Grazing generally describes a type of feeding
Eating is the ingestion of food to provide for all organisms their nutritional needs, particularly for energy and growth. Animals and other heterotrophs must eat in order to survive: carnivores eat other animals, herbivores eat plants, omnivores consume a mixture of both plant and animal matter,...

, in which a herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 feeds on plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...

s (such as grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...

es), and also on other multicellular autotroph
An autotroph, or producer, is an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions . They are the producers in a food chain, such as plants on land or algae in water...

s (such as algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

). Grazing differs from true predation because the organism being eaten from is not generally killed
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

, and it differs from parasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...

 as the two organisms do not live together
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

, nor is the grazer necessarily so limited in what it can eat (see generalist and specialist species
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...


Many small selective herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s follow larger grazers, who skim off the highest, tough growth of plants, exposing tender shoots. For terrestrial animals, grazing is normally distinguished from browsing
Browsing (predation)
Browsing is a type of herbivory in which an herbivore feeds on leaves, soft shoots, or fruits of high growing, generally woody, plants such as shrubs. This is contrasted with grazing, usually associated with animals feeding on grass or other low vegetation...

in that grazing is eating grass or other low vegetation, and browsing is eating woody twigs and leaves
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 from tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

s and shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...


Grazing is important in agriculture, in which domestic livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

 are used to convert grass and other forage
Forage is plant material eaten by grazing livestock.Historically the term forage has meant only plants eaten by the animals directly as pasture, crop residue, or immature cereal crops, but it is also used more loosely to include similar plants cut for fodder and carried to the animals, especially...

 into meat, milk and other products.

The word graze derives from the Old English
Old English language
Old English or Anglo-Saxon is an early form of the English language that was spoken and written by the Anglo-Saxons and their descendants in parts of what are now England and southeastern Scotland between at least the mid-5th century and the mid-12th century...

 (OE) grasian, "graze", itself related to OE graes, "grass".

United States

The use of livestock grazing can be dated back to the Civil War. During this time, land ownership was not common, and ranchers grazed their cattle on the surrounding, often federal, land. Not having a permanent home, these cowboys would frequently graze an area down, and then continue on their way. More commonly, however, cattle were rotated between summer and winter ranges. Soon, the public saw how profitable cattle could be and many tried to get into the cattle business. With the appearance of free, unlimited grass and feed, the land became overcrowded and the forage rapidly depleted. Ranchers tried to put a stop to this by using barbed wire fences to barricade their land, water sources, and cattle. After failed attempts, the Taylor Grazing Act was enacted in 1934. This act was put into place to help regulate the use of public land for grazing purposes and allotted ranchers certain paddocks of land. Additionally, “fees collected for grazing livestock on public lands was returned to the appropriate grazing district to be used for range improvements”. The Taylor Grazing Act helped to stabilize rancher’s operations and allow them to continue raising their livestock.

Grazing systems

In the 19th century, grazing techniques were virtually non-existent. Pastures would be grazed for long periods of time, with no rest in between. This led to overgrazing and it was detrimental to the land, wildlife, and livestock producers. Today, ranchers have developed grazing systems to help improve the forage production for livestock, while still being beneficial to the land.

Controlled vs. continuous

The two major types of grazing management are controlled and continuous. With continuous grazing, the livestock have free selection of forage, while with controlled grazing, the producer regulates forage availability and quality.


Seasonal grazing incorporates “grazing animals on a particular area for only part of the year”. This allows the land that is not being grazed to rest and allow for new forage to grow.


Rotational grazing “involves dividing the range into several pastures and then grazing each in sequence throughout the grazing period”. Utilizing rotational grazing can improve livestock distribution while incorporating rest period for new forage.

Rest rotation

Rest rotation grazing "divides the range into at least four pastures. One pasture remains rested throughout the year and grazing is rotated amongst the residual pastures." This grazing system can be especially beneficial when using sensitive grass that requires time for rest and regrowth.

