Biodiversity provides the raw materials, combinations of genes, that produce the plant varieties and animal breeds upon which agriculture depends. Thousands of different and genetically unique varieties of crops and animal breeds owe their existence to 3 000 million years of natural biological evolution and to careful selection and nurturing by our farming and herding ancestors during 12 000 or so years of agriculture.
Whether they are used in traditional farming systems, conventional or modern breeding or genetic engineering, the genetic resources of plants and animals are a global asset of inestimable value to humankind. As genetic diversity erodes, our capacity to maintain and enhance crop forest and livestock productivity decreases along with the ability to respond to changing conditions. Genetic resources hold the key to increasing food security and improving the human condition.
The plant genetic diversity used in agriculture—the crops that feed us and their wild relatives—is being lost at an alarming rate. Just nine crops (wheat, rice, maize, barley, sorghum/millet, potato, sweet potato/yam, sugar cane and soybean) account for over 75 percent of the plant kingdom's contribution to human dietary energy.
None of the world's staple crops is likely to disappear. Yet they, too, are threatened—not by the loss of a single crop species such as wheat or rice, but by the loss of diversity within species.
Seeds of survival
All major food crops, the staple crops grown and consumed by the vast majority of the world's population, have their origins in the tropics and subtropics of Asia, Africa and Latin America. Over the years, farmers selected and domesticated all major food crops on which humankind depends today. Wheat and barley originated in the Near East, for example. Soybeans and rice came from China. Sorghum, yams and coffee came from Africa. Potatoes and tomatoes originated in the Andes of South America, and maize in South and Central America.
Crop genetic diversity is still concentrated mainly in regions known as “centres of diversity”, and located in the developing world. Farmers in these areas, who still practice traditional agriculture, cultivate local varieties known as “land races” that have been selected over many generations. Closely related species that survive in the wild are known as “wild relatives” of crops. Together, land races and their wild relatives are the richest repositories of crop genetic diversity.
Thousands of different and genetically distinct varieties of major food crops owe their existence to millions of years of evolution and to careful selection and nurturing by our farmer ancestors during some 12 000 years of agriculture. This diversity protects the crop and helps it meet the demands of different environments and human needs. Potatoes, for instance, originated in the Andes, but nowadays they can be found growing below sea level behind Dutch dykes or high in the Himalayan mountains.
One variety of rice survives on just 60 centimetres of annual rainfall, another floats in 7.5 metres of water.
Agriculture's vanishing heritage
FAO estimates that since the beginning of this century about 75 percent of the genetic diversity of agricultural crops has been lost. We are becoming increasingly dependent on fewer and fewer crop varieties and, as a result, a rapidly diminishing gene pool. The primary reason is that commercial, uniform varieties are replacing traditional ones—even, and most threateningly, in the centres of diversity. When farmers abandon native land races to plant new varieties, the traditional ones die out. The introduction, beginning in the 1950s, of high-yielding grains developed by international crop breeding institutions led to the Green Revolution. The spread of the new varieties in the developing world was dramatic. By 1990 they covered half of all wheat lands, and more than half of all rice lands—a total of some 115 million ha. This resulted in large increases in yields…but large decreases in crop diversity.
The twelve megacentres of cultivated plants
(panels show selected food crops)
The erosion of crop genetic diversity poses a serious threat to food supplies. To maintain pest and disease resistance in major food crops, for instance, or to develop desirable traits such as drought tolerance or improved flavour, plant breeders require fresh infusions of genes from the farms, forests and fields of the developing world. Developing the high-yielding, élite cultivars of modern agriculture depends on a steady stream of new, exotic germplasm. Plant breeders continuously try to develop new varieties to keep one step ahead of thousands of pests and diseases. Without access to traditional land races and their wild relatives, modern agriculture would be seriously endangered.
Dangers of genetic uniformity
Industrialized agriculture favours genetic uniformity. Typically, vast areas are planted to a single, high-yielding variety—a practice known as monoculture—using expensive inputs such as irrigation, fertilizer and pesticides to maximize production. In the process, not only traditional crop varieties, but long-established farming ecosystems are obliterated. Genetic uniformity invites disaster because it makes a crop vulnerable to attack—a pest or disease that strikes one plant quickly spreads throughout the crop.
The Irish Potato Famine of the 1840s is a dramatic example of the dangers of genetic uniformity. None of the few varieties of the New World potato introduced into Europe in the 1500s were resistant to a potato blight that struck Ireland in the 1840s. The potato crop was wiped out. Over a million people died in the famine and a million more emigrated to the New World.
More recently, in 1970, genetic uniformity left the United States maize crop vulnerable to a blight that destroyed almost $1 000 million worth of maize and reduced yields by as much as 50 percent. Over 80 percent of the commercial maize varieties grown in the United States at that time were susceptible to the virulent disease, southern leaf blight. Resistance to the blight was eventually found in an African maize variety called Mayorbella. A major catastrophe was averted by incorporating this resistance into commercial varieties.
The value of crop genetic diversity
The value of genetic diversity to modern plant breeding is enormous. The United States Government estimates that a 1 percent gain in crop productivity means a $1 000 million benefit to the American economy. Italian scientists calculate that the benefits of exotic germplasm for a single crop, durum wheat, amount to $300 million per year. Not only cultivated species but also the genes from wild relatives are enormously valuable. Between 1976 and 1980, wild species contributed an estimated $340 million per year in yield and disease resistance to the farm economy of the United States.
Stunted rice: a wild plant to the rescue
During the 1970s the grassy-stunt virus devastated rice fields from India to Indonesia, endangering the world's single most important food crop. After a four-year search which screened over 17 000 cultivated and wild rice samples, disease resistance was found. Only one population of the species Oryza nivara, growing wild near Gonda in Uttar Pradesh, was found to have a single gene for resistance to grassy-stunt virus strain 1. Today, resistant rice hybrids containing the wild Indian gene are grown across 110 000 km2 of Asian rice fields.
In the developing world, crop genetic diversity enables farmers to select crops suited to ecological needs and cultural traditions. Without this diversity, options for long-term sustainability are lost. This is particularly true in marginal areas with highly varied environments. The variety to a large extent determines the need for fertilizers, pesticides and irrigation. Communities that lose traditional varieties, adapted to local needs and conditions over centuries, risk becoming dependent on external sources of seeds and the inputs needed to grow and protect them. Without an agricultural system in harmony with a community and its environment, self-reliance in agriculture is impossible.
To feed an increasing world population, all available genetic resources, including wild relatives, will need to be tapped. Modern plant breeding as well as new biotechnologies offer the potential to exploit little-known plant species as sources of food, and to enhance the qualities of those plants that are underutilized—especially traditional plants of special significance to poor people, such as local grains, legumes, oilseeds, fruits and vegetables.
Traditional food crops, often grown by rural families to see them through the “hungry season” just prior to harvest, offer many advantages. Many of them are drought resistant, can be grown without expensive inputs and have good storage qualities. For many developing nations, self-reliance in food production will depend on low-input agriculture in poor production environments. The capacity to grow varieties, particularly those resistant to pests and diseases and adapted to marginal lands, is vital for sustainable agriculture and food security.
Geopolitics of plant genetic resources
Historically, scientists from the industrialized countries have ventured southwards in search of exotic plants for plant breeding. Seeds found in tropical centres of diversity have been freely collected and later deployed in plant breeding. As a result, much of the collected diversity of Third World origin has come to be stored in the northern hemisphere or in gene banks established by developed countries.
The issue of control, ownership and access to plant genetic diversity has come to the fore over the past two decades. Plant breeding in the industrialized world has become increasingly commercialized and is now dominated by transnational seed and agrochemical corporations. To promote innovation and to enable breeders to recoup their research investment, many governments in the industrialized world have adopted a system of “plant breeders' rights”. This gives patent-like protection to breeders with limited monopoly rights over the production, marketing and sale of their varieties for a period of up to 20 years.
The disparity between unrestricted access to genetic resources, including farmers' land races, and the existence of proprietary rights such as “breeders' rights” on improved varieties has fuelled intense debate over the inequity in the flow of germplasm from the developing world to the industrialized world. At the United Nations, representatives from the developing world ask: Why are patented seeds, originally from developing countries, bringing profits to seed companies in the industrialized countries without corresponding compensation for the developing world? What compensation will be made to those who have tended and nurtured the world's crop genetic diversity and continue to conserve and make it available today?
Promoting the use and conservation of plant genetic resources
The farmer uses plant genetic resources as seeds or vegetatively propagated material; they are often the one input that farmers can produce for themselves. FAO assistance includes projects for the production and use of good-quality seed, training and guidance in propagation and multiplication, quality control, and processing, storage and distribution of improved seed. FAO provides samples and information to research centres, scientists and field projects for use in crop introduction, evaluation and breeding.
F A C T S
Several thousand plant species have been used for human food in history, but now only about 150 are cultivated and no more than three supply almost 60 percent of the calories and protein derived from plants.
Since the beginning of this century about 75 percent of the genetic diversity of agricultural crops has been lost.
Kenaf (Hibiscus cannabinus), an East African plant related to cotton and okra, may provide an alternative source of pulp for making paper; in the southern United States it yields three to five times more pulp than trees do and requires minor chemical treatment to whiten the fibres.
From wild pineapples found in the dry open Chaco of South America, breeders have imparted high-sugar content and a distinctive “wild fruit” flavour to cultivated varieties.
Genes transferred from a wild relative of the tomato found on the shores of the Galapagos Islands has conferred salt tolerance to cultivated varieties so that they can be irrigated by one-third sea water.
FAO, as a sponsor of the Consultative Group on International Agricultural Research (CGIAR), supports plant breeding and other research carried out at international research centres. Many of its projects focus on traditional food crops such as roots and tubers which in some developing regions contribute up to 46 percent of total calories consumed. Roots and tubers can tolerate a wide range of conditions and are well suited to traditional farming systems. They can be intercropped with other plants and most of them can be grown year-round, providing extra calories during the hungry season. Traditional crops have yet to be explored genetically, but their potential for improvement through breeding seems promising.
FAO has pioneered the collection of plant genetic resources. An early activity was to field seed-collecting missions, particularly in centres of diversity, where modern cultivars were already displacing traditional varieties. Recently, these and related activities have been undertaken in cooperation with the International Board for Plant Genetic Resources (IBPGR), a CGIAR centre that was established in 1974.
Since 1983, FAO has developed a global system on plant genetic resources based on the principle that plant genetic diversity is the heritage of humanity. The objective is to ensure safe conservation, sustainable use and unrestricted availability of plant germplasm (see page 23).
Animal genetic resources include all species, breeds and strains that are of economic, scientific and cultural interest to humankind for agriculture, both now and in the future. Common agricultural species include sheep, goats, cattle, horses, pigs, buffaloes and chickens, but there are many other domesticated animals such as camels, donkeys, elephants, reindeer, rabbits and rodents that are important to different cultures and regions of the world.
Animal domestication began some 10 000 years ago when people began selecting animals for food, fibre, draught and other agricultural uses. Livestock provide valuable products, such as hides, wool and manure, that are important both for subsistence and as sources of income for rural communities. Livestock process forage and crop waste, inedible to humans, into nutritionally important food products.
Approximately 40 percent of the total land available in developing countries can only be used for some form of forage production. An estimated 12 percent of the world's population lives in areas where people depend almost entirely on products obtained from ruminant livestock— cattle, sheep and goats.
Centuries of human and natural selection have resulted in thousands of genetically diverse breeds of domestic animals adapted to a wide range of environmental conditions and human needs. Some are resistant to parasites or disease, for example, while others are adapted to humidity or drought or extremes of heat and cold. Animal genetic diversity, represented by this wide range of breeds, is essential to sustain the productivity of agriculture.
Animals account for 19 percent of the world's food basket directly, but they also provide draught power and fertilizer for crop production, bringing their overall contribution up to 25 percent. In addition, livestock serve as a very important form of cash reserves in many of the mixed farming systems. Taking this into account, animals contribute an estimated 30 percent of total human requirements for food and agriculture.
A sinking ark
In Europe, half of the breeds that existed at the beginning of the century have become extinct; a third of the remaining 770 breeds are in danger of disappearing over the next 20 years. In Germany, for example, only five out of at least 35 indigenous breeds of cattle remain. In North America, over one-third of all breeds of livestock and poultry are considered rare or in decline.
Much less is known about breeds in the developing world. As with plants, domestic animal diversity is greatest in the developing world. Asia, for instance, is home to more than 140 breeds of pig, while North America can claim only 19. Based on preliminary data, FAO predicts that one in four of all non-European livestock breeds may be at risk of extinction, and more than half of them are likely to be found in developing countries.
Worldwide, the greatest threat to domestic animal diversity is the highly specialized nature of modern livestock production. In the developed world, commercial livestock farming is based on very few breeds that have been selected for the intensive production of meat, milk or eggs in highly controlled and regulated conditions. The spread of intensive production systems to the developing world places thousands of native breeds at risk. Commercial breeds imported from North America and northern Europe are usually unable to sustain high production in less hospitable environments. They require intensive management and high levels of inputs such as high-protein feed, medication and protective housing. Introduction of intensive animal production creates dependency on imported technologies: it is neither affordable nor sustainable for most farmers in the developing world.
