Ecological release
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Ecological release refers to a population increase or population explosion that occurs when a
species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
is freed from limiting factors in its environment. Sometimes this may occur when a plant or animal species is introduced, for example, to an island or to a new territory or environment other than its native
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
. When this happens, the new arrivals may find themselves suddenly free from the competitors, diseases, or predatory species, etc. in their previous environment, allowing their population numbers to increase beyond their previous limitations. Another common example of ecological release can occur if a disease or a competitor or a keystone species, such as a top predator, is removed from a community or ecosystem. Classical examples of this latter dynamics include population explosions of sea urchins in California's offshore kelp beds, for example, when human hunters began to kill too many sea otters, and/or sudden population explosions of jackrabbits if hunters or ranchers kill too many coyotes. The foreign species either flourishes into a local population or dies out. Not all released species will become invasive; most released species that don't immediately die out tend to find a small
niche Niche may refer to: Science *Developmental niche, a concept for understanding the cultural context of child development *Ecological niche, a term describing the relational position of an organism's species *Niche differentiation, in ecology, the ...
in the local ecosystem. Ecological release also occurs when a species expands its niche within its own
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
or into a new habitat.


Origin

The term ''ecological release'' first appeared in the scientific literature in 1972 in the ''
American Zoologist ''Integrative and Comparative Biology'' is the scientific journal for the Society for Integrative and Comparative Biology (formerly the American Society of Zoologists). Prior to volume 42 (2002), the journal was known as ''American Zoologist'' . ...
'' journal discussing the effects of the introduction of a sea snail on an isolated ecosystem, Easter Island. One of the first studies that linked niche shifts to the presence and absence of competitors was by Lack and SouthernLack, D., and H. N. Southern (1949). Birds on Tenerife. ''Ibis'' 91: 607-26. where habitat broadness of song birds was positively correlated to the absence of a related species.


Common example

Invasive species are an excellent example of successful ecological release because low levels of biodiversity, an abundance of resources, and particular life history traits allow their numbers to increase dramatically. Additionally, there are few predators for these species.


Causes and mechanisms


Cascade effect

When a keystone species, such as a top predator, is removed from a community or ecosystem, a
cascade effect A cascade effect is an inevitable and sometimes unforeseen chain of events due to an act affecting a system. If there is a possibility that the cascade effect will have a negative impact on the system, it is possible to analyze the effects with a ...
can occur through which a series of secondary extinctions take place. Keystone predators are responsible for the control of prey densities, and their removal can result in an increase in one or a number of predators, consumers, or competitors elsewhere in the food web.Paine, R.T. (1966). Food web complexity and species diversity. The American Naturalist 100: 65-75. Several prey or competitor species can consequently suffer a population decline and potentially be extirpated; the result of this would be a decrease in community diversity. Without the keystone species, prey populations can grow indefinitely and will, ultimately, be limited by resources such as food and shelter. Due to these secondary extinctions, a niche is left unfilled: this allows a new species to invade and exploit the resources that are no longer being used by other species.


Human causes ecological release

Ecological release by human means,
intentional Intentions are mental states in which the agent commits themselves to a course of action. Having the plan to visit the zoo tomorrow is an example of an intention. The action plan is the ''content'' of the intention while the commitment is the ''a ...
or unintentional, has had drastic effects on ecosystems worldwide. The most extreme examples of invasive species include: cane toads in Australia, kudzu in the
Southeast United States The Southeastern United States, also referred to as the American Southeast or simply the Southeast, is a geographical region of the United States. It is located broadly on the eastern portion of the southern United States and the southern por ...
, or
beavers Beavers are large, semiaquatic rodents in the genus ''Castor'' native to the temperate Northern Hemisphere. There are two extant species: the North American beaver (''Castor canadensis'') and the Eurasian beaver (''C. fiber''). Beavers a ...
in
Tierra Del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla ...
. But ecological release can also be more subtle, less drastic and easily overlooked such as
mustangs The mustang is a free-roaming horse of the Western United States, descended from horses brought to the Americas by the Spanish. Mustangs are often referred to as wild horses, but because they are descended from once-domesticated animals, they ...
and
dandelions ''Taraxacum'' () is a large genus of flowering plants in the family Asteraceae, which consists of species commonly known as dandelions. The scientific and hobby study of the genus is known as taraxacology. The genus is native to Eurasia and Nor ...
in North America,
musk oxen Musk ( Persian: مشک, ''Mushk'') is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial sub ...
in Svalbard,
dromedaries The dromedary (''Camelus dromedarius'' or ;), also known as the dromedary camel, Arabian camel, or one-humped camel, is a large even-toed ungulate, of the genus ''Camelus'', with one hump on its back. It is the tallest of the three species of ...
in Australia, or
peach The peach (''Prunus persica'') is a deciduous tree first domesticated and cultivated in Zhejiang province of Eastern China. It bears edible juicy fruits with various characteristics, most called peaches and others (the glossy-skinned, non-f ...
es in
Georgia Georgia most commonly refers to: * Georgia (country), a country in the Caucasus region of Eurasia * Georgia (U.S. state), a state in the Southeast United States Georgia may also refer to: Places Historical states and entities * Related to the ...


References

{{DEFAULTSORT:Ecological Release Biogeography Behavioral ecology