Deferred rotation

Deferred rotation “involves at least two pastures with one not grazed until after seed-set”. By using deferred rotation, grasses can achieve maximum growth during the period when no grazing occurs.

Patch-burn grazing

Patch-burn grazing burns a third of a pasture each year, no matter the size of the pasture. This burned patch attracts the grazers (cattle or bison) which graze the area heavily because of the fresh grasses that grow in. The other patches receive little to no grazing. During the next two years the next two patches burn consecutively and then the cycle begins anew. In this way, patches receive two years of rest and recovery from the heavy grazing. All this results in a diversity of habitats that different prairie plants and birds can utilize, mimicking the effects of the pre-historical bison/fire relationship where bison heavily graze one area and other areas have opportunity to rest.

The Tallgrass Prairie Preserve in Northeast Oklahoma is within the Flint Hills ecosystem, and they have been patch-burn grazing with bison herds for over ten years now. Their efforts have effectively restored the bison/fire relationship on a large landscape scale of 30000 acres (12,140.6 ha).

Riparian area grazing management

Riparian area grazing is used more towards improving wildlife and their habitats. It uses fencing to keep livestock off ranges near streams or water areas until after wildlife or waterfowl periods, or limiting the amount of grazing to a short period of time.

Ecological effects

A number of ecological effects derive from grazing, and these may be either positive or negative. Negative effects of grazing (or more usually over-grazing) include increased soil erosion, adverse water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...

 impacts from increased runoff and loss of biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

. For example historical grazing, along with other land consversion, in Northern
Northern California
Northern California is the northern portion of the U.S. state of California. The San Francisco Bay Area , and Sacramento as well as its metropolitan area are the main population centers...

 and Central California
Central California
Central California, sometimes referenced as Mid-State, is an area of California south of the San Francisco Bay Area and north of Southern California...

 has reduced native chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

 and forest lands by approximately 70 percent. Ongoing grazing expansion {and land conversion} driven by human population growth in this region threatens the remaining integrity of California chaparral and woodlands
California chaparral and woodlands
The California chaparral and woodlands is a terrestrial ecoregion of lower northern, central, and southern California and northwestern Baja California , located on the west coast of North America...

* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...

 in this region.

In some habitats, appropriate levels of grazing may be effective in restoring or maintaining native grass and herb diversity in rangeland
Rangelands are vast natural landscapes in the form of grasslands, shrublands, woodlands, wetlands, and deserts. Types of rangelands include tallgrass and shortgrass prairies, desert grasslands and shrublands, woodlands, savannas, chaparrals, steppes, and tundras...

 that has been disturbed by overgrazing
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, or by overpopulations of native or non-native wild animals.Overgrazing reduces the...

, lack of grazing (such as by the removal of wild grazing animals), or by other human disturbance. Conservation grazing
Conservation grazing
Conservation grazing is the use of semi-feral or domesticated grazing livestock to maintain and increase the biodiversity of natural or semi-natural grasslands, heathlands, wood pasture, wetlands and many other habitats....

 is the use of domestic livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

 to manage such habitats, often to replicate the ecological effects of the wild relatives of livestock, or those of other species now absent or extinct. For example, heathland
Heath (habitat)
A heath or heathland is a dwarf-shrub habitat found on mainly low quality acidic soils, characterised by open, low growing woody vegetation, often dominated by plants of the Ericaceae. There are some clear differences between heath and moorland...

 in Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 requires grazing by cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

, sheep or other grazers to maintain its structure and diversity.

Much grazing land has resulted from a process of clearance or drainage of other habitats such as woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

 or wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....



By utilizing grazing systems, livestock production has the potential to be maximized. “Approximately 85 percent of U.S. grazing lands are unsuitable for producing crops. Grazing animals on this land more than doubles the area that can be used to produce food. Cattle serve a valuable role in the ecosystem by converting the forages humans cannot consume into a nutrient-dense food”. Some could say ranchers themselves are conservationists. They work to use natural resources and often perform tests on their land to analyze soils, control weeds, and utilize smart grazing practices. Through this, they benefit themselves by using profitable land to maximize their livestock production in turn for a profit.


