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Irrigated Area Expands Slowly
The global area equipped for irrigation expanded by 0.3 percent to 280 million hectares between 2004 and 2005, the last year for which global data are available.1 (See Figure 1.) The advance is one of the slowest in the past decade and is consistent with the generally sluggish pace of irrigation growth since the late 1970s.2 (See Figure 2.) The slowdown occurs in the context of a world of steadily growing demand for food and limited opportunities for farmland expansion.
Irrigated area accounts for about 20 percent of cultivated land, but it provides roughly 40 percent of the world’s food.3 Irrigation allows farmers to apply water when crops need it and in the quantities required, leading to yields two to four times greater than in rainfed farming.4 Along with fertilizer and improved crop varieties, the expansion of irrigation is responsible for the dramatic increase in global agricultural output since the 1960s.5
Yet irrigation growth has slowed perceptibly in the past few decades as investment in surface irrigation infrastructure (dams, canals, and the like) has declined. This has happened for a variety of reasons: the choicest irrigation areas have been developed and remaining options are expensive; the generally declining price of food over the past 40 years has lowered irrigation’s return on investment; and the social and environmental liabilities of some projects (residents displaced by dam building, for example, and river flows diminished to a point harmful to fish or other wildlife) have made projects politically unfeasible.6
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