The Grass Remembers the Horses

A herd of mustangs grazes on public land in Eastern Oregon.

The United States currently faces a range crisis on its public lands. Federally protected mustangs (Equus caballus) share a degraded range with millions of grazing livestock. Mustangs’ contentious status as an alleged invasive species is at odds with their protective status. Not managed as wildlife yet not classified as livestock, mustangs are removed from the range in the thousands only to live out their lives in costly government holding facilities which eat up most of the Bureau of Land Management’s wild horse and burro budget. The BLM faces heavy opposition to mustangs from ranchers and political lobbyists. The entire public rangeland situation is a tangled web of public outcry, bureaucratic mismanagement, and dueling interests.

This paper seeks to untangle the issues within the rangeland crisis through a “land management design” approach. It presents a thorough background in the natural, cultural, and ecological history of the wild horse in North America and focuses on the current management approaches utilized in the United States. It is possible for all parties with stake in the rangeland crisis to benefit from a land management design approach. The conclusion of the project discusses this at length, and further delves into the socio-political changes that must take place for our public lands and our wild horses to be saved.

Chapter 1: Natural history of the mustang

“You occasionally see one, and it’s the thrill of a lifetime. But mostly all you ever see is a cloud of dust after they’re gone. It’s their stubborn ability to survive that makes them so remarkable.”

— Velma ‘Wild Horse Annie’ Johnston

A young mustang runs from the author on public rangeland in Eastern Oregon.

Mustangs (Equus caballus), also known as feral horses or wild horses, have a varied and contentious natural history that is not agreed upon by experts, and this disagreement over their status as native or introduced has led to a battle over their appropriate management within the United States. There are three dominant theories of the native classification of E. Caballus; (1) that the species originated in North America, spread to Europe, then went extinct in its homeland before being reintroduced as a domestic species in the 1400s and is therefore a genetically native species reoccupying the vacant niches of the North American prairie¹, (2) that the species originated in North America, spread to Europe, then went extinct in its homeland before being reintroduced as a domestic species in the 1400s and is therefore an invasive species², (3) and that the species originated in North America, spread to Europe, and continued to exist in the Americas in reduced numbers well past the end of the Pleistocene era, then interbred and hybridized with domestic horses which were brought over by colonists in the 1400s, increasing their numbers. There is a saying amongst several plains First Nation tribes; “The grass remembers the horses”.

There is no debate that horses originated in North America between 4 and 4.5 million years ago³. As a keystone species in the grassland ecology of the prehistoric continent, horses thrived and spread from North America to other continents. According to the dominant Western historical perspective, horses eventually died out in their homeland near the end of the Pleistocene along with much of the other megafauna of the American plains². This major extinction was allegedly triggered by early human hunting and climatic changes⁴. In contrast to this widely accepted history, several first nation tribes allege that the aboriginal North American horse survived through the end of the Pleistocene and were integral to the pre-colonial contact culture of Great Plains tribes. This claim is backed up by petroglyphs of wild horses dated hundreds of years prior to Columbus’s arrival and the more commonly accepted time that horses were reintroduced to the continent between 1493 and 1540⁵. It is a mark of the Eurocentric belief that all “civilization” came from Europe that colonists and conquerors took credit for the establishment of horsemanship in the Americas⁶. A greater exploration of the mustang as a native species utilized by indigenous tribes long before the arrival of white settlers can be found in section 1.3, Mustangs through a cultural lens.

Due to the dismissal of indigenous oral histories, the arrival of horses back to their ancestral homeland is therefore attributed to Columbus and other Spanish explorers, who bred horses in their missions and colonies, spreading the species across the plains. Today, the United States considers mustangs to be an invasive species, and their management and status within the regulatory bodies of the government is indicative of this classification.

1.2 Mustangs through an ecological lens

Horses provide a variety of ecosystem benefits. Plant species richness and pollinator populations have been found to be higher in areas grazed by horses compared to ungrazed areas and can even mitigate the decline of pollinator-dependent plants⁷. Horses have other interesting effects on the ecosystems they inhabit; by trampling certain vegetation and wallowing near water mustangs can create microhabitats and redistribute nutrients through seed dispersal⁷. Their feces, in addition to spreading seeds, builds the humus layer of soils and increases soil’s absorption of water, lowering wildfire risk. These characteristics are unique to horse feces compared with ruminants such as cattle, sheep, goats⁸, or deer¹. Mustangs have also been shown to commonly graze on cheatgrass (Bromus tectorum), an invasive graminoid which outcompetes native grasses in the western United States. Cheatgrass is a dangerously dry, flammable species which can contribute to the intensity of wildfires in the west. Through the grazing of cheatgrass and other flammable grasses and forbs, wild horses can effectively reduce fire danger on their ranges¹. In addition, a natural behavior displayed by mustang herds is rubbing and scratching trees, knocking off dead and dying limbs, reducing “fire ladders” while simultaneously grazing grasses and browsing on brush fuel beneath the trees they use for shelter⁸.

Like all grazing species, horse overpopulation on scarce land can cause ecological degradation. In Australia, the Brumby, an introduced feral horse species descended from colonial stock, occupies the arid landscapes of the outback in the hundreds of thousands. Australia, a continent whose ecosystems evolved without large hoofed herbivores, has been overwhelmed by enormous populations of Brumbies with no natural predators and no ecological niche. The plants in the arid environment are especially vulnerable to degradation from large herds. Ecological catastrophe brought on by wild horse populations similar to the crisis in Australia is a deep-seated fear amongst range managers and the Bureau of Land Management. Though the total number of mustangs on the range in the United States is several hundred thousand less than those currently running wild in Australia, there is no denying that the vast majority of the United States’ public lands are degraded from decades of livestock grazing and agriculture, requiring that wild horses be carefully managed to avoid ecological disaster in an ever-dwindling habitat.

How can mustangs’ natural ecological benefits be best used, and how can these uses work alongside the dilemma of management the BLM now faces? The answer lies in the plains, where horses were once extirpated from their preferred ranges along with other prairie-dwelling species such as elk, bears, bison, and wolves² as eastern settlers moved west⁹. The largest biome in North America, covering 40% of the continent, the grasslands of the American prairie are now just a fraction of their former range, having been degraded by agriculture. Secondary grassland sites that remain, such as the Little Missouri National Grasslands in North Dakota, are grazed by over 25,000 cattle and covered in acres of oilfields.

