The availability of broadly based gene pools is an essential condition for adaptation to environmental change, both natural and man-made, such as: the replacement of pesticides by genetic defences; the adaptation of high-yield varieties to local conditions; the development of resistance to evolving parasites; and the correction of nutritional defects, such as low content of protein or specific amino-acids. Genetic diversity is required to counter the inadaptability to local conditions that sometimes follows the introduction of highly selected animal species. Continual selection for specific traits within a breed or type sometimes dangerously reduces genetic variability.
Man's impact on the biosphere is increasingly reducing the genetic resiliency of many species. Not only agricultural plant varieties, but also forest species, aquatic organisms, and certain types of animals and micro-organisms are affected. The full variety of microscopic organisms provides the indispensable link in the carbon and nitrogen cycles upon which all life depends: micro-organisms include bacteria, yeasts, molds, algae, protozoa, and viruses. The quality and flavour of man's food and drink often depends upon beneficial bacteria and fungi and industry uses micro-organisms to manufacture chemical products, including antibiotics. Micro-organisms help man to understand the underlying causes of many pathological conditions and pollutant organic wastes are rendered harmless by the use of bacteria.
The development, transforming and disrupting new areas for man's use is depleting or displacing valuable genetic resources. Wild species and primitive domesticates are lost. Areas in Asia, Latin America and Africa are threatened that have traditionally served as the 'centres of natural diversity' or the natural habitation of wild varieties and as the source of genetic resources for plant improvement. Indigenous crops are replaced by new higher yielding varieties of greater genetic uniformity and less adaptability to local conditions. Many plant characteristics, such as: protein quality, oils, unique growth habit, and dwarfness, may someday be required, but are being lost with the disappearance of wild species. The introduction by man of exotic diseases and insects poses a great risk to some of the world's gene resources. For example, the chestnut blight has wiped out all but scattered remnants of the American chestnut tree. Also threatened are the remnants of forest species whose populations, often critical for breeding, can be substantially reduced and sometimes eliminated.
The narrowing of the genetic base of many of the world's crops leaves them vulnerable to pests, diseases, and changes in soil and climate. Concurrent with this is the depletion of those genetic resources essential for both the reduction of that vulnerability as well as for the production of a large number of pharmaceutical and industrial products.
Mankind shares the Earth with 5 to 10 million other species, all of which have the right to survive. Almost entirely through loss of habitat, which in turn reflects the upsurge in human numbers and consumption, species are becoming extinct at a rate of hundreds and perhaps thousands each year – the majority of these extinctions occurring in the tropics. Up to one half of the world's genetic diversity is concentrated on only 6% of its land surface, mostly in tropical forests, and the world's topical rainforests are disappearing at the rate of 7.3 hectares a year.
One species per day is being lost in these forests alone. Many species are losing sub-units such as races and populations, at a rate that greatly reduces their genetic variability. Even though these species are not being endangered in terms of their overall numbers, they are suffering a decline in their genetic stocks which leads to their having only a fraction of the genetic diversity they harboured only a few decades ago.
If present trends are not reversed, humanity may witness the elimination of one million of the planet's plant and animal species by the end of this century. This represents an irreversible loss of unique genetic materials. Such extinction means a loss of crucial ecological services such as the control of pests. Increasingly, species are contributing to agriculture, medicine, industry and energy.
Through their genetic resources, the 5-10 million species that inhabit this planet along with man provide essential materials for agriculture, medicine, industry, energy and other economic uses. The potential for further application has only begun to be explored but, considering the manifold benefits we already enjoy, the genetic reservoir is among the most valuable natural resources with which we can confront the unknown challenges of the future.
Maintaining natural genetic diversity will become less important over the very long term as advances in genetic engineering make possible substitution of genes among species.