Captive breeding is the process of breeding animals in human controlled environments with restricted settings, such as wildlife preserves, zoos and other conservation facilities; sometimes the process is construed to include release of individual organisms to the wild, when there is sufficient natural habitat to support new individuals or when the threat to the species in the wild is lessened.
This technique has been used with success for some species for some time, with probably the oldest known instances of captive breeding being attributed to menageries of European and Asian rulers, a case in point being the Pere David's Deer. The idea was popularized among modern conservationists independently by Peter Scott and Gerald Durrell in the 1950s and 1960s, founders of the Wildfowl and Wetlands Trust and Jersey Zoo - who demonstrated success with a wide variety of life forms in the 1970s ranging from birds (e.g. Pink Pigeon), mammals (e.g. Pygmy Hog), reptiles (e.g. Round Island Boa) and amphibians (e.g. Poison arrow frogs). Their ideas were independently validated by the success of Operation Oryx (under the auspices of the Fauna and Flora Preservation Society), which captive bred the Arabian Oryx starting in 1963 for eventual reintroduction to the wild. The Przewalski's horse has recently been re-introduced to the wild in Mongolia, its native habitat.
If the captive breeding population is too small, inbreeding may occur due to reduced gene pool, which may lead to the population lacking immunity to diseases and other problems. Over sufficient number of generations, inbred populations can regain "normal" genetic diversity. 
The breeding of endangered species is coordinated by cooperative breeding programmes containing international studbooks and coordinators, who evaluate the roles of individual animals and institutions from a global or regional perspective. There are regional programmes for the conservation of endangered species:
Impacts of captive breeding include behavioral problems in released animals and lack of conservation of habitats being destroyed while a species is being bred. Behavioral problems include not being able to hunt or forage for food leading to starvation. Released animals do not avoid predators and are not able to find ample shelter for themselves so they die as a result. When a species is born in captivity and released into the wild they are not able to survive because they lack these skills. Golden Lion Tamarin mothers often die in the wild before having offspring because they do not have the climbing and foraging skills they need to survive. This results in populations continuing to decline despite reintroduction because the species does not produce viable offspring.
Another problem with captive breeding is the habitat loss that occurs while they are in captivity. This makes release of the species unviable because there is no habitat left to support larger populations. Since release is the ultimate goal of captive breeding, habitat loss defeats the purpose. Funds being used for captive breeding could be used for preserving wild populations and their habitat. The Sumatran Rhino will not survive purely in captivity and loss of habitat is a major factor to their extinction. If their habitat disappears, captive populations as well as wild ones will disappear along with it.