Giant sinkholes discovered containing untouched ancient forests

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They're considered "heavenly" for a bloody good reason.

A number of these have been found containing untouched ancient forests.

Australian explorers venturing into the outback stumbled upon one of these massive holes, which experts claimed probably contained species of tiny animals that were new to scientific discovery.

Measures an impressive 300 metres in length, 150 metres in width and is over 190 metres deep.

” – which translates as “heavenly pits” – in the region.

The reason for the name of these trenches is that they are some of the last remaining natural habitats for ancient forests and are home to species not found anywhere else in the world.

.”

Considering their great depth, very little sunlight filters down to the bottom of the tiankeng, and yet, they're home to a surprising variety of vegetation.

Published on 20 July, a study has shown how a number of species have been able to survive and flourish in their depths.

The scientists discovered that nettles, ferns and other plants that reside within them are nourished by plentiful supplies of nitrogen, phosphorus, potassium, calcium and magnesium.

These elements hold plant growth back in other parts of the world where they're scarce, but because there's such an abundance of them in the tiankeng, the plants have adapted to make the most of them, allowing them to grow tall and take advantage of the drips of sunlight that reach them.

"Plants can adapt to harsh environments by changing the amount of nutrients in them," the study's authors wrote, according to a translation by

Because of the massive cliffs and rugged terrain of the tiankeng, it's been less affected by human activities.

The deep holes have plants that prefer moist and shaded areas, including species found only in this region, the researchers say. These include modern karst forest plants, such as the Nepalese hog plum (Choerospondias axillaris) and the Chinese rain bell (Strobilanthes cusia).

So how do these massive sinkholes and their surrounding forests come into being?

These extraordinary sinkholes appear when the roof of an underground cavern expands and caves in, Jianmin says.

About 30 percent of the world's tiankengs can be found in China's Guangxi Zhuang Autonomous region, particularly within its World Heritage listed karst landscapes.

Australian landscapes formed from soluble rocks like limestone are shaped by erosion, resulting in features like sinkholes, caves and underground waterways.

Jianmin goes on to explain how these sinkholes are formed, saying: “Karst tiankeng is a relatively closed environment with high humidity, low temperatures, and a high concentration of negative oxygen ions.

Its base is linked with an underground water supply, supporting a lush green haven throughout the year.

“Unique and pristine ecosystems containing a variety of indigenous animals, plants and microorganisms are found in such environments.”

A total of 300 tiankeng have been found worldwide, with China accounting for two-thirds of them. They've also been discovered in Papua New Guinea, Malaysia and Madagascar, Slovenia, Croatia, Italy and Spain, among other countries.

Why are they important?

These sinkholes are more than just a breathtaking natural wonder – they're also vital ecosystems.

Jianmin pointed out that he and his fellow researchers have found many rare and endemic plants in the tiankeng area, confirming its reputation as a "sanctuary for endangered plants and ancient forest ecosystems".

“There’s also a fair dinkum chance that previously unknown species will be found in these environments,” he added.

This article was first published on 31 July 2024.

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