Maintaining Biodiversity in the Wild

Maintenance of plant and animal genetic material in the wild (in situ) and maintenance of wild or domesticated material in gardens, orchards, seed collections, or laboratories (ex situ) are both essential aspects of managing the human use of genetic diversity. In situ conservation maintains not only a variety's genetic diversity but also the evolutionary interactions that allow it to adapt continually to shifting environmental conditions, such as changes in pest populations or climate. In agriculture,in situ conservation is also the best way to maintain knowledge of the farming systems in which the varieties have evolved.

Landraces

One of the innovative techniques that has been suggested for maintaining both genetic diversity and knowledge of farming systems where traditional varieties are being lost involves the use of village-level "landrace custodians." Landraces are a crop cultivar or animal breed that evolved with and has been genetically improved by traditional agriculturalists, but has not been influenced by modern breeding practices. At a limited number of key sites (perhaps between 100 and 500) in areas where diseases, pests, and pathogens strongly influence the evolution of local crop varieties, individuals could be paid to grow a sample of the endangered native landraces. These farms would backstop ex situ conservation efforts, maintain the potential for further evolution in important landraces, preserve knowledge of traditional farming systems, and provide regional education on the importance of biodiversity conservation. If it seems economically inefficient to subsidize the in situ maintenance of traditional landraces, consider how often their loss is hastened by subsidies for such agricultural inputs as fertilizers and pesticides.For instance, in 1985. Indonesia had an 85-percent subsidy on pesticides, at an annual costs of $120 million.

Conserving Germplasm

The greatest untapped potential for in situ germplasm conservation resides in protected areas set aside to conserve species that cannot be preserved ex situ and wild crop relatives. A number of species possess recalcitrant seeds--seeds unsuited to long-term storage in seed banks. With greater research, better storage techniques may eventually be developed, but for now in situ conservation represents one of the few conservation techniques available. In addition, in situ conservation of wild crop relatives maintains not only the target species, but also a host of other species that share the same habitat.

The International Board for Plant Genetic Resources (IBPGR) has identified numerous species whose wild relatives are prime candidates for in situ conservation. These include relatives of groundnut, oil palm, banana, rubber, coffee, cocoa, members of the onion family, citrus fruits, mango, cherries, applies, pears, and many forage species. Some pilot efforts are now under way to develop such in situ conservation programs. A gene sanctuary has been established in India for Citrus species, two reserves have been established in Zambia to conserve Zambesi teak (Baikiaea plurijuga), and one has been set up in Canada for jack pine (Pinus banksiana). The existing 4,500 protected areas monitored by the World Conservation Monitoring Center can be expected to harbor many wild relatives, though no actual field inventory has been conducted.

Conserving Forest Species

Little effort has been directed at conserving the genetic diversity of forestry species. A number of populations of the two dozen species that have been intensively bred survive in various types of protected areas, so it seems unlikely that the genetic base of the species will shrink. However, several hundred wild or semi-domesticated tree species of economic value throughout the world are at risk of being lost in all or part of their ranges. In a review in 1986, the FAO identified 86 such threatened species, and this list has lengthened since. Only about half of the populations threatened in 1989 are represented with protected areas.

Wild forest species are particularly susceptible to genetic erosion because of the practice of high grading, whereby the best trees are removed each harvest cycle and the less useful trees become the breeding stock. This type of genetic erosion has reduced a number of once vigorous timber-producing forests in Japan, Korea, Turkey, and the Himalayas to stands of stunted and malformed trees. The best defense against the erosion of forest genetic diversity is a combination of in situ conservation, ex situ storage, and the use of living collections of plants (known as ex situ field gene banks). How long the seeds of many tree species will last in storage has not yet been tested; particularly among tropical species, long-term storage may be difficult and field gene banks necessary. In addition, even species whose seed can be stored in seedbanks will have to regenerated periodically; given the long generation time of forest species, continual maintenance in field gene banks will be needed.