Rangeland and Herd Management
Healthy Horses on Healthy Ranges
The BLM’s goal is to ensure and maintain healthy wild horse populations on healthy public lands. To do this, the BLM works to achieve what is known as the Appropriate Management Level (AML) – the point at which wild horse and burro herd populations are consistent with the land’s capacity to support them. In the context of its multiple-use mission, AML is the level at which wild horses and burros can thrive in balance with other public land uses and resources, including vegetation and wildlife.
The AML is a range of low to high values that allows for population growth over a four to five year period. To establish AML, the BLM evaluates several years of rangeland resource and population data. Those evaluations include such data as vegetation, soils, weather, and water quality.
Each Herd Management Area (HMA) has its own AML. When AML is exceeded, the excess animals are gathered and then prepared for adoption or sent to long-term pastures.
This type of rangeland management is different from management of wildlife, which are controlled by hunters and natural predators, or livestock, which are controlled by grazing permits. Because of Federal protection and a lack of natural predators, wild horse and burro herds can double in size about every four years. As of February 2011, the BLM estimated that 38,500 wild horses and burros roamed BLM-managed rangelands in 10 Western states, or nearly 12,000 more than the West-wide AML of 26,600.
In 1971, wild horses and burros were found roaming across 53.8 million acres of Herd Areas, of which 42.4 million acres were under the BLM's jurisdiction. Today the BLM manages wild horses and burros in subsets of these Herd Areas (the subsets are known as HMAs) that comprise 33.7 million acres, of which 26.9 million acres are under BLM management.
To do its work, the BLM uses qualified science and technology staff and a citizen-based advisory board. The agency also supports research to keep track of the health of wild horses and burros and the condition of the range. This includes research on population suppression techniques.