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Yosemite Nature Notes 47(3) (1978)


James Sano
Alexander Moad

On August 25, 1916, the National Park Service was created by an Act of Congress “to conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations.” In Yosemite National Park, where total visitation was over 2.75 million people last year, the National Park Service is faced with a rather perplexing dilemma: that of preserving the park resources for tomorrow’s visitors while providing a recreational experience for today’s visitors.

Particularly vulnerable to the adverse influence of overuse are Yosemite’s backcountry areas. Increased visitation in backcountry areas, 10 to 20 percent greater each year, has resulted in considerable environmental damage. Such problems as trampling of fragile meadows, creation of new trails, improperly placed firerings, and the accumulation of litter has received considerable attention within the past decade and has resulted in the creation of the Wilderness Permit System by the Park Service. This system was established to determine how and where the backcountry is being used, to limit the numbers of visitors to the highly impacted and fragile areas, and also to provide a quality wilderness experience for as many people visiting the backcountry as possible (we’re sure you wouldn’t want to hike 10 miles to a backcountry lake and find 200 other people camped there).

One facet of park use which has received less attention is the use of stock in and its impact upon the Yosemite backcountry. The use of stock in Yosemite precedes its genesis as a National Park. Explorers introduced stock into Yosemite in the mid-1800’s, the cavalry regularly patrolled the area on horseback around the turn of the century, and both the Park Service and the park concessioners have consistently made use of stock in their operations. Currently, stock use in Yosemite’ can be divided into four categories: the National Park Service (horse patrols, backcountry patrols, cleanup of the backcountry, and trail crews) comprises 15.6% of the total usage; the Yosemite Park and Curry Company (recreational rides, and supplying the High Sierra Camps) 40.7%, other permitted packers 1.3%, and private parties 42.3%.*

[*Use determined by estimated animal unit month of use per group]

At present, the effects of stock on the Yosemite ecosystem are only generally known. Stock impact can essentially be divided into three types: (1) the physical impact of stock on trails and meadows (2) grazing effects and (3) aesthetic factors.

Although the use of stock constitutes less than 3% of total backcountry use, the physical impact of a horse on both trail and off trail areas is generally much greater than that of a human. This disproportionate impact is perhaps greatest in wet areas, particularly in alpine and subalpine meadows, where studies indicate between 10 to 100 times the impact of a single human. The animal’s greater weight carried upon it’s narrow sharp hooves easily punch holes in wet meadows and create new trails (i.e. Mono Pass and vicinity, around Sunrise High Sierra Camp, around Elizabeth Lake and Nelson Lake, and the trail between Delaney Meadows and the Dog Lake junction). Studies indicate that in fragile wet meadows, all it takes is 2 or 3 animals to get a trail underway. On established trails stock often deepen and dig up the soil by dragging their feet (especially packstrings) — backpackers, avoiding loose soil, rutted trails, or manure, then walk along the margins of these trails, widening them or creating new trails.

During the later part of the 1800’s grazing of domestic animals, including stock, resulted in considerable damage to Sierran meadows. One of the primary reasons John Muir and other conservationists advocated the need for the establishment of Yosemite National Park was to eliminate this grazing damage. Muir wrote in 1882, “Most of the level floor of the Valley is fenced with barbed wire and about three hundred head of horses are turned loose every night to feed and trample the flora out of existence. I told the hotel and horsemen that they were doing all they could to prevent lovers of wild beauties from visiting the Valley . . .”

Studies by Park Naturalist Carl Sharsmith have shown that stock grazing is highly selective with regard to species chosen, sometimes resulting in the elimination of certain species, in favor of other species, often non-native. Besides species composition changes within the meadow vegetation, there are also indications that grazing along meadow forest fringes disturbs the topsoil, enhancing the encroachment of lodgepole seedlings.

Finally there are the aesthetic problems associated with manure on trails (John Manure Trail, anyone?). We are not particularly offended by the presence of manure on trails, although we have never really learned to become fond of it. However, we realize that some people are bothered by it, and thus it does present a problem.

The use of stock in the backcountry is currently being regulated by the Park Service to minimize environmental damage. Overnight stock parties like backpacking groups, are limited to 25 head (25 backpackers are considered to have the same impact as 25 people and 25 head of stock.) The use of stock off of park trails, the shortcutting of switchbacks, and the grazing of stock in meadows near High Sierra Camps are prohibited. Although grazing is allowed in meadows other than those surrounding High Sierra Camps, stock users are asked to use picket lines stretched between trees instead of staking stock in meadows.