1.3 Mustangs through a cultural lens

As covered in Chapter 1.1, Natural history of the mustang, the definition of “native” versus “invasive” is a key distinction that is argued by warring management entities¹⁰, and considered unimportant to the First Nations peoples who consider the horses and their land to be a key element of their cultural landscape and heritage, regardless of whether they are federally designated as invasive or native. Western academia still supports the claims of Spanish conquistadors that they brought the first horses to the Americas, despite contradictory accounts from indigenous peoples stating that the wild horse was always a critical element of their history, culture, and spirituality. According to Doctor Yvette Running Horse Collin in her dissertation “The relationship between the indigenous peoples of the Americas and the horse: Deconstructing a Eurocentric myth”;

“Despite proof of this long-standing relationship, the dominant Western culture remains adamant that it is responsible for introducing the Indigenous Peoples of the Americas to the horse. This action has served as a fundamental attempt to diminish these Indigenous Peoples and their cultures by asserting a Eurocentric position of dominance. In making this claim, the dominant Western culture is saying: “Without us, you would not have these sacred and critical elements of your culture,” and therefore, “Your culture is derivative of our own.” The psychology behind such “factual redoing” combined with a compulsory educational system that teaches “Native history” through the eyes of the colonizer has had grave consequences for Indigenous American communities.”

Wild horses were vital to many Native American communities, especially those that lived on the plains. Horses provided increased mobility, transportation of goods, and status amongst peers. In Choctaw culture, warriors were even buried with their horses “…to help those who were frightened to make a safe transition from this world into the afterlife”¹¹.

Though no longer a key means of transportation in modern communities, horses are still important to life for many tribes. For example, free-roaming horses in the Chilcotin region of British Columbia have been captured and trained for community use for centuries by the Tsilhqot’in First Nations people, who contemporarily use horses for backcountry travel, hunting and harvesting food in remote areas, cultural ecotourism, and community youth activities¹². The Tsilhqot’in people also identify with the horses’ behavior and “…the seasonal movement of small family herds throughout the landscape, which parallel the traditional seasonal movements of small Tsilhqot’in family and community groups” ¹³. Wild horses ground tribes in local cultural and Traditional Ecological Knowledge (TEK) and are vital to the experience of First Nations cultures across North America.

Mustangs were important to the culture of white, black, and Hispanic settlers, as well. This was acknowledged by the government in the 1971 Wild Horse and Free-Roaming Burro Act (Public Law 92–195), which stated, “Congress finds and declares that free-roaming horses and burros are living symbols of the historic and pioneer spirit of the West and enrich the lives of the American people” ¹⁴.

Known as “mustangers”, mesteñera, or vaqueros, different types of men and women captured wild horses in Mexico and the southwestern US territories in the 1800s and “broke” them to ride. Rounding up wild horses was considered an extreme sport to some but was also a means of income and of livelihood for companies of ranch men catching mounts, families of traveling mesteñera who followed wild herds and sold colts, and lone buckaroos looking for bounty money for the capture famous stallions¹⁵. Black cowboys had a particular bond with wild horses. During the second half of the nineteenth century, when the owners of enormous cattle operations needed similarly large labor forces, the roughest jobs were given to black cowboys more often than their white counterparts. Taming wild horses was a dangerous and sometimes deadly occupation and became the work of the black cowboy¹⁶. Bob Lemmon was a particularly famous black mustanger who would ride alone after bands of wild horses for weeks on end until the horses accepted him as their leader, then lead entire herds into corrals without ever using a rope¹⁵.

Cowboy culture depended upon having mustangs to capture and tame. Not only were wild horses a key aspect of the frontier experience, but they were inspirations for artists and became visual symbols of the west. As the pioneer lifestyle faded into the past, novels, movies, and television shows embraced the romantic appeal of horses running wild and free across the landscape¹⁷. Free-roaming horses are ingrained into the fabric of the west and remain a cultural touchstone for the region to this day.

Between Native American and settler culture, the wild horse was the lynchpin for a period of cultural upheaval and the creation of significant tradition in nomadic and agricultural life⁹. The wild horse is one of the most culturally important animals in North American history, having shaped the Great Plains and the West into their current form.

1.4 Rewilding and ecotourism

The daunting task of restoring the north American grasslands, tackled by nonprofit groups such as the American Prairie Reserve, has begun turning towards the restoration model of rewilding. Rewilding is the restoration of landscapes through large-scale, conservation efforts focused on biodiversity, ecosystem health and the reintroduction of apex predators and keystone grazing species¹⁸.

Rewilding is becoming a common ecological practice throughout Europe, and many of these programs use large grazing species, including feral horses, as part of their rewilding practices¹⁹. The introduction of horses in rewilding projects increase biodiversity and maintain or preserve natural grassland mosaics, increasing their suitability for other species²⁰. While most of these European projects fence their horses into smaller pastures and supplement feed in the winter²¹, hardy mustangs have proven that their populations can thrive in their natural environment. With a commitment to allowing natural processes and healthy predator populations on restoration land, mustang populations can be limited by predators alone²². Rewilding has not caught on in North America as it has in Europe, though there are pilot programs, including research with Canadian wild horse populations.

Rewilding and carbon mitigation go hand in hand, and the largest potential biome for rewilding is the world’s grasslands, which cover 25% of the planet’s land surface. Horses are considered mesograzers, which are classified as species with the highest per capita potential to shape climate change drivers. Horse herds affect ecosystem nutrient transportation, landscape fire regimes, and vegetation mosaics, while emitting far less methane than cattle and sheep²³ due to their classification as hind-gut fermenters rather than ruminants.

1.5 Mustangs through a design lens

In the past, industrial capitalism romanticized ranching and pastoralism as noble work, and public lands embraced this. The modern “New West” economy, however, places an emphasis on recreation, leisure, and landscapes dedicated to non-consumptive consumption²⁴. There is no reason that these non-consumptive public landscapes cannot coexist with mustangs. Many residents of states which are home to mustangs are shocked to hear that wild horses exist there and are even more surprised to hear that they are on public land and can be sought out. With the proper infrastructure in place, what parents of a horse-obsessed young girl would deny her a weekend trip to attempt to spot a wild mustang? Given a choice between a regular BLM campground and one on a landscape where wild herds roam, what couple wouldn’t jump on the chance to camp where they could see stallions sparring at dawn?

