Strategies for Ex-Situ Conservation
There are several strategies which can be utilized for ex-situ conservation of animals:
· Adoption of different ex-situ methods of conservation.
· Advanced technology in the service of endangered species.
· Animal reintroduction.
· Animal translocation.
· Identification of species to be conserved.
· Long-term captive breeding and propagation for the species which have lost their habitats permanently.
· Short-term propagation and release of the animals in their natural habitat.
Ex-situ conservastion strategies.
They are conservation strategies in which the endangered or threatened species are reared and preserved outside their natural habitats in homes, botanical gardens,zoological gardens, aquaria, seed gene banks, field genes banks and cryopreservation.
(1) Sacred plants.
Some endangered species of plants have been declared sacred. They are grown in homes, village and religious places e.g., Ocimum sanctum, Nyctanthes arbor tristis, Elaeocarpus floribundus, Ficus religiosa, prosopis cineraria.
(2) Home Gardens
A number of useful, ornamental and peculiar plants are grown in home gardens. Channeling the endangered plants to home gardens will help conserve them, e.g., Murraya koenigii, aloe barbadensis, thymus vulgaris.
(3) Offsite collections
They are live collections of biological diversity in botanical gardens, arboreta and zoos. Arboreta are botanical garden having only specific trees and shrubs. Currently there are over 1500 botanical gardens and arboreta in the world having some 80,000 live species. All modern botanical gardens have seed gene banks, tissue culture labs and other technologies for storing and growing germplasm. Plant breeding centre also maintain the whole range of old varieties of cultivated plants and their wild relatives. They provide plant breeders and genetic engineer with source material for improvement of varieties. There are over 800 professionally managed zoos, zoological parks and wildlife safari parks with more than 3000 species of emammals, birds, reptiles and amphibians. there is a regular exchange of animals amongst different zoots. this helps in keeping alive many of the endangered species. zoos also have facilities for captive breeding. captive breeding (breeding in captivity) helps in meeting requirements of different zoos as well as restoration of critically endanfered species. because of it, some animals which have become extinct in the wild contibute to be maintained in zoological parks. large aquaria are maintained to similarly rear and breed endangered aquatic animals. plants and animals thus multiplied in offsite collections are first acclimitised and then releases into wild to restore degraded land, reintroduce species in the wild and restock depleted populations.
4. Gene Banks
They are institutes that maintain stocks of the whole array of biodiversity in the form of seeds, seeslings, pollens, tissue culture, frozen germplasm and gene libraries (=DNA banks ).
(i) House Seed Gene Banks
Orthodox seeds are seeds capable of tolerating partial dehydration, maerobiosis and low temperature. Fresh seeds are first dehydrated to reduce moisture contents to 5%. They are then stored in special rooms under anaerobic conditions and a temperature of −10∘ to −20∘ C. After interval of several decades small lots of seeds are taken out, made to germinate and form plants that produce fresh seeds for storage, e.g., wheat, Rice, Oat, Barley, Gram, Pea, Bean.
(ii) Field seed gene banks
seeds which cannot tolerate partial desiccation, anaerobiosis and low temperature are called recalcitrant seeds. seeds can be stored only for a short period, e.g., Tea, Cocoa, Jack-fruit, Litchi, Rubber, Coconut, Oil palm. The endangered species and various large areas while plants requiring conservation are numerous. therefore, tissue culture and cryopresrvation are used for them.
(iii) Tissue Culture
It is an in vitro technique of growing cells, tissues and organs on artificial medium under controlled aseptic conditions. the method is highly efficient in multiplication of rare and critically endangered plants. seedless plants and plants with recalcitrant seeds can be maintained indefinitely. tissue culture technique is helpful in maintaining the whole range of germplasm of all types of plants in a small area from which as many number of plants as required can be raised quickly, shoot tio culture, which is virus free, is often used in international exchange of gemplasm.
(iv) Cryopreservation
It is a mode of in intro conservation in which gametes, tissues, organs, embryos, seeds, etc. are stored at very low temperature of −196∘C (temperature of liquid nitrogen). At this temperature the living material can be stored indefinitely in compact low maintenances refrigeration units. it can be revived and when required. cryopreservation is of two type (a) very rapid cooling for storing seeds, (b) gradual cooling with simultaneous dehydration, e.g., tissues, embryos.
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