The Chinese Caterpillar Fungus (Ophiocordyceps sinensis) is a terrestrial fungus parasitizing larvae of ghost moths and produces a fruiting body that since long has been used as one of the most valued Traditional Chinese Medicines. Recent studies have also demonstrated that the fungus can be used to treat a wide range of conditions. It has been officially classified as a drug in the Chinese Pharmacopoeia since 1964, and listed as an endangered species under the second class of state protection since 1999. The conservation status of the species is deteriorating due to its strict host-specificity on moth insects, and confined geographical distribution, and over exploitation by humans in recent decades. The price of natural products of O. sinensis has increased sharply in recent years and is now sold at the price of gold or higher.
The mean annual harvest of this species has declined in many if not all areas across its range, e.g. in the Gurjakhani area of Barse block of Myagdi district, Nepal, the collection of O. sinensis declined by 37% (based on collected weight) between 2008 and 2010. An analysis of harvesters’ perceptions of resource abundance and sustainability in Nepal shows that virtually all harvesters (95.1%) believe the availability of this fungus to be declining in pastures, and 67% consider current harvesting practices to be unsustainable. The evidence from interviews of harvesters and traders in Bhutan and China largely mirrors that found in Nepal. Although information on the extent of the declines is not available across the whole range of the species, it appears to be reasonable to suspect that the population reduction in the past 15 years (three generations) has been greater than 30%, that the future reduction in the next 15 years may be even larger approaching 50% and that the ongoing reduction using mostly the time period in the past 12 years is also >30%. As a result the species is here assessed as Vulnerable under criteria A2bcd+3bcd+4bcd.
Surveys across the whole range of the species are required as the declines may well be larger than suspected here and the species could well qualify for a more threatened listing.
It is a challenge to estimate the population size and trends of Ophiocordyceps sinensis due to natural fluctuations of the hosts, increasing commercial activities and few monitoring initiatives. A small-scale study in Bhutan indicated a 60% variation in numbers of individuals in a research plot over a three-year period, probably due to natural fluctuations in population size of the host caterpillars (Paul Cannon pers. comm.). However, the harvest size and market price of the fungus may serve as a gross population estimate. The local market price has increased by up to 2,300% over the last 10 years in Dolpa, Nepal. This has encouraged local harvesters to collect more intensively and to focus more carefully on suitable locations. Based on interviews with 203 harvesters and 28 traders, and focus group discussions in Dolpa, Nepal, Shrestha and Bawa (2013a) quantified the amount of harvest and trade. Since legalization of trade in Nepal in 2001, trade volume has increased consistently, reaching a peak of 2,442.4 kg in 2009 and subsequently declining to 1,170.8 kg in 2011. The mean annual harvest declined from 260.66 ± 212.21 pieces per person in 2006 to 125.82 ± 96.84 pieces per person in 2010. Their analysis of harvesters’ perceptions of resource abundance and sustainability shows that virtually all harvesters (95.1%) believe the availability of this fungus to be declining in pastures, and 67% consider current harvesting practices to be unsustainable. The evidence from interviews of harvesters and traders in Bhutan and China largely mirrors that found in Nepal. In Gurjakhani area of Barse block of Myagdi district, Nepal, the collection of O. sinensis has declined by 37% — based on collected weight (kg) — between 2008 and 2010 (Thapa et al. 2014). The opinion of harvesters throughout the range of this species is that populations are in decline (see also Shrestha et al. 2019, Yadav et al. 2019).
In the mountains of northern India, in March–April, as soon as the snow starts melting, whole villages, except the elderly and small children, go and stay in the alpine meadows for nearly three months to collect the fungus (Negi et al. 2006). Family members working elsewhere come back on leave to help in collecting because the economic return is higher. Before 1995 prices were not good and there were few collectors. The number of collectors and the harvest then increased steadily until 2007. The size of harvest subsequently gradually declined, probably because of disturbance of the fragile ecology and habitat of this fungus by the increased numbers of collectors. In a single season, a primary collector may collect 45 to 55 mummified larvae with the fungus. In Munsyari market in Pithoragarh district (Uttarakhand, north India) alone nearly 90 kg of these were sold in 2009. The state government has put in place regulations for collection of this fungus policed through local village cooperative bodies with the aim of legalizing the trade. This has not been universally successful. About 3–5 quintals (i.e. 300–500 kg) of O. sinensis per annum is estimated to be traded illegally from Dharchula (India) to Nepal and finally to the international market. During the collecting season local tea shops and restaurants arrange transportation of food to the collection areas, generating about 48,000 employment days per year for the local economy (G.C. Pant pers. comm.).
