The crops used for food and agriculture at present are the product of years of natural evolution, selection by farmers and Scientific plant breeding. But, today, the diversity of plant species is subject to serious threats, among them pollution, resource degradation, destruction of habitats and alteration of ecosystems. Loss of species irreversibly reduces the genetic store on which future crop improvement and adaptability depends.
BEFORE the rise of the earliest civilizations, our ancestors were identifying, developing and using plant genetic resources, favouring certain wild plants over others for their unique characteristics and selecting those most suited to their needs. Slowly, these practices have led to the domestication of virtually all of the agricultural species we depend on today for food, feed, flavouring, fibre, materials for shelter, fertilizers, fuel and medicines. Even so, cultivated crops represent a very small portion of what is available in nature.
Of the several hundred thousand known plant species, some 120 are cultivated for human food. But just nine of these crops supply over 75 percent of global plant-derived energy intake and of these, only three - wheat, rice and mane -account for more than 50 percent. At the local level, however, many less commercial crops are important for subsistence. An estimated 80 percent of the vitamin A and more than a third of the vitamin C in the diet of Africa's people are supplied by traditional food plants.
Forest dwellers, who use at least 1 300 plant species for medicinal and related purposes, have contributed to the discovery of an estimated three-quarters of the plant-derived prescription drugs widely used in the developed world today. The active ingredients found in 25 percent of prescription drugs come from plants.
THE GENES found in the largely untapped wealth of undomesticated plants can I provide the key to the improved crops we will need to feed the world's population in the future. For example, during the 1970s, the grassy-stunt virus devastated rice fields from India to Indonesia, endangering the world's single most important food crop. A gene from an Indian wild relative was used to confer resistance to varieties that are now grown across 11 million ha of Asian rice fields.
Genetic diversity helps crops to withstand changes in environment, climate and agricultural methods as well as threats from pests and diseases. In each of the planet's diverse ecosystems, biological diversity is at the root of a complex ecological balance.
The CHIEF CAUSE of loss of genetic diversity- referred to as genetic erosion - has been the spread of modern, commercial agriculture. The introduction of new, highly uniform varieties has resulted in the loss of traditional farmers' varieties. Unfortunately, genetic erosion is almost always associated with - or even preceded by loss of the knowledge regarding varieties and their uses.
Genetic erosion reduces the material available for use in plant improvement. At the same time, uniformity makes crops much more vulnerable to changes in the presence of pests and diseases by narrowing their genetic base - the stockpile of characteristics that can provide crucial resistance or immunity.
Deforestation is a major cause of loss of species, be they plant or animal. It has been estimated that the clearing of closed tropical rainforests could account for the loss of as many as 100 species each day. Deforestation will be the single greatest cause of species loss in the next 50 years.
Main causes genetic erosion
THE WORLD'S plant resources are found either ex situ, including as seed in genebanks and botanical gardens, or in situ, for instance, in farmers' fields, on rangelands or in forests.
Today, about 6 million accessions are stored worldwide in more than l 000 genebanks. But much remains to be done if we are to realize the full value of our plant genetic heritage. To keep seeds in genebanks viable, for instance, they need to be regenerated and regrown periodically. Many of the world's genebanks are facing problems in maintaining seed quality. In a recent survey, 77 countries reported that they had seed storage facilities, but probably fewer than half could offer secure, long-term conservation and management of seeds.
At the same time, anywhere from 80 to 95 percent of the plant material in genebanks worldwide is still uncharacterized - in other words, it is still unknown what these seeds may contain in their genetic makeup. This information is fundamental if we are to use this material to produce better crops, both through traditional breeding methods and by applying advanced biotechnological techniques.
Farmers continue to play a key role in maintaining biological diversity. Globally, 1.5 billion farmers are involved in on-farm conservation and breeding, selecting varieties and improving crops on a day-to-day basis. But most of the farm families that are responsible for this type of management and improvement of plant genetic resources are limited by lack of resources.
Centres of origin of some common crops
EFFORTS to make the most of the world's plant genetic resources must concentrate on three basic spheres of activity:
Well-founded efforts to tap the wide array of plant genetic resources, including carefully planned conservation, management and distribution schemes, can allow these seeds of life to play a major role, today and in the future, in protecting millions of people from hunger.
Biological diversity for food: a leargly untapped resource
For further information, please contact:
Food and Agriculture Organization of the United Nations
Viale delle Terme di Caracalla, 00100 Rome, Italy
Information Division, Tel: (39-6) 5225-3276/5225-4781/5225-4243
Plant Production and Protection Division, Tel: (39-6) 5225-4986
Internet, http://www.fao.org or gopher.fao.org
United Nations Environment Programme, P.O. Box 30552 Nairobi, Kenya
Information and Public Affairs
Tel: (254-2) 621234; Fax: (254-2) 226831;
Telex: 22068 UNEP KE