There are currently little to no public amenities or infrastructure relating to the wild horse herds on our public lands. Maps of Herd Management Areas (HMAs) are opaque and often inaccurate. HMAs are difficult to reach, peppered with private property warning signs, and property lines are unclear. Access roads are not maintained and often unmarked. Visitors hoping to find horses face the difficulty of navigating the gates, lack of signage, and potholed roads of the landscape, all while facing the possibility of mistakenly trespassing into someone’s private land, which may be dangerous.

Mustangs are a cultural touchstone for connecting the public with our public lands. Designing these landscapes while using mustangs as both ecological place-makers and a draw for visitors would create a non-consumptive use on HMAs which could replace the consumptive uses of livestock grazing, timber harvesting, and mining that currently occupy and degrade them.

Chapter 2: Management

“I think having land and not ruining it is the most beautiful art that anybody could ever want.”

-Andy Warhol

A formerly captive BLM mustang rolls in the dust at Skydog Sanctuary in Prineville, Oregon.

2.1 Analysis of current mustang management

Free-roaming horses are not managed as wild or as domestic animals; they currently occupy an entirely unique status among North American mammals²⁵. Rather than being managed by the United States Fish and Wildlife Service, management and control of the majority of mustangs falls to the Bureau of Land Management (BLM), which controls public land use for mining, recreation, and livestock grazing, and a few herds fall under United States Forest Service (USFS) regulation.

For centuries wild horses existed in the millions on American lands. Cowboys and mustangers working for cattle companies in the 18th century began removing the horses to free up forage for livestock, and herds were managed locally well into the 1900s. Ranchers would release horses into herds for new blood and gather prime colts to use as cow ponies. Wild horses were even sold to assist war efforts, being used as mounts in World War 1⁹. The system was self-regulating, keeping herds at stable numbers.

In 1934 the Taylor Grazing Act was passed, which privatized the range and allowed the federal government to lease land for ranching operations. Because of this act and the sudden war for grazing territory, horses began to be removed by the thousands to free up land⁹. Wild herds were decimated and sent to slaughterhouses across North America. Advocates realized that the mustangs would disappear without regulation, and in 1971 The Wild Free-Roaming Horse and Burro Act (WFHBA) passed by Congress classified wild horses and burros as “living symbols of the West” and stated that they would be legally “protected from capture, branding, harassment, or death; and to accomplish this they are to be considered in the area where presently found”. The language “where presently found” refers to the 53.8 million acres of public lands occupied in 1971 when the WFHBA was enacted. Currently, however, horses have been removed from 22.2 million of those acres and are restricted to only 31.6 million acres of their original range, 29.4 million of which they share with livestock. In 2014 there were 37 livestock animals on the range for each wild horse, and 97 percent of forage was allocated to private livestock²⁶.

Some explanation of the BLM’s practices is necessary to understand the context in which mustangs are regulated. Approximately 80 percent of BLM land is authorized for livestock grazing²⁶. As part of their livestock management on public lands, the BLM administers permits and leases to ranchers who graze their cattle and sheep on over 21,000 allotments across the west for a fee¹⁴. These fees change based on yearly calculations. Ninety-four percent of grazing costs are covered by taxpayers²⁹. The grazing fee for 2018 was $1.41 per Animal Unit Month (AUM). An AUM is defined as the use of public lands by a cow and calf, a horse, or five sheep or goats for a single month¹⁴. In 2016, the AUM was 12.3 million²⁶. This count does not include mustangs, of which there were 60,000 on the range¹⁴.

The BLM manages mustangs within 177 HMAs (Herd Management Areas) on public lands in 11 different states¹⁴. The only management tool broadly used to control wild horse populations on federal lands has been the capture and removal of horses from the range²⁷. For the 155 million acres of BLM land being managed, 55.6 million are classified as HMAs and the Bureau has determined that 26,000 horses is the desired carrying capacity. This number is called the Appropriate Management Level (AML). This number is calculated solely by the BLM, and often reduces horse populations within an HMA to below 150 animals, though HMA sizes range from 20,000 to over 500,000 acres each. The recommended number of individual horses for a healthy, viable population by the Equid Specialist Group of the IUCN Species Survival Commission is 2,500¹.

There is currently a rangeland health crisis in the west. From 2013 to 2015, 40 million acres of BLM land (or one-third of the land assessed) did not meet the agency’s standards for rangeland health²⁶. The continued removal of mustangs from public lands has been justified by the BLM as vital to prevent range degradation. However, the impact of 60,000 horses on a range shared by 17.4 million cattle and sheep is not likely to be significant. Studies funded by the Bureau of Land Management claim that horses are far more detrimental to the land than cattle, citing erosion, riparian degradation, and overgrazing²⁸. In direct conflict with these results, several studies have shown instead that pollinators and prairie biodiversity can benefit from¹ equids⁷. The BLM also regularly excludes livestock grazing from Rapid Ecoregional Assessments, instead attributing the bulk of range degradation to the presence of wild horses²⁶. Data are confusing, often biased, and in conflict. To further complicate the issue, research has found that it is impossible to separate grazing effects of cattle and horses when both species forage in the same area, even if at different times of year. Most public rangelands have been managed for cattle for so long that pre grazing conditions are unknown. Unlike other consumptive uses, livestock grazing’s environmental effects are highly variable over time and difficult to discern, making environmental assessments even more obscure²⁴.

There are few areas of public rangeland that remain ungrazed by cattle for extended time periods and even fewer that experience horse grazing but not cattle grazing³⁰, since wild horses and burros share 93% of their range with livestock.

2.2 Political issues on the range

It is clear to all interested groups, from wild horse advocates to cattle ranchers, that the western rangelands are in a crisis. The BLM’s solution of the continued removal of horses. Despite the importance of bottom-up limiting ecological mechanisms of population regulation, between 7,000 to 11,000 mustangs are removed from the range each year to keep horse densities low on lands prioritized for livestock grazing²⁹. Before the 1970s these horses were often euthanized or sold to slaughter, but after the passing of the Wild Horse and Burro Act in 1971, federal law prohibited the slaughter of mustangs, which were instead placed into holding facilities to be adopted out. Unfortunately, due to the increasing economic difficulties in owning horses, adoption rates have fallen. Only 46 percent of the mustangs removed from the range between 2007 and 2015 were adopted²⁶. The remaining thousands of unadopted horses arbitrarily removed from the range live out their lives in small holding facilities and are extremely costly to maintain. In 2013, the BLM spent 64% of the total Wild Horse and Burro program budget on simply keeping these animals in holding facilities²⁰. Assuming no changes are implemented, the current management program is unsustainable.