After thousands of generations of controlled interbreeding, most domesticated animals no longer have wild relatives from whom germplasm can be obtained. When a variety becomes extinct, an already narrow genetic base shrinks irreversibly. Commercial breeds suited to intensive production do not offer an adequate genetic reservoir for the future. Their genetic base reflects the emphasis on maximizing production. The turkey that is mass-produced on factory farms in North America and Europe, for example, has been selected for such a meaty breast that it can no longer breed unassisted. This broad-breasted breed —which accounts for 99 percent of all turkeys in the United States today— would become extinct in one generation without human assistance in the form of artificial insemination.
What value animal genetic diversity?
The genetic diversity now found in domestic animal breeds allows farmers to select stocks or develop new breeds in response to changes in the environment, threats of disease, market conditions and societal needs, all of which are largely unpredictable. Indigenous livestock breeds often possess valuable traits such as disease resistance, high fertility, good maternal qualities, longevity and adaptation to harsh conditions and poor-quality feed, all desirable qualities for low-input, sustainable agriculture.
The rare Taihu pigs of China, for instance, offer valuable traits for swine breeders worldwide. This group of pigs has thick, wrinkled skin and long, droopy ears. They can use a high proportion of forage foods in their diet. The adult pig has little lean meat—whence the Chinese passion for sucking pig. But Taihu pigs reach sexual maturity in just 64 days and are extraordinarily fertile, producing an average litter of 16 piglets compared with only ten for western breeds. Researchers in Europe and the United States are exploring ways to incorporate these beneficial qualities into commercial breeds. A company in the United Kingdom, National Pig Development, has already produced a commercial hybrid of the Meishan, one of seven strains of Taihu pig. Announced in 1992, it combines the fecundity of the traditional Chinese breed with a higher lean meat content.
Ancient African cattle breed offers resistance to a devastating livestock disease
Thirty percent of Africa's cattle population, approximately 160 million cattle, are at risk from trypanosomiasis — a debilitating and frequently fatal disease transmitted by the tsetse fly in 36 African countries covering over 10 million square kilometres. This devastating disease jeopardizes not only African milk and meat supplies, but important by-products and services such as hides, manure, fuel and draught power. Annual losses in meat production alone are estimated at US$5 000 million.
Several traditional African cattle breeds, among them the small humpless N'Dama, have developed resistance (trypanotolerance) over thousands of years of exposure to the parasite — a trait that relatively modern African breeds do not possess. This genetically based resistance offers hope of reducing or controlling the impact of trypanosomiasis.
Small numbers of trypanotolerant N'Dama cattle have long been maintained by West African farmers in marginal farming areas. They thrive on low-quality forage and, though less productive than modern breeds of cattle, their high survival and reproductive rates and longevity make them extremely valuable in harsh environments.
Using a technique known as “embryo transfer”, the population of trypanotolerant N'Dama cattle has already been increased in order to conserve this rare breed, improve its performance and study its disease resistance. The N'Dama's hardiness, heat tolerance and disease resistance have also been recognized. N'Dama cattle have been crossed with the Red Poll, an endangered British breed, to produce the Senepol breed. The Senepol has been introduced successfully in the Caribbean and the southern United States.
Conserving animal genetic diversity
There is already less genetic diversity in farm animals than in crop plant species and over a third of the remaining animal genetic resources is currently at risk. In 1992, FAO launched a comprehensive programme for the global conservation of animal genetic resources. It includes:
A global inventory of animal genetic resources including a database to characterize and enumerate all breeds of livestock used in agriculture.
Action to identify breeds at risk of extinction as well as ways of protecting them.
Promotion of programmes in developing countries to conserve endangered breeds in their native habitats. The aim is to enhance the attraction of indigenous breeds at risk of being substituted by imported breeds which are often brought in without considering local conditions or sustainability.
Improvement of livestock breeding capacities in the developing world. In particular, new technologies will be used to identify livestock diversity and the specific genes responsible for valuable traits.
FAO is exploring the possibility of establishing a global centre for domestic animal genetic diversity to serve as the focus for efforts to overcome the present erosion of these irreplaceable resources and to promote their effective and sustained use. Conservation of animal genetic diversity is essential to global food security and to protect our ability to meet the challenges of the future.
F A C T S
In Europe, half of the livestock breeds that existed at the beginning of the century have become extinct and a third of the remaining 770 breeds are in danger. Almost 20 percent of breeds in the developing world are at risk.
