Every day for more than 20 years, an average of almost eight square miles of irrigated land in arid and semiarid areas across 75 countries have been degraded by salt, according to the study Economics of Salt-Induced Land Degradation and Restoration, by United Nations University’s Canadian-based Institute for Water, Environment and Health.

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, which triggers the accumulation of salt in the root zone, affecting soil quality and reducing productivity. In the Colorado River Basin alone, studies peg the annual economic impact of salt-induced land degradation in irrigated areas at $750 million.

The cost of investing in preventing and reversing land degradation and restoring it to productive land would be far lower than letting degradation continue and intensify. Methods successfully used to facilitate drainage and reverse soil degradation include tree planting, deep plowing, cultivation of salt-tolerant varieties of crops, mixing harvested plant residues into topsoil and digging a drain or deep ditch around salt-affected land.