The caves of Yunnan Province offer insight into how diseases are transmitted from animals to humans. They’re also a unique challenge for adventurous explorers.
Before the Covid-19 pandemic, there was another outbreak caused by the same family of coronaviruses that wreaked havoc in Asia.
The SARS epidemic of 2002-03 sickened over 8,000 and killed nearly 800 people. In 2017, Chinese scientists managed to trace the source of that virus to a bat species in a cave in Yunnan Province, southwestern China.
Dotting the mountainous landscape of Yunnan and neighboring Guizhou, the caves have been the haunt of explorers for centuries. There are even spelunking clubs that take people into the deepest reaches of their chambers.
For epidemiologists, the caves also offer insight into how diseases are transmitted from animals to humans. Besides the SARS-associated bat species, there is also Histoplasma capsulatum, a fungus that lives on bat droppings and can cause the potentially fatal “caver’s disease.”
(Read more: Don’t blame wet markets for the coronavirus)
Peter Mortimer, a South African mycologist and professor at the Kunming Institute of Botany in Yunnan, is an accomplished caver and climber who has been studying the caves’ species.
“All worth exploring,” he says, pointing to the limestone formations in the surrounding mountains as we drive from Kunming, the capital of Yunnan, to Yanzidong, a cave about 10 miles north.
Without specialized equipment, one can go only explore the caves as far down as the main chamber. The lower levels of the cave are accessible only by a series of rappels through a narrow shaft recently discovered by Mortimer.
It’s advisable to explore the caves with experienced guides.
“There is an underground river in Guizhou that you can run in a raft, for two full days, all inside a cave system.”
“Those guys are legit,” Mortimer says. “They can take you on a real caving adventure. There is an underground river in Guizhou that you can run in a raft, for two full days, all inside a cave system.”
A unique adventure
Southwest China is riddled with caves, and the sheer number of them means most remain unexplored, despite caving becoming increasingly popular in China.
For today’s climb, we use a climbing rope to rappel down into the main chamber of the cave. Ropes are the preferable mode of transport, especially when you’re scrambling down a rotten tree trunk dropped into the shaft. This is how locals used to harvest stalagmites in the cave.
Down on the floor, masses of ghostly white millipedes feast on thick piles of bat droppings. On the walls, cave leeches try to creep up on sleeping bats. In the light of headlamps, the leeches look blue.
“This part of the cave is totally safe.”
“This part of the cave is totally safe,” Mortimer says. “Let’s go deep down to the underground river. It is a much more full-on experience.”
It’s very easy to run into serious trouble in these inner sections. We rappel and squeeze down into another chamber—a stream flows into it before vanishing into a wall. The low ceiling is studded with large, loose blocks. We’re now about 300 feet below the surface.
“We have once tried to follow this stream up,” Mortimer says. “We could see the light—there is an opening—but it was blocked by rockfall.”
We do not get far this time either. Very soon, the ceiling and floor converge to such an extent that Mortimer decides to turn around. It is rainy season, and a rainstorm can flood this passage in minutes.
“We should come back later,” Mortimer says. “It would be great to find an exit from here. This would save us going up the ropes to get out.”
Discovering new species
The cave systems are home to all sorts of wildlife, and it’s not unusual to find a previously undiscovered species.
On our climb down, Mortimer finds a fluffy white ball with bones sticking out of it—a dead bat being devoured by a fungus. He packs the carcass into a plastic bag.
“I will get its DNA sequenced, he says. “This fungus may well be new to science.”
Yunnan has the highest biodiversity of fungi in the world. The province is home to 90% of China’s mushroom species, and Mortimer’s research group has identified over a thousand new ones.
The bat-eating fungus he finds that day turns out to be a very unusual beast. DNA sequencing results show it’s a completely new species, related to the famous Cordyceps sinensis, which is highly prized in traditional Chinese medicine.
The discovery excites Mortimer. “Molecular evidence shows it to be very isolated from its nearest relatives,” he says, “and it is also morphologically totally distinct from anything I have seen before.”
Just one of many ways that Yunnan’s caves offer a unique adventure.
Adapted from an article first published in the South China Morning Post.