In 2016 the National Wild Horse and Burro Advisory Board recommended that BLM sale restrictions should be lifted, allowing anyone, including slaughter buyers, to purchase wild horses and burros and to allow euthanasia of animals that could not be sold, in an attempt to empty the overcrowded holding facilities²⁶. This proposal was met with extreme public backlash, and the BLM did not accept the recommendations. The dance of BLM, wild horse advocacy groups, and ranchers all dueling for their own interests to take precedence over the others’ is a common thread in the management of wild horses. In a typical scenario, the BLM announces a plan to remove mustangs from a Herd Management Area (HMA), which livestock ranchers who run their animals on the land are in favor of, and which horse advocacy groups and other public organization groups oppose. The result is public outcry and debate, and many times the BLM has been brought to court, where their decisions are almost always upheld. The mustangs are removed and taken to holding facilities, and the BLM must spend more money maintaining them. Horse advocacy groups protest the crowded facilities, and some groups suggest the destruction or sale of horses, which is also opposed, and the BLM continues the cycle by announcing another horse gather.

The healthy management of mustangs on their range is at odds with the domestic livestock grazing interests of the Bureau of Land Management. During interviews, BLM range managers interviewed for a 2011 study expressed a belief “…that it was their job to advocate for the interests and values of the cattle ranching industry” ³¹, and most ranchers consider mustangs to be pests competing with cattle for limited grazing³². While horse populations are naturally limited by predation²², predators such as mountain lions and wolves are eradicated on BLM land to protect livestock and to ensure that unnaturally large deer populations require hunting, promoting the purchase of hunting licenses and tags¹. Further information on predation can be found in section 2.5 Predation.

The federal government considers wild horses and burros to be a resource value, rather than a land use. Other examples of federally designated resource values include cultural resources, historic, scenic, and rangeland resources, and timber and mineral resources³³. Herd Management Area (HMA) boundaries may be changed through the Land-Use Proposal process to “mitigate unacceptable impacts to other resource values” ³³. This means that wild horses may be legally removed from lands that the BLM considers to be of greater importance as timber, mining, or livestock grazing land.

The Congressional Research Service found in 2005 that forage eaten on BLM lands by livestock amounted to up to 6,835,458 AUMs, while mustang consumption was less than 6% that number. And yet during times of drought, mustang populations were reduced by the BLM by 17% while cattle populations were only reduced by 4%²⁰. Give the discrepancies outlined above, it appears that cattle are the primary concern of the BLM. Colorado, Montana, and Wyoming are home to 109 federal wildlife refuges, and cattle graze on 103 of them². In 2004 critical sections of an environmental analysis of livestock grazing on public lands were removed, and significant rephrasing changed the conclusion of the scientists involved to favor the viability of livestock on public lands and downplay their adverse impact on³⁴ wildlife³⁵.

2.3 Healthy Appropriate Management Levels

The state of Oregon has 2,978,751 acres of land classified as wild horse Herd Management Areas (HMAs), with the goal Appropriate Management Level (AML) of 1,353 horses total³⁶. Most HMAs have a goal AML of 30–50, with the highest recorded AML of 150 individual horses¹⁴. The Equid Specialist Group of the IUCN Species Survival Commission’s recommended number for a healthy and viable wild horse population is 2,500¹. Since 1971, the BLM has removed over 16,900 horses from Oregon rangelands¹⁴.

By keeping mustang numbers so low, normal bottom-up population limitations such as food and density dependence are prevented, which leads to an increase in the population growth rate²⁰. While bottom-up regulation due to resource limitation can potentially limit wild horse populations, we do not let it operate at the scale required for natural regulation to be effective²⁷. These small population sizes are also predicted to lead to a loss of genetic variability within the HMAs³⁷. A minimum population size 150 to 200 animals is recommended by the Department of the Interior to maintain an acceptable level of genetic diversity within herds, with the rate of loss of genetic variation at one percent per generation³³.

Wild horses also compensate in population growth when large numbers of their populations are quickly removed, as happens when the BLM gathers a herd³⁶. A BLM Herd Management Area Plan for Palomino Buttes stated that “…past census and gather data indicate horse populations regularly exceed high AML by the third or fourth year following a gather”³⁸.

2.4 Birth control

Over the past 40 years, research and trials have been employed to develop effective contraceptives for use in wild horse population control, each of which have different strengths and limitations²⁷.

Porcine zonae pellucidea (PZP) is a contraceptive agent that is effective for two years. PZP is classified as an Investigational New Animal Drug (INAD) and may only be administered if a research protocol has been established and guidelines are followed³⁸. PZP is administered to mares via a shot and may not be administered to the same mare more than once every four years. PZP has been found to be effective, but while contraceptive vaccines may be effectively delivered to adequate numbers of animals in small herds through ground-based darting, efficacy of remotely delivered vaccines is lower than manual delivery via syringe²⁷. Therefore, the more effective method of shot delivery is to capture the animals and manually deliver each shot, which the BLM considers to be cost-prohibitive in most cases³⁸.

Castration is also an effective means of birth control, and less expensive³⁸, but is considered an unfavorable approach due to its irreversibility³⁹.

Spaying mares involves major abdominal surgery, is risky, and requires extensive post-operative care³³. In June of 2019, a bipartisan group of 130 members of congress delivered a letter of concern to David Bernhardt, the then-secretary of the US Department of the Interior, expressing their reservations with the proposed surgical sterilization experiment to be conducted on wild horses in the Warm Springs Herd Management Areas in Oregon. This letter urged the BLM to abandon plans to pursue the experiments, citing the withdrawal of experimental academic partners on three separate occasions and the Bureau’s decision to continue with the experiment without academic backing or welfare observations⁴⁰.

2.5 Predation

Predators are removed from public lands not only to protect non-native livestock populations and ranching interests, but to ensure that game animal populations remain high, allowing for federal and state income generated by hunting licenses, tags, and other hunting-related revenue. In a 2004 guideline for wildlife management, Texas A&M suggested that wildlife managers ask themselves these questions when thinking about predator control:

• Is predation limiting game populations?
• What game animals (and what age animals) are most affected by predators?
• In what season of the year is most predation occurring?
• Will the habitat support more game animals if predators are controlled?

None of these questions aimed at wildlife managers focuses on ecological balance or healthy community ecology. These questions instead focus on profit from hunting and increasing that profit where possible.

The majority of the wild horse populations in the US that require population control are in regions where most or all of the top predators have been extirpated through aggressive predator control programs designed to protect rancher and hunter interests⁴¹. A healthy wild horse population in British Columbia, located in a wilderness area in which all top North American predators also thrived, was found by researchers to have minimal signs of range degradation and small herd sizes of 20–30 individuals each⁴², without outside management by governing bodies.

