A farmer carrying a hoe walks past a dried-up pond in Shilin Yi Autonomous County of Kunming, Yunnan province February 28, 2013. (STRINGER/CHINA/REUTERS)

THE WORLD Bank has warned countries that one of climate change’s most significant impacts will be on a precious resource that many people, particularly in advanced nations, take for granted: water. The concerns go far beyond sea-level rise, which is perhaps the most predictable result of the planet’s increasing temperature, or an uptick in extreme weather. Countries must worry about whether their people will have enough fresh water to farm, produce electricity, bathe and drink.

Global warming will not change the amount of water in the world, but it will affect water’s distribution across countries, making some much worse off. The World Bank calculates that water strain from population growth and climate change could reduce growth in some major economies by an astonishing 6 percent by 2050. That would push some countries into “sustained negative growth,” which would mean prolonged suffering for millions of people.

The countries most responsible for climate change are not most at risk; instead, a belt of nations from Africa through the Middle East to central and east Asia are in most danger, the World Bank concluded. And within those relatively poor countries, water stresses “are felt disproportionately by the poor, who are more likely to rely on rain-fed agriculture to feed their families, live on the most marginal lands which are more prone to floods, and are most at risk from contaminated water and inadequate sanitation.”

About 4 billion people already live in areas suffering from water stress. By 2030, “the world may face a shortfall in water availability of approximately 2,700 billion cubic meters,” the bank reports, “with demand exceeding current sustainable water supplies by 40 percent.” Though the bank tamps down speculation that countries will fight with one another for water, it warns that water scarcity could encourage other sorts of conflict and dislocation, such as civil wars.

The first order of business is to limit the amount of warming humans will induce. That means slashing the greenhouse gas emissions responsible for driving up global temperatures. The world has started down this path, but the effectiveness of the global climate effort likely depends, in the first instance, on the results of this year’s presidential election.

And limiting emissions will not be enough. Warming is happening, areas of the world are already experiencing significant water challenges, and population growth will place increasing demands on existing resources. Countries have to manage water use more rationally. As California’s drought exposed, the United States is hardly a great role model. Rather, the answer is to treat water like any other precious resource: Create a fair and transparent market for it, allowing supply to meet demand, which will let the water flow to its most efficient uses. Meanwhile, governments should invest in water storage and gird their infrastructure against floods and other extreme weather events.

Reforms that override the parochial arrangements that often govern water access will not be easy. But, as the World Bank made clear, the alternative may be widespread misery.

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