It's been called one of the priciest biological commodities on the planet. Its medicinal properties are said to range from curing aches and pains to treating cancer and boosting sexual virility. Turf wars connected to its harvest have turned deadly.

Tiger bone? Elephant ivory? Bear gallbladder? Nope. Try fungus-stricken caterpillar mummy.

Codyceps Bowl 2016 07 15

We're talking here about the "cordyceps": the small, drab-looking result of rather grisly parasitism that, in recent years, has spawned a billion-dollar global industry centred on the bleak alpine steppes of the Himalayan margins.

First off, let's talk terminology. In Tibet, it's widely known as yartsa gunbu, meaning "summer grass, winter worm", though the Chinese often shorten this to "worm-grass" (chong cao). Grass or worm it's most certainly not, but rather a caterpillar of the ghost moth genus (Thitarodes) that's been parasitised by the so-called Chinese caterpillar fungus, Ophiocordyceps sinensis. Oh, and you can also add "Himalayan Viagra" to the list of its aliases. Here, though, we’ll mostly use a pithy Tibetan shorthand for yartsa gunbu: bu.

Cordyceps Map 2016 07 15
The range of Ophiocordyceps sinensis, based on the work of Daniel Winkler.

The caterpillar fungus inhabits the grasslands of central Asia, its range centred on the Tibetan Plateau but stretching north to the Qilian Mountains, south to the highlands of northwestern Yunnan Province and west to Uttarakhand state in the Indian Himalaya. It often dwells above 9,800 feet in elevation, and has been recorded at a lofty 17,000 feet in Bhutan. 

As with many a parasite, the lifecycle leans towards the macabre. The fungus infects ghost-moth larvae, which spend their formative years tucked under the windswept sod, happily munching roots. Happily, that is, until the fungus takes up residence inside a doomed caterpillar's body, which seems to happen most often when the larvae are shedding and regrowing their cuticles in the height of summer.

The parasite threads itself through the caterpillar's innards, feeding off the host tissues. The "fungified" larvae usually dies within a few weeks, often choosing a final resting place just a few centimetres underground, which – how convenient! – works perfectly for O. sinensis's next act.

The caterpillar's exoskeleton remains intact and recognisable, but its body has been essentially mummified. When spring arrives, the fungus bores its fruiting body (or stroma) right out of the head of its dead host, and up above the soil. This entire package – the subterranean caterpillar mummy and the substantially longer stroma jutting out amid the alpine grasses – is the cordyceps, aka yartsa gunbu, aka bu, aka Himalayan Viagra.

And it's this entire package that people covet. The medicinal and tonic effects of bu have been promoted in Tibet since at least the fifteenth century, with one ancient treatise listing a whole range of pharmacological benefits. Most noteworthy: ramped-up semen production. Some sources suggest Tibetans first keyed into bu when they observed the heightened energy of yaks that had eaten it.

By the seventeenth century, bu was a fixture of traditional Chinese medicine, but one mostly used by royals and nobles who could afford the hard-to-procure product. Its profile got a major boost during the 1993 World Athletic Championships in Germany, when the record-setting performance of Chinese distance runners was popularly attributed to a cordyceps supplement.

In the past couple of decades, demand has truly skyrocketed. Market prices in Tibet – responsible for some 96 percent of the harvest – grew by 900 percent between 1997 and 2008, and in Nepal they ballooned a whopping 2,300 percent between 2001 (when the trade there was legalised) and 2011. A pound of the finest calibre can fetch US$50,000. Most of the dug-up bu is ultimately bound for China, where, in addition to its use as a medicine and supplement, the product is now flaunted as a sign of wealth and status.

Weighing Caterpillar Fungus 2016 07 14
Caterpillar fungus is weighed in southern Qinghai, China. Just a pound of the finest calibre can fetch up to US$50,000. Image: Mario Biondi 

Where the fungus flourishes, the bu "gold rush" has transformed rural ways of life. In spring and early summer, harvesters scour the highlands for the well-camouflaged black or brown stroma, and use a knife or hoe to excavate the entire cordyceps, taking pains not to sever that fungal "blossom" from the caterpillar remains below, which are considered the main storehouse of beneficial properties. Typical collectors are pastoralists and farmers, and many are locals foraging as a family – children are valued as especially sharp-eyed stroma spotters. Plenty of other pickers also travel to harvest hubs from outside of the region. In parts of Tibet, the industry now generates anywhere from 40 to 80 percent of local income.

Perhaps inevitably, territorial conflicts over bu grounds have also intensified, some of them bloodily. In 2009, Nepalese villagers murdered seven harvesters from another region; two years before that, eight gatherers in China's Yushu region died in a shootout over access.

Given the explosion of the caterpillar-fungus harvest, foragers and conservationists alike have raised concerns about its impact on the resource and the environment. Researchers who interviewed 203 bu harvesters and 28 traders in Nepal in 2011 found that the majority believed caterpillar fungi were declining and that the present level of gathering wasn't sustainable. "Based on our findings and other reports, it is apparent that the caterpillar fungus is either heading towards or already in a declining phase," the study's authors concluded. In Nepal, some locals blame rampant bu excavation for degrading yak pastures. And besides the digging itself, alpine meadows and shrublands may suffer from the side effects of the harvest, from soil compaction to the cutting of juniper, rhododendron and willow for firewood.

The booming bu market has also raised questions about its long-term economic and societal repercussions. A good haul of caterpillar fungus takes just a month or two of work, yet it can well exceed a whole year's worth of revenue for pastoralists, leading some observers to wonder whether Tibet's nomads may be shifting away from herding. On the other hand, the bu harvest may keep rural Tibetans in the same remote pastures they've traditionally roamed. "[T]he caterpillar fungus economy has actually been able to allow Tibetans to stay in their pastoral livelihoods and make money," Michelle Stewart, an Amherst College researcher who's studied the phenomenon, told VOA. This, she suggests, may be contrary to China's efforts to encourage more Tibetans into sedentary, urban lifestyles.

This past February, the China Food and Drug Administration raised a warning flag about the use of bu as a health food, citing evidence that supplements made from cordyceps may contain unsafe levels of arsenic. The announcement could cool the red-hot industry, but as VOA reported in June, it has since been questioned by scientists, as well as some advocates for Tibetan sovereignty, who suspect the Chinese government views a profitable rural trade as a threat to its authority in Tibet.

Meanwhile, this year's bu gathering was comparatively meagre. Nomads told photographer Kevin Frayer, who chronicled the Tibetan harvest this May, that it was the scantiest in memory, possibly due to low rainfall. Indeed, the effects of climate change, including a diminished and earlier-melting snowpack, may pose as grave a risk to the coveted fungus (and its hosts) as overharvesting.