While many articles and books erroneously describe mustangs as having no natural predators, plenty of data can be found on predation rates for wild horses where predators still exist. In the Montgomery Pass Wild Horse Territory on the border of California and Nevada, where a population of five individual mountain lions lived, the population of free-roaming horses was significantly influenced through foal predation. The average yearly number of foals killed by mountain lions was 13.5, which was 45% of the foals produced⁴³. Wild horses killed by cougars were less than six months old, and almost half of the annual foal losses, most due to cougar predation, occurred during the peak foaling period of late May through June. In this case, cougar predation on foals was sufficient to strongly limit the growth of the wild horse population and had beneficial stabilizing effects on wild horse numbers⁴⁴. Other studies have confirmed that foal predation from mountain lions effectively limits population growth²².

Government predator control programs eliminated wolves and grizzly bears in the west and have continued to target mountain lions and coyotes²⁴. The complicit relation of government agencies and livestock interests has led to the direct destruction of nearly all predators on public lands, yet there are no current programs focused on predator reintroduction or population growth on public lands or Herd Management Areas where they might control wild horse populations. The federal government maintains that mustangs have no natural predators, though this is often refuted. A wildlife refuge manager in Arizona even referenced mountain lion predation as a reason for removing a genetically unique herd of Spanish mustangs from a newly obtained property; “It’s pretty obvious that lions are taking some of the colts; that’s why we think it’s important to get them off the refuge as quickly as possible.” The herd was 100 animals strong, and encroaching development and land sales had pushed them onto a small acreage which was overgrazed²⁴.

The multi-use status of most of the Herd Management Areas on public land as grazing allotments is detrimental to the possibility of natural predator-prey interactions limiting horse populations in most areas. Livestock grazing directly affects cougar numbers, because depredating individuals may be killed, and stock also may compete with native ungulates, thereby influencing predation patterns on native prey⁴⁴. Wolves are also often killed by livestock owners, to protect sheep, goats, or young cattle from possible predation. Interestingly, in a study on a population of wild horses in Canada, local interviewees reported that wolves preyed on free-roaming horses and observed wolves to preferentially prey on horses over cattle in surrounding areas¹².

2.6 Disturbance regimes

As ecosystem engineers, horses create other beneficial changes through their physical actions. In the winter horses break ice with their hooves, allowing other species access to water, and in the summer dig to create small water catchments, creating intermittent riparian habitat for desert species¹. Large-scale herd movements in deep snow may also reduce snow insulation in northern landscapes, leading to an increase in permafrost freezing, potentially mitigating methane loss and woody plant encroachment²³.

Horse’s unique single-unit or soliped hooves can loosen topsoil as they move across the landscape in high-intensity short-duration grazing bouts. This nomadic soil loosening, combined with their moisture-rich dung, can increase carbon sequestration in soils and promote nutrient cycling²³.

Horse herds use their ranges heterogeneously, with daily and seasonal movements over large tracts of lands²⁵. These wide-spread movements are confined to narrow trails throughout the landscape, which are frequently used as travel routes by many species of wildlife¹². In a single study, remote cameras recorded movements on horse trails of moose, mule deer, grey wolf, mountain lion, Canada lynx, and others⁴⁵. In more vegetative understories, these trails also create more diverse forest conditions of wind and light exposure, allowing for a greater diversity of plant and animal species to fill in niches. In cold seasons, herd movements open trails through snow, letting smaller animals move through the environment more easily¹.

A mustang herd makes it was across a patchy landscape on an HMA in Eastern Oregon.

While established horse trails do have adverse effects such as soil compaction and the reduction of vegetation cover, these effects have been found to be limited and localized to the trails themselves, much like human hiking trails or cattle runs. Offsetting these local adverse effects, areas around horse trails show increased plant species diversity, and the presence of horse feces increases native plant diversity⁴⁶.

2.7 Precedents

Precedents for alternative management of free-roaming horse populations exist across the globe, as equids are present on every continent except Antarctica. In Chilcotin, British Columbia, the Elegasi Qayus Wild Horse Preserve is an excellent example of a blending of cultural and ecological significance within a management framework. Founded in 2002, the Preserve was created by the Xeni Gwet’in First Nations government with the objective of maintaining and restoring the threatened population of wild horses to be used as part of the Xeni Gwet’in cultural and wilderness tourism program and for capture for domestic use⁴⁷. The First Nation members manage the wild horse population in the preserve, which sits within a larger Aboriginal Wilderness Preserve roughly the size of Yellowstone National Park, without any outside influence from the British Columbian government⁴⁸. There are an estimated 800 to 1,000 horses present on Xeni Gwet’in land, with about 42% living within the Wild Horse Preserve. Due to the tribal government’s refusal to degrade the wilderness with mining, livestock, or timber practices, the Elegasi Qayus Wild Horse Preserve remains in pristine condition, and is home to all top North American predators⁴⁵. Due to the presence of these predators and the harsh northern climate, very little population management is necessary. In keeping the horses at a more ecologically sound population size, limiting population factors also help to regulate growth rate of horses in the preserve. The Xeni Gwet’in people also capture and train horses for backcountry travel, hunting and harvesting food in remote areas, and use them in cultural ecotourism, and community youth activities¹². After the official designation of the preserve the Xeni Gwet’in and the Friends of the Nemaiah Valley (FONV) volunteer network created the Wild Horse Ranger Patrol program, which provides surveillance and protection to horses and other wildlife living within the preserve from poachers and tracks the numbers and health of herds⁴⁸. The Xeni Gwet’in also fund and hire environmental consultants and independent researchers, and host graduate student studies within the preserve. As a precedent for hands-off management, the Elegasi Qayus Wild Horse Reserve offers a glimpse of how simple wild horse management can be on a landscape that is untouched by extensive deforestation, agriculture, or livestock grazing. It also provides an example of embracing free-roaming horses as a cultural and ecological resource within a healthy wilderness landscape.

