Human activities can have serious effects on the sensitive Great Basin ecosystem. Federal public lands constitute the vast majority of the area. The Bureau of Land Management (BLM), an agency of the Department of the Interior, is charged with managing most of these public lands. Land managers are grappling with how to accommodate both human needs and long-term sustainability of the ecosystem. Once degraded, arid ecosystems, such as the Great Basin, are generally unlikely to return to their original state and hence are termed "fragile," because they exhibit little resilience in the face of human-induced changes.

Scarce Water Resources: California's Mono Lake, located at the base of the Sierra Nevada mountains in the southwestern Great Basin, typifies what has happened to many Great Basin lakes in recent years. In 1941, the city of Los Angeles extended the Owens Valley aqueduct to the Mono Basin to provide water to its burgeoning population. Since then, the lake has been lowered more than 12 meters. This has halved the storage capacity of the lake, doubled its salinity, and transformed shorelines into alkali flats. It also created a causeway from the mainland to a former island, allowing coyotes to reach and destroy the resident gull population. Fortunately, a recent agreement between the affected parties will begin the restoration of the lake.

In another part of the Great Basin, Las Vegas city water engineers are proposing to tap into the underground waters beneath remote valleys of eastern Nevada. Preliminary environmental studies suggest that the effects of this proposed engineering effort could be widespread. Groundwater pumping could lower the water table and destroy streams and marshes that support plant and animal life in desert basins. Even Death Valley National Monument, some 160 km away, could be affected.

Mining: For more than a decade, Nevada has been the nation's principal gold-producing state. Apart from its obvious uses for jewelry-making, gold's physical and chemical properties are without equal for use in such high-tech fields as medicine, space, architecture, and electronics. But the extraction of minerals does not come without a price. The mining of hard rock minerals- a group that includes gold, silver, and copper - is governed on the public lands by the Mining Law of 1872. This law allows miners and mining companies to acquire public lands with "commercial quantities" of mineral ore at a cost of only $2.50 an acre, with no royalties paid to the government. Many believe that the law is an anachronism, a relic of a bygone era when the government owned vast open areas that nobody else wanted and sought to promote interest in these lands. Others feel that the law provides still-needed incentives to encourage mining exploration and development, with their inherent risks.
The effects of historic mining on the public lands are dramatic. Often shafts from abandoned mines pose health and safety hazards, threatening hikers with dangerous falls and exposure to radioactive materials. Unreclaimed mines are also the source of acid runoff and heavy metal contamination of streams. The pond-like reservoirs of cyanide solution used in modern heap leach gold mining have posed a threat to migratory waterfowl poisoned after mistaking the ponds for natural lakes.

Tourism: The expanses of the Great Basin provide one of the last refuges for people seeking solitude or an escape from urban congestion. While tourism is generally considered a "clean" industry that can be compatible with environmental protection, it usually carries considerable baggage. Hotel and infanstructure development (sewer, water, utilities), air and water pollution, erosion and sedimentation of heavily visited areas, trampling and degradation of vegetation and wildlife habitat, and illegal artifact collecting and vandalism at archaeological and historic sites are activities that can result in negative effects on the ecosystem.

Grazing: Many small towns in the Great Basin are carrying on a traditional ranching culture that dates back to the 1850s, and many ranchers depend on public lands for grazing of their cattle and sheep. Overgrazing at the end of the last century and the early part of this century, combined with frequent large floods, led to degraded riparian (streamside) areas. When cattle congregate along riparian areas, they urinate and defecate into the streams, and they trample streamsides and cause the banks to erode. As a result, stream channels widen, and sediment in the water increases; ultimately, streams become shallower. The loss of riparian vegetation exposes the waters to the sun's rays, raising water temperatures. Certain fish species cannot tolerate the higher temperatures. Increased sediment also threatens fish by reducing the amount of available oxygen in the water. In upland areas away from streams, congregating cattle can compact the soil, which reduces water infiltration, leading to erosion, gullying and channel cutting. Today, government land managers and individual ranchers are working to restore and improve riparian areas. Although much work remains to be done, considerable progress has been made to improve conditions.

