Grazing and grasslands

DEFINITIONS: Grazing is the consumption of any plant species by any animal species; grasslands are ecosystems where grasses and other nonwoody vegetation predominate

While grazing is of mutual benefit to plants and animals, overgrazing is ultimately detrimental to both the plant and animal populations, as well as to grassland ecosystems. Maintaining a balance between grazing animals and the plants on which they feed prevents deleterious consequences.

Grasslands are characterized by the presence of low plants, mostly grasses, and are distinguished from woodlands, tundra, and deserts. Grasslands experience sparse to moderate rainfall and are found in both temperate and tropical zones. Grassland plants coevolved over millions of years with the grazing animals that depended on them. Wild ancestors of cattle and horses, as well as antelope and deer, were found in Eurasian grasslands. On the North American prairie, bison and antelope prospered. Wildebeest, gazelle, zebra, and buffalo dominated African savannas, whereas the kangaroo was the preponderant grazer in Australia. Grasslands occupied vast areas of the world more than ten thousand years ago, before the development of agriculture and industrialization, and the subsequent explosive growth of the human population.

Grazing is a symbiotic relationship whereby animals gain their nourishment from plants, which, in turn, benefit from the activity. Grazing removes the vegetative matter required for grasses to grow, facilitates seed dispersal, and disrupts mature plants, permitting young plants to take hold. Urine and feces from grazing animals recycle nutrients to the plants. The grassland also attracts other animals, including invertebrates, birds, rodents, and predators. The grasses, grazing animals, and grassland carnivores, such as wolves or cat species, constitute a food chain.

Grasses are generally well suited to periods of low rainfall because of their extensive root systems and can go dormant during periods of drought. Humans have been an increasing presence in grassland areas, where more than 90 percent of modern crop production occurs and much urbanization and industrialization have taken place. The remaining grasslands, unsuitable for crops because of inadequate rainfall or difficult terrain, are used for grazing by domesticated or wild herbivores. In addition, many woodland areas around the world have been cleared and converted to grasslands where animals can graze.

Impacts of

Continued heavy grazing of a given area leads to deleterious environmental consequences. Even repeated removal of leaf tips will not adversely affect the regeneration of grasses, provided that the basal zone of the plant remains intact. Whereas animals can generally safely eat the upper half of the grass shoot, if they ingest the lower half, which sustains the roots and fuels regrowth, they will eventually kill the plants. Overgrazing leads to denuding of the land, invasion by less nutritious plant species, caused by decreased of rainwater by soil, and starvation of animal species. Because the loss of plant cover changes the reflectance of the land, climate changes can follow that make it virtually impossible for plants to return, with desertification an ultimate consequence.

The number of animals is not the only factor in overgrazing; the timing of the grazing can also be detrimental. Grasses require time to regenerate, and continuous grazing will inevitably kill them. Consumption too early in the spring can stunt their development. Semiarid regions are particularly prone to overgrazing because of low and often unpredictable rainfall; regrettably, these are the areas of the world to which much livestock grazing has been relegated, because the moister grassland areas have been converted to cropland.

Overgrazing has contributed to environmental devastation worldwide. Excessive grazing by cattle, sheep, goats, and camels is partly responsible for the deserts of the Middle East. Uncontrolled livestock grazing during the late nineteenth century and early twentieth century negatively affected many areas in the American West, where sagebrush and juniper trees invaded the grasslands. Livestock overgrazing has similarly devastated areas of Africa and Asia. Feral horses in the American West and the Australian outback continue to damage those environments.

Overgrazing by wildlife can also be deleterious. The Kaibab Plateau deer disaster in Arizona is one such example, where removal of natural predators and livestock that competed with the deer for food led first to a deer explosion, then to overgrazing by the deer, followed by starvation and large die-offs within the deer population. Protection of elk and bison in Yellowstone National Park has similarly led to high populations, excessive grazing, and changes to the environment. Only the provision of winter feed has prevented the die-offs that would otherwise naturally ensue. Ironically, winter feeding has perpetuated the problem by maintaining these populations at levels higher than grazing can sustain. Feeding has also encouraged the animals to congregate in unusually large numbers, which has contributed to the spread of disease. In 2010 a coalition of conservation groups lost a lawsuit to stop the supplemental feeding of elk and bison on the National Elk Refuge in Wyoming.

Grasslands Management

Grassland areas need not deteriorate if they are properly managed, whether for livestock, wild animals, or both. The land’s carrying capacity, or the number of healthy animals that can be grazed indefinitely in a given area, must not be exceeded. Because of year-to-year changes in weather conditions and hence food availability, determining carrying capacity is not simple; worst-case estimates typically have been used as guidelines to minimize the of exceeding carrying capacity. The goal should be a grassland rendered and kept healthy by optimizing, not maximizing, the number of animals. For private land, optimizing livestock numbers is in the long-term self-interest of the landowner. For publicly held land, managed in common or with unclear or disputed ownership, restricting animals to the optimum level is particularly difficult to achieve. Personal short-term benefit often leads to long-term disaster, in a phenomenon known as the tragedy of the commons.

