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[SYDNEY] Overharvesting and climate change are decimating the medicinally valued Himalayan caterpillar fungus (Ophiocordyceps sinensis), forcing thousands of collectors in the region to look for alternate sources of income, says a new study.

Known in the Tibetan language as yartsa gunbu (summer grass, winter worm), the caterpillar fungus’ reputation as an aphrodisiac has resulted in its overharvesting. The fungus is found only in the highlands above 4,500 metres in parts of Bhutan, China, India and Nepal — regions that have seen warmer temperatures in recent decades.

“A species that really likes to be cold is losing its coldest temperatures”

Kelly Hopping, Boise State University

Climate data from 1979 to 2013 show that winters have warmed significantly in Bhutan, India and Nepal, with further warming projected, says Kelly Hopping, assistant professor at Boise State University in Idaho but was a researcher at Stanford University when she worked on the study as a lead author, published last month (October) in Proceedings of the National Academy of Sciences of the United States of America (PNAS). “A species that really likes to be cold is losing its coldest temperatures,” she tells SciDev.Net.

Hopping says the fungus, ranked among the world’s most valuable biological commodities, has been a “real lifesaver” for many communities in the impoverished high-altitude Himalayas. She believes that placing restrictions on harvesting may not reverse the decline of the fungus and that continued harvesting may result in its extinction.

The fungus invades caterpillars of the ghost moth in late summer while they are buried a couple of inches in the soil feeding on plant roots. The fungus slowly consumes the caterpillar from within until it emerges out of the head of the mummified caterpillar as a dark-brown stalk and out from the soil as the winter snows melt. Its supposed therapeutic benefits, including in the treatment of cancer and asthma, fetches prices up to US$ 140,000 per kilogramme — making it far costlier than gold.  

While earlier studies of the fungus were based on surveys of collectors and traders, Hopping and her colleagues collated data into a comprehensive assessment of the entire region. They used statistical models to determine how ecological processes affect populations of the rare fungus.

The models show that, more than overharvesting, the cause for diminishing parasite populations is climate change disturbing the cold dry winters of higher elevations that foster the growth of the fungus within the caterpillar. “The findings give clarity to local people, and support to governments in taking the right steps to intervene,” says Uttam Shreshta, environmental scientist at the University of Southern Queensland.

Communities are trying to find alternative sources of income, says Shrestha. Some collectors have begun to supplement their yields by harvesting other medicinal plants found in nearby areas, he says.
 
This piece was produced by SciDev.Net’s Asia & Pacific desk.