ASSESSMENT

A Grazing and Rangeland Strategy

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Historic Rangeland Ecosystems

Poorly managed or unmanaged livestock use of Sierra Nevada rangelands, especially during the late 1800s, contributed to reduced productivity and impaired health of these ecosystems. Continuing problems in some riparian areas and the persistent dominance of exotic annual grasses in foothill and east-side rangelands, with the accompanying decline in potential productivity of these sites, warrants an examination of historical causes and possible remedies for these problems.
Historical accounts of rangeland condition and use in the late 1800s indicate that highly productive rangeland communities existed throughout the study area when Europeans arrived. Large elk herds were present on the west side of the range. Native perennial grasses were dominant in the grassland communities, although exotic annuals had begun their invasion even before the arrival of the first missions in 1769, evidently resulting from the travels of early Spanish explorers throughout the Southwest more than two hundred years earlier.
During the late Pleistocene (before 10,000 years ago), a grass-sagebrush rangeland existed where montane and subalpine forests occur today, while at lower elevations conifers occurred. The sagebrush grasslands supported a diverse ecosystem of now extinct megafauna, including a large number of herbivores and a formidable group of mammalian predators. The disturbance regime associated with these herbivores, quite unlike livestock disturbance under traditional livestock management, would have presumably provided several crucial functions for sustaining the high productivity of rangeland ecosystems, including the breakdown of dead plant material and the recycling of nutrients, while allowing seed germination and seedling establishment. These landscape-level energy and nutrient transfers increased energy flows and perennial plant cover, thereby increasing the net productivity of rangeland vegetation, improving the rangeland water cycle, and increasing water capture by plants. The synergistic nature of the relationship between Pleistocene herbivores and rangeland productivity, although not known for certain, is supported by recent research with alternative livestock management practices that have substituted high-intensity, short-duration grazing for the traditional low-level, chronic grazing disturbance. Also unknown is whether or not the Sierra Nevada grassland ecosystems encountered by Euro-Americans were disturbance adapted, as might have been the case prior to the extinction of the Pleistocene megafauna.

Effects of Early Use of Rangelands

The first extensive use of Sierra Nevada rangelands for livestock began in the 1860s. A number of observers reported severe and repeated overstocking until about 1900, due in part to a lack of regulation of the common rangelands. The combination of poor grazing practices and extended periods of drought contributed to the conversion of Sierra foothills from perennial to annual grasslands and is also implicated in the expansion of juniper woodlands on the east side of the range.
Without regulation of access during the late 1800s, overutilization of the common rangelands of the Sierra Nevada occurred. With unregulated use of this common-pool resource by many livestock operators, no user had incentive to reduce usage or conserve resources, because any benefit so conserved was quickly captured by other users. As a result, Sierra Nevada rangelands were overgrazed, in that native forage plants did not have enough time to recover after severe, repeated grazing. As unregulated grazing was eliminated, recovery of some of the rangeland vegetation in many areas was fairly rapid, at least in terms of forage production.
Fire has perhaps had the largest effect on Sierra Nevada rangeland. From 1880 to 1910 sheepherders set large fires every fall as they left the public lands. These fires opened vast areas of western montane slopes and foothill chaparral shrubland areas to livestock grazing and left large areas subject to erosion. Where there was regrowth of nutritious forbs and shrubs, deer numbers increased dramatically. In contrast, fire-suppression policy since that time has generally allowed decadent habitat conditions to develop except where wildfire or vegetation management programs have restored some of the natural role fire has in these ecosystems.
Until the Taylor Grazing Act of 1934, little attention was given to livestock grazing capacity limits. During World Wars I and II, increased livestock use occurred again on public rangelands, often without regard to appropriate stocking rates. It is clearly apparent from well-documented Forest Service allotment reports that managers recognized that grazing problems were occurring. Given the emphasis at the time, managers believed that transient cattle and sheep use and range depletion were jeopardizing the local livestock economy. From the 1950s through the early 1970s, stocking rates on many allotments were reduced to levels closer to sustainable grazing capacity but still above that threshold and without adequate safeguards for riparian habitats. Range improvement activities common during this period included water developments, range seedings, brush control, and other practices that attempted to restore former grazing capacities.
Sierra Nevada and Modoc Plateau rangelands are susceptible to exotic annual grass and forb invasion following depletion of native perennial grasses. Overgrazing can also influence soil compaction, erosion, and lowering of water tables. Reducing perennial grasses allows for increased water availability in soil, which then promotes continued invasion by exotic annual plants, sagebrush, and juniper. For the same reason, yellow star thistle, an exotic annual forb, has spread and is altering native biodiversity and ecological functions of Sierra Nevada foothill annual grassland and oak woodlands. When short-season annual grasses and forbs replace perennial grasses, forage productivity and carrying capacity are reduced for livestock and wildlife.
In the 1970s, stream riparian wildlife and fisheries habitat concerns began to surface, and public land-management agencies developed various riparian initiatives. Following numerous demonstration projects, interdisciplinary research projects, symposia, and workshops, major new management actions began. Widespread adoption of practices is slow in coming, but riparian-sensitive management has continued to increase over the last twenty-five years. Today it is a prime factor in livestock grazing management.