Humans depend on plant genetic resources for food and agriculture (PGRFA) for many aspects of survival, including food, fuel, and fiber. A study conducted by the United Nations Food and Agriculture Organization (FAO) concluded that plants contribute the vast proportion of the world's food supply, particularly for developing countries in Africa, Asia, and the Pacific. At a global level, the total dietary energy and protein provided by plants is 84% and 63%, respectively, while animal sources contribute 16% and 37%, respectively ( Table 1 ). Plant resources are even more critical in Africa, where about 93% of food energy and 79% of protein are derived from plant sources. The history of the development and use of PGRFA has been characterized by relatively rapid movements of domesticated crops and animals across and among continents, with ultimately a relatively small number of species representing a very high percentage of the daily diets of people around the world. FAO estimates that four crops—rice, wheat, sugar (beet and cane), and corn—account for over 60% of human calorie intake from plants. Many agricultural scientists and development practitioners believe that PGRFA are the foundation for modern agriculture and are essential for achieving food security. They say that much of the increase in food production over the last half-century can be attributed to innovations achieved through plant breeding, drawing on existing genetic resources. FAO estimates that more than three-quarters of the increased crop productivity of the past 30 years is the result of plant breeding. FAO and other agricultural experts believe that future global food security depends to a large extent on the continued improvement of food crops—for example, developing new varieties that are higher-yielding, resistant to pests and diseases, resistant to extreme weather events such as drought or flood, and/or regionally adapted to different environments and growing conditions. Crop improvement has also resulted in significant gains in the nutritional value of crop plants. Plant genetic resources serve as the raw material used by plant breeders and farmers to create new crop varieties. Feeding a growing global population will require a significant increase in food production. Despite a 70% growth in world population, agriculture today provides over 15% more calories per capita than it did 30 years ago. By 2050 the world's population is estimated to reach 9.1 billion, 34% higher than today. About 70% of the world's population will be urban (compared to 49% today), and income levels will be higher than they are today. FAO estimates that farmers will need to increase production by at least 70% by 2050 to satisfy the demand for food due to population growth, urbanization, and rising incomes. All countries are interdependent with respect to plant genetic resources for food and agriculture—each relies on others for the genetic basis of its major food crops and for food security. Modern crops and forages have a multitude of parent materials, as exemplified by the development of rice varieties grown all over the world ( Table 2 ). The diets of people around the world have evolved and adapted to such an extent that most countries and regions rely heavily on nonindigenous, imported germplasm of staple crops from other parts of the world. For example, corn is one of the world's three most important staple crops, especially for millions of people in sub-Saharan Africa. Corn originated in South America, but the United States is the largest global producer of corn and holds one of the world's largest genebank collections of corn varieties. Cassava, which also originated in South America, is another major food source in Africa today, while African millets and sorghums are major food crops in South Asia and Latin America. Latin America's extensive cattle pastures depend largely on African grasses. Alfalfa from southwestern Asia is now cultivated around the globe. A plate of pasta with red sauce, a dish typical in Italy, relies on crops that originated in South America (tomatoes) and in west and central Asia (wheat). The exchange of plant genetic resources has taken place over centuries, and without it few typical "local" meals would exist. A recent study concluded that for the major food crops, all regions were dependent on PGRFA from other regions to a high degree—over 50% for most regions. Interdependence in central Africa ranges from 67% to 84%, and in south Asia ranges from 85% to 100%. No country in the study was ranked as completely self-sufficient. The high degree of interdependence argues for continued access by countries to a wide range of plant genetic resources in other regions as essential for crop improvement and the development of modern agriculture. The U.S. food supply is based on intensive agriculture. Intensive agriculture benefits from genetic uniformity in crops, but it can also increase the potential for crop vulnerability to new pests, diseases, and environmental stresses. An example of that vulnerability occurred in 1970, when a widespread outbreak of a disease called southern corn blight hit from the southeastern United States into the Great Plains. The epidemic cost farmers 15% of the nation's corn crop that year because nearly all the corn planted was genetically susceptible to the fungus that caused