Image: Bill & Brigitte Clough/AgStock Images/Corbis
By Sarah Zielinski
In the upcoming film Interstellar, Earth’s soil has become so degraded that only corn will grow, driving humans to travel through a wormhole in search of a planet with land fertile enough for other crops. In the real world things aren’t quite so dire, but degraded soil is a big problem—and one that could be getting worse. According to a new estimate, one factor, the buildup of salt in soil, causes some $27.3 billion annually in lost crop production.
“This trend is expected to continue unless concrete measures are planned and implemented to reverse such land degradation,” says lead author Manzoor Qadir, assistant director of water and human development at the United Nations University Institute for Water, Environment and Health. Qadir and his colleagues published their findings October 28 in Natural Resources Forum.
Irrigation makes it possible to grow crops in regions where there is too little rainfall to meet the plants’ water needs. But applying too much water can lead to salinization. That’s because irrigated water contains dissolved salts that are left behind when water evaporates. Over time, concentrations of those salts can reach levels that make it more difficult for plants to take up water from the soil. Higher concentrations may become toxic, killing the crops.
Qadir and his colleagues estimated the cost of crop losses from salinization by reviewing more than 20 studies from Australia, India, Pakistan, Spain, Central Asia and the United States, published over the last two decades. They found that about 7.7 square miles of land in arid and semi-arid parts of the world is lost to salinization every day. Today some 240,000 square miles—an area about the size of France—have become degraded by salt. In some areas, salinization can affect half or more of irrigated farm fields.
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