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Genetic pollution is a controversial[1][2] term for uncontrolled[3][4] gene flow into wild populations. It is defined as "the dispersal of contaminated altered genes from genetically engineered organisms to natural organisms, esp. by cross-pollination",[5] but has come to be used in some broader ways. It is related to the population genetics concept of gene flow, and genetic rescue, which is genetic material intentionally introduced to increase the fitness of a population.[6] It is called genetic pollution when it negatively impacts on the fitness of a population, such as through outbreeding depression and the introduction of unwanted phenotypes which can lead to extinction.

Conservation biologists and conservationists have used the term to describe gene flow from domestic, feral, and non-native species into wild indigenous species, which they consider undesirable. They promote awareness of the effects of introduced invasive species that may "hybridize with native species, causing genetic pollution". In the fields of agriculture, agroforestry and animal husbandry, genetic pollution is used to describe gene flows between genetically engineered species and wild relatives. The use of the word "pollution" is meant to convey the idea that mixing genetic information is bad for the environment, but because the mixing of genetic information can lead to a variety of outcomes, "pollution" may not always be the most accurate descriptor.

Gene flow to wild population

Some conservation biologists and conservationists have used genetic pollution for a number of years as a term to describe gene flow from a non-native, invasive subspecies, domestic, or genetically-engineered population to a wild indigenous population.[3][7][8]

Importance

The introduction of genetic material into the gene pool of a population by human intervention can have both positive and negative effects on populations. When genetic material is intentionally introduced to increase the fitness of a population, this is called genetic rescue. When genetic material is unintentionally introduced to a population, this is called genetic pollution and can negatively affect the fitness of a population (primarily through outbreeding depression), introduce other unwanted phenotypes, or theoretically lead to extinction.

Introduced species

An introduced species is one that is not native to a given population that is either intentionally or accidentally brought into a given ecosystem. Effects of introduction are highly variable, but if an introduced species has a major negative impact on its new environment, it can be considered an invasive species. One such example is the introduction of the Asian Longhorned beetle in North America, which was first detected in 1996 in Brooklyn, New York. It is believed that these beetles were introduced through cargo at trade ports. The beetles are highly damaging to the environment, and are estimated to cause risk to 35% of urban trees, excluding natural forests.[9] These beetles cause severe damage to the wood of trees by larval funneling. Their presence in the ecosystem destabilizes community structure, having a negative influence on many species in the system. Introduced species are not always disruptive to an environment, however. Tomás Carlo and Jason Gleditch of Penn State University found that the number of invasive honeysuckle plants in the area correlated with the number and diversity of the birds in the Happy Valley Region of Pennsylvania, suggesting introduced honeysuckle plants and birds formed a mutually beneficial relationship.[10] Presence of introduced honeysuckle was associated with higher diversity of the bird populations in that area, demonstrating that introduced species are not always detrimental to a given environment and it is completely context dependent.

Invasive species

Conservation biologists and conservationists have, for a number of years, used the term to describe gene flow from domestic, feral, and non-native species into wild indigenous species

The introduction of genetic material into the gene pool of a population by human intervention can have both positive and negative effects on populations. When genetic material is intentionally introduced to increase the fitness of a population, this is called genetic rescue. When genetic material is unintentionally introduced to a population, this is called genetic pollution and can negatively affect the fitness of a population (primarily through outbreeding depression), introduce other unwanted phenotypes, or theoretically lead to extinction.

Introduced species

Conservation biologists and conservationists have, for a number of years, used the term to describe gene flow from domestic, feral, and non-native species into wild indigenous species, which they consider undesirable.[3][7][8] For example, TRAFFIC is the international wildlife trade monitoring network that works to limit trade in wild plants and animals so that it is not a threat to conservationist goals. They promote awareness of the effects of introduced invasive species that may "hybridize with native species, causing genetic pollution".[11] Furthermore, the Joint Nature Conservation Committee, the statutory adviser to the UK government, has stated that invasive species "will alter the genetic pool (a process called genetic pollution), which is an irreversible change."[12]

Invasive species can invade both large and small native populations and have a profound effect. Upon invasion, invasive species interbreed with native species to form sterile or more evolutionarily fit hybrids that can outcompete the native populations. Invasive species can cause extinctions of small populations on islands tha

Invasive species can invade both large and small native populations and have a profound effect. Upon invasion, invasive species interbreed with native species to form sterile or more evolutionarily fit hybrids that can outcompete the native populations. Invasive species can cause extinctions of small populations on islands that are particularly vulnerable due to their smaller amounts of genetic diversity. In these populations, local adaptations can be disrupted by the introduction of new genes that may not be as suitable for the small island environments. For example, the Cercocarpus traskiae of the Catalina Island off the coast of California has faced near extinction with only a single population remaining due to the hybridization of its offspring with Cercocarpus betuloides.[13]

Increased contact between wild and domesticated populations of organisms can lead to reproductive interactions that are detrimental to the wild population's ability to survive. A wild population is one that lives in natural areas and is not regularly looked after by humans. This contrasts with domesticated populations that live in human controlled areas and are regularly, and historically, in contact with humans. Genes from domesticated populations are added to wild populations as a result of reproduction. In many crop populations this can be the result of pollen traveling from farmed crops to neighboring wild plants of the same species. For farmed animals, this reproduction may happen as the result of escaped or released animals.