Land managers and private land owners are concerned about the spread of noxious weeds for many reasons. Noxious weeds are reducing the diversity and quantity of native plants, rendering habitats nearly unusable by wildlife, reducing forage, decreasing water quality, accelerating erosion, and increasing the economic costs of maintaining recreation and wilderness areas. The squarrose knapweed (Centaurea virgata), for example, expands its range by releasing a chemical inhibitor into the soil so that more desirable plants are prevented from growing in the same area. Another exotic, saltcedar (Tamarix ramosissima), increases evapo-transpiration to the point that invaded springs cease to flow: the lower water table around these springs effectively precludes native species from surviving. Ranchers and those associated with the hunting industry suffer an economic impact because less forage is available to livestock and wildlife.
Native grasses of the Great Basin are easily destroyed by overgrazing. Overgrazing, in turn, helps speed the growth of noxious weeds such as cheatgrass. Like most other exotics, cheatgrass (Bromus tectorum) was introduced into the United States from the Asiatic steppe. Because it evolved under pressure from camels, horses and other grazers, it can comfortably coexist with cattle. In fact, overgrazing gives cheatgrass a decisive advantage over native plant species. This plant also grows throughout the winter, which allows it to send roots into deep pockets of moisture before its competitors can. Even on well-managed grazing land, cheatgrass is a tenacious competitor. It can also invade areas where no grazing has occurred. Eventually, cheatgrass becomes so dense that fire spreads faster; fire further weakens the native plant community, which evolved under a less frequent fire regime. Allowed to continue unabated, this cycle will result in a plant community of low diversity.

Wild Horses and Burros: In sharp contrast to exotic weeds, which people generally disdain, wild horses and burros tend to intrigue most people, although these animals also can pose a threat to the Great Basin ecosystem. More than 40,000 wild horses and burros roam the western ranges, descendants of domestic horses and burros that escaped or were turned loose from early Spanish settlements, ranches, mining communities, Native American tribes and the U.S. Cavalry. Three wild horse herds even exhibit characteristics of the early Spanish Barb horse, brought to American in the 1600s. The Spanish Barb is related to the extinct tarpan horse, from which it derives such features as tiger-striped legs, mask-like facial markings, and an extra lumbar vertebra.

In 1971, Congress passed the Wild Free Roaming Horse and Burro Act to protect these animals; this law, together with the absence of natural enemies, has led to steadily increasing herd sizes. To ensure the health and welfare of wild horses and burros, provide adequate forage for wildlife and domestic livestock, and maintain a thriving ecological balance, herd size must be controlled. Since 1973, BLM has administered the Adopt-a-Horse-or-Burro program, whereby excess animals are rounded up from the range and placed in private care.

An Ecosystem Approach
In the past, land managers focused on one issue at a time, whether it was wildlife, recreation, cultural resources, or cattle grazing. Today, managers acknowledge that such a singular focus rarely works, because ecosystems are complex integrated systems. Consequently, land management agencies are shifting to an ecosystem-based approach to their task (see Smith, Brook, Tisdale, 1994). The holistic philosophy involves resource users in implementing resource management practices and decisions, and in establishing goals for an area (for example, quality of life, forage production, or desired landscape). Because users are involved in setting these goals, and because the goals are constantly being monitored, evaluated, and updated to take into account critical issues, holistic resource management is gaining wider acceptance.

James Kirk Gardner

Kangaroo rats are part of the Great Basin Ecosystem. One species, the chisel-toothed kangaroo rat, has teeth that allow it to eat leaves from the shadscale bush, a salty plant that few other animals want. During the spring, kangaroo rats can eat the succulent leaves whole. During the rest of the year, the rats pass the "dry" leaves over their chisel-shaped incisors, extracting the inner tissue, which contains only 3 percent sodium, and discarding the rest of the leaf. Their specialized teeth allow the rat to reduce salt intake, control water balance problems, and sidestep competition with other rodents that survive primaeily on seeds.