Grazing is claimed by vested interests to be very beneficial to the ecosystem. It is advantageous towards the soil and grasses, promoting nutrient dense soil and stimulating the growth of plant varieties. Through grazing, livestock encourages plant growth, consequently increasing forage production. Furthermore, the animal’s urine and feces "recycle nitrogen, phosphorus, potassium and other plant nutrients and return them to the soil". It also acts as rations for insects and organisms found within the soil. These organisms “aid in carbon sequestration and water filtration”. Nutrients and organisms, all of which are necessary for soil to be prosperous and capable for production.

Grazing also helps to promote the growth of native plants and grasses. Often, these indigenous plants are not able to compete with the surrounding plants that utilize the majority of water and nutrients. By livestock grazing, the non-native grasses are controlled and the native plants can redevelop. As well as using grazing to increase plant growth, the actual hoof action of the livestock also promotes growth. The trampling helps to imbed the seeds into the soil so that the plants and grasses can continue to germinate.
Additionally, management in many parks makes use of grazing to help lower fire hazards by reducing the amount of potential fuel, such as large buildups of forage. When the land is not grazed, dead grasses accumulate. These dead grasses are often a large fire hazard in the summer months. On the other hand, grazing can also allow for "accumulation of litter (horizontal residue)" helping to eliminate soil erosion. Soil erosion is important to minimize because with the soil erosion comes a loss of nutrients and the topsoil. All of which are important in the regrowth of vegetation.


Grazing may also promote biodiversity. Many species are dependant on ranch lands and grazing animals to maintain their habitat. The grasses that are stimulated through grazing provide a habitat for many species. When the land is left unattended or is not grazed, grasses will die with the seasons and accumulate as litter on the ground. For many birds, this is not attractive and they avoid making a nesting area of it. However, when the grass is grazed, the dead litter grass is reduced and allows for the birds to utilize it, while at the same time the livestock benefit. Just as importantly, it increases species richness. When grazing is not used, many of the same grasses grow, for example, brome and bluegrass, consequently creating a monoculture.

In North American tallgrass prairies, diversity and productivity are controlled to a large extent by nitrogen availability…Nitrogen availability in prairies was driven by interactions between frequency of fires and grazing by large herbivores…Spring fires enhance growth of certain grasses, and herbivores such as bison preferentially graze these grasses, keeping a system of checks and balances working properly, and allowing many plant species to flourish.


The negative impacts of cattle grazing on the habitat of native species are
readily acknowledged by the agencies and organizations most knowledgeable about these species. Federal
wildlife agencies have identified cattle grazing as a factor leading to the listing under the Endangered Species
Act (“ESA”) of multiple species that occur on or have been extirpated from rangelands


The Center for Biological Diversity(“CBD”) has provided extensive documentation and scientific
research papers as part of a review of grazing. These included a reference
list of over 150 scientific, peer-reviewed research papers and articles detailing the detrimental
environmental impacts of livestock grazing in the western U. S., and a 13 page summary of livestock
grazing impacts onsoil, stream, wildlife, and ecosystemfunctionfrompeer-reviewed,scientific studies,with

Also included was a comprehensive Survey of Livestock Influences on Stream and Riparian
Ecosystems in the WesternUnited States(Belskyet al. 1999), a survey of over 140 peer-reviewed studies
on the biological and physical effects of livestock on western rivers, streams, and riparian areas. Belsky
et al. (1999) conducted a systematic literature review which specifically searched for peer-reviewed
experimental studies showing the positive environmental impacts of grazing, but none could be found.

There is not a single peer-reviewed scientific study demonstrating any positive environmental impacts from cattle grazing.

Studies overwhelming show that livestock grazing negatively affects
water quality and seasonal quantity, stream channel morphology, hydrology, riparian zone soils, instream
and streambank vegetation, and aquatic and riparian wildlife.

