Genetic erosion (also known as genetic depletion) is a process where the limited gene pool of an endangered species diminishes even more when reproductive individuals die off before reproducing with others in their endangered low population. The term is sometimes used in a narrow sense, such as when describing the loss of particular

allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chro ...

s or genes, as well as being used more broadly, as when referring to the loss of a phenotype or whole species. Genetic erosion occurs because each individual organism has many unique genes which get lost when it dies without getting a chance to breed. Low genetic diversity in a population of wild animals and plants leads to a further diminishing gene pool – inbreeding and a weakening immune system can then "fast-track" that species towards eventual

extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

. By definition, endangered species suffer varying degrees of genetic erosion. Many species benefit from a human-assisted breeding program to keep their population viable, thereby avoiding extinction over long time-frames. Small populations are more susceptible to genetic erosion than larger populations. Genetic erosion gets compounded and accelerated by

habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...

and habitat fragmentation – many endangered species are threatened by habitat loss and (fragmentation)

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 ...

. Fragmented habitat create barriers in gene flow between populations. The gene pool of 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 ...

or a

population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...

is the complete set of unique alleles that would be found by inspecting the genetic material of every living member of that species or population. A large gene pool indicates extensive genetic diversity, which is associated with robust populations that can survive bouts of intense

selection Selection may refer to: Science * Selection (biology), also called natural selection, selection in evolution ** Sex selection, in genetics ** Mate selection, in mating ** Sexual selection in humans, in human sexuality ** Human mating strateg ...

. Meanwhile, low genetic diversity (see

inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders and o ...

and population bottlenecks) can cause reduced biological fitness and increase the chance of

of that species or population.

Processes and consequences

Population bottlenecks create shrinking gene pools, which leave fewer and fewer fertile mating partners. The genetic implications can be illustrated by considering the analogy of a high-stakes poker game with a crooked dealer. Consider that the game begins with a 52-card deck (representing high genetic diversity). Reduction of the number of breeding pairs with unique genes resembles the situation where the dealer deals only the same five cards over and over, producing only a few limited "hands". As specimens begin to inbreed, both physical and reproductive congenital effects and defects appear more often. Abnormal sperm increases, infertility rises, and birthrates decline. "Most perilous are the effects on the immune defense systems, which become weakened and less and less able to fight off an increasing number of bacterial, viral, fungal, parasitic, and other disease-producing threats. Thus, even if an endangered species in a bottleneck can withstand whatever human development may be eating away at its habitat, it still faces the threat of an epidemic that could be fatal to the entire population."

Loss of agricultural and livestock biodiversity

Genetic erosion in agricultural and

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 animal ...

is the loss of biological genetic diversity – including the loss of individual genes, and the loss of particular recombinants of genes (or gene complexes) – such as those manifested in locally adapted

landraces A landrace is a domesticated, locally adapted, often traditional variety of a species of animal or plant that has developed over time, through adaptation to its natural and cultural environment of agriculture and pastoralism, and due to isolation ...

domesticated Domestication is a sustained multi-generational relationship in which humans assume a significant degree of control over the reproduction and care of another group of organisms to secure a more predictable supply of resources from that group. A ...

animals or plants that have become adapted to the natural environment in which they originated. The major driving forces behind genetic erosion in crops are variety replacement, land clearing, overexploitation of species,

population pressure Population pressure, a term summarizing the stress brought about by an excessive population density and its consequences, is used both in conjunction with human overpopulation and with other animal populations that suffer from too many individuals ...

, environmental degradation,

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, game reserves, or nature res ...

, governmental policy, and changing agricultural systems. The main factor, however, is the replacement of local varieties of domestic plants and animals by other varieties or species that are non-local. A large number of varieties can also often be dramatically reduced when commercial varieties are introduced into traditional farming systems. Many researchers believe that the main problem related to agro-ecosystem management is the general tendency towards genetic and ecological uniformity imposed by the development of modern agriculture. In the case of Animal Genetic Resources for Food and Agriculture, major causes of genetic erosion are reported to include indiscriminate cross-breeding, increased use of exotic breeds, weak policies and institutions in animal genetic resources management, neglect of certain breeds because of a lack of profitability or competitiveness, the intensification of production systems, the effects of diseases and disease management, loss of pastures or other elements of the production environment, and poor control of inbreeding.

Prevention by human intervention, modern science and safeguards

''In situ'' conservation

With advances in modern bioscience, several techniques and safeguards have emerged to check the relentless advance of genetic erosion and the resulting acceleration of endangered species towards eventual extinction. However, many of these techniques and safeguards are too expensive yet to be practical, and so the best way to protect species is to protect their

and to let them live in it as naturally as possible.

Wildlife sanctuaries 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 or ...

and national parks have been created to preserve entire

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

s with all the web of species native to the area.

Wildlife corridor A wildlife corridor, habitat corridor, or green corridor is an area of habitat connecting wildlife populations separated by human activities or structures (such as roads, development, or logging). This allows an exchange of individuals between ...

s are created to join fragmented habitats (see Habitat fragmentation) to enable endangered species to travel, meet, and breed with others of their kind. Scientific

conservation Conservation is the preservation or efficient use of resources, or the conservation of various quantities under physical laws. Conservation may also refer to: Environment and natural resources * Nature conservation, the protection and managem ...

and modern

wildlife management Wildlife management is the management process influencing interactions among and between wildlife, its habitats and people to achieve predefined impacts. It attempts to balance the needs of wildlife with the needs of people using the best availabl ...

techniques, with the expertise of scientifically trained staff, help manage these protected ecosystems and the wildlife found in them. Wild animals are also translocated and reintroduced to other locations physically when fragmented wildlife habitats are too far and isolated to be able to link together via a wildlife corridor, or when local extinctions have already occurred.

''Ex situ'' conservation

Modern policies of

zoo associations This is a partial list of zoo and aquaria associations: Global * Alliance of Marine Mammal Parks and Aquariums (AMMPA) * International Marine Animal Trainers Association (IMATA) * Species 360 (formerly International Species Information Sys ...

and

zoo A zoo (short for zoological garden; also called an animal park or menagerie) is a facility in which animals are kept within enclosures for public exhibition and often bred for conservation purposes. The term ''zoological garden'' refers to zoo ...

s around the world have begun putting dramatically increased emphasis on keeping and breeding wild-sourced

and subspecies of animals in their registered endangered species breeding programs. These specimens are intended to have a chance to be reintroduced and survive back in the wild. The main objectives of zoos today have changed, and greater resources are being invested in breeding species and subspecies for then ultimate purpose of assisting conservation efforts in the wild. Zoos do this by maintaining extremely detailed scientific breeding records (''i.e.''

studbook A breed registry, also known as a herdbook, studbook or register, in animal husbandry and the hobby of animal fancy, is an official list of animals within a specific breed whose parents are known. Animals are usually registered by their breeders ...

s)) and by loaning their wild animals to other zoos around the country (and often globally) for breeding, to safeguard against

by attempting to maximize genetic diversity however possible. Costly (and sometimes controversial)

ex-situ conservation Svalbard GLOBAL SEED BANK, an ''ex situ'' conservation. ''Ex situ'' conservation literally means, "off-site conservation". It is the process of protecting an endangered species, variety or breed, of plant or animal outside its natural habitat; ...

techniques aim to increase the genetic

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'') l ...

on our planet, as well as the diversity in local gene pools. by guarding against genetic erosion. Modern concepts like

seedbank A seed bank (also seed banks or seeds bank) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease res ...

s, sperm banks, and

tissue bank A tissue bank is an establishment that collects and recovers human cadaver tissue for the purposes of medical research, education and allograft transplantation. A tissue bank may also refer to a location where biomedical tissue is stored under cry ...

s have become much more commonplace and valuable. Sperm,

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

, and embryos can now be frozen and kept in banks, which are sometimes called "Modern Noah's Arks" or "

Frozen Zoo A frozen zoo is a storage facility in which genetic materials taken from animals (e.g. DNA, sperm, eggs, embryos and live tissue) are stored at very low temperatures (−196 °C) in tanks of liquid nitrogen. Material preserved in this way c ...

s".

Cryopreservation Cryo-preservation or cryo-conservation is a process where organisms, organelles, cells, tissues, extracellular matrix, organs, or any other biological constructs susceptible to damage caused by unregulated chemical kinetics are preserved by co ...

techniques are used to freeze these living materials and keep them alive in perpetuity by storing them submerged in liquid nitrogen tanks at very low temperatures. Thus, preserved materials can then be used for

artificial insemination Artificial insemination is the deliberate introduction of sperm into a female's cervix or uterine cavity for the purpose of achieving a pregnancy through in vivo fertilization by means other than sexual intercourse. It is a fertility treatment ...

, ''in vitro'' fertilization,

embryo transfer Embryo transfer refers to a step in the process of assisted reproduction in which embryos are placed into the uterus of a female with the intent to establish a pregnancy. This technique (which is often used in connection with in vitro fertilizati ...

, and

cloning Cloning is the process of producing individual organisms with identical or virtually identical DNA, either by natural or artificial means. In nature, some organisms produce clones through asexual reproduction. In the field of biotechnology, c ...

methodologies to protect diversity in the gene pool of critically endangered species. It can be possible to save an endangered species from

by preserving only ''parts'' of specimens, such as tissues, sperm, eggs, etc. – even after the death of a critically endangered animal, or collected from one found freshly dead, in captivity or from the

wild Wild, wild, wilds or wild may refer to: Common meanings * Wild animal * Wilderness, a wild natural environment * Wildness, the quality of being wild or untamed Art, media and entertainment Film and television * ''Wild'' (2014 film), a 2014 A ...

. A new specimen can then be "resurrected" with the help of cloning, so as to give it another chance to breed its genes into the living population of the respective threatened species. Resurrection of dead critically endangered wildlife specimens with the help of cloning is still being perfected, and is still too expensive to be practical, but with time and further advancements in science and methodology it may well become a routine procedure not to far into the future. Recently, strategies for finding an integrated approach to ''in situ'' and ''ex situ'' conservation techniques have been given considerable attention, and progress is being made.Se
DIVERSEEDS online discussion
forum on the integrated approach.

References