Central Asia is a huge landmass situated between the world’s largest inland water body, the Caspian Sea, and the mountain ranges of the Tian Shan, Pamirs and the Hindukush. For centuries, caravans travelled along the famed Silk Road-actually there were many-to connect the civilizations of Europe and Asia, crossing deserts, grassy steppes and mountain ranges. Powerful Khans built cities and centres of Islamic scholarship and developed sophisticated irrigation systems to compensate for the region’s low rainfall. Starting in the 1960s, the Soviet authorities began a massive irrigation expansion that drew water from both rivers to increase cotton production. The result was that much less water reached the Aral Sea, then the world’s fourth-largest inland lake, than was required to compensate for evaporation. The sea is now a tenth of its size half a century ago.