Genetic erosion is a process whereby an already limited gene pool of an endangered species of plant or animal diminishes even more when individuals from the surviving population die off without getting a chance to meet and breed with others in their endangered low population. The term is sometimes used in a narrow sense, such as when describing the loss of particular alleles or genes, as well as being used more broadly, as when referring to the loss of varieties or even 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.
All the endangered species of the world are plagued to varying degrees by genetic erosion, and most need a human-assisted breeding program to keep their population viable, thereby avoiding extinction over long time frames. The smaller the population is on a relative scale, the more magnified the effect of genetic erosion becomes, as weakened individuals from the few surviving members of the species are lost without getting a chance to breed.
Genetic erosion also gets compounded and accelerated by habitat fragmentation – today most endangered species live in smaller and smaller chunks of (fragmented) habitat, interspersed with human settlements and farmland, making it much more difficult to naturally meet and breed with others of their kind, so many die off without getting a chance to breed at all, and thus are unable to pass on their unique genes to the living population.
The gene pool of a species or a population 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. Meanwhile, low genetic diversity (see inbreeding and population bottlenecks) can cause reduced biological fitness and increase the chance of extinction of that species or population.
Read more about Genetic Erosion: Processes and Consequences, Loss of Agricultural and Livestock Biodiversity
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