IMPORTANCE OF CAVES & KARSTS
Karst areas in Peninsular Malaysia are estimated to cover 26,000ha, mostly concentrated in the northern states, and 50,000ha in Sabah and Sarawak. These consist of limestone islands in the Langkawi archipelago, and major limestone outcrops in Kelantan, Perlis, Kedah, Perak and northern Pahang, lowlands of eastern Sabah and in southwest and northeast Sarawak. Many of the species in limestone areas show a high degree of endemism. Some invertebrates such as the trapdoor spiders of the genus Liphistius are highly endemic with some species restricted to just one cave, for example Liphistius batuensis which is only found in Batu Caves.
Some plants are adapted to the harsh environment of limestone hills and there is a high degree of endemicity of limestone flora. Due to their restricted range and the degradation of limestone habitats, many plants found on limestone hills, such as begonias, orchids, gesneriads, balsams and wild gingers are increasingly threatened species, such as the white slipper orchid (Paphiopedilum niveum), which is in danