reported that it would need to conduct a similar monitoring program that would include re-examining the entire HMA and potentially reallocating forage for all animals.

One district reported that in the 1975 HMA planning process, forage-production calculations from 1952 were used to estimate how many animals could be supported on BLM-managed land in the HMA. That carrying capacity was revised in 1975 because of rangeland seedings conducted in the HMA in 1974. BLM then identified the forage allocated to existing livestock grazing privileges in the HMA and subtracted that amount to calculate forage available to horses and wildlife. The state department of fish and wildlife was consulted to determine the forage required by wildlife. Forage allocations to livestock, wildlife, and free-ranging horses were made commensurate with the available forage within a reasonable distance from water and in consultation with the state wildlife agency.

Managers in one state reported limiting forage use to 55 percent of production. No details were provided as to how annual plant production was determined.

The committee received the most comprehensive response to the question of allowable use from managers who used forage production maps from 1958 to estimate total forage production and determined the forage available on the basis of 50-percent utilization rate. The biologists reported currently using monitoring studies to assess and evaluate forage allocations in the HMAs.

Because horses are on the range year-round but cattle are not, temporal separation has been used to distinguish horse and cattle effects on water holes and other features. Surveyed managers of districts in California, Oregon, and Wyoming cited effects on watersheds and riparian areas, riparian utilization, riparian trend, and insufficient or unreliable water as causes for adjustment. “Timing and duration of flow” was also provided as a reason for changing AMLs.

Managers of the 40 surveyed HMAs reported that AMLs often had been adjusted or reaffirmed since 1971. For example, on one HMA, AMLs were changed 13 times from 1979 to 2007. Reasons for the changes were related either to four essential habitat components (forage, water, cover, and space) or to the political process. Examples of reasons included emergency gathers after extensive wildland fire, free-ranging horse distribution data, absence or inadequacy of winter range available for horses, climate and weather, and change in space available to free-ranging equids (for example, because of land closures, land trades, land-use planning efforts, boundary discrepancies, or a “checkerboard” jurisdictional pattern adjoining HMAs). Responders also cited splitting current herds into smaller groups, adverse effects of horses on cultural resources, improving vegetation conditions, enhancing wildlife habitat, and updating management plans as reasons for adjusting AMLs.


a “All Bureau of Land Management grazing allotments are periodically evaluated to assess rangeland health and evaluate the trend in rangeland condition and the influence grazing management has on the multiple rangeland resources associated with these allotments. [As an example, one district] employs two methods of evaluating grazing allotments. The first strategy involves a one-time field assessment by an Interdisciplinary Team composed of various BLM resource specialists. This team completes an assessment based on observations of vegetation and soil conditions. The second, and most commonly used strategy, involves a formal allotment evaluation process. During this process, an interdisciplinary team composed of various resource specialists evaluates resource conditions and creates management recommendations for the allotment. The end product of this process is an allotment evaluation document which summarizes resource conditions and trend and makes recommendations for future grazing management and range improvements on the allotment. Typically allotment evaluations occur every five to 10 years depending on the resource concerns for a given allotment.” (Sharp, no date, p. 1)

does not foster deliberation (Hourdequin et al., 2012). In any case, the decision-making process should be clearly distinguished from the data-gathering and analysis that provide the information used in decision-making. The committee’s focus is on the scientific analysis that feeds into decisions that ultimately must reflect social values, compromise, and economic realities.

A multitiered analysis process is stipulated by the handbook for establishing and adjusting AMLs. Tier One instructs managers of free-ranging horses and burros to “determine

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