On a much smaller scale, the 501(c)3 nonprofit sanctuary Return to Freedom, located in Central California, provides a precedent for healthy herd management techniques using birth control. Covering only about 1500 acres and providing a habitat for over 350 mustangs, the sanctuary prides itself on being a model of solution-based non-invasive wild horse management. Unlike most wild horse sanctuaries which geld stallions or separate mares from stallions to prevent population growth on small acreage, Return to Freedom (RTF) maintains harem herds to allow for natural social behaviors⁴⁹. RTF utilizes the porcine zonae pellucidea (PZP) birth control vaccine on all of it’s mares, darting them remotely from a distance, as they would be treated on BLM land if usage of the contraceptive was widely adopted. From 1999 to 2011, RTF found the PZP to be 85–91% effective on their herds. From 2012 onward, they have achieved 98% efficacy⁴⁹. Though Return to Freedom is an extremely small sanctuary, their population of horses is well over the Bureau of Land Management’s desired AML for any of their Herd Management Areas, and RTF is a positive example of minimally invasive and humane mustang management that could be applied at large or small scales on federal land.

The Greater Côa Valley rewilding project in Northern Portugal is an example of healthy land management at the ecosystem scale. This massive rewilding project set aside approximately 250,000 acres of land for conservation and utilizes grazing horses as part of their restoration process. The Côa Valley suffered from agricultural abandonment, excessive forest fires, and economic depression before the rewilding project was established. Core rewilding zones were established to connect habitat and create ecological buffer zones, and 87 horses were released to reduce fire danger and enhance grassland functionality. The reintroduction of the Iberian wolf has created a healthy predator-prey system, and the Rewilding Europe foundation has plans to release a second herd of horses into the landscape in the near future. What makes the Côa Valley rewilding project a truly unique precedent is its pioneering nature-based tourism model, which seeks to boost the local economy of the valley. Rewilding Europe offered loans to locals to create rewilding focused-enterprises across the valley, including bed and breakfasts, campgrounds, an extensive hiking and horseback riding trail, and safari and wildlife-tourism programs⁵⁰. The foundation also has the long-term goal of creating a 300,000-acre wildlife corridor connecting the valley to the Malcata mountain range and has begun the process by purchasing parcels of land and signing land-use agreements with local landowners. The rewilding project chose a wild horse as the logo for the Great Coa Valley Project. In an interview team leader Pedro Prata explained, “We decided to change the animal on the trademark too because the Rewilding Project Team will work more with wild horses… in the future.” He also noted that ancient engravings of wild horses are found in the area, further connecting the landscape to horses.

The Greater Côa Valley rewilding project is an example of how Herd Management Areas in the United States can be transformed into ecologically viable landscapes which promote healthy populations of wildlife and horses while creating opportunities for economic growth and the development of the ecotourism industry in the American west. Through the creation of vast areas of restored wilderness and reintroducing predators, the BLM could reduce its budget for mustang gathers and turn that money towards advertising campaigns targeted towards bringing visitors to the great outdoors, and benefit in turn from the revenue generated by tourism and increased recreational opportunities.

2.7 A Call to Action

In order for meaningful strides to be made towards increasing the health of our treasured public lands and saving the remaining wild horses on those lands, certain changes must be implemented:

• We must remove or drastically reduce livestock AUMs within herd areas. This can be achieved through offering to buy private land parcels within HAs or providing ranchers with subsidies for removing livestock from their land.
• We should significantly decrease extractive land-uses such as timber harvesting and mining in herd areas.
• Unless specifically prohibited, public lands managed by the BLM are currently open to licensed hunting. Disallow hunting of predators within HAs, including cougars, coyotes, bobcats, bears, and wolves to allow natural top-down ecosystem regulation to take place.
• The BLM needs to reduce the number of gathers. Gather only when AML surpasses IUCN recommendation of 2,000 horses and allow for the natural population limitation to occur when necessary.
• In tandem, the BLM should significantly increase AML to at least half of the IUCN’s recommended 2,000 horses.
• The US Department of Fish & Wildlife needs to increase conservation and population growth efforts for predators in HAs. Reintroduce large predators such as cougars and wolves to HAs whenever possible. Partner with nonprofits and wildlife conservation funds to study animal behavior.
• The BLM needs to release excess horses currently in holding to increase the ALM of currently depleted HAs and relieve the BLM of the economic burden of maintaining these individuals in holding.
• The US Government should offer an incentive program to landowners looking to restore degraded agricultural land who will host small herds of gathered mustangs on their properties for periods of 5 to 10 years.
• The BLM must increase use of PZP birth control in all HAs.
• The government should partner with local communities to increase ecotourism potential. Spend extensive capital on advertisements and funding the creation of tourism enterprises like viewpoints on HAs, hiking/biking trails through HAs, and nearby camping/lodging opportunities to economically revitalize towns.
• The BLM could create annual local horseback round-up and sale events embracing the history of the mustang in the creation of the west. Embrace the tourism aspects of these events.
• Similarly, the BLM could create a mounted range manger program to monitor herds.
• The BLM should utilize natural barriers of HAs to create natural edges and reduce the need for range fencing. This may remove from or add land to HAs.
• They should also promote opportunities for habitat connection between HAs to increase genetic viability of herds and increase the health and vitality of rangeland ecosystems as a whole.

Chapter 4: A Tangled Rope

“But some animals, like some men, leave a trail of glory behind them. They give their spirit to the place where they have lived, and remain forever a part of the rocks and streams and the wind and sky.”

— Marguerite Henry

Black and white mustangs trot amongst the sagebrush on public rangeland in Eastern Oregon.

Over the past fifty years, hundreds of individuals both within the BLM and without have expressed the belief that wild horse management must change. Countless scientific and popular articles about the range crisis and the exploding population of mustangs in holding facilities have been published, and outraged advocacy groups have called for reform without understanding the complexities of the public land systems in the United States. This paper provides only the barest understanding of the tangled rope of bureaucracy, stakeholders, private interest groups, animal rights organizations, and corporate ranches which snares and trips up anyone who might attempt to untangle it.

The most frustrating aspect of writing this paper was the feeling that a solution- one that leaves all parties relatively content, that benefits our public lands and allows an iconic species to live on the range while drawing the public to enjoy our wilderness spaces- is possible but is ever so slightly out of reach due to one thing or another; Congress’ refusal to deny the beef industry, wild horse advocacy groups’ inability to budge on matters such as spaying or euthanasia, the BLM’s stubborn adherence to obsolete land-use plans, or ecologists’ dismissal of new evidence of wild horses’ status as a native species. Were any one group to give ground or any two organizations to compromise, a solution seems maddeningly attainable. As it stands, no one will back down or accommodate, wild horses continue to be removed, the BLM continues to hemorrhage money, and public rangelands continue to suffer.

