The decline in species populations, combined with the fragmentation of landscapes, inland water bodies and marine habitats, have necessarily led to an overall significant decline in the genetic diversity of life on Earth.

While this decline is of concern for many reasons, there is particular anxiety about the loss of diversity in the varieties and breeds of plants and animals used to sustain human livelihoods. A general homogenization of landscapes and agricultural varieties can make rural populations vulnerable to future changes, if genetic traits kept over thousands of years are allowed to disappear.

An example of the reduction in crop diversity can be found in China, where the number of local rice varieties being cultivated has declined from 46,000 in the 1950s to slightly more than 1,000 in 2006. In some 60 to 70 per cent of the areas where wild relatives of rice used to grow, it is either no longer found or the area devoted to its cultivation has been greatly reduced.

Significant progress has been made in ex situ conservation of crops, that is the collection of seeds from different genetic varieties for cataloguing and storage for possible future use. For some 200 to 300 crops, it is estimated that over 70% of genetic diversity is already conserved in gene banks, meeting the target set under the Global Strategy for Plant Conservation. The UN Food and Agriculture Organization (FAO) has also recognized the leading role played by plant and animal breeders, as well as the curators of ex situ collections, in conservation and sustainable use of genetic resources.

However, major efforts are still needed to conserve genetic diversity on farms, to allow continued adaptation to climate change and other pressures. Additional measures are also required to protect the genetic diversity of other species of social and economic importance, including medicinal plants, non-timber forest products, local landraces (varieties adapted over time to particular conditions) and the wild relatives of crops.

Standardized and high-output systems of animal husbandry have led to an erosion of the genetic diversity of livestock. At least one-fifth of livestock breeds are at risk of extinction. The availability of genetic resources better able to support future livelihoods from livestock may be compromised.

Twenty-one per cent of the world's 7,000 livestock breeds (amongst 35 domesticated species of birds and mammal) are classified as being at risk, and the true figure is likely to be much higher as a further 36 per cent are of unknown risk status [See Figure 13]. More than 60 breeds are reported to have become extinct during the first six years of this century alone.

The reduction in the diversity of breeds has so far been greatest in developed countries, as widely-used, high-output varieties such as Holstein-Friesian cattle come to dominate. In many developing countries, changing market demands, urbanization and other factors are leading to a rapid growth of more intensive animal production systems. This has led to the increased use of non-local breeds, largely from developed countries, and it is often at the expense of local genetic resources.

Government policies and development programmes can make matters worse, if poorly planned. A variety of direct and indirect subsidies tend to favour large-scale production at the expense of small-scale livestock-keeping, and the promotion of "superior" breeds will further reduce genetic diversity. Traditional livestock keeping, especially in drylands, is also threatened by degradation of pastures, and by the loss of traditional knowledge through pressures such as migration, armed conflict and the effects of HIV/AIDS.

The loss of genetic diversity in agricultural systems is of particular concern as rural communities face ever-greater challenges in adapting to future climate conditions. In drylands, where production is often operating at the limit of heat and drought tolerances, this challenge is particularly stark. Genetic resources are critically important for the development of farming systems that capture more carbon and emit lower quantities of greenhouse gases, and for underpinning the breeding of new varieties. A breed or variety of little significance now may prove to be very valuable in the future. If it is allowed to become extinct, options for future survival and adaptation are being closed down forever.