Genetic diversity is the variation in the genes within a species or a population. A population is a group of individuals of the same species that live in a specific geographic area.
Genetic diversity is a major component of biodiversity (biological diversity), which also includes species diversity (the number and variety of species in a given area) and ecosystem diversity or habitat diversity (the variety of ecosystems and ecological processes in a region or in total).
Having a high genetic diversity (i.e., a greater range of genetic variations) is important because it increases the chances that some individuals in the species or population will have traits better suited for survival and reproduction under changing environmental conditions, such as a warming climate or the emergence of a new disease. That is, it provides more raw material for adapting to environmental changes through evolution.
Small populations generally have lower genetic diversity than large ones because inbreeding is more likely to occur. Low genetic diversity increases the chances for a decline in the number of individuals and the eventual extinction of a species or population.
Genetic diversity worldwide has decreased substantially, particularly during the past several decades, and especially among mammals and birds. The fundamental cause is human activity, mostly as a result of habitat destruction and fragmentation, climate change, and hunting and harvesting.
Concerns about genetic diversity are particularly important for large mammals due to their typically small populations and high levels of human-caused population effects as well as to their important roles in many ecosystems. Even if the population of a species with a small population increases in size, the genetic diversity often continues to be low because beneficial mutations are rare and usually only occur over thousands, or even millions, of years. This is an important consideration when working toward species preservation and species restoration.
Habitat restoration and climatic reversal would be ideal ways to slow the decline in genetic diversity, or to even reverse it in some cases. Things that could be done even in their absence include increasing the connectivity of fragmented habitats through the establishment of protected wildlife corridors and implementing assisted migration, genetic rescue and captive breeding programs.
One of the most notable successes in increasing genetic diversity has been with regard to the Florida panther. This mammal's population was estimated to have dropped to fewer than 30 individuals in the U.S. state of Florida in the mid-1990s and was suffering from the harmful effects of intense inbreeding. Conservationists then introduced eight female Texas pumas (the same species but a different subspecies) to increase the panthers' genetic diversity, resulting in significant improvements in their health, growth and resilience. Genetic studies have shown that these benefits have persisted. Additional translocations are planned for the future in order to maintain this diversity because of the still very small population size.