A new UN paper reveals that excess salt in the soil has destroyed 20 percent of all irrigated land worldwide — an area equal to the size of France. Every day for more than 20 years, an average of 2,000 hectares of irrigated cropland in arid and semi-arid areas across 75 countries have been degraded by salt. With the world population expected to hit nine to 10 billion people by 2050, obviously we can’t afford to be losing productive, arable land. Thankfully, the report also makes a number of recommendations for swift action to reverse the trend before it becomes too expensive to do so.
Currently, about 62 million hectares, or 20 percent, of the world’s irrigated lands are affected by excess salinitydue to irrigation, up from 45 million hectares in the early 1990s. Why does this happen? In areas where rainfall is too low for a regular flow of rainwater through the soil and where irrigation is practiced without a natural or artificial drainage system, salt begins to build up in the soil – even if the irrigation uses the freshest water possible. As the water in the soil evaporates it leaves behind salt particles, which build up and up over time. Crops also selectively filter out the salt from the water they take up through their root systems, further concentrating the salt load in the soil.
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The paper, “Economics of salt-induced land degradation and restoration,” was published this week in the journal Natural Resources Forum. Authored by a team from the United Nations University (UNU), it shows that the extensive costs of salination include $27.3 billion in lost crop value per year. In the Colorado River Basin alone, the annual economic impact of salt-induced land degradation in irrigated areas is estimated at $750 million. Zafar Adeel, Director of UNU-INWEH, points out that the UN Food and Agriculture Organization projects a need to produce 70 percent more food by 2050, including a 50 percent rise in annual cereal production to about 3 billion tonnes. However, Adeel notes, “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.”
The paper’s abstractnotes: “The findings indicate that it can be cost-effective to invest in sustainable land management in countries confronting salt-induced land degradation. Such investments in effective remediation of salt-affected lands should form part of a broader strategy for food security and be defined in national action plans. This broader strategy is required to ensure the identification and effective removal of barriers to the adoption of sustainable land management, such as perverse subsidies.” Successful methods known to reverse soil degradation include such simple solutions as 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 the salt-affected land. While there are certainly costs associated with reversing the effects of salinity, they are much less than the cost of doing nothing and allowing the situation to worsen.
Photos by Jeanne Menj, the Natural Resources Conservation Service and the Agricultural Research Service via Wikimedia Commons