As with many of the “wicked problems” ⁵¹ facing the world and especially the United States, the issue of the management of wild horses and our public lands is ingrained within the cultural mold of our government, capitalism, and how we value the environment. Wild horse herds will not be self-sustainable without healthy rangelands and dynamic predator systems. Intact predator systems will not exist while consumptive uses such as hunting and livestock grazing are prioritized on public land. Consumptive uses on public lands will continue until society decides that healthy ecosystems take priority over capital gain.

This is not to say that there is no hope for future reform. The current strides in the production of cultured meat could revolutionize the meat industry, replacing most range-raised beef with lab-grown alternatives in the not-so-distant future⁵². These developments will doubtless have impacts on the cattle industry and subsequently our public rangelands. What this will mean for wild horses remains to be seen, but a collapse of the traditional meat industry and the removal of livestock from public lands could provide a rare opportunity for an overhaul of public land policy and management and a switch to environmentally focused stewardship.

Even without a drastic change in the overall management of our public lands, reform in how the BLM’s Wild Horse and Burro Program manages excess wild horses is very possible. As the concept of ecological restoration has become integrated into North American culture in recent years⁵³, landowners and managers are beginning to seek out more and varied alternative management and restoration methods. The burgeoning popularity of using wild or feral horse herds in the restoration of degraded agricultural lands²⁰ in Europe¹⁹sets a successful precedent for utilizing mustangs in the United States. As of March 2021, the BLM reported that there were 52,832 “excess” wild horses and burros held in off-range government holding facilities at a cost of approximately $50 million a year¹⁴. Ecological restoration or “rewilding” represents untapped potential for revenue, environmental benefit, and a solution to the dilemma of maintaining horses in holding facilities. A government program offering financial incentive or tax breaks to landowners who host small herds of gathered mustangs on their properties for periods of 5 to 10 years with the goal of restoring degraded agricultural land would benefit landowners, the BLM, the environment, and wild horses. This elegant solution would be relatively easy to enact with minimal upheaval of the current system and maximum beneficial impact.

The knot of problems facing mustangs is not going to untangle itself. While simple and innovative ideas like incentive programs or predator reintroduction present solutions to parts of the issue, there is no blanket approach which will solve all aspects of the problem. A way forward will require concerted effort and collaboration on the part of all parties involved, and compromises for the sake of preserving an icon of the west and the public lands that it calls home.

[1] Downer, C. C. (2014). The Horse and Burro as Positively Contributing Returned Natives in North America. American Journal of Life Sciences, 2(1), 5. https://doi.org/10.11648/j.ajls.20140201.12

[2] Manning, Richard (1995). Grassland: The History, Biology, Politics, and Promise of the American Prairie. Viking penguin, New York, New York. ISBN 0–670–85342–9

[3] Olsen, F. W., & Hansen, R. M. (1977). Food Relations of Wild Free-Roaming Horses to Livestock and Big Game, Red Desert, Wyoming. Journal of Range Management, 30(1), 17. https://doi.org/10.2307/3897326

[4] Garrot, R. A. (2018). Wild Horse Demography: Implications for Sustainable Management within Economic Constraints. Human-Wildlife Interactions 12(1): 46–57.

[5] Ryden, Hope (1999). America’s Last Wild Horses. The Lyons Press, Guilford, Connecticut. ISBN 978–1–59228–873–1

[6] Kirkpatrick, J.F., & Fazio, P.M. (2010). Wild Horses as Native North American Wildlife. The Science and Conservation Center, Zoo Montana. Billings, Montana.

[7] Garrido, P., Mårell, A., Öckinger, E., Skarin, A., Jansson, A., & Thulin, C. (2019). Experimental Rewilding enhances Grassland Functional Composition and Pollinator Habitat use. Journal of Applied Ecology, 56(4), 946–955. https://doi.org/10.1111/1365-2664.13338

[8] Simpson II, W.E (2019). “Impact of Wild Horses on Wilderness Landscapes & Wildfire: Preliminary Findings Report.” N.P

[9] Mott, A. L. (2014). Running Wild, Running Free? Changing Perceptions of Wild Horses in the American Landscape. North Dakota State University. Fargo, ND.

[10]Bhattacharyya, J., Slocombe, D. S., & Murphy, S. D. (2011). The “Wild” or “Feral” Distraction: Effects of Cultural Understandings on Management Controversy Over Free-Ranging Horses (Equus ferus caballus). Human Ecology, 39(5), 613–625. https://doi.org/10.1007/s10745-011-9416-9

[11] Running Horse Collin, Y. J. (2017). The Relationship Between the Indigenous Peoples of the Americas and the Horse: Deconstructing a Eurocentric Myth. Doctor of Philosophy in Indigenous Studies Dissertation. University of Alaska Fairbanks.

[12] Bhattacharyya, J., & Murphy, S. D. (2015). Assessing the role of Free-Roaming Horses in a Social-Ecological System. Environmental Management 56: 533–446. Hhttps://doi.org/10.10007/s00267-015-0508-y

[13] Bhattacharyya, J., & Murphy, S. D. (2015). Assessing the role of Free-Roaming Horses in a Social-Ecological System. Environmental Management 56: 533–446. Hhttps://doi.org/10.10007/s00267-015-0508-y

[14] Bureau of Land Managment (2020). Hhttps://blm.gov

[15]Dobie, J. F. (1936). The Mustangs. United Kingdom: University of Nebraska Press.

[16] Mrzon, M. A. (2016). “Black Cowboys of the Cattle Frontier”. Legacy. 16(1): Article 3. Available at: https://opensiuc.lib.siu.edu/legacy/vol16/iss1/3

[17]Slatta, R. W. (2001). The Mythical West: An Encyclopedia of Legend, Lore, & Popular Culture. ABC-CLIO. Oxford.

