Species reintroduction

Species reintroduction is the deliberate release of a species into the wild, from captivity or other areas where the organism survives. The goal of species reintroduction is to establish a healthy, genetically diverse, self-sustaining population to an area where it has been extirpated, or to augment an existing population. A species that needs reintroduction is usually one whose existence has become threatened or endangered in the wild. However, reintroduction of a species can also be for pest control. For example, wolves being reintroduced to a wild area because of an overpopulation of elk or deer. Because reintroduction may involve returning native species to localities where they had been extirpated, some prefer the term "reestablishment".

Humans have been reintroducing species for food and pest control for thousands of years. However, the practice of reintroducing for conservation is much younger, starting in the 20th century.

There are a variety of approaches to species reintroduction. The optimal strategy will depend on the biology of the organism. The first matter to address in choosing a method is sourcing individuals in situ, wild populations, or ex situ, such as a zoo or botanic garden.

In situ sourcing for restorations involves removing individuals from an existing wild population and moving them to the new site where they were formerly extirpated. Ideally, populations should be sourced from in situ when possible as there are numerous risks with reintroducing organisms in the wild from captive population. In order to ensure that the reintroduced populations have the best chance of surviving, the population the individuals are collected from should closely resemble the extirpated population genetically and ecologically. Generally, sourcing from nearby populations with similar habitat to the reintroduction site will maximize the chance that reintroduced individuals will be similar to the original population.

One consideration for in situ sourcing is at which life stage the organisms should be collected, transported, and reintroduced. For instance, with plants, it is often ideal to transport them as seeds as they have the best chance of surviving translocation at this stage. Some plants are difficult to establish as seed however and may need to be translocated as juveniles or adults.

In situations where in situ collection of individuals is not feasible, for instance too few individuals exist in the wild, ex situ collections may be used. There are a number of types of ex situ collections. Germplasm may be stored in the form of seed banks, sperm and egg banks, cryopreservation, and tissue culture. These method allows the storage of many individuals and have high potential for reintroduction. Since this method allows for storage of a high number of individuals, it maximizes genetic diversity. Once collected, the material can last for relatively long periods in storage.However some species lose viability when stored as seed. However tissue culture and cryopreservation techniques have only been perfected for a few species. Organisms may also be kept in living collections. Living collections are more costly than storing germplasm and hence can support only a fraction of the individuals that ex situ sourcing can. When sourcing for living collections, the risks increase. There are fewer individuals so loss of genetic diversity becomes a concern. The individuals may also become adapted to captivity so efforts should be made to replicate wild conditions and time spent in captivity should be minimized whenever possible.

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