Diversity of species used

When you visit the supermarket it may seem as if we use an incredible variety of different plant species to provide food. In fact, we depend on a vanishingly small proportion of the existing diversity of plants.

• There are roughly 250,000 species of land plants currently extant.

• Of those, roughly a quarter (60,000) are thought to possess some food value for humans.

• Over the course of human history, about 3,000 have actually been used by one or more cultures as a regular source of foodstuffs (about 1% of the total).

• Only about 150 have been commercially cultivated.

• In 1974⁷ only seven of the 30 major cultivated crops had harvests in excess of 100 million tons.
  • wheat

  • rice

  • corn

  • potato

  • barley

  • sweet potato

  • cassava

• Only three species account for over two-thirds of the world's total grain crop:
  • wheat

  • rice

  • corn

Many minor crops (and ``heritage varieties'' of major crops) are in danger of economic extinction, e.g.,

• tarwi (Lupinus mutabilis)

• relatives of swordbean (Canavalia plagiosperma, C. regalis)

• African yeheb nut (Cordeauxia edulis)

A similar pattern is seen with domesticated animals. Over 3000 breeds of donkey, cattle, horse, pig, sheep, and water buffalo are known, and over 1000 are at risk of extinction [1]. I'll focus on genetic resource of crop plants, because that's what I am most familiar with.

Concern about the narrow base species and the narrow base of diversity within those species⁸ on which human welfare depends led to the formation of the

• International Board for Plant Genetic Resources (IBPGR) within the framework of the

• Consultative Group on International Agricultural Research (CGIAR)

• to promote the collection, conservation, documentation, evaluation and use of crop plant genetic resources.

What does such an organization do? What problems does it face? To answer these questions we must address the following questions first:

• What are the consequences of domestication?

• What are the uses of genetic resources?

• What are the techniques that can be used to conserve them?