Assessing importance of ex-situ conservation of biodiversity

Ex-situ conservation is the conservation of biodiversity away from its natural habitat. Viable populations of many organisms can be maintained in cultivation or in captivity. Plants may also be maintained in seed banks and germplasm collections; similar techniques are under development for animals (storage of embryos, eggs, sperm) but are more problematic. In any event, ex-situ conservation is clearly only feasible at present for a small percentage of organisms. It is extremely costly in the case of most animals, and while it would in principle be possible to conserve a very large proportion of higher plants ex-situ, this would still amount to a small percentage of the world's organisms. It often involves a loss of genetic diversity through founder effects and the high probability of inbreeding.

Protected areas are the main device for in-situ conservation, relying on ecosystems to sustain themselves, with some help. An alternative for endangered species is to establish a captive population away from its natural habitat. This ex-situ approach includes captive breeding, release schemes and biodiversity banks such as seed collections. Several species have famously been saved from extinction by ex-situ schemes. Some species still only survive in captivity. The earliest known example of an ex-situ success is Pere David's deer, extinct in the Chinese wilds some 3,000 years ago but surviving in a park. Other celebrity examples include the NeNe goose of Hawaii, nurtured at the Wildfowl and Wetlands Trust, the black footed ferret in the USA, the entire remnant population taken into captivity between 1987 and 1991 to escape canine distemper, and the partula snails of Hawaii, a rare example of populated invertebrate conservation due to the survivors living in sandwich boxes at London zoo.

Ex-situ and in-situ conservation should not be thought as alternatives or rivals. Ex-situ schemes should be linked to in-situ projects to augment remaining populations or establish new ones. Ex-situ schemes can link directly with protected areas, providing stock to release, research data and, in the case of zoos, funds from ticket sales. Ex-situ populations are a refuge while in-situ threats can be dealt with. Captive stock create additional benefits as popular icons, inspiring interest and finance. They act as flagship and are important for education, spotlighting endemism, hot spots or particular threats. Successful release schemes are effective symbols, building more support for conservation. Wild population will be important to captive stock to maintain genetic diversity and reinforce captive bred stocks. Ex-situ programmes raise problems equal to their benefits.

The variety of past schemes and failure have driven attempts to codify principles and practice for ex-situ conservation. Ex-situ schemes are now seen as support for populations in their natural habitat. Ex-situ projects should be used as refuges for populations in immediate danger of extinction, as part of programmes to ensure the long-term survival and for education and research. Projects should promote the longevity, health and quality of life for captives, ensure reproduction maintains stocks to avoid taking more from the wild and maintains natural patterns of genetic diversity, sex ratios and age structures. Captive breeding can then support releases, re-establish ecologically or culturally important species and perhaps bring economic benefits. These goals need an understanding of the biology of small populations, the experience, training and technologies to carry them out and management to co-ordinate work, not just with the captive stock but responsive to changes in wild populations. The result is international co-ordination of ex-situ schemes, controlling both the management of captive stocks and attentive to wider priorities for species conservation.

The IUCN World Conservation Union have a Species Survival Commission to which the Captive Breeding Specialist Group (CBSG) reports on individual species. The International Species Information System (ISIS) uses tools such as the Animal Records Keeping System (ARKS) and studbooks which record the ancestry and whereabouts of individual animals. ISIS handles data on 4,200 animals, from 395 zoos in 39 countries. There are over 300 breeding programmes, featuring over 200 endangered species. Co-ordination extends beyond cataloguing existing schemes. The CBSG and taxon Advisory Groups use Conservation Assessment and Management Plans (CAMPs), which include Population and Habitat Viability Assessment (PHVAs) to identify priorities and future needs or opportunities. CAMPs are strategic plans for management of threatened taxa. Workshops collate existing data and assess threats and extinction probabilities and population estimates for both in-situ and ex-situ stocks. The species is then assigned to a category (critical, endangered, vulnerable or safe) and recommendations are made for action. These can include the need for PHVAs, management plan workshops, conservation ex-situ, gaps in research and technology or captive breeding. The outcome of a CAMPs review is a Global Captive Action Plan (GCAP), an international or regional plan for captive breeding but in support of in-situ conservation. GCAPs assess which species should remain in captivity, be added or need not be, and review available resources and technology plus research and financial benefits to wild populations (after: J. Jeffries, 1997).