Managing grasslands involves controlling the numbers of animals and enhancing the habitat. Cattle and sheep can be physically restricted through the use of herding and fencing, although requiring such restrictions can be difficult to achieve through political means. Much more problematic is controlling wildlife when natural predators have been eliminated and hunting is severely restricted. As for improvement, the prudent use of chemical, fire, mechanical, and biological approaches can increase carrying capacity for domesticated and wild herbivores. Removing woody vegetation by burning or mechanical means can increase grass cover, fertilizing can stimulate grass growth, and reseeding with desirable species (plants native to the particular region) can enhance the habitat. Effective grassland management also requires matching animals with the grasses on which they graze.

An approach to grazing known as holistic management may have the potential not only to stave off ecosystem damage of grasslands but also to reverse desertification. This approach operates on the essential principle that, because herbivores and perennial grasses evolved together, the grasses will thrive only in combination with herbivores grazing and roaming naturally. Contrary to common wisdom regarding best management practices for grazing, holistic management involves grazing livestock in ultradense, constantly moving herds that mimic big-game grazing patterns. The livestock till the soil with their hooves and fertilize it with their excrement. By grazing the grasses, they allow sunlight to reach the grasses’ growth buds; by contrast, when grazing is so restricted that the vegetation is able to die upright, the growth buds are shielded from the sun and the entire plant dies the following year. The common management practice of allowing grazed land an extended period to rest and recover, then, may not promote a resurgence of vegetative cover; rather, this practice may cause the land to remain barren and dry.

In 1992 holistic management pioneer Allan Savory began a program in Zimbabwe, Africa, in which livestock herds were increased by 400 percent on 2,630 hectares (6,500 acres) of land that had been barren for hundreds of years. By 2010, after years of holistic planned grazing, this area had become healthy grassland with open water. In 2009, Savory cofounded the Savory Institute, which began as a management consulting firm but soon transitioned to a nonprofit organization committed to using holistic management to regenerate the world's grassland. In 2024, the organization reported that it had more than 29 million hectares (71.6 million acres) of land regenerating and had set a goal of having 500 million hectares (1,236 million acres) regenerating by 2040.

Grazing in the United States

There are roughly 312 million hectares (770 million acres) of rangelands (grasslands, forests, wetlands, and other ecosystems that are suitable for grazing) in the United States, more than half of which are privately owned. The federal government manages 43 percent, and the remainder is under state and local government control.

Laws pertaining directly to grazing in the United States include the Taylor Grazing Act of 1934, the Federal Land Policy and Management Act of 1976, and the Public Rangelands Improvement Act of 1978. The Taylor Grazing Act introduced measures to control the unregulated grazing practices of homesteaders that had led to overgrazing, enhanced erosion, damage to streams and springs, and the land’s reduced productivity; however, rancher needs still tended to take precedence over range condition. Four decades later, heightened environmental awareness led to passage of the Federal Land Policy and Management Act, which established a multiple-use mandate for land management agencies to serve present and future generations in their practices. Not long after came passage of the Public Rangelands Improvement Act, which sought to improve the condition of public rangelands so that they might meet their potential for grazing and other uses. US laws pertaining to environmental quality and also have impacts on rangeland management.

The Bureau of Land Management (BLM) manages livestock grazing on 64 million hectares (157 million acres) of the 99 million hectares (245 million acres) of public lands that it administers. The BLM administers roughly eighteen hundred permits and leases, which are held mostly by cattle and sheep ranchers. The US Forest Service, which administers the 77 million hectares (191 million acres) of national forest system lands, manages some 39 million hectares (96 million acres) of rangelands. The Forest Service became the nation’s first grazing control agency in the early 1900’s. In 1934 the Department of the Interior’s Division of Grazing Control (soon renamed the Division of Grazing) joined it; this division became the Grazing Service in 1939, which merged with the General Land Office in 1946 to form the BLM.

Both the Forest Service and the BLM implement a regulatory system of permits, rental fees, herd size limits, and grazing seasons. They must maintain a balance among several often-conflicting objectives: providing forage for grazing and browsing animals, ensuring the land’s long-term health and productivity, protecting watersheds, managing wildlife habitat, administering permitted and energy resource exploration and extraction, offering recreational opportunities, and preserving the land’s distinctive character and aesthetic appeal. In order to meet the array of resource needs, rangeland management agencies inventory, classify, and monitor rangeland conditions. Where rangeland health needs improvement, they implement measures to restore ecosystem functions. Public land decision makers must take into account a variety of factors that affect rangelands, including severe and extensive wildfires, invasive plant species, rural residential development driven by population increases, and global climate change.

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