The Desatoya HMA covers 157,836 acres of public lands in central Nevada and has an AML of 180. The stocking rate allowed by plan is 1.1 horses per thousand acres, slightly more than the average rate of one animal per thousand acres across all areas managed for wild horses and burros.
The horses allowed by plan require 180 × 12 = 2,160 AUMs per year.
The HMA intersects four grazing allotments. Table 3-2 in the Draft EA for wild horse management actions provides grazing seasons and permitted forage inside the HMA but does not provide the allotment sizes. Those were obtained from the Allotment Master in the Rangeland Administration System.
Although cattle and sheep are allowed, the following calculations are based on cow/calf pairs only, for a direct comparison to wild horses. The resource requirements of wild horses and cow/calf pairs are said to be equivalent.
The total allotment acreage inside the HMA is approximately equal to the size of the HMA so the HMA was assumed to be 100% subject to permitted grazing.
The Clan Alpine permittees would have to place 851 cow/calf pairs inside the allotment to graze off 10,210 AUMs in 12 months. The Porter Canyon permittee would have to place 605 cow/calf pairs inside the allotment to consume 7,256 AUMs in 12 months.
Note that the stocking rates (densities) for the allotments are several times larger than that for wild horses, consistent with an observation made earlier that productivity goes up when land is designated for livestock.
The forage available to livestock inside the HMA was provided in Table 3-2, so no calculations are required in that column. The total across the four allotments is 9,608 AUMs per year.
The Porter Canyon permittee would have to place 529 cow/calf pairs inside the HMA to consume 6,352 AUMs in 12 months. The total number of cow/calf pairs allowed by plan inside the HMA is 811 and the weighted average grazing season is 11.8 months per year, almost identical to that of the horses.
The stocking rate allowed by plan is 811 ÷ 157,836 × 1,000 = 5.1 cow/calf pairs per thousand acres.
These figures are compared in the following charts.
The HMA—an area set aside for wild horses—is managed primarily for livestock, with the horses receiving just 18% of the authorized forage, excluding wildlife.
The forage assigned to livestock would support an additional 801 horses, for a true AML of 981.
The current population of 215 horses, according to Section 1.2 of the EA, is well within that range, so there are no excess animals and there is no justification for a roundup or fertility control program.
However, given the current management philosophy, and the absence of any meaningful opposition by the so-called advocacy groups, those will be the preferred methods for enforcing the resource allocations and improving rangeland health.