Estimates of wildlife trade for traditional Asian medicine should include that of the caterpillar fungus Ophiocordyceps sinensis (Nature 480, S101–S103; 2011).

The fungus, used to treat asthma and other diseases, is legally harvested on a huge scale in Tibet and the Himalayas, and is one of the world's most expensive natural medical resources. Some 85–185 tonnes are collected annually by the local population for a global market worth between US$5 billion and$11 billion.

Large increases in the price (up by 900% from 1997 to 2008) and trade of caterpillar fungus have encouraged more intensive harvesting. My informal survey of harvesters in the Himalayas reveals that caterpillar fungus abundance is dwindling: the average harvest per collector dropped by around half between 2006 and 2010. Harvesters are extending their range as a result, risking overexploitation of a pristine landscape and more ecosystem degradation.

Conservation efforts must be initiated to halt the decline of this species, which is causing a loss of biodiversity and threatening local livelihoods.