Over the past 30 years or so, most of the increase - more than three-quarters - has come from increases in yield, mainly as a result of the Green Revolution. This is also expected to be the case in developing countries over the next 30 years, with 69 percent of the production increase being covered by yield increase, 12 percent by increases in cropping intensity, and the rest from increase in the area of arable land.
Much of the increase in crop production will come from irrigated land, three-quarters of which is in developing countries. Currently, some 20 percent of agricultural land in the developing countries is irrigated, providing about 40 percent of their total crop production. Over the past 30 years, the irrigated area expanded at about 2 percent a year, giving a total increase of some 94 million hectares during 1962-96. The irrigated area in developing countries in 1996 was nearly double what it was in 1962.
An FAO analysis of 93 developing countries reaches comparatively encouraging conclusions on this question. During the period 1996-2030, irrigation water withdrawal in these countries is expected to grow by a total of only about 14 percent, from the current 1,840 km 3 /year to 2,060 km3/year in 2030. This increase is low compared to the increase projected in the harvested irrigated area. Most of this difference is explained by an expected improvement in irrigation efficiency, leading to a reduction in the withdrawals needed for irrigation water per irrigated hectare. A small part of this reduction will also be due to a change in cropping patterns for some countries, such as China, where a substantial shift from rice to wheat production is expected: irrigation water requirements for rice are usually twice those of wheat.
Improving rainfed and irrigated production. FAO says that increasing the productivity of rainfed agriculture, which still supplies some 60 percent of the world's food, would make a significant impact on global food production. However, the potential to improve yields depends strongly on rainfall patterns. In dry areas, rainwater harvesting can both reduce risk and increase yields. There are various forms of rainwater harvesting:
Irrigated agriculture has been an extremely important source of food production over recent decades. The highest yields that can be obtained from irrigation are more than double the highest yields that can be obtained from rainfed agriculture. Even low-input irrigation is more productive than high-input rainfed agriculture. Such are the advantages of being able to control, precisely, water uptake by plant roots.
Policies, institutions and laws can be devised to increase water productivity at many different levels. At the level of individual consumption, policies that encourage people to eat less water-intensive foods - wheat rather than rice, poultry rather than beef, for example - could increase water efficiency markedly. At the local level, improved irrigation management would do much to improve efficiency: the best way of doing this is to give those who actually use irrigation waterthe power to plan and manage their own supplies, at least at the local level. In addition, transparency and accountability must be improved, and incentives provided for saving water. At the river basin level, a major priority is to improve integration not only between land and water-use planning but also among the many other water users involved - for example, hydroelectric schemes, industry and urban populations.
Rural men and women would participate in a global improvement of the standard of living and its dividends reflected in quality of life, health and leisure. Agriculture and other activities would be carried out in harmony with the environment, with clean water in streams, lakes and aquifers, surrounded by and integrated with healthy natural ecosystems. Water would be managed efficiently and on a sustainable basis. Access to water and other agricultural resources would be available on an equitable basis and in a fair economic environment that provided opportunities for all.
Such a future will not come about automatically: it requires that people be given access to their human, political and economic rights. Society needs to be organized in such a way that food and water are accessible to all, even its weakest members. Each generation has an obligation to preserve the natural and agricultural heritage for its successors, so that today's production does not reduce the capacity of future generations to produce what is necessary for life. Most importantly, both men and women must have a voice in the decisions that affect them, including those that relate to water allocation and management. Decisionmaking authority needs to be devolved to the lowest possible level and people need to have access to the information required to make such decisions.
Text by the FAO Multimedia Group (GII)
Published April 2000