The sheep of North Ronaldsay island in Scotland have adapted to feeding on seaweed while Ming pigs have adapted to the cold winters and hot summers of northeastern China.
The cattle of Secotra (an island off Yemen) are among the highest milk-producing cattle per kilogram of body weight in the world.
The broad-breasted turkey—which accounts for 99 percent of all turkeys in the United States today—would become extinct in one generation without the assistance of artificial insemination.
Oceans, lakes and rivers cover four-fifths of the earth's surface, but little is known about their living resources. Fewer aquatic than terrestrial species have been described, but there is no reason why aquatic biodiversity should be less.
Alaska pollack, a demersal fish, accounts for almost 6 percent of the marine fish catch
Tropical waters are the richest in terms of species diversity. The Indo-West Pacific Ocean, for example, contains an estimated 1 500 species of fish and over 6 000 species of mollusc, compared with only 280 fish and 500 mollusc species in the Eastern Atlantic.
Inland waters are also rich in diversity, the greatest concentration once again being in the tropics. Thailand, for example, could have as many as 1 000 species of freshwater fish, but so far only 475 have been documented. Brazil is believed to have more than 3 000 freshwater fish species — three times more than any other country.
South American pilchard, a small pelagic fish, accounts for about 5 percent of the marine catch
For the most part, the aquatic harvest consists of wild rather than farmed species. World production, 90 percent of it finfish, stands at almost 100 million tonnes a year. Of this, only about 13 million tonnes come from aquaculture. Over 4 million tonnes of algae are also harvested annually.
Importance of fisheries
Fishing, fish processing and fish trading have provided food, employment and income in coastal and inland communities for centuries. Fish contribute substantially to the world supply of animal protein, either directly or through their use as feedstuff for livestock — almost a third of the fish catch is converted into meal and oil.
The developing countries account for more than half the world catch. Their fisheries are dominated by small-scale or artisanal producers. Artisanal fisheries, typically using small boats and canoes, account for more than 25 percent of the world catch. They supply more than 40 percent of the fish used for human consumption. These fisheries are also a significant source of employment — an estimated 100 million people in the developing world depend upon them for all or part of their livelihood.
By the turn of the century, demand for fish is expected to exceed by some 20 million tonnes the productive capacity, estimated at about 100 million tonnes, of stocks now exploited by the capture fisheries. Increased incomes and appreciation of the dietary value of fish are spurring the demand for fish and fish products in the industrialized countries, especially for luxury products such as oysters, shrimp, salmon and tuna. In the developing regions, population increases and the need to tap every potential source of food and foreign exchange provides the main impetus for increased fishing activities.
One response to the growing demand for fish and its falling availability has been the development of aquaculture. This rapidly expanding source of food poses some threats to biodiversity by concentrating on a very small range of species and an equally narrow genetic base in these species. Large-scale escapes of cultured fish, or deliberate releases of stocks for ranching, are thought to influence the genetic composition of the wild resource.
The Peruvian anchoveta, once a source of the world's largest single species fishery, declined because of over-fishing and environmental change
Aquatic biodiversity is threatened primarily by human abuse and mismanagement of both the living resources and the ecosystems that support them. Loss of habitats, over-exploitation and introduction of exotic species are the prime hazards.
Overexploitation. Fish stocks are a renewable resource, but already many of them are strained to the limit. Over the years, they have suffered from a widespread notion that the seas are inexhaustible, economic pressures that have encouraged overexploitation and, until just over a decade ago, an international regime that gave almost unlimited access to the majority of them. All fishing activities depend on a fragile resource base which, if mismanaged and overexploited, can easily collapse.
Efforts to regulate marine fisheries can be traced back to the late 1800s with the creation in Europe of the Intergovernmental Commission for the Exploration of the Seas (ICES). Many fishery bodies for developing and regulating fisheries, in both marine and inland waters, have been established since — nine of them under the auspices of FAO. Despite this appreciation of the threat posed by overfishing, stocks have continued to be exploited at a non-renewable rate.
All demersal (deep water) species such as cod, haddock and pollack are now either fully exploited, overfished or depleted. Larger pelagic (surface water) species such as herring, sardines and anchovy, stocks of which can fluctuate greatly from year to year, are in serious need of management. Crustacea such as shrimp, lobster and crab are also overexploited. Only the bivalve molluscs, such as mussels and clams, and cephalopods such as squid and octopus, offer much scope for expanded production.
The world fish catch has increased more than fourfold in the past 40 years, but the misuse of modern technology, coupled with government support for otherwise non-economic production, has had a devastating impact on fish stocks. Fleets using sophisticated fish detection, non-selective nets (up to 50 km long) and bottom trawls are driving some species to extinction. FAO estimates that the cost of overexploitation amounts to some US$30 000 million per year.
Production of crustaceans, mostly from aquaculture, has increased dramatically over the past ten years, exceeding 4.25 million tonnes in the early 1990s.
The impact of overexploitation of fisheries may be greatest in the developing world. Commercial fishing in tropical waters can often mean valuable foreign exchange for developing nations, but it can also lead to intense competition with declining catch rates for small-scale fisheries, many of which provide fish for local consumers and markets. Higher fish prices, the result of increased demand exacerbated by overfishing, are making fish unaffordable to an increasing number of poor people. Fish is no longer “a cheap meat dish” — a marketing slogan used in the United Kingdom in the 1950s.
|Selectivity of fishing methods
Traditional fishing gears, ranging from a simple harpoon to a basket- work fishtrap, are typically selective for both size and species and are adapted to the diversity of fish captured, whereas commercial gears, such as the purse seine, large driftnet and trawl, often have a by- catch of unwanted species. The displacement of traditional fishing methods, combined with the introduction of new materials and highly mechanized fisheries, has contributed to overexploitation of resources in both marine and freshwater environments.
Environmental degradation. To the pressure of exploitation must be added the degradation or destruction of aquatic ecosystems caused by pollution or competing uses. The oceans function as a sink for carbon dioxide, eroded soils, contaminants, fertilizers, human and industrial wastes. Most urban and industrial activities and, indeed, much of human life, are concentrated close to coastal waters, rivers and lakes. Six out of ten people live in coastal areas, and migration towards them is increasing.
The development of intensive aquaculture has, in some cases, damaged coastal ecosystems and water resources, causing conflicts over land use and resources, and even undermining local sources of employment and food. In parts of Asia, thousands of hectares of rice paddy have been replaced by high-value shrimp farming or had their productivity reduced by salinization caused by neighbouring aquaculture enterprises. In the Indo-Pacific, more than one million hectares of mangrove forests have been converted to aquaculture ponds. Mangroves provide spawning and nursery areas for many marine species and are vital to maintaining ecological balance and biodiversity.
Introduction of exotic species.
The introduction of exotic fish species can have many unforeseen consequences. The release of the Nile perch in Africa's Lake Victoria is a classic example. Introduced in the late 1950s as a sports fish, its voracity and large size has driven many of the smaller indigenous species to extinction. Some scientists speculate that 200–300 species of fish may have been lost.
The expanding population of Nile perch is making Lake Victoria one of the most productive lake fisheries in the world, yielding 200 000 to 300 000 tonnes per year. But increased productivity may have been achieved at serious ecological and social cost. The lake is increasingly providing fish for export rather than local consumption. Lakeside fishing communities have lost species that traditionally provided food and supported the local economy. The long-term impacts remain to be seen, but this example provides a valuable lesson for future introductions and transfers of fish species.
Tilapia: an “aquatic chicken”
Tilapias, consisting of species of the genera Tilapia, Oreochromis and Sarotherodon, have been widely distributed around the world from their original African home. They are now the mainstay of small-scale aquaculture for many poor farmers in the developing world, as well as for enterprises in the developed world. They are most widely cultured in Asia, particularly China, the Philippines and Thailand.
Dubbed the “aquatic chicken”, tilapias possess many positive attributes that suit them for a wide range of aquaculture systems: excellent growth rates on a low-protein diet; tolerance of a wide range of environmental conditions; high resistance to diseases and parasitic infections; ready breeding in captivity and ease of handling; and wide acceptance as food fish.
Because tilapias are so widely farmed in the developing world, the Philippines-based ICLARM, the CGIAR centre devoted to fisheries, has established the Genetic Improvement of Farmed Tilapia (GIFT) programme. Its aim is to increase food production and income by and for small-scale producers. The GIFT programme has collected strains of tilapia and evaluated their culture and growth in different environments.
Scientists have discovered, for example, that tilapia breeds in Asia are deteriorating as a result of generations of inbreeding. Future breeding efforts must draw on a wider genetic base, incorporating genetic material from Africa. This underscores the importance of future conservation and utilization of Africa's native tilapia breeds.
In May 1992, the International Conference on Responsible Fishing at Cancún, Mexico, called upon FAO to draft, in consultation with other international organizations, an International Code of Conduct for Responsible Fishing. The concept of “responsible fishing” embraces sustainable utilization of fisheries resources in harmony with the environment, and the use of capture and aquaculture practices that do not harm ecosystems, resources or food quality.