Aquaculture

Aquaculture is the practice of farming aquatic animals or plants for the purpose of consumption. This practice is becoming increasingly common for the production of salmon. This is specifically termed aquaculture of salmonoids. One of the dangers of this practice is the possibility of domesticated salmon breaking free from their containment. The occurrence of escaping incidents is becoming increasingly common as aquaculture gains popularity.[14][15][16] Farming structures may be ineffective at holding the vast number of fast growing animals they house.[17] Natural disasters, high tides, and other environmental occurrences can also trigger aquatic animal escapes.[18][19] The reason these escapes are considered dangers is the impact they pose for the wild population they reproduce with after escaping. In many instances the wild population experiences a decreased likelihood of survival after reproducing with domesticated populations of salmon.[20][21]

The Washington Department of Fish and Wildlife cites that "commonly expressed concerns surrounding escaped Atlantic salmon include competition with native salmon, predation, disease transfer, hybridiz

The Washington Department of Fish and Wildlife cites that "commonly expressed concerns surrounding escaped Atlantic salmon include competition with native salmon, predation, disease transfer, hybridization, and colonization."[22] A report done by that organization in 1999 did not find that escaped salmon posed a significant risk to wild populations.[23]

Crops refer to groups of plants grown for consumption. Despite domestication over many years, these plants are not so far removed from their wild relatives that they could reproduce if brought together. Many crops are still grown in the areas they originated and gene flow between crops and wild relatives impacts the evolution of wild populations.[24] Farmers can avoid reproduction between the different populations by timing their planting of crops so that crops are not flowering when wild relatives would be. Domesticated crops have been changed through artificial selection and genetic engineering. The genetic make up of many crops is different than that of its wild relatives,[25] but the closer they grow to one another the more likely they are to share genes through pollen. Gene flow persists between crops and wild counterparts.

Genetically engineered organisms

Environmentalist perspectives

The use of the word "pollution" in the term genetic pollution has a deliberate negative connotation and is meant to convey the idea that mixing genetic information is bad for the environment. However, because the mixing of genetic information can lead to a variety of outcomes, "pollution" may not be the most accurate descriptor. Gene flow is undesirable according to some environmentalists and conservationists, including groups such as Greenpeace, TRAFFIC, and GeneWatch UK.[47][33][35][48][7][11][49]

"Invasive species have been a major cause of extinction throughout the world in the past few hundred years. Some of them prey on native wildlife, compete with it for resources, or spread disease, while others may hybridize with native species, causing "genetic pollution". In these ways, invasive species are as big a threat to the balance of nature as the direct overexploitation by humans of som

The use of the word "pollution" in the term genetic pollution has a deliberate negative connotation and is meant to convey the idea that mixing genetic information is bad for the environment. However, because the mixing of genetic information can lead to a variety of outcomes, "pollution" may not be the most accurate descriptor. Gene flow is undesirable according to some environmentalists and conservationists, including groups such as Greenpeace, TRAFFIC, and GeneWatch UK.[47][33][35][48][7][11][49]

"Invasive species have been a major cause of extinction throughout the world in the past few hundred years. Some of them prey on native wildlife, compete with it for resources, or spread disease, while others may hybridize with native species, causing "genetic pollution". In these ways, invasive species are as big a threat to the balance of nature as the direct overexploitation by humans of some species."[1]

It can also be considered undesirable if it leads to a loss of Invasive species have been a major cause of extinction throughout the world in the past few hundred years. Some of them prey on native wildlife, compete with it for resources, or spread disease, while others may hybridize with native species, causing "genetic pollution". In these ways, invasive species are as big a threat to the balance of nature as the direct overexploitation by humans of some species."[1]

It can also be considered undesirable if it leads to a loss of fitness in the wild populations.[50] The term can be associated with the gene flow from a mutation bred, synthetic organism or genetically engineered organism to a non GE organism,[26] by those who consider such gene flow detrimental.[47] These environmentalist groups stand in complete opposition to the development and production of genetically engineered organisms.

From a governmental perspective, genetic pollution is defined as follows by the Food and Agriculture Organization of the United Nations:

"Uncontrolled spread of genetic information (frequently referring to transgenes) into the genomes of organisms in which such genes are not present in nature."[51]

Use of the term 'genetic pollution' and similar phrases such as genetic deterioration, genetic swamping, genetic takeover, and genetic aggression, are being debated by scientists as many do not find it scientifically appropriate. Rhymer and Simberloff argue that these types of terms:

"...imply either that hybrids are less fit than the parentals, which need not be the case, or that there is an inherent value in "pure" gene pools."[1]

They recommend that gene flow from invasive species be termed genetic mixing si

"...imply either that hybrids are less fit than the parentals, which need not be the case, or that there is an inherent value in "pure" gene pools."[1]

They recommend that gene flow from invasive species be termed genetic mixing since:

<

" "Mixing" need not be value-laden, and we use it here to denote mixing of gene pools whether or not associated with a decline in fitness."[1]

Patrick Moore has questioned whether the term "genetic pollution" is more political than scientific. The term is considered to arouse emotional feelings towards the subject matter.[9] In an interview he comments:

"If you take a term used quite frequently these days, the term "genetic pollution," otherwise referred to as genetic contamination, it is a propaganda term, not a technical or scientific term. Pollution and contamination are both value judgments. By using the word "genetic" it gives the public the impression that they are talking about something scientific or technical--as if there were such a thing as genes that amount to pollution."[2]

Thus, using the term "genetic pollution" is inherently political. A scientific approach to discussing gene flow between introduced and native species would be to use terms like genetic mixing or gene flow. Such mixing can definitely have negative consequences on the fitness of native populations, so it is important not to minimize the risk. However, because genetic mixing can also lead to fitness recovery in cases that could be described as "genetic rescue", it is important to distinguish that just mixing genes from introduced into native populations can lead to variable outcomes for the fitness of native populations.



The term "genetic pollution" and "genetic admixture" is also used in ideological arguments by black supremacists in relation to mixing of ethnic groups within multi-cultural populations.

See also