In 20 years, tens of millions more Latin Americans and hundreds of millions more Africans will be short of water, and by 2050 one billion Asians could face water shortages. The glaciers of the Himalayas, which feed the great rivers of the continent, are likely to melt away almost completely by 2035, threatening the lives of 700 million people. And when your resources run out, you go try to take someone else’s.