Land use plans for the Jackson Mountains HMA assign 10,151 AUMs per year to privately owned livestock, according to Table 3.7 in an environmental assessment from 2012, with 2,604 AUMs per year allocated to wild horses.
The HMA covers 283,775 acres, with an AML of 217. The stocking rate allowed by plan is 0.8 wild horses per thousand acres.
The HMA fits the pattern noted two months ago: Low stocking rates correlate with large amounts of forage assigned to domestic livestock.
The HMA intersects six grazing allotments. Grazing seasons were not given in the EA so a period of 4.5 months was assumed. Although cattle and sheep may be authorized on those pastures, the stocking rate was computed for cow/calf pairs, whose resource requirements are said to be equivalent to those of wild horses.
The entire HMA is subject to permitted grazing. The ranchers would have to place 2,256 cow/calf pairs on the land to graze off 10,151 AUMs in 4.5 months, for a stocking rate of 7.9 cow/calf pairs per thousand acres. If the grazing season was longer, the stocking rate would be lower. The AUM distribution would not change.
These figures are compared in the following charts.
The forage assigned to livestock would support an additional 846 wild horses, for a new AML of 1,063.
The rationale for dividing forage in the Jackson Mountain allotment, which represents 67% of the HMA, was 18% to horses and 82% to livestock, per Section 3.3.4 of the EA.
On two other allotments, the forage allocated to wild horses was zero.
And you wonder why there are so many of them in long-term holding.
The problem is public-lands ranching.