Overgrazing occurs when plants are exposed to intensive
grazing
In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and ot ...
for extended periods of time, or without sufficient recovery periods. It can be caused by either
livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to ani ...
in poorly managed
agricultural
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled peopl ...
applications,
game reserves, or
nature reserve
A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological o ...
s. It can also be caused by immobile, travel restricted populations of
native
Native may refer to:
People
* Jus soli, citizenship by right of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Native Americans (disambiguation)
In arts and entert ...
or
non-native wild animals
Wildlife refers to undomesticated animal species, but has come to include all organisms that grow or live wild in an area without being introduced by humans. Wildlife was also synonymous to game: those birds and mammals that were hunted fo ...
.
Overgrazing reduces the usefulness,
productivity
Productivity is the efficiency of production of goods or services expressed by some measure. Measurements of productivity are often expressed as a ratio of an aggregate output to a single input or an aggregate input used in a production proces ...
, and
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...
of the land and is one cause of
desertification
Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused ...
and
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...
. Overgrazing is also seen as a cause of the spread of
invasive species
An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species adv ...
of
non-native plants and of
weeds. Degrading land,
emissions from animal agriculture and reducing the biomass in a ecosystem contribute directly to climate change.
Overgrazing can be reversed or prevented by removing
grazers in order to give plants time to recover between grazing events. Successful planned grazing strategies have been support in the American bison of the Great Plains,
or migratory
Wildebeest
Wildebeest ( , , ), also called gnu ( or ), are antelopes of the genus ''Connochaetes'' and native to Eastern and Southern Africa. They belong to the family Bovidae, which includes true antelopes, cattle, goats, sheep, and other even-toe ...
s of the African
savanna
A savanna or savannah is a mixed woodland- grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground ...
s, or by
holistic planned grazing.
["Holistic Land Management: Key to Global Stability"](_blank)
by Terry Waghorn. Forbes. 20 December 2012.
Ecological impacts
Overgrazing typically increases
soil erosion
Soil erosion is the denudation or wearing away of the upper layer of soil. It is a form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, a ...
.
With continued overutilization of land for grazing, there is an increase in degradation. This leads to poor soil conditions that only
xeric and early
successional species can tolerate.
Native plant
In biogeography, a native species is indigenous to a given region or ecosystem if its presence in that region is the result of only local natural evolution (though often popularised as "with no human intervention") during history. The term is eq ...
grass
Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...
species, both individual
bunch grasses and in
grassland
A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...
s, are especially vulnerable. For example, excessive browsing by
white-tailed deer
The white-tailed deer (''Odocoileus virginianus''), also known as the whitetail or Virginia deer, is a medium-sized deer native to North America, Central America, and South America as far south as Peru and Bolivia. It has also been introduced t ...
can lead to the growth of less preferred species of grasses and ferns or non-native plant species that can potentially displace native, woody plants, decreasing the biodiversity.
Economic theory
Overgrazing is used as an example in the economic concept now known as the
Tragedy of the Commons devised in a 1968 paper by
Garrett Hardin.
[Garrett Hardin]
"The Tragedy of the Commons"
''Science'', Vol. 162, No. 3859 (December 13, 1968), pp. 1243-1248. Also availabl
here
an
/ref> This cited the work of a Victorian economist who used as an example the over-grazing of common land. Hardin's example could only apply to unregulated use of land regarded as a common resource.
Normally, rights of use of Common land in England and Wales were, and still are, closely regulated, and available only to "commoners". If excessive use was made of common land, for example in overgrazing, a common would be "stinted", that is, a limit would be put on the number of animals each commoner was allowed to graze. These regulations were responsive to demographic and economic pressure; thus rather than let a common become degraded, access was restricted even further. This important part of actual historic practice was absent from the economic model of Hardin.
In reality the use of common land in England and Wales was a triumph of conserving a scarce resource using agreed custom and practice.
By region
Africa-Sahel region
There have been overgrazing consequences in the region Sahel
The Sahel (; ar, ساحل ' , "coast, shore") is a region in North Africa. It is defined as the ecoclimatic and biogeographic realm of transition between the Sahara to the north and the Sudanian savanna to the south. Having a hot semi-arid cli ...
region. The violent herder–farmer conflicts in Nigeria
Herder–farmer conflicts in Nigeria are a series of disputes over land resources across Nigeria between mostly Muslim Fulani herders and mostly Christian non-Fulani farmers. They have been especially prominent in the Middle Belt (North Central) ...
, Mali
Mali (; ), officially the Republic of Mali,, , ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, italics=no, ar, جمهورية مالي, Jumhūriyyāt Mālī is a landlocked country in West Africa. Ma ...
, Sudan
Sudan ( or ; ar, السودان, as-Sūdān, officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a country in Northeast Africa. It shares borders with the Central African Republic t ...
and other countries in the Sahel region have been exacerbated by land degradation and overgrazing. See 2010 Sahel famine.
Sub-Sahara Africa
Various countries in Sub-Sahara Africa are affected by overgrazing and resulting ecological effects.
In Namibia
Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...
, overgrazing is considered the main cause of woody plant encroachment at the expenses of grasses on a land area of up to 45 million hectares.
Australia
In many arid zones in Australia, overgrazing by sheep and cattle during the nineteenth century, as pastoralism
Pastoralism is a form of animal husbandry where domesticated animals (known as "livestock") are released onto large vegetated outdoor lands ( pastures) for grazing, historically by nomadic people who moved around with their herds. The anim ...
was introduced by European settlers, caused many long-lived species of trees and shrubs to give way to short-lived annual plant
An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one growing season, and then dies. The length of growing seasons and period in which they take place vary according to geographical ...
s and weed species. Introduced feral rabbits, cats
The cat (''Felis catus'') is a domestic species of small carnivorous mammal. It is the only domesticated species in the family Felidae and is commonly referred to as the domestic cat or house cat to distinguish it from the wild members o ...
and foxes exacerbated the threat to both flora and fauna
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fungi ...
. Many bird species have become extinct or endangered, and many of the medium-sized desert mammals are now completely extinct or only exist on a few islands of Australia.
Overgrazing can also occur with native species. In the Australian Capital Territory
The Australian Capital Territory (commonly abbreviated as ACT), known as the Federal Capital Territory (FCT) until 1938, is a landlocked federal territory of Australia containing the national capital Canberra and some surrounding township#Aust ...
, the local government in 2013 authorised a cull of 1455 kangaroos due to overgrazing. Maisie Carr (1912-1988), Ecologist and Botanist, undertook significant research and studies in overgrazing and established consequences on the surrounding land in Australia.
See also
* Land degradation
* Desertification
Desertification is a type of land degradation in drylands in which biological productivity is lost due to natural processes or induced by human activities whereby fertile areas become increasingly arid. It is the spread of arid areas caused ...
References
Further reading
*
{{Authority control
Land use
Land management
Livestock
Sustainable agriculture
Agroecology
Grasslands
Habitat