全世界每天有2000公顷土地盐碱化

Every day for more than 20 years, an average of 2,000 hectares of irrigated land in arid and semi-arid areas across 75 countries have been degraded by salt, according to a study by UN University's Canadian-based Institute for Water, Environment and Health, published Oct. 28. Today an area the size of France is affected -- about 62 million hectares (20%) of the world's irrigated lands, up from 45 million hectares in the early 1990s.

Salt-degradation occurs in arid and semi-arid regions where rainfall is too low to maintain regular percolation of rainwater through the soil and where irrigation is practiced without a natural or artificial drainage system.

Irrigation practices without drainage management trigger the accumulation of salts in the root zone, affecting several soil properties and reducing productivity.

"To feed the world's anticipated nine billion people by 2050, and with little new productive land available, it's a case of all lands needed on deck," says principal author Manzoor Qadir, Assistant Director, Water and Human Development, at UN University's Canadian-based Institute for Water, Environment and Health. "We can't afford not to restore the productivity of salt-affected lands."

The study, "Economics of Salt-induced Land Degradation and Restoration,"is published Tuesday Oct. 28 in the UN Sustainable Development journal Natural Resources Forum.

Zafar Adeel, Director of UNU-INWEH, notes the UN Food and Agriculture Organization projects a need to produce 70% more food by 2050, including a 50% rise in annual cereal production to about 3 billion tonnes.

"Each week the world loses an area larger than Manhattan to salt-degradation. A large portion of the affected areas in developing countries have seen investments made in irrigation and drainage but the infrastructure is not properly maintained or managed. Efforts to restore those lands to full productivity are essential as world population and food needs grow, especially in the developing world."