Climate change, overexploitation can condemn an ​​expensive parasite

A parasitic fungus that grows wild throughout the Himalayas and sells for more than its weight in gold could disappear if current harvest and weather patterns continue, according to a new study from the US. Stanford University.

The mushroom, Ophiocordyceps sinensissurvives by feeding on caterpillar larvae in some of the highest parts of the Himalayas. The fungus infects and eats inside a caterpillar that digs under the ground for the winter. What the parasite will do next is perhaps too macabre to be mentioned in a bowl of aphrodisiac soup allegedly healer (price: $ 688) made in Las Vegas with only a quarter of an ounce of substance.

"It kills them and makes them gush out of the head, like a unicorn horn," said lead author Kelly Hopping, an ecologist who led the research as a postdoctoral researcher at the School of Earth Sciences. Stanford Energy and Environment.

From the 1990s, mushroom demand as an aphrodisiac treatment, a cure for impotence and a cure for the lethal SARS virus – unsupported by scientific evidence – helped revive world trade. Since then, belief in a wide range of healthy mushroom effects has fueled a market valued at around $ 11 billion, as well as concern that harvest rates have become unsustainable.

Official harvest records, however, are unreliable because much of the trade in crawler mushrooms is through illegal channels. This new study, published in the peer-reviewed journal Proceedings of the National Academy of Sciences, presents the most comprehensive data to date on whether and why mushroom production is declining, as well as the likely consequences of a possible crash for the communities that depend on it for their livelihood.

Species and livelihoods threatened

Eric Lambin, co-author of Hopping and Study, professor of Earth System Science at Stanford, is interested in the mushroom in order to understand what happens when a biological niche product gives wealthy consumers an influence disproportionate on rural livelihoods, land-use choices and ecosystems in producing regions.

Research on ecosystem degradation tends to focus on the expansion of traded agricultural commodities, such as oil palm, soybean, livestock and timber – the main factors deforestation. The driving effects of commodities that are developing and trading on a smaller scale are less well understood – but potentially profound, Lambin said. He cites rhinoceros horn as an example.

"An iconic mammal species is disappearing because of the demand for a product considered by some traditional cultures as having virtues," said Lambin.

The mushrooms of the caterpillar may not have the charisma of a rhinoceros, but it is one of the most expensive biological products in the world, it has become an essential source of income for hundreds of thousands of collectors . And at a time when up to one-third of the world's parasite species could disappear within a few decades (potentially opening up new niches to other invasive pests to exploit), conservation biologists are increasingly recognizing the need for protect the parasites and their hosts.

According to Mr. Lambin, who is also a senior member of the Stanford Woods Institute for the Environment, there is no doubt that intensive harvesting has negative consequences for both the population and the environment in a landscape of more and more vulnerable. While many local collectors are trying to minimize the impacts, he said, large influxes of people attracted to the Himalayan pastures during the harvest season may end up degrading the ecosystems disturbing fragile soils, cutting windrows from shrubs and trees and leaving waste to their crops. camps.

"Himalayan gold"

Widely known in Tibet as yartsa gunbu, or "summer grass, winter worm," the caterpillar fungus has been used in traditional medicine in the Himalayan region and in China for centuries to treat conditions ranging from cancer to nephropathies through Inflammation and aging. In recent years, it has been dubbed "Viagra of the Himalayas" and "Gold of the Himalayas".

To solve the problem of uneven trade data for the valuable mushroom, the team relied on collectors' own knowledge of production trends in China, Bhutan, Nepal, and India, as indicated in dozens of 'case studies. The researchers then reinforced the published reports by interviewing 49 collectors on the Tibetan plateau.

With these data and 400 records of where the fungus has been found in the four countries since the 1970s, the group has constructed models to predict fungus growth in a given area based on factors such as climate and climate change. # 39; altitude. The results show that the fungus tends to be more prolific in the higher and colder areas around areas covered by permafrost.

Warmer winters

Currently, the caterpillar fungus is sufficiently abundant in the spring in the main production areas to allow many people to harvest enough in one or two months to meet their needs for the rest of the year. However, production is already down due to an intensive harvest – and warmer winter can exacerbate this trend.

In an area where average winter temperatures in some areas have already risen to 4 degrees Celsius since 1979 – "a huge warming," Lambin said – researchers have found that winter-induced warming makes the fungus more difficult to prosper. As permafrost disappears at lower altitudes, the fungus can adapt by moving to cooler slope habitats than if its caterpillar – and the vegetation and seasonal regimes on which it depends – also move toward the top.

The study suggests that if the caterpillar fungus' incomes can be sustained in the long run, they could provide a significant financial cushion for those whose livelihoods raising their livestock in high altitude grasslands face threats. climate change. "Caterpillar mushroom collection has emerged as a way for people in these areas to make money relatively easily," said Hopping, "and in some cases to really improve their standard of living."

However, if demand continues to grow in line with declining supply, this could exacerbate the strain on people who have access to harvesting areas, Hopping said. "Communities in areas where it is still developing will need to remain alert to potential conflicts and poaching, as people seek to exploit this increasingly rare and valuable species."

Lambin is also provostial professor George and Setsuko Ishiyama. Hopping is now an adjunct professor at Boise State University's College of Innovation and Design. Stephen Chignell, co-author of the study, is now a PhD student at the University of British Columbia.