FAO supports comprehensive programmes on fisheries management, focusing on both coastal zones and high seas. It is also committed to international efforts to introduce ecologically safe fishery technologies. FAO provides technical assistance aimed at environmentally sound aquaculture practices, as well as incorporating aquaculture in rural development planning.
To conserve aquatic biodiversity, FAO emphasizes the sustainable use of aquatic resources. Activities include genetic selection programmes in aquaculture; the elaboration of codes of practice for the introduction and transfer of aquatic organisms and on access to genetic resources and biotechnology; and maintenance of a world database on introductions and transfers, as well as a database on species, strain and race identification.
F A C T S
Capture fisheries have reached or may even have exceeded their sustainable yield at 100 million tonnes, leaving a gap between supply and demand which will reach an estimated 20 million tonnes by the year 2000.
About 300 kinds of finfish are cultured for food, but 85 percent of production comes from carp while tilapias account for much of the remainder.
In the northwestern United States, 159 genetically distinct populations of ocean-migrating fish species are at high or moderate risk of extinction.
Approximately 7 000 species of marine fish have been described from Indonesia, which has over 13 000 islands and the largest total coastline of any tropical country.
About 30 percent of the world's ice-free land surface is forest or woodland. Forested areas of the world today comprise between 3 000 million and 3 500 million ha — an area equal to the size of North and South America. According to recent estimates, temperate forests cover approximately 1 430 million ha in the industrialized countries and another 210 million hectares in non-tropical developing countries. Tropical forests, both moist and dry, cover an estimated 1 760 million ha.
Benefits and use of forests
Forests supply food, fodder, medicine and timber, poles and fuelwood as well as raw materials for industry. The income earned from trees and forests is of vital importance to both rural populations and national incomes. Forests are home for an estimated 300 million people — shifting cultivators and hunter-gatherers — around the world. In the past, the slash-and-burn agriculture practised by forest-dwelling people was sustainable, but population pressures are reducing the land available for shifting cultivation; shorter fallow periods and overuse are turning traditionally sustainable methods into destructive ones.
Rural people living in and around forest areas depend on a large variety of forest products for subsistence. Forest foods form a major part of the diet of some population groups in rural areas in developing countries. They include leaves, seeds and nuts, fruit, roots and tubers, sap and gums, fungi and animals. Forest foods often increase in importance during the hungry season, which reaches its peak just before crops are harvested, and when crops fail.
Woody species provide three-quarters or more of the population in developing countries with their primary energy source. In developing countries, eight times more wood is used for fuel than is logged for industrial purposes. In many areas, fuelwood is being harvested faster than it is being replenished. By the year 2000, nearly 3 000 million people could face fuelwood shortages.
Forests provide vital ecological functions. Their absorption of carbon dioxide and release of oxygen through photosynthesis help control the level of greenhouse gases and provide an atmosphere essential to support life. Forest vegetation helps recycle nutrients. Forest cover also reduces soil erosion by slowing the runoff of water, reducing the hazard of floods and the silting of reservoirs and waterways.
Forests, woodlands and other wilderness areas are increasingly valued as sites of natural and cultural heritage, as well as for education and recreation. Ecotourism is the third most important source of income in Rwanda, for instance, largely because it is home to the mountain gorilla.
Non-wood products and services, many of which have long been used by people living in and around forests, are increasingly appreciated as a source of sustainable development. Many food crops and industrial, commercial and pharmaceutical products originated as non-wood forest products. The economic and social incentives provided by non-wood forest products encourage conservation and offer a defence against the loss of biodiversity.
World forest decline
The world's forests are declining at unprecedented rates. Major threats are deforestation and atmospheric pollution. Another threat is the narrowing of the genetic base of tree species as a result of commercial forestry operations.
Whereas reforestation of temperate forest lands now exceeds removal of trees, the loss of tropical forests gives cause for concern. The tropical forests were destroyed at an annual rate of 15.4 million ha between 1980 and 1990 according to a recent FAO survey. In terms of area, the greatest losses were in Latin America and the Caribbean (an average of 7.4 million ha per year) followed by Africa (4.1 million ha per year) and Asia and the Pacific (3.9 ha per year).
The causes of deforestation vary from region to region. The most important include: conversion of forest land to agricultural use; excessive use of fuelwood and charcoal; shifting cultivation where fallow periods are too short; unsustainable logging; expansion of urban and industrial areas; and overgrazing and fodder collection. Poverty is the underlying cause of many of these environmentally degrading activities.