According to Snyder (1996) ex-situ conservation efforts have certain basic limitations in comparison with in situ preservation.

Population size. To prevent genetic drift, ex situ populations of at least several hundred individuals need to be maintained. No one zoo can maintain such large numbers of the larger animals, and only a few vertebrate species can be maintained in captivity at such numbers globally. In botanical gardens, only one or a few individuals of most species typically are maintained, especially in the case of trees.

Adaptation. Ex situ populations may undergo genetic adaptation to their artificial environment. For example, animal species kept in captivity for several generations may exhibit changes in mouthparts and digestive enzymes due to the diet of zoo food; when the animals from this altered population are returned to the wild, they may have difficulty eating their natural diet.

Learning skills. Individuals in ex situ populations may be ignorant of their natural environment and unable to survive in the wild. For example, captive-bred animals may no longer recognize wild foods as edible or be able to locate water sources if they are released back into the wild. This problem is most likely to occur among social mammals and birds in which juveniles learn survival skills and locations of critical resources from adult members of the populations. Migratory animals will not know where or when to migrate.

Genetic variability. Ex situ populations may represent only a limited portion of the gene pool of the species. For example, a captive population started using individuals collected from a warm lowland site may be unable to adapt physiologically to colder highland sites formerly occupied by the species.

Continuity. Ex situ conservation efforts require a continuous supply of funds and a steady institutional policy. While this is also true to some extent for in situ conservation efforts, interruption of care in a zoo, aquarium, or greenhouse lasting only days or weeks can result in considerable losses of both individuals and species. Frozen and chilled collections of sperm, eggs, tissues, and seeds are particularly vulnerable to the loss of electric power. The breakup of the former Soviet Union, the deterioration of the Russian economy, and civil wars in its outlying states provide abundant examples of how rapidly conditions can shift in a country. Zoos are not going to be able to maintain their animal collections under such circumstances.

Concentration. Because ex situ conservation efforts are sometimes concentrated in one relatively small place, there is a danger of an entire population of an endangered species being destroyed by a catastrophe such as fire, hurricane, or epidemic.

Surplus animals. Some species breed too easily in captivity. What should be done with surplus animals in captivity that no other zoo wants and that have no chance of surviving in the wild? This ethical issue must be addressed: the welfare of any animal taken into human custody is the responsibility of its captors, so it may be unacceptable to kill or sell an individual animal, particularly when each animal in a highly threatened species might represent a key component of the species future survival.

In spite of these limitations, ex situ conservation strategies may prove to be the best, perhaps the only alternative when in situ preservation of a species is difficult or impossible. (after: Primack 1998). In Bangladesh, we have many important places and spots which are mostly suitable for the use of 'ex-situ' conservation of biodiversity purpose. These are the Ecoparks, national parks, sanctuaries, different forest areas and even some agro-ecosystem areas for the terrestrial biodiversity conservation. In these 'ex-situ' situation, both plants and animal germ-plasm maintenance could made not only for biodiversity conservation but also for augmentation of materials for biotechnology development and sustenance. Of the animals, deer breeding and its population maximization could be made for commercial use and trade purposes easily in 'ex-situ' areas. In our country, haors, baors, bills, lakes and ponds could be used or modified as 'ex-situ' conservation sites for aquatic biodiversity and wetland biodiversity. In this way, both the species and genetic biodiversity conservation could be maintained in Bangladesh in a better way than of the other countries in the continent.

DR. M. A. Bashar is Prof. Department of Zoology, Dhaka University, and Pro-Vice Chancellor, Bangladesh Open University, Gazipur.