What we know so far about the newly discovered forest in a massive Chinese sinkhole
- Giant sinkholes – also named ‘heavenly pits’ by Chinese geologists – offer unique habitats where a variety of plant and animal life can thrive
- The latest discovery has raised hopes that it will host unknown species and scientists have already identified some rare ones inside
Geologists found “shoulder-height” plants and ancient trees growing up to a height of 40 metres (130 feet), and are hoping that undiscovered plant and animal species may be found inside the forest in the southern region of Guangxi.
Zhang Yuanhai, a senior engineer from the Institute of Karst Geology at the China Geological Survey, said there were three big caves along the sinkhole walls along with the primitive forest at the bottom.
“[The discovery] is of high scientific and popular science value both on the evidence of the evolution of the sinkhole and the unique ecosystem that developed since its formation,” Zhang told state news agency Xinhua.
The trees at the bottom of the sinkhole were tall and skinny, stretching upwards to get enough sunshine, local newspaper Guangxi Daily reported.
Explorers found a large area of wild plantain at the bottom, as well as a rare species of square bamboo with thorns 2cm to 3cm long growing around its joints. Experts told the daily that this species could only grow in a good climate.
Sinkholes are formed when underground water dissolves soft rocks such as limestone, carbonate or salt beds.
As the rocks are worn away, spaces and caverns develop underground. A sudden collapse may happen if the underground spaces are too big and there is not enough support for the land.
The landscape formed by this process are known as karsts, and usually include towers, pinnacles, cones and sinkholes – the largest of which are known to geologists as tiankeng – after the Chinese word for “heavenly pit”.
South China has one of the world’s largest continuous karsts, a World Heritage site that spans the provinces of Yunnan, Guangxi, Guizhou and Chongqing municipality, and is known for its rich biodiversity.
Previous sinkhole discoveries – including the Xiaozhai Tiankeng, the world’s largest with a depth of 662 metres – have been a boon for scientists.
Explorers have found about 100 caves inside the sinkhole since it was first discovered in 1994, and some 2,000 plant species.
Zhang, who discovered another cluster of giant sinkholes with colleagues in Guangxi’s Napo county in 2019, told Xinhua the vegetation there was largely intact and there was little trace of human activity.
Leye, the county where the new sinkhole was found, is home to the world’s largest group of sinkholes, which number 29 in total, but Zhang said the new discovery had been formed by a separate river system and it may also have formed other karsts.
Researchers from Guangxi Normal University suggested in a 2017 paper that giant sinkholes could provide a model for habitat conservation and forest restoration in the region, as they had allowed ancient forests and rich biodiversity to survive without human interference.
The researchers compared the range of species and plant life in two habitats found inside a giant sinkhole with two in the outside world, and discovered that there was far greater diversity in plant and animal life inside the sinkholes.
Because of the long-time natural process, the indigenous vegetation in the region had been ruined or fragmented but the sinkholes preserved a unique and rich type of biodiversity.
“It provides a genetic pool for indigenous flora and possibilities for scientific research and revegetation in the degraded karst areas,” the authors concluded.