Prevention: Prevention of resource degradation is clearly the cheapest, most effective, and highest priority technique for addressing ecosystem challenges. Monitoring an ecosystem's components is the critical first step in determining where a system is at risk.
One such BLM effort, the "Riparian Wetland Initiative," involves inventorying the approximately 280,000 km of streams that the agency manages, including many in the Great Basin, to determine whether the streams are in "proper functioning condition." The BLM examines such characteristics as the width of the riparian zone, the presence of active beaver dams, the type and age of vegetation along the stream, the stability of the streambanks, and the stream sinuosity.

The BLM also is developing new methods to classify, inventory, and monitor rangelands under the "Rapid Assessment Program." Scientists select indicators of the biotic and physical environment to characterize an area in comparison to a reference area, where ecological processes are functioning properly.
The Environmental Protection Agency heads up another monitoring and assessment effort known as the "Environmental Monitoring and Assessment Program" (EMAP). This collaborative project attempts to place local monitoring results in perspective within a larger geographic context and to develop innovative methods for anticipating emerging problems before they reach crisis proportions.
Once areas are inventoried, prevention measures can be implemented to reverse trends toward degradation. In the case of weed management, history shows that if preventive measures are not initiated when the problem is first identified, the eventual control and restoration costs will be substantially higher down the road. One example from outside the Great Basin illustrates this point. In 1955, Okanogan County, Washington, could have spent $1,500 for knapweed control. Instead, in 1971 they spent $1.5 million in "cleanup" costs. According to one researcher, nine new weed species enter this county yearly, so early detection is very important.
To prevent or reduce the impacts of noxious weeds on natural ecological processes, land managers can change the period of use so that livestock graze when cheatgrass is most plentiful and before it reproduces; set prescribed burns to destroy stands of exotic weeds before their seeds ripen; apply chemical treatments and herbicides; reseed with "desireable" exotics or adapted native species that can outcompete invading weeds; or greenstrip, which involves planting strips of fire-resistant vegetation to reduce the size and frequency of wildfires. Insects are also being tested as a means of controlling noxious weed infestations. Also, uprooting goes a long way in controlling certain noxious weeds, such as the Scottish thistle.

Mitigation: Public lands in the Great Basin support extensive livestock grazing. Some adverse effects of this activity can be mitigated by wise range-management practices, such as rotating grazing use on three, four, or even five pastures over the course of several years. Under this system, grazing is rotated seasonally or annually, and ranchers base the rotation on the condition of available forage. A seasonal rotation gives plants time to complete their growth cycle and set seed for regrowth, while annual rotations allow pastures to be rested periodically. Rotational grazing also benefits wildlife that may be competing for the same forage as livestock.
To minimize damage to riparian areas caused by livestock, the BLM and the ranchers involved have begun to construct fences along certain streams. These "exclosures" have openings to allow livestock to reach the water, but the openings are placed in confined, unshaded areas with little forage to discourage livestock from congregating there. Fencing has allowed riparian plants to become reestablished; the riparian plants increase the storage capacity of stream banks which, in turn, raises the water table and provides a buffer against drought.

Restoration: A BLM project undertaken in Elko County, Nevada, in cooperation with a host of partners, demonstrates some of the measures that can be employed to restore or rehabilitate an ecosystem after it has been degraded.
The BLM acquired about 18,800 rangeland hectares in exchange for 264 high-value hectares in Las Vegas. The city gained land crucial for future growth and development. In exchange, the BLM acquired key habitat for the threatened Lahontan cutthroat trout, consolidated some of its land holdings, restored the fishery along the Marys River, and met some of the recreational needs in Elko County. An activity on the accompanying foldout provides a detailed account of how the citizens of Elko County worked with the BLM to improve the health of the land in a manner that resulted in economic and other benefits.

As tomorrow's decision-makers, today's students will play a key role in determining how our public lands are used, in developing new environmental technologies, and in finding creative solutions to tough problems. Their contributions will affect environmental conditions not only in this country but also in other countries around the world, who look to America for help in combating environmental challenges. To fulfill this responsibility, students will need to be informed about all sides of an issue and to understand why healthy ecosystems benefit everyone.

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