Fungi, commonly valued as meat substitutes, supply large amounts of protein and essential minerals
Despite a net increase in the forested area in Europe, pollution and forest fires have caused a severe decline in biodiversity and forest vigour. Forests in Germany and the former Czechoslovakia have been particularly affected. Less obvious, but equally alarming, is the decline in genetic diversity within forest species in both Europe and North America. This genetic erosion results mainly from deforestation, compounded for a few economically important species by intensive breeding for commercial forestry. FAO estimates that about 400 tree species are endangered in whole or in significant parts of their gene pools.
When forests decline or are removed, much more than trees is lost. Forests harbour many animals and plants that depend on their environment for survival. Many of these species, their potential value to society and their ecological importance have yet to be discovered. Untapped treasures include possible crops, pharmaceuticals, timbers, fibres, pulp, soil-restoring vegetation, petroleum substitutes and countless other products and amenities. The bark of the rare western yew tree Taxus brevifolia, which is now found only in the old-growth coniferous forest of the northwestern United States, was recently found to be the source of taxol, one of the most potent anticancer substances ever found. If forest felling continues at the present rates, new sources of scientific information are likely to be lost and inestimable biological wealth destroyed.
Even where conservation measures have been taken, they may not halt the decline in biodiversity and therefore the overall genetic resources of the forest ecosystem. At present less than 5 percent of the earth's land surface is allocated for conservation as national parks, scientific stations or other types of legally protected land. Conservation areas have been set aside for many reasons, but rarely with reference to the location of valuable gene pools. Frequently they are too small to maintain viable populations of the threatened species and varieties they do contain. At the same time, experience shows that policies to control and protect such reserves will not succeed without the active support of local people and complementary programmes aimed at meeting their everyday needs.
Sustainable development of forests
Properly managed, forest ecosystems can provide goods and services while, at the same time, perpetuating the genetic resources contained in them. Progress is being made towards new styles of management. The sustainable harvesting of non-wood forest products can improve food security and nutrition, while increasing income and job opportunities. Agroforestry — a farming system that combines trees, crops and livestock — enables farmers, even the poorest, to diversify agricultural production and reclaim degraded land. The degradation of forests can also be reduced by harvesting practices that enable logging to take place while promoting and conserving forest regeneration.
The sustained utilization of forests, coupled with the maintenance of a network of areas dedicated to the protection of ecosystems and their functions, provides the only solution for lasting genetic conservation.
FAO activities to conserve forest genetic resources
The FAO Panel of Experts on Forest Gene Resources, established 25 years ago, guides the Organization's actions to conserve forest genetic resources. FAO's Forestry Department collaborates with national or regional institutes that are or wish to become involved in these activities. Its field projects offer technical advice and assistance to governments in planning and carrying out conservation projects, as well as the integration of genetic resource conservation in land-use and forestry planning.
Specific activities include assistance in the exploration, collection and evaluation of forest genetic resources, planning and developing seed centres, and establishing and managing the conservation, both in situ and ex situ, of priority species. The FAO Forestry Department also publishes and disseminates a wide range of educational and training materials on the use and conservation of forest genetic resources.
FAO's Global System for the Conservation and Utilization of Plant Genetic Resources includes forest tree species. Within the framework of FAO's International Undertaking on Plant Genetic Resources, FAO's Forestry Department is the focal point for activities related to in situ conservation of plant genetic resources.
F A C T S
Deforestation of closed tropical rain forests could account for the loss of as many as 100 species every day.
Kalimantan, Indonesia, is an important centre of genetic variation for tropical fruit trees, including mango, breadfruit and durian. Of 16 species of mango in East Kalimantan Province, 13 are edible.
Exports of chicle, allspice and xate (edible palm fronds) earn Guatemala US$7 million annually and support some 6 000 families in the Petén region of the country.
Collecting, extracting and processing the kernels of the fruit of babassu palm provides an estimated 25 percent of household income for 300 000 families in Brazil's Maranhão State.
In Côte d'lvoire, harvesting giant snails (Achatina achatina) in the buffer zone around Tai National Park provides a source of food and income: each snail provides some 100 to 300 g of meat and the shells provide calcium for animal feed or crop fertilizer.
More than 20 tonnes of mushrooms, mainly chanterelles (Cantharellus spp.) are gathered and consumed every year by the 700 000 or so residents of the Upper Shaba area of Zaire.