Storm in an Andean teacup

TOURISTS who visit Bolivia’s capital, La Paz, or Cusco, Peru’s former Inca seat, are routinely given welcome cups of coca tea to mitigate soroche (altitude sickness). For centuries, people who live in the high Andes have chewed coca leaves, whose alkaloids act as a mild stimulant and help to ward off cold and hunger. The Spanish conquistadors declared coca a tool of the devil, until they saw how it improved the work rate of the Indians they sent down the mines.

But refine the alkaloids in coca, and you get cocaine. In 1961 a United Nations convention on narcotics banned the leaves, giving countries 25 years to outlaw this ancestral practice. Half a century on, consuming coca remains legal in Bolivia, Peru, Argentina and some parts of Colombia, in defiance of the convention. In Bolivia and Peru, some cultivation is legal too. In 2009 Bolivia, where a new constitution protects coca as part of the country’s cultural heritage, proposed an amendment to the convention that would remove the obligation to prohibit traditional uses of coca. Other South American countries agree.