Limestone habitats

Characterised by dramatic hills and caves that have been carved out through erosion over millennia, limestone landscapes – also known as karst – form some of the most breathtaking vistas on our planet. The often isolated nature of these unique features, and the extreme soil and water conditions found within them, have created the perfect recipe for a highly biodiverse landscape, rich in endemic species that are unique to the area.

And what species they are.

The steep, inaccessible nature of karst landscapes means that many limestone hills have retained their forest cover, even while the surrounding areas have been deforested. As a result, these striking towers act as natural refuges for species that have been wiped out from much of their range, such as the Tonkin snub-nosed monkey, cao vit gibbon and Delacour’s langur in Vietnam, the last of which has specially adapted pads on its hand, feet and rump to allow it to run, jump and sit on the razor-sharp limestone.

Not all of the species found in these ecosystems are quite so cute and cuddly looking – but looks have nothing to do with biological importance. Even the most aesthetically challenged species are vital within their ecosystems, and perhaps the best examples of this are the bizarre, unusual, rarely seen species found within limestone caves.

These extraordinary environments each have their own unique light, heat, moisture and nutrient conditions, and their own unique communities of species that have evolved to cope with these conditions.

Bats are among the most abundant and familiar of these cave dwellers. In many cases, it is their guano, deposited on the cave floor, that supports entire food webs made up of weird and wonderful creatures found nowhere else on Earth, including blind fish and crickets, hairy earwigs, long-legged centipedes and beetles, ghost snails, cave-adapted whip scorpions, trapdoor spiders, crabs, geckos and a highly specialised bat-eating snake, the cave racer, to name just a few.

Although karst caves and towers can take millions of years to form, they can disappear very quickly—and they take entire ecosystems with them when they go.

Unfortunately, these landscapes are made up of a substance that is very valuable to humans: limestone, a key ingredient in the manufacture of cement, concrete and mortar, and a commonly used material for buildings and stonework. Industrial-scale quarrying represents a serious and increasing threat to limestone environments around the world.

Caves have also featured prominently throughout human history as places of shelter and as sites of religious, spiritual or cultural significance. As such, they are a magnet for pilgrims, worshippers and recreational visitors. If these caves aren’t carefully protected and sympathetically managed – for example, if lights, walkways and ventilation systems are added – the delicate balance of these ecosystems can be disrupted, and biodiversity rapidly lost.

Many species found in limestone ecosystems are so precisely adapted to their habitat that they cannot withstand changes, nor can they survive outside (or travel beyond) their own small range – which can be as restricted as a single cave. The recently discovered Hon Chong ghost snail is known only from two caves in Vietnam, for example, while all 15 of the new gecko species recently discovered in Myanmar are thought to be restricted to the individual limestone blocks where they were found.

The existence of such species is already precarious, so if their habitat were degraded or destroyed, their future would be bleak – and a single misjudged blast as part of quarrying activity could wipe an entire species from the face of the Earth.

For many years, Fauna & Flora International (FFI) has been working in areas where limestone rock formations are a dominant feature of the landscape, most notably in China, Myanmar and Vietnam.

However, but we are now developing a broader, dedicated programme aimed specifically at focusing global attention on these ecologically unique and irreplaceable natural features, to ensure that they are recognised as much for their rich and threatened biodiversity as for their cultural and commercial value. Examples of FFI’s work in this area include:

• Identifying priority sites for karst biodiversity conservation in Myanmar and developing best practice guidelines for tourist cave management and limestone quarrying
• Co-chairing the IUCN-SSC Specialist Group for Cave Invertebrates, which aims to encourage a more environmentally sensitive approach to limestone quarrying
• Actively engaging with a global leader in cement production to ensure that its business strategy and operational activities in Malaysia, Indonesia and Philippines take full account of limestone biodiversity in order to minimise the company’s environmental footprint