[18]Rewilding Europe (2021). Hhttps://rewildling.org

[19] Corlett, R. T. (2016). The Role of Rewilding in Landscape Design for Conservation. Current Landscape Ecology Reports, 1(3), 127–133. https://doi.org/10.1007/s40823-016-0014-9

[20] Nuñez, Cassandra M.V.; Scorolli, Alberto; Lagos, Laura; Berman, David; and Kane, Albert J., “Management of Free-Roaming Horses” (2016). Natural Resource Ecology and Management Publications. 280. https://lib.dr.iastate.edu/nrem_pubs/280

[21] Vitkalova, AV, Feng, L, Rybin, AN, et al. “Transboundary cooperation improves endangered species monitoring and conservation actions: A case study of the global population of Amur leopards”. Conservation Letters. 2018; 11: e12574. https://doi.org/10.1111/conl.12574

[22] Turner Jr., J. W., Wolfe, M. L., & Kirkpatrick, J. F. (1992). Seasonal mountain lion predation on a feral horse population. Canadian Journal of Zoology, 70(5), 929–934. https://doi.org/10.1139/z92-132

[23] Teitelbaum, C. S., Sirén, A. P. K., Coffel, E., Foster, J. R., Frair, J. L., Hinton, J. W., Horton, R. M., Kramer, D. W., Lesk, C., Raymond, C., Wattles, D. W., Zeller, K. A., & Morelli, T. L. (2021). Habitat use as indicator of adaptive capacity to climate change. Diversity and Distributions, 27(4), 655–667. https://www.jstor.org/stable/26991456

[24] Sayre, N. F (2002). Ranching, Endangered Species, and Urbanization in the Southwest: Species of Capital. The University of Arizona Press Tucson.

[25] Beever, A., & Brussard, P.E. (2000). Examining Ecological Consequences of Feral Horse Grazing Using Exclosures. Western North American Naturalist. 60(3): 236–254.

[26]Hurwitt, M. C., (2018). Freedom Versus Forage: Balancing Wild Horses and Livestock Grazing on the Public Lands, 53 Idaho L. Rev. 425

[27]Garrot, R. A. (2018). Wild Horse Demography: Implications for Sustainable Management within Economic Constraints. Human-Wildlife Interactions 12(1): 46–57.

[28]Kaweck, M. M., Severson, J. P., & Launchbaugh, K. L. (2018). Impacts of Wild Horses, Cattle, and Wildlife on Riparian Areas in Idaho. Rangelands, 40(2), 45–52. https://doi.org/10.1016/j.rala.2018.03.001

[29] Devlin, M (2018). 2018 Investigation of Paisley Desert Wild Horse Program. Report on five Wild Horse Herds and Herd Management Areas in Oregon. Wild Voices.

[30] Beever, A., & Brussard, P.E. (2000). Examining Ecological Consequences of Feral Horse Grazing Using Exclosures. Western North American Naturalist. 60(3): 236–254.

[31] Bhattacharyya, J., Slocombe, D. S., & Murphy, S. D. (2011). The “Wild” or “Feral” Distraction: Effects of Cultural Understandings on Management Controversy Over Free-Ranging Horses (Equus ferus caballus). Human Ecology, 39(5), 613–625. https://doi.org/10.1007/s10745-011-9416-9

[32] Rubenstein, D. I., Cao, Q., & Chiu, J. (2016). Equids and ecological niches: Behavioral and life history variations on a common theme. In Wild Equids: Ecology, Management, and Conservation (pp. 58–67). Johns Hopkins University Press.

[33] United States Department of the Interior, W.E (2021)

[34]N.A (1991). Three Rivers Resource Management Plan (PMP): Environmental Impact Statement. United States. N.P

[35] Dalke, K. (2011). A Translocal Perspective: Mustang Image in the Cultural, Economic, and Political Landscape. Animals, vol 1. 27–39. https://doi.org/10.3390/ani1010027

[36]Downer, C. C. (2018). Report on five Wild Horse Herds and Herd Management Areas (HMA) in Oregon, with Results of Detailed Ecological Evaluations of two HMAs conducted in 2017. Wild Voices.

[37]Garrot, R. A. (2018). Wild Horse Demography: Implications for Sustainable Management within Economic Constraints. Human-Wildlife Interactions 12(1): 46–57.Garrot, R. A. (2018). Wild Horse Demography: Implications for Sustainable Management within Economic Constraints. Human-Wildlife Interactions 12(1): 46–57.

[38]BLM, (2009). “Palomino Buttes Herd Management Area Plan”. Bureau of Land Management Burns District Office. Hines, Oregon

[39] BLM, (2009). “Paisley Desert Herd Management Area Wild Horse Population Control & Gather. Environmental Assessment”. Bureau of Land Management Lakeview District Office. Lakeview, Oregon. DOI-BLM-OR-L050–2009–0066-EA

[40] Congressional Communication, 2019

[41]McCrory, W. (2002). Preliminary Conservation Assessment of the Rainshadow Wild Horse Ecosystem, Brittany Triangle, Chicotin, B C Canada: A Review of Grizzly and Black Bears, Other Wildlife, Feral Horses, and Wild Salmon. British Columbia, Canada.

[42] McCrory, W. (2015). A Preliminary Genetic Study of the Wild Horse in the Brittany Triangle Region of the Elegesi Qayus Wild Horse Preserve of British Columbia. British Columbia, Canada.

[43]Turner Jr., J. W., Wolfe, M. L., & Kirkpatrick, J. F. (1992). Seasonal mountain lion predation on a feral horse population. Canadian Journal of Zoology, 70(5), 929–934. https://doi.org/10.1139/z92-132

[44] Hornocker, M, & Negri, S. (2009). Cougar: Ecology and Conservation. University of Chicago Press.

[45] McCrory, W. (2015). A Preliminary Genetic Study of the Wild Horse in the Brittany Triangle Region of the Elegesi Qayus Wild Horse Preserve of British Columbia. British Columbia, Canada.

[46]Otterman-Kelm, S. D., Atwill, E. A., Rubin, E. S., Hendrickson, L.E., & Boyce, W. M. (2009). Impacts of feral horses on a desert environment. Biomed Central Ecology.

[47]Hurwitt, M. C., (2018). Freedom Versus Forage: Balancing Wild Horses and Livestock Grazing on the Public Lands, 53 Idaho L. Rev. 425

[48]Friends of the Nemiaiah Valley, (2021)

[49] Return to Freedom, (2021). https://returntofreedom.org

[50] Rewilding Europe, (2021) http://rewildingeurope.org

[51]Rittel, H. W., & Webber, M. M. (1973). “Dilemmas in a General Theory of Planning.” Policy sciences, 4(2), 155–169.

[52]Choudhury, D., Tseng Ting, W., & ,Swartz, E (2020). The Business of Cultured Meat. Trends in Biotechnology. Volume 38, Issue 6, Pages 573–577. ISSN 0167–7799. https://doi.org/10.1016/j.tibtech.2020.02.012.

[53]Aronson, J., Clewell, A.F., Blignaut, J.N., & Milton, S.J (2006). Ecological Restoration: A new frontier for nature conservation and economics. Journal for Nature Conservation, V 14: 3–4. ISSN 1617–1381.