Wild Horses and the Ecosystem

The Wild Free-Roaming Horse and Burro Act recognizes the wild horse as an "integral component of the natural system." It stipulates that horses can only be removed from public lands if it is proven that they are overpopulating or are causing habitat destruction. It further mandates that the government "maintain specific ranges on public lands as sanctuaries for their protection and preservation."

In order to remove wild horses from public lands, the Bureau of Land Management (BLM) has claimed that horses are destroying critical habitat, competing for grazing lands, and overpopulating. But reports by the General Accounting Office and the National Academy of Sciences dispute such claims: BLM has never presented any evidence that horses destroy habitat, nor that their population levels are what it claims they are. In fact, reducing horse populations in a given area has a negligible effect on range conditions: after massive wild horse roundups, herd areas show little or no improvement, especially in instances when cattle numbers remain the same (or increase).

In stark contrast with BLM’s assertions, scientific studies have shown that horses actually benefit their environment in numerous ways; vegetation seems to thrive in some areas inhabited by horses, which may be one reason the Great Plains were once a "sea of grass." Generally, range conditions in steep hilly areas favored by horses are much better than in lower areas frequented by cattle.

Cows have no upper front teeth, only a thick pad: they graze by wrapping their long tongues around grass and pulling on it. If the ground is wet, they will pull out the grass by the roots, preventing it from growing back. Horses have both upper and lower incisors and graze by "clipping the grass," similar to a lawn mower, allowing the grass to easily grow back.

In addition, the horse’s digestive system does not thoroughly degrade the vegetation it eats. As a result, it tends to “replant” its own forage with the diverse seeds that pass through its system undegraded. This unique digestive system greatly aids in the building up of the absorptive, nutrient-rich humus component of soils. This, in turn, helps the soil absorb and retain water upon which many diverse plants and animals depend. In this way, the wild horse is also of great value in reducing dry inflammable vegetation in fire-prone areas. Back in the 1950s, it was primarily out of concern over brush fires that Storey County, Nevada, passed the first wild horse protection law in the nation.

The fact that horses wander much farther from water sources than many ruminant grazers adds to their efficacy as fire preventers. This tendency to range widely throughout both steep, hilly terrain and lower, more level areas, while cattle concentrate on lower elevations, also explains why horses have a lesser impact on their environment than livestock: when one looks at a boundary fence where horses range on one side and cattle range on the other, the horses’ side typically reveals about 30% more native grasses. Their nomadic grazing habits cause horses to nibble and then move to the next bunch of grass. This is why horse range is seldom denuded unless the horses' natural grazing patterns are disrupted by human interference, mostly in the form of fencing.

A team of Russian scientists, part of a cooperative venture with the United States, came in 2001 to study the effects of grazing animals on riparian areas in Nevada. They tested streams for nutrients and examined the desert and Sierra to learn techniques to improve the environment of their homeland. The scientists found that cows, which tend to camp around water sources, cause more damage to the stream banks than wild horses, which tend to drink and move on: "When we saw horses drinking from creeks, we didn't see much impact except for hoof prints. The water looked clean, had good overhanging branches and there was no sign of erosion on the banks. There was an abundance of insects and animals, including frogs and dragonflies and water-striders." Areas extensively used by cattle had fewer nutrients in the water and showed signs of bank erosion and other damage, concluded the study.

Horses have proven useful to other species they share the range with: in winter months, they have the instinct to break through even deep crusted snow where the grass cannot be seen. They also open up frozen springs and ponds with their powerful hooves, making it possible for smaller animals to drink. During the historic blizzard of 1886, hundreds of thousands of cattle were lost on the Plains. Those that survived followed herds of mustangs and grazed in the areas they opened up. Another positive effect of wild horses on biodiversity was documented in the case of the Coyote Canyon horses in the Anza Borrega National Park (California). After wild horses were all removed from the Park to increase big horn sheep population, bighorn sheep mortality actuality skyrocketed: mountain lions, wild horse predators, compensated the loss of one of their prey species by increasing their predation on other species.

Wild horses should not be used as scapegoats for range degradation that is in fact primarily caused by private livestock: for instance, environmentalists have determined that in Nevada, home of the vast majority of America's remaining wild horses, the herds have little impact on the ecosystem compared with the hundreds of thousands of cattle that also roam the Nevada range. The Western Watersheds Project acknowledges that "the main cause of degradation of public lands in the arid west is livestock use and not wild horses."

Emerging Research on Wild Burros

Wild burros (donkeys) are boosting the availability of water in desert landscapes across the American West, according to new research published today in Science. Similar behavior has been observed in wild horses in Australia and Canada. 

The research is challenging the view of these animals as invasive species and is prompting the American Wild Horse Campaign (AWHC), the nation’s largest wild horse and burro protection organization, to call on the U.S. Interior Department to re-evaluate plans to cull federally-protected wild equid herds in the American West to near-extinction levels. 

The research, co-authored by Erick Lundgren, a postdoctoral researcher at Aarhus University in Denmark, focused on wells dug by wild burros in the Sonoran and Mojave Deserts. The findings suggest that the animals are creating unique water sources that are used by more than five dozen native vertebrate species, become vegetation nurseries for keystone trees, and in some cases, represent the only water in the area.

“One of the remarkable things about this to me is that this behavior, and its importance in these ecosystems, has been hiding in plain sight,” said Lundgren. “Pervasive attitudes towards introduced species, based on the idea that some ‘belong’ and some don’t, can prevent us from seeing the world as it really is.”

“When we relax these attitudes and stop chasing fantasies of how the world should be, we find unexpected resilience and emerging interdependencies in modern ecosystems,” he continued. 

Based on data collected through wildlife cameras, Dr. Lundgren documented that burros: 

  • Increased the density of water features, reduced distances between waters, and, at times, provide the only water present in surveyed desert ecosystems
  • Provided water to 59 native vertebrate species
  • Influenced vegetation serving as germination nurseries for native trees to grow
  • Had the strongest effect/provided the most water to critical intermittent streams, which are projected to decrease due to mining, agriculture, and climate change

“We hope that this groundbreaking research dispels the false narrative of wild burros and horses as invaders and establishes their vital role in the desert ecosystems where they live,” said Suzanne Roy, executive director of the AWHC. “We believe that the Biden Administration, which has prioritized science-based  policy-making, must consider this research and immediately re-evaluate the current plans to round up and remove the majority of wild burros and horses living in the American West over the next five years.” 

The report cites previous research on the removal in the1990’s of the majority of wild burros from the Ash Meadows Wildlife Reserve in Nevada. After the burros were removed, open springs were choked by vegetation, destroying open-water habitat for endangered native fish populations. Despite best efforts of land managers to mimic the wild burros by manually removing the vegetation, at least one pupfish population went extinct.

In 2013, the National Academy of Sciences warned that the federally protected burro population was facing a genetic crisis due to small, geographically dispersed populations that are regularly subjected to capture and removals by the Bureau of Land Management (BLM), the Interior Department agency responsible for their management. 

Despite this, the BLM has continued to pursue mass wild burro roundups, like the one pending in the Lake Mead area of Nevada, which aims to eradicate wild burros from 1.7 million acres of public land that borders Dr. Lundgren’s study area.