ATV and helmet in Mojave Desert.
Surviving the 140-degree heat of the Mojave Desert requires a mean set of survival skills that the desert tortoise holds second to none. But while the tortoise can live without water for a year or more, the loss of habitat has caused its numbers to decline by 90 percent since the 1980s. Today, the desert tortoise is listed as a threatened species.
With the tortoise down on its luck, another threat has come into play- off-road vehicles (ORVs). Vehicles like ATVs and dirtbikes often destroy the underground burrow that provides refuge for the tortoise and their young during daylight hours. Some tortoises meet their end crushed under the wheels of larger ORVs.
The good news is that a recent federal district court ruling against illegal ORV routes in the Mojave gives the tortoises a fighting chance at survival. But California is not the only one dealing with the intrusion of ORVs, which do much more than crush burrows.
The use of ORVs has risen dramatically over the years. Because of their noise levels and their ability to travel across a wide range of landscape, their impact on wildlife can be devastating.
TWS ecologist Michele Crist undertook an extensive review of scientific literature on her report Addressing the Ecological Effects of Off-Road Vehicles to catalog the various impacts of ORVs in the environment.
Most recently, attempts have been made to open the pristine backcountry of the Lewis and Clark National Forest in Montana to ORVs and other motorized transport. The National Forest currently only allows travel on foot or horseback. A state-of-the-art landscape analysis employed by Wilderness Society scientists showed that the proposed changes would result in the fragmentation of key wildlife areas and the disruption of the wildlife’s natural behavior and movement patterns.
Wildlife species that must move from place to place to breed, forage, and overwinter are particularly vulnerable to habitat fragmentation produced by dense road or trail networks created by ORVs. Studies have shown that female bobcats will not cross roads or trails, which become defacto boundaries of their territories. Elk, when exposed to ORV traffic, will abandon large areas even if they are abundant in food only to shift into small overgrazed forests patches where ORV trails are absent.
ORVs are also responsible for the spread of invasive or noxious plants. In Montana, seeds of an invasive plant, spotted knapweed, were shown to hitchhike at an undercarriage of the ORV for distances up to 10 miles. This plant rapidly invades pasture and rangeland and causes declines in native grasses and forbs.
Another concern is air and water pollution. Researchers have found that some vehicle types vent 25 to 30 percent of their oil and gas unburned, a far greater quantity than do vehicles not intended for off-road use. When ORV users ford streams, they cause the erosion of the stream bank and removal of vegetation. Vegetation loss may result in increased water temperature which increases the metabolic rate and oxygen demand of fish and other aquatic species.
As ORV off-trail riding increases, along with demands for more ORV recreation opportunities, the environmental effects of ORV use need to be carefully analyzed and incorporated into strategic travel management plans to cope with arising conflicts between recreation and environmental protection. Also, land management agencies should protect public lands by permitting ORV use only to the extent that monitoring and enforcement are annually funded and properly implemented. Education of the public and self-policing on the part of ORV users can also help ensure the success of ORV management and therefore protect and conserve public land for future generations.
ATV and helmet in Mojave Desert.
Desert tortoise. Courtesy USFWS.