the blight. Congress responded to this event by establishing the National Plant Germplasm System (NPGS) within the United States Department of Agriculture's (USDA's) Agricultural Research Service (ARS). The NPGS is a national network of public agencies (federal and state agencies including more than 20 federal gene banks located across the country), private institutions, and individuals. It is the primary entity in the U.S. effort to conserve and use crop germplasm for crop improvement. With a collection that includes about 85 crops, the NPGS collects plant germplasm from all over the world. It is "devoted to the free and unrestricted exchange of germplasm with all nations and permits access to U.S. collections by any person with a valid use," such as for research or breeding, although medical and other uses are included. Germplasm users in other countries have the same privileges as those in the United States. According to ARS, this policy has "grown out of the belief that germplasm, like the oceans and air, is a world heritage to be freely shared for the benefit of all humanity." Through these efforts, NPGS assists in improving the quality and productivity of crops in the United States and in the world. The Germplasm Resources Information Network (GRIN) provides support to NPGS and gives germplasm users continuous access to databases for the maintenance of passport, characterization, evaluation, inventory, and distribution data important for the effective management and use of national germplasm collections. GRIN is also administered by ARS. In 1990, Congress authorized the establishment of a National Genetic Resources Program (NGRP). NGRP has the responsibility to acquire, characterize, preserve, document, and distribute to scientists germplasm of all life forms important for food and agricultural production, which, in addition to plants, includes animals, microbes, and invertebrates. The National Genetic Resources Advisory Council (NGRAC) advises and makes recommendations to the Secretary and Director of the NGRP. The NGRAC responds to national issues pertaining to the conservation and utilization of genetic resources for food and agriculture. The International Treaty on Plant Genetic Resources for Food and Agriculture (the Treaty on PGRFA) provides a general framework for conservation and sustainable use of plant genetic resources. The treaty's preamble acknowledges that the conservation, exploration, collection, characterization, evaluation, and documentation of PGRFA are essential for sustainable agriculture development and to meet the global goals of ending hunger and poverty, as stated in the Rome Declaration on World Food Security and the World Food Summit Plan of Action. The treaty sets up a multilateral system of access and benefit sharing, where all members, in exercise of their sovereignty, provide free (or nearly free) access to each other's plant genetic resources for research, breeding, conservation, and training. The multilateral approach allows members access to germplasm to promote food security and improve crop productivity, lowers transaction costs, and redistributes back to the governing body financial benefits derived from the commercial exploitation of the genetic resources. The treaty is unlike other international laws governing global genetic resources, such as the Convention on Biological Diversity (CBD; see text box below), which extends private or sovereign control and limitations over genetic resources through bilateral interactions, and which many feel is inappropriate for food and agriculture. By establishing a multilateral approach that provides for a standardized protocol and framework applying to all contracting parties, the treaty deals with access and benefit-sharing of agricultural biodiversity in a different way than they are treated under the CBD. The treaty originated from and eventually replaced the International Undertaking on Plant Genetic Resources (IU), a voluntary non-legally binding agreement adopted by FAO in 1983. The IU was the first international instrument that sought "to ensure that plant genetic resources of economic and/or social interest, particularly for agriculture, will be explored, preserved, evaluated and made available for plant breeding and scientific purposes." The IU reflected the widely held view of the time that plant genetic resources were a heritage of humanity that should be available to all for research and breeding. While the IU attracted considerable support, some countries did not find the concept of free availability of genetic resources under the IU compatible with the intellectual property protection afforded by plant breeders' rights. Some tension existed concerning farmers' rights, in that intellectual property regimes that rewarded formal breeders often ignored the contributions of generations of farmers to the development and conservation of the PGRFA that breeders utilize. Many critics were also concerned that any system addressing PGRFA should reflect more fully the sovereign rights that countries have over those resources. These concerns were addressed in a series of agreed interpretations of the IU, adopted in 1989, that sought to balance the rights of breeders and farmers. A further conference resolution in 1991 reiterated the sovereign rights of states over their plant genetic resources.