Ground temperatures have slowly risen in Qumalai county so a permanent frozen layer of soil just beneath the ground has melted away. The permafrost had acted to hold water near the surface allowing the grasslands to thrive but without it, the rain drains away leaving no water for the grass to feed on. The area is home to the sources of three of Asia’s great rivers, the Yangzi, the Yellow and the Mekong. Any ecological catastrophe here would affect hundreds of communities downstream.