Cattle grazing in general has severely
degraded all aspects of creek function, processes and ecology. These impacts obviously have significant
cumulative negative effects for special-status species dependent on aquatic and riparian habitat.
general impacts of cattle grazing (extensive documentation and references can be found in Belsky et al.
1999) can be summarized as follows:

- Water quality - Cattle grazing increases nutrient concentrations and bacteria and protozoa levels. Sediment load and
turbidity are increased, as well as water temperature. Dissolved oxygen levels often decline.

- Stream channel morphology - Channel width increases, and water depth decreases with cattle grazing. Gravels in the channel bed tend
to be lost in the erosional environment and fine sediments increased in the depositional environment.
Streambank stability is reduced, streambank undercuts are reduced in quality and quantity, and pools
decrease in number and quality.

- Hydrology (stream flow patterns)- With cattle grazing, overland flow from runoff increases, and peak flow and flood water velocity also
increase. Summer and late-season flows decrease, and the water table is lowered.

- Riparian zone soils - Grazing increases erosion, the amount of bare ground, and soil compaction. Infiltration of water decreases.
Litter layer decreases and soil fertility declines.

- Instream vegetation - Algae growth increases with grazing, but higher plants (submerged and emergent) often decline in

- Streambank vegetation - Herbaceous cover, biomass, productivity, and native plant diversity decline due to grazing. Overhanging
vegetation and tree and shrub biomass and cover decline. Plant species composition is altered and plant
structure (horizontaland vertical) issimplified. Plant age structure becomes even-aged and plant succession
is impeded.

Grazing management

It is apparent that proper land and grazing management techniques need to be utilized to optimize forage production and livestock production, while still maintaining biodiversity and consideration of the ecosystem. Through the utilization of grazing systems and making sure to allow proper recovery periods for regrowth, both the livestock and ecosystem will benefit. Along with recovery periods, producers can keep a low density on a pasture, so as not to overgraze. Controlled burning of the land can be valuable in the regrowth of indigenous plants, and new lush growth. Additionally, producers can increase plant and species richness through grazing, by providing an adequate habitat. Although grazing can be problematic for the ecosystem at times, it is clear that well-managed grazing techniques can reverse damage and improve the land.

Non-grass grazing

Although the word grazing is typically associated with mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s feeding on grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

s, or more specifically livestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...

 in a pasture
Pasture is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep or swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...

, ecologists sometimes use the word by extension in a broader sense, to include any organism that feeds on any other species without ending the life of the prey organism.
Use of the term varies even more than this, for example a marine biologist may describe herbivorous sea urchin
Sea urchin
Sea urchins or urchins are small, spiny, globular animals which, with their close kin, such as sand dollars, constitute the class Echinoidea of the echinoderm phylum. They inhabit all oceans. Their shell, or "test", is round and spiny, typically from across. Common colors include black and dull...

s that feed on kelp as grazers, even when they kill the organism by cutting the plant at the base. Malacologists sometimes will apply the word to aquatic snails that feed by consuming the microscopic film of algae, diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

s and detritus, a biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

, that covers the substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...

 and other surfaces underwater.

An example of a grazer that may seem counterintuitive is a mosquito
Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

, which is not a parasite in that it does not form any lasting association with its prey, and is not a true predator in that it does not kill them by this process (although they can act as a vector for fatal diseases such as malaria
Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

). In this sense it is the antithesis of parasitoidism, in which an organism (typically the larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

l stage of a wasp
The term wasp is typically defined as any insect of the order Hymenoptera and suborder Apocrita that is neither a bee nor an ant. Almost every pest insect species has at least one wasp species that preys upon it or parasitizes it, making wasps critically important in natural control of their...

) feeds on another by eating it from within. In that case, the prey is inevitably killed by predation, and has an intimate association with its predator, such that its premature death would also see the parasitoid die as well.
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