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.
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.
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.
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, which they consider undesirable. 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". 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."
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.
Domestic populations
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 contrast 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. Farming structures may be ineffective at holding the vast number of fast growing animals they house. Natural disasters, high tides, and other environmental occurrences can also trigger aquatic animal escapes.
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.
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" A report done by that organization in 1999 did not find that escaped salmon posed a significant risk to wild populations.
Crops
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.
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,
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
Genetically engineered organisms are genetically modified in a
laboratory, and therefore distinct from those that were bred through
artificial selection. In the fields of agriculture, agroforestry and animal husbandry, genetic pollution is being used to describe gene flows between GE species and wild relatives.
An early use of the term "genetic pollution" in this later sense appears in a wide-ranging review of the potential ecological effects of genetic engineering in The Ecologist magazine in July 1989. It was also popularized by environmentalist Jeremy Rifkin in his 1998 book The Biotech Century. While intentional crossbreeding between two genetically distinct varieties is described as hybridization with the subsequent introgression
of genes, Rifkin, who had played a leading role in the ethical debate
for over a decade before, used genetic pollution to describe what he
considered to be problems that might occur due the unintentional process
of (modernly) genetically modified organisms (GMOs) dispersing their genes into the natural environment by breeding with wild plants or animals.
Concerns about negative consequences from gene flow between
genetically engineered organisms and wild populations are valid. Most
corn and soybean crops grown in the midwestern USA are genetically
modified. There are corn and soybean varieties that are resistant to
herbicides like glyphosate and corn that produces neonicotinoid pesticide within all of its tissues. These genetic modifications are meant to increase yields of crops but there is little evidence that yields actually increase.
While scientists are concerned genetically engineered organisms can
have negative effects on surrounding plant and animal communities, the
risk of gene flow between genetically engineered organisms and wild
populations is yet another concern. Many farmed crops may be weed
resistant and reproduce with wild relatives.
More research is necessary to understand how much gene flow between
genetically engineered crops and wild populations occurs, and the
impacts of genetic mixing.
Mutated organisms
Mutations
within organisms can be executed through the process of exposing the
organism to chemicals or radiation in order to generate mutations. This
has been done in plants in order to create mutants that have a desired
trait. These mutants can then be bred with other mutants or individuals
that are not mutated in order to maintain the mutant trait. However,
similar to the risks associated with introducing individuals to a
certain environment, the variation created by mutated individuals could
have a negative impact on native populations as well.
Preventative measures
Since 2005 there has existed a GM Contamination Register, launched for GeneWatch UK and Greenpeace International that records all incidents of intentional or accidental release of organisms genetically modified using modern techniques.
Genetic use restriction technologies
(GURTs) were developed for the purpose of property protection, but
could be beneficial in preventing the dispersal of transgenes. GeneSafe
technologies introduced a method that became known as “Terminator.” This
method is based on seeds that produce sterile plants. This would
prevent movement of transgenes into wild populations as hybridization
would not be possible.
However, this technology has never been deployed as it
disproportionately negatively affects farmers in developing countries,
who save seeds to use each year (whereas in developed countries, farmers
generally buy seeds from seed production companies).
Physical containment has also been utilized to prevent the escape
of transgenes. Physical containment includes barriers such as filters
in labs, screens in greenhouses, and isolation distances in the field.
Isolation distances have not always been successful, such as transgene
escape from an isolated field into the wild in herbicide-resistant
bentgrass Agrostis stolonifera.
Another suggested method that applies specifically to protection
traits (e.g. pathogen resistance) is mitigation. Mitigation involves
linking the positive trait (beneficial to fitness) to a trait that is
negative (harmful to fitness) to wild but not domesticated individuals.
In this case, if the protection trait was introduced to a weed, the
negative trait would also be introduced in order to decrease overall
fitness of the weed and decrease possibility of the individual’s
reproduction and thus propagation of the transgene.
Risks
Not all
genetically engineered organisms cause genetic pollution. Genetic
engineering has a variety of uses and is specifically defined as a
direct manipulation of the genome of an organism. Genetic pollution can
occur in response to the introduction of a species that is not native
to a particular environment, and genetically engineered organisms are
examples of individuals that could cause genetic pollution following
introduction. Due to these risks, studies have been done in order to
assess the risks of genetic pollution associated with organisms that
have been genetically engineered:
- Genetic In a 10-year study of four different crops, none of the genetically engineered plants were found to be more invasive or more persistent than their conventional counterparts. An often cited claimed example of genetic pollution is the reputed discovery of transgenes from GE maize in landraces of maize in Oaxaca, Mexico. The report from Quist and Chapela, has since been discredited on methodological grounds. The scientific journal that originally published the study concluded that "the evidence available is not sufficient to justify the publication of the original paper." More recent attempts to replicate the original studies have concluded that genetically modified corn is absent from southern Mexico in 2003 and 2004.
- A 2009 study verified the original findings of the controversial 2001 study, by finding transgenes in about 1% of 2000 samples of wild maize in Oaxaca, Mexico, despite Nature retracting the 2001 study and a second study failing to back up the findings of the initial study. The study found that the transgenes are common in some fields, but non-existent in others, hence explaining why a previous study failed to find them. Furthermore, not every laboratory method managed to find the transgenes.
- A 2004 study performed near an Oregon field trial for a genetically modified variety of creeping bentgrass (Agrostis stolonifera) revealed that the transgene and its associate trait (resistance to the glyphosate herbicide) could be transmitted by wind pollination to resident plants of different Agrostis species, up to 14 km from the test field. In 2007, the Scotts Company, producer of the genetically modified bentgrass, agreed to pay a civil penalty of $500,000 to the United States Department of Agriculture (USDA). The USDA alleged that Scotts "failed to conduct a 2003 Oregon field trial in a manner which ensured that neither glyphosate-tolerant creeping bentgrass nor its offspring would persist in the environment".
Not only are there risks in terms of genetic engineering, but there
are risks that emerge from species hybridization In Czechoslovakia, ibex
were introduced from Turkey and Sinai to help promote the ibex
population there, which caused hybrids that produced offspring too
early, which caused the overall population to disappear completely.
The genes of each population of the ibex in Turkey and Sinai were
locally adapted to their environments so when placed in a new
environmental context did not flourish. Additionally, the environmental
toll that may arise from the introduction of a new species may be so
disruptive that the ecosystem is no longer able to sustain certain
populations.
Controversy
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:
"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."
It can also be considered undesirable if it leads to a loss of fitness in the wild populations. The term can be associated with the gene flow from a mutation bred, synthetic organism or genetically engineered organism to a non GE organism, by those who consider such gene flow detrimental.
These environmentalist groups stand in complete opposition to the
development and production of genetically engineered organisms.
Seeds of Destruction: Hidden Agenda of Genetic Manipulation is a book by American writer, Frederick William Engdahl. In his book, Engdahl explains how the (oil-rich) Rockefeller family is planing to control world farming by the Green Revolution plan. Rockefeller family is trying to finish other family farms in the United States and also is trying do same as this plan to other countries and finally take the whole world food security on their hands. Engdahl believes that green revolution is happening by the new world empire. He also sees the Rockefeller family hand behind the great Genetically modified organism (GMO) project to control world population.
Governmental definition
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."
Scientific perspectives
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."
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.
Environmentalists such as Patrick Moore, an ex-member and cofounder of Greenpeace,
questions if the term genetic pollution is more political than
scientific. The term is considered to arouse emotional feelings towards
the subject matter. 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.
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.
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