Water

Ironically, the hunt for energy alternatives to replace oil could make the water problem much worse. Some biofuels use significant amounts of water, including otherwise efficient sugar cane (unlike rain-soaked ethanol giant Brazil, most sugar-cane producers have to irrigate). Similarly, the various technologies that are seen as essential to the clean use of coal are water hogs. Plug-in hybrid cars also increase water use because they draw electricity, and most types of power plants use water as a coolant. Even seemingly unrelated technologies, such as silicon chips (key to everything from smart-grid technologies to more efficient energy use) require a great deal of water to produce.

Many countries could begin to address this by working out schemes to charge for water, the single best way to grapple with this problem. Alternatively, they may build nuclear desalination plants that make saltwater drinkable. Neither course is perfect. A de facto privatization of water has occurred throughout the world, with low-income populations forced to purchase bottled water to avoid contamination, but even so, the ideal of the right to free water has held firm and governments have found it politically untenable to charge even nominal sums. And those nuclear desalination plants? As countries that have deployed this technology, such as India, Japan, and Kazakhstan, have found, they're bloody expensive, at hundreds of millions of dollars a pop.