Kathmandu, April 17 -- The natural world does not respect manmade boundaries. We demarcate rivers as the frontiers between nation states, but they change their course in open defiance of cartographers and politicians.

Air pollution also travels across national boundaries with impunity. Industrial and vehicular emissions from the Gangetic plains are carried by prevailing winds to Nepal and the Himalaya. In November, north India and the Nepal Tarai is shrouded in a thick blanket of smoke from crop-residue burning on both sides of Punjab and other Indian states.

These past weeks, the sky over Nepal has been thick with haze from wildfires fanned by winds, burning out of control on mountain slopes and along the East-West Highway. But travell...