We have found the issue of stock impact to be a highly controversial one, fraught with emotional overtones. On the one hand we have encountered individuals who are vehemently opposed to stock, largely based upon emotional responses rather than careful analysis of the issue. We have also encountered stock users who refuse to admit that stock may have any adverse effects upon the environment. Research conducted on stock use indicates that both of these positions are unrealistic — stock can have adverse environmental effects, but it represents only one component of total backcountry use resulting in environmental impact.

The consensus of most researchers is that off trail stock use is highly detrimental, especially in wet meadow environments, and it seems obvious that the Park Service should continue to prohibit cross-country travel by stock. However, there exists some confusion as to what constitutes an established trail suitable for stock use. A possible solution to this problem is for the Resources Management Office to determine which areas and trails are appropriate for stock use — thus closing areas and trails to stock where major deterioration of the ecosystem results from such use.

With respect to established trails there is a general agreement among Park Service employees involved with stock use, that the impact of stock is not so much a problem of stock but rather insufficient trail maintenance. There are methods of trail construction that minimize the adverse impact of stock. However, these methods are expensive — the Park Service has only limited funding available for trail maintenance. One means of sharing the additional burden of trail maintenance would be to charge a small fee to private parties bringing stock into Yosemite. Also, the cost of maintaining trails to and from the High Sierra Camps could be shared with the park concessioner. Furthermore, additional attention should be given to the question of overnight and day party sizes of stock, currently the same as hikers, in view of the greater impact of stock.

Research has shown that extensive grazing on meadows can result in elimination of species and the general deterioration of this environment. What is not known is how much grazing constitutes overgrazing. Until further quantitative research is conducted to determine this, extreme care must be taken to preserve fragile high altitude meadows, which require long periods of time to recover from damage. Possible means of doing this might include rotational grazing of certain areas to allow rest periods for the meadows, the avoidance of grazing in the early part of the season when the meadows are wet, and a moratorium on grazing in the alpine and subalpine meadows until the grazing impact can be determined.

Whatever one’s attitude toward stock it must be remembered that the use of stock plays an integral role in the management of Yosemite National Park. Horses are regularly used for campground and backcountry patrols, saddlestock are used in trail maintenance, and to pack out trash. The alternative to these uses would be the intrusion of helicopters into the backcountry. Stock when used on maintained trails have only slightly more impact than hikers. However, stock when used improperly can have a much greater impact than hikers alone. If Park resources are to be preserved for future generations stock users, both public and private sectors must therefore take great care to minimize their impact.


Bennett, Peter S., An Investigation of the Impact of Crazing on Ten Meadows in Sequoia and Kings Canyon National Parks. M.A. Thesis, Dept. of Biology, S.J. State College, CA., unpublished. 1965.

Boche, Kenneth, Factors Affecting Meadow Forest Borders in Yosemite National Park, CA. M.A. Thesis, Geography Dept., U.C.L.A., unpublished. 1974.

Briggs, George S., Yosemite National Park, A Report on Backcountry Conditions and Resources, With Management Recommendations, unpublished. 1974.

Holmes, Daniel O., et. al., The Effects of Human Trampling and Urine on Subalpine Vegetation: A Survey of Past and Present Backcountry Use, and the Ecological Carrying Capacity of Wilderness. Yosemite National Park, unpublished. 1973.

Laing, Charles C., A Report on the Effects of Visitors on the Natural Landscape in the Vicinity of Lake Solitude, Grand Teton National Park, Wy., unpublished. 1961.

Sargent, Shirley, JOHN MUIR IN YOSEMITE, Flying Spur Press, Yosemite, CA. 1971.

Sharsmith, C., Report of the Status, Changes, and Ecology of Backcountry Meadows of Sequoia and Kings Canyon National Parks, unpublished report USNPS. 1959.

. . . . . , A Report on the Status, Changes and Comparative Ecology of Selected Backcountry Areas in Yosemite National Park That Receive Heavy Visitor Use, unpublished USNPS. 1961.

Storer, T., et. al., SIERRA NEVADA NATURAL HISTORY: AN ILLUSTRATED HANDBOOK. University of California Press, Los Angeles, CA. 1961

Strand, S., Wilderness Impact Study Report: Progress Report on Pack Animal Impact on Wilderness Meadows, Sierra Club Outing Committee. 1972.

Sumner, L., Special Report on Range Management and Wildlife Protection in Kings Canyon National Park, unpublished USNPS. 1940.

Wood, S., Holocene Stratigraphy and Chronology of Mountain Meadows, Sierra Nevada, CA. Ph.D. Dissertation, Calif. institute of Technology, Pasadena, CA. unpublished. 1975.

Willard, Beatrice, Effects of Visitors on Natural Ecosystems in Rocky Mountain National Park: Report #5, unpublished. 1962.

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Online Library: Title Author California Geology History Indians Muir Mountaineering Nature Management