, MS, Esque, TC, & Schwalbe, CR. " Effects of exotic
grasses via wildfire on desert tortoises and their habitat." 24th Annual Meeting, The Desert Tortoise Council, 1999, www.deserttortoise.org/

Center for Biological Diversity (CBD).
Http://www.biologicaldiversity.org/ accessed 6/9/03

Forman and Deblinger. "Estimate of the area affected
ecologically by the road system in the United States." Conservation Biology 14:36-46, 2000.

Forman. "The ecological road-effect zone of a Massachusetts
(USA) suburban highway." Conservation Biology 14:31-35, 2000.

Gelbard, JL & Belnap, J. "Roads as conduits for exotic plant
invasions in a semiarid landscape." Conservation Biology 17:420-432, 2003.

James, Meg. "Highways Taking Toll on Wildlife; The
mountain lion population in Southern California is dwindling, and cars are the animals' biggest threat." Los Angeles Times [Orange County Edition]. (Record edition).Los Angeles, Calif.: Sep 3, 2000. pg. 1 Accessed 8/04/03 at www.latimes.com

Jennings, WB. "Habitat Use and food preferences of the
desert tortoise, Gopherus agassizii, in the Western Mojave Desert and impacts of Off-Road Vehicles. Proceedings: Conservation, Restoration, and Management of Tortoises and turtles-An International conference, pp. 42-45, 1997.

Stebbins RC. "Off road vehicle impacts on desert plants and
animals." The California Desert: An introduction to Natural Resources and Man's Impact. Latting J, Rowlands PG, eds., Vol II, 1995, p 467-480.

Copyright 2003 by Janet Anderson

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