The wars of the future may be fought not over gold or oil, but instead over a resource far more mundane: water.

In a study published this week, researchers at the Potsdam Institute for Climate Impact Research in Germany warned that climate change will put further strain on the world's water sources, as warming temperatures and changing precipitation patterns expose more regions to drought and shortages. More than a billion people currently live in areas where water is scarce, and experts say climate change and anticipated population growth could jeopardize supplies for at least half a billion more.

The paper, published in the journal Environmental Research Letters, found that an average global temperature increase of 2 degrees Celsius — a best case scenario — would expose an additional 486 million people to new or more severe water scarcity. If population growth continues and emissions are not reduced, that number could soar to well over one billion, according to the researchers' models.

Millions of lives may be at risk

"The earth is not only getting warmer, but precipitation intensities and patterns are changing," Dieter Gerten, the study's lead author, said in an interview with The Verge. "Regions in the high north and parts of the tropics would benefit from more precipitation, but regions in the sub-tropical zone, spanning from the southwest US to north Africa to Central Asia, would see less precipitation due to the circulation patterns in the atmosphere."

Gerten's results echo findings from the World Bank and other organizations that have linked global warming to water scarcity. It's not clear when the world's water crisis will come to a head, but many countries are already starting to feel the pinch. In the US, states have begun waging battles over water supplies, and politicians are starting to take action.

Just this week, California Governor Jerry Brown signed a slew of new laws to increase water access across the state, where persistent droughts have wreaked havoc for farmers and consumers alike. One of the newly signed laws calls for the state to begin developing technology to recycle wastewater for drinking or cooking, while another offers funding to poor communities to help clean water that has been contaminated by fertilizers or agricultural chemicals.

Un

Source: United Nations World Water Development Report 4

Governor Brown's announcement comes just one week after Florida filed a federal lawsuit against Georgia, accusing its neighbor of consuming more than its fair share of water from a shared river basin. In the lawsuit, filed with the US Supreme Court, Florida blames Georgia's overconsumption for depleting the basin's freshwater and devastating the oyster industry that depends on it. This consumption, Florida argues, has raised salinity levels and disease rates along the Gulf Coast, but Georgia blames the oyster collapse on recent droughts.

Similar disputes have erupted across the southwestern US, but the crisis isn't limited to traditionally drought-stricken areas. New York's Rockland County, which sees comparatively regular precipitation, is considering building a new desalination plant amid fears that its current water supply won't sustain the county's mushrooming population.

"We use water inefficiently because it's cheap."

In a paper published earlier this year, the Columbia University Water Center said the water crisis may impact far more US metropolitan areas than previously believed, including New York, Los Angeles, and Washington, DC. Population growth is widely seen as the primary driver behind water scarcity; the Columbia study notes that the US population has grown 99 percent since 1950, while water withdrawals have increased by nearly 130 percent. Assuming these trends continue, the only solution is to manage water use more efficiently.

"The drivers of water scarcity are often mismanagement rather than a true lack of resources," Tess Russo, a postdoctoral research scientist at Columbia University’s Earth Institute, said in an email to The Verge. "We use water inefficiently because it's cheap."

Russo says that the technology to efficiently manage water already exists, citing low flow fixtures and irrigation sensors that can automatically regulate agricultural flows. But it's difficult for farmers and companies to decide whether to invest in these tools without an accurate way to measure the true value of water. Last year, the Environmental Protection Agency (EPA) said it is "unable to systematically analyze the value of water to the US economy, resulting in potentially inefficient resource protection and management decisions."

Studies have cited hydraulic fracking as another driver behind US water scarcity, pointing to the vast amounts of water the drilling process requires, but agriculture demands far more resources both nationally and across the globe. According to the UN, an estimated 70 percent of the world's water use goes toward irrigation; in developing countries, that figure can be as high as 90 percent. The challenge, then, is to balance efficient water use with the humanity's rising demand for food.

"The timeline is relatively short."

In rural areas of India, the Earth Institute has begun testing new moisture sensor technology, which can automatically irrigate crops based on the dryness of the soil. The idea is to prevent crops from being over watered, though the technology is still above the target price point for most developing world farmers.

In the US, the challenges are far larger in scope. In its annual report card on the state of US infrastructure, for instance, the American Society of Civil Engineers assigned a "D" grade to the country's dams and drinking water systems, calling for new investments to meet the growing demands of industries and civilians. Federal spending has been a divisive topic on Capitol Hill, but experts say that failing to invest in the nation's water infrastructure could lead to disastrous results down the road.

"Many dams around the country are nearing their end-of-life, and huge investments will be required to maintain the current water storage and supply," Russo says. "We will need to invest heavily in infrastructure maintenance and improvement over the next few decades. The timeline is relatively short."