Crops and animals

Posted: 6 May 2008

Biodiversity - in the form of genetic diversity - is a value even in the variety of crops and animals used in agriculture. Here too it is under threat.

  • Out of an estimated total of some 320,000 vascular plants, some 25,000 are used or have been used for medicinal purposes, and around 3,000 are regularly used for food. However, of the world's 50,000 species of edible plants, just 15 food crops provide 90 per cent of the world's food energy intake. Three of them - rice, wheat and maize - are the staple foods of 4 billion people.

  • Out of the 50,000 vertebrate species on earth some 30-40 mammals and birds and 200 fish are reared domestically.

Livestock in Rwanda© ILRILoss of diversity

  • Loss of genetic diversity leaves crops and livestock less able to adapt to local conditions, more vulnerable to epidemics and more dependent on pesticides, herbicides and fungicides for protection. It also reduces the genetic basis from which future varieties can be bred. Since 1900, about three-quarters of the genetic diversity of cultivars have been lost, as well as nearly half of the wild gene pool of domestic animals.

  • Three main factors are responsible for the declining genetic diversity of crops and livestock. These are: destruction of the original habitats; the development of genetically uniform breeds by international companies and research centres; and farmer and/or consumer preferences for certain varieties and breeds.

  • Out of the 6,379 breeds of domestic livestock in the world, 2,255 are at risk of extinction. The proportion at risk is highest in Western Europe, and is generally higher the more developed and commercialised is farming.

  • The FAO estimates that somewhere in the world at least one breed of traditional livestock dies out every week.

  • In China nearly 10,000 wheat varieties were in use in 1949. Only 1,000 were still in use by the 1970s. There have also been significant losses of diversity in wild groundnut, wild rice, and an ancestor of cultivated barley.rice varieitesThere are thousands of varieties of rice but the genetic diversity of rice is being threatened by the development of genetically uniform breeds.© IRRI
  • In the United States 7,098 apple varieties were documented as having been in use between 1804 and 1904. Of these, approximately 86 per cent has been lost. Similarly, 95 per cent of the cabbage, 91 per cent of the field maize, 94 per cent of the pea, and 81 per cent of the tomato varieties no longer exist.

  • Of almost 6,500 breeds of cattle, buffalo, goats, pigs, sheep, horses, and yaks, rabbits, chickens, turkeys, ducks, geese, pigeons, donkeys, even ostriches, one-third are at risk of becoming extinct. About 1,000 breeds have become extinct in the last hundred years.

  • World-wide, gene banks house some 6.1 million samples of plant genetic resources stored in over 1300 collections. Almost half of these, however, are advanced cultivars or breeding lines. Only 36 percent are landraces or old cultivars and about 15 per cent are wild or weedy plants or crop relatives. Fewer than half of the collections can offer secure, long-term management of accessions.

Sources:The State of the World's Plant Genetic Resources for Food and Agriculture, FAO, Rome, 1997V. Heywood, ed., Global Biodiversity Assessment, Cambridge University Press, 1996Domestic Animal Diversity Information System (FAO)