Are we facing a drinking water shortage? Yes, although few want to talk about it. While you barely go five minutes without someone mentioning global warming or the planet running out of oil, the lack of drinking water is arguably a more pressing concern. It seems strange that this should be a problem given 70 percent of the planet’s surface is covered by oceans or ice. But the key thing is how much of it is drinkable. Only 2.5 percent is fresh water and the majority of that share is hard to access, stuck either deep below the earth’s surface or in glaciers and snowfields at the poles. This leaves 0.4 percent to sustain over seven billion people. Around two-thirds of that half-a-percent is in lakes, with the rest to be found in soil moisture (twelve percent), the atmosphere (9.5 percent), wetlands (8.5 percent), rivers (1.5 percent) and vegetation (one percent).

This water, it should be noted, is finite. No new water is being created. In his book The Big Thirst, Charles Fishman points out that “The water coming out of your kitchen tap is four billion years old and might well have been drank by aTyrannosaurus rex.”

As population increases so does the problem. According to a University of Oxford study this year, 2.7 billion people are currently affected by water shortages, and by 2025 two-thirds of the world’s population could be living under water- stressed conditions.

To have an idea of how world-changing this can be, it’s worth looking at the Agricultural Revolution roughly 7,000 to 10,000 years ago. The advent of irrigation techniques allowed humans to progress from hunter-gatherers to farmers who grew crops and raised animals that could sustain them, work for them, or be traded for other goods. Modern society was born.

As access to water recedes, so will this way of life. Our basic way of living for several thousand years will be threatened. Problems occurring from water shortages are already occurring. Since 1990 at least 18 violent conflicts worldwide have been triggered by competition for resources. Economist Dambisa Moyo recently said that, “Global demand for food and water is expected to increase by 50 percent and 30 percent respectively by 2030.” Moyo also told The Guardian “The people who are saying: ‘We’ll  muddle through,’ are people sitting in the West who get clean water when they turn the tap on. If you’re in India, and the Brahmaputra river is being rerouted by the Chinese, you’re not muddling through; lives are being lost. Wars are being fought right now.”

While many in the developed countries see battles for clean water as a distant problem, it’s worth noting that the U.S. Department of State published a study this year titled the “Intelligence Community Assessment on Global Water Security”. It concluded that water challenges worldwide will post a threat to U.S. security interests if left unaddressed. When American Intelligence gets involved then it’s a sure sign that people at the top are concerned. Indeed, Secretary of State Hillary Clinton said: “The water crisis is a health crisis, it’s a farming crisis, it’s an economic crisis, it’s a climate crisis, and, increasingly, it is a political crisis.”

There are no quick fixes. Desalination is costly, consumes vast amounts of energy and has environmental impacts on the ocean. Lowering our consumption would be a better option but the prognosis isn’t great. A huge amount of fresh water is already devoted to agriculture. Changing land use and food consumption patterns will place even greater pressures on these resources. Compounding this problem, the global middle class is expected to grow from 1.8 billion to 4.9 billion by 2030.

Wealthier populations consume more meat, requiring a shift to more energy- and water-intensive agriculture in order to raise livestock and grow feed grain. There are multiple other examples of how water is needlessly wasted. According to the American Society of Civil Engineers, an estimated seven billion gallons of water leak from faulty pipes in the U.S. every day. And it seems perverse that in an arid place like Dubai a golf course can use a million gallons of fresh water per day, while one-in-six people worldwide have no access to clean water.

One million gallons would keep 4,000 people alive for 500 days. Meanwhile each day, nearly 4,000 people — mostly children under five — die from preventable diseases caused by contaminated water.

Soon it won’t just be “others” who are struggling to get the water they need. In the next twenty years, global demand for fresh water will vastly outstrip reliable supply in many more parts of the world. If we don’t change our habits, how we all live will change in ways most people have never even imagined.