Appropriate Management Level (AML)

Under the provisions of the 1971 Wild Free-Roaming Horses and Burros Act (WFRHBA), a thriving natural ecological balance among wild horse and burro populations, domestic livestock, wildlife and vegetation must be achieved. As first steps, the land’s ability to provide habitat (food, water, cover and space) over the long-term is evaluated and the amount of vegetation available for use as forage is determined. Then the available forage is allocated among wildlife, wild horses and burros and domestic livestock.

Without proper management, the range may be damaged. Desirable native species may be replaced by invasive species such as cheatgrass or Red brome, or noxious weeds such as knapweed or perennial pepperweed. These weedy species out-compete native species, further reducing vegetation diversity. Under these conditions, the range may become unable to produce forage and habitat for the many animals that live there. Healthy rangelands are the foundation for healthy wild horse and burro populations, wildlife, and others who call the public lands their home.

The number of wild horses and burros which can graze without causing damage to the range is called the Appropriate Management Level (AML). In establishing the AML, BLM relies on an intensive monitoring program over several years involving studies of grazing utilization, trend in range condition, actual use, precipitation (climate) and other factors. AML is based on consideration of wildlife, permitted livestock, and wild horses and burros in the area. BLM sets AML with public involvement through an in-depth environmental analysis and decision process.

In Nevada, appropriate management levels of wild horses and burros are generally determined through the multiple-use decision process. This process begins with an evaluation of range conditions; the evaluation assesses whether or not management and stocking levels for livestock, wild horses and/or burros, and wildlife are achieving rangeland objectives. If rangeland health objectives are not being met, changes in management or stocking levels are proposed. Proposed changes are analyzed in an environmental assessment and a proposed multiple-use decision (PMUD) is issued. Proposed decisions are subject to review and protest by parties affected by the proposal. BLM considers all protests filed and then issues a final multiple-use decision (FMUD). BLM’s final decisions are subject to administrative review (appeal).

Did You Know? Most western rangelands produce only a few hundred pounds of vegetation per acre. Because a horse can eat their weight in dry forage every month, in many parts of Nevada, it can take 20 or more acres to feed one horse for a month.

Frequently Asked Questions (FAQs)

Q – What is the appropriate management level of wild horses (or burros)?
A –The Interior Board of Land Appeals (IBLA) has defined the appropriate management level as the ‘optimum’ number of wild horses (or burros) which results in a thriving natural ecological balance and avoids a deterioration of the range. (109 IBLA 119; also reference Dahl vs. Clark, supra at 592).

Q – How does BLM determine the appropriate management level of wild horses and burros?
A – BLM determines the appropriate management level of wild horses and burros based on an ongoing program of monitoring over several years involving studies of grazing utilization, trend in range condition, actual use, precipitation (climate) and other factors. In Nevada, appropriate management levels of wild horses and burros are generally determined through the multiple-use decision process. This process begins with an evaluation of range conditions; the evaluation assesses whether or not management and stocking levels for livestock, wild horses and/or burros, and wildlife are achieving rangeland objectives. If rangeland health objectives are not being met, changes in management or stocking levels are proposed. Proposed changes are analyzed in an environmental assessment and a proposed multiple-use decision (PMUD) is issued. Proposed decisions are subject to review and protect by parties affected by the proposal. BLM considers all protests filed and then issues a final multiple-use decision (FMUD). BLM’s final decisions are subject to administrative review (appeal).

Q – What is the ‘optimum’ number of horses or burros in an area?
A – IBLA ruled that proper range management dictates the removal of horses (or burros) before the herd size causes damage to the rangeland. Thus, the optimum number of horses is somewhere below the number that would cause damage. (118 IBLA 75).

Q – What is a thriving ecological balance?
A – IBLA defined “thriving ecological balance” as follows: “The goal of wild horse and burro management should be to maintain a thriving ecological balance between wild horse and burro populations, wildlife, livestock and vegetation, and to protect the range from the deterioration associated with overpopulation of wild horses and burros.” (109 IBLA 115; also reference Dahl vs. Clark, supra at 592).

Q – Is AML set as a single number or a range in number?
A – AML is generally expressed as a range in number (from low to high). To assure horses and burros have adequate forage and an ecological balance is maintained, BLM periodically conducts gathers to remove excess animals from the range. BLM generally removes numbers in excess of the low range of the AML – this allows the population to grow from low AML to the high AML over a 4-5 year period, without gathers in the interim. This results in less disturbance to individual horses and the social structure of the herd over the long-term.

Q – Why does BLM reduce wild horse or burro numbers without a corresponding reduction in authorized livestock use?
A – As discussed above, BLM Nevada generally establishes a permitted level of livestock use and the appropriate management level of wild horses and burros through the multiple-use decision (MUD) process. The final decision is based on in-depth analysis of range conditions. Through this process, objectives for wildlife habitat management area also determined. Commonly, changes in both livestock management and wild horse and burro appropriate management levels are proposed in order to meet rangeland health objectives. In emergency situations, adjustments for both livestock and wild horses and burros are made.

Q – Why doesn’t BLM further reduce livestock grazing and allow for more use by wild horses and burros?
A – As discussed above, livestock grazing is authorized on about 48 million acres of public land, while wild horse and burro use is limited to about 16 million acres where the animals were found in 1971. Where livestock and wild horse and burro use overlap, BLM evaluates range conditions, establishes management and monitoring objectives, and allocates forage through the multiple-use decision process. Typically, changes in both livestock management and wild horse and burro appropriate management levels are proposed in order to meet rangeland health objectives. Interested public are provided with an opportunity to participate throughout BLM’s planning and evaluation process and are also provided with an opportunity for administrative review (appeal) of BLM’s final decisions.

Q – Can the public participate in BLM decisions which set AML?
A – Yes. BLM sets AML with public involvement through an in-depth environmental analysis and decision process. To participate in BLM’s planning process, write to the Field Office and ask to be placed on their Interested Party mailing list. Also ask to be notified of any proposed decisions for the specific HMAs you are interested in.

Q – How does authorized livestock use compare with wild horse and burro use in Nevada over the past 30 years?
A – Authorized livestock use in Nevada has declined about 45% over the past three decades from about 2,198,371 animal unit months (AUMs) to 1,218,541 AUMs use in 2006. (An animal unit month is the amount of forage needed to feed a cow, one horse or five sheep for one month).

Livestock use is authorized on about 48 million acres of public land. By contrast, under the law, wild horse and burro use is limited to those areas where they existed in 1971 and there is adequate food, water, cover and space to maintain healthy and diverse horse and burro populations -- or about 16 million acres in Nevada.

During the same approximate period, wild horse and burro numbers have ranged from about 16,000 to as many as 35,000 animals (192,000 to about 420,000 AUMs). The first inventory estimated Nevada’s population of wild horses and burros to be about 20,000 horses and 1,000 burros (1973).

Q – Why is it important to maintain the appropriate management level of wild horses and burros on the range?
A – It is important to maintain the appropriate management level of wild horses and burros on the range to assure that Nevada rangelands are healthy and diverse. BLM is also required to ensure a balance is achieved between the land’s ability to produce forage and the demand for that forage by wildlife, livestock, and wild horses and burros.

Q – BLM Nevada’s estimated AML (statewide) is about 13,000 animals. Why can’t more wild horses and burros be managed on 16 million acres of land?
A – Although BLM Nevada manages wild horses and burros on nearly 16 million acres of public land, the use of this land is shared under the principles of multiple-use management and sustained yield (Federal Land Management and Policy Act, 1976). In addition to providing habitat for wildlife and wild horses and burros, many of these lands also provide forage for domestic livestock. They are also used for recreation, wilderness, off road vehicle use, archaeology, mining, forestry, geothermal development, and a host of other uses. Moreover, much of the 16 million acres is too steep or too far from water to be used by wild horses and burros. BLM is required to consider all of these factors in establishing the AML for wild horses and burros.