Given its high altitude habitat there is also some evidence that there could be complimentary declines as a result of climate change (Yan et al. 2017), but this does contrast with work by Shrestha and Bawa (2014) who did not find strong evidence for such an impact.
Population Trend: decreasing
Ophiocordyceps sinensis, a fungus endemic to the Himalaya and Tibetan Plateau, is found largely in isolated patches of alpine grasslands at 3,000-5,000 m elevation. It parasitizes underground dwelling larvae of moths (Lepidoptera), especially species of Thitarodes (Ghost Moths). The larvae of the host insects live underground for their entire larval stage of three to four years or longer, feeding on roots and caudexes of alpine plants. If infected by the fungus, they usually die in the winter. The body of the insect host is used by the fungus as substratum to form the mycelium, and is finally converted into a sclerotium, leaving the exoskeleton intact. The fungal stroma comes out in spring or early summer of the following year.
There are probably many species of Thitarodes associated with O. sinensis, few of which are well-known (T. armoricanus and T. jianchuanensis). Some at least will face the same threats as O. sinensis. There is some evidence that O. sinensis co-evolved with its hosts (Quan et al. 2014a,b), but little information as yet to show that particular populations or other subgroups are specific to particular Thitarodes taxa.
Thitarodes caterpillars seem to be generalist feeders and recent information suggests that they prefer roots of grasses and other herbaceous plants over those of Rhododendron species that are frequently present in the same habitats. Spread of Rhododendron may therefore threaten O. sinensis populations.
The infection process and life cycle of the fungus and its host need more research. There are indications in some areas that the caterpillar is infected soon after hatching and the fungus may stay dormant within its body for several years until the caterpillar is ready to pupate. Physiological changes caused by pupation may stimulate active growth of the fungus and death of the caterpillar.
The major threat is the largely unregulated large scale and increasing harvest of the fungus throughout its range fueled by high demand and increasingly high prices. Besides over-collection by humans, there are numerous other minor threats. Over-grazing leading to desertification has been observed; paradoxically there are concerns also that under-grazing is deleterious to the species as the increased vegetation height reduces the effectiveness of spore dispersal. Ecosystem-level threats caused by harvesters chopping down trees for firewood are important in some parts of the fungus’s range, and nitrogen pollution from the growing human population probably has a negative effect on the habitat of the species. Changes in vegetation cover are reported; especially increase in growth of dwarf rhododendron which probably does not benefit the species. Ground-dwelling birds and charismatic megafauna are also deterred by the harvesters, reducing the value of the collection sites for ecotourism. Climate change may also cause further desertification of the Tibetan plateau and reduce the altitudinal islands in the Himalayas that are suitable for Ophiodordyceps sinensis.
To-date, various actions have taken place. In Bhutan and in some areas of China, collection is restricted to the local indigenous human population. Restrictions have also been placed on the number of family members allowed to collect, and on the period in which harvest is allowed. In Bhutan, collection at the end of the season was/is restricted, to allow the remaining stromata to sporulate. Immature specimens have a higher economic value so this rule minimized the financial impact on the harvesters. In Bhutan, support for the harvesters by regulating the market and preventing exploitation in the economic chain, and through education in post-harvest processing, has improved incomes and hopefully also trust between harvesters and conservation officials. Despite all of these measures, there is some pessimism that they have actually achieved even a degree of sustainability, due to the sheer value of the product stimulating a short-term approach. In Bhutan and other parts of the fungus’s range, much of the land is already protected through designation as national parks or nature reserves. However, under-resourced regulatory organizations mean that their protection is limited and is particularly weak in border areas. A participatory approach which gives some decision-making power to the indigenous people is more likely to succeed, unless the protected areas are sufficiently remote.
The species occurs in a number of protected areas across its range e.g. Baima Xueshan Nature Reserve in China. However, more protected areas should be established, e.g. in the mountainous areas of southwestern China and the Qinghai-Tibetan Plateau.
There is currently a substantial amount of research into cultivation of the species, which could reduce the impact on natural populations. While numerous claims have been made, it appears that there has been very limited success in rearing the caterpillar hosts and infecting them with Ophiocordyceps sinensis to produce farmed stromata; although there does appear to have been some recent progress on this front (Li et al. 2019, Liu et al. 2019). Successful artificial rearing of host insect species for O. sinensis under low temperature conditions will allow the cultivation of this important fungus-insect complex to ensure its protection as a bio-resource and for commercial supply (Tao et al. 2016).