Find water and you find life. This simple maxim guides scientists searching distant planets for aliens. But if the astrobiologists were to reverse their telescopes and look at our own globe, they would find a conundrum: billions of people living in places with little or no water.

That unsustainable paradox is now unravelling before our eyes in the Middle East and north Africa. The 16 most water-stressed states on Earth are all in that troubled region, with Bahrain at the top of the ranking from risk analysts Maplecroft. Libya, Yemen, Egypt, Tunisia and Syria follow not far behind.

All are built on an environmental Ponzi scheme, using more water than they receive: 700 times more in Libya's case. The unrest of the Arab spring of course has many causes, but arguably the most fundamental is the crumbling of a social contract that offered cheap water – and hence food – in return for subservience to dictators.

The region's population is rocketing – there are 10,000 new mouths to feed each day – just as grain production plummets. The deep, ancient aquifers that enabled crops to green the deserts are almost exhausted, and the oil that fires the desalination plants to make up the loss is dwindling too.

It's a perfect storm of water, food and energy crises and has arrived two decades sooner than even the most sober analysts expected. And while the Middle East is the first region to feel the wrath of that storm, across the world warning signs are flashing – from the sinking of Mexico City as its aquifers are sucked dry to the docking of freshwater tankers in Barcelona.

The world's population tripled in the 20th century, but the thirst for water grew six-fold, the large majority sprinkled on fields. The UN predicts that, by 2025, two-thirds of us will experience water shortages, with nearly two billion suffering severe shortfalls. Today China, struck by terrible droughts in its agricultural heartlands, is the world's biggest importer of "virtual water": the billions of tonnes of water used to produce the food and other goods brought into the world's most populous nation.

China, along with other water-stressed nations such as Saudi Arabia and South Korea, has sought to cut out the middlemen and acquire land in wetter places for themselves in order to grow and send food home. The so-called "land grabs" across the global south are the result.

From Australia to Hong Kong to India to Spain, nations caught between the stormy equator and the damp high latitudes are running out of water. Global warming will evaporate more moisture into the air, but in all likelihood this will fall in harder downpours in already wet areas rather than bring relief to arid lands. Increasingly, warming will lead to "global weirding" of the weather, with freak events uprooting thousands of years of farming knowledge.

Desalination – with 14,000 plants already in existence – is one solution that is growing fast, but is energy-intensive, expensive and heavy on carbon. Even the few trials of solar-powered desalination plants will leave hypersaline water polluting the seas. Mega-engineering projects, such as China's 50-year south-north water-diversion scheme, might also offer relief, at vast cost. And none of these address the other water problem: the lack of clean water and sanitation in wet nations too poor to provide them.

Ultimately, as appears to be happening in the Middle East, Ponzi schemes crash. Fresh or virtual water can be imported from distant rainy nations, but only at a price many cannot afford. The ultimate solution is as simple as it is challenging: plug leaks, recycle waste and treasure each drop. Only when the water consumed is less than the water falling from the sky will nations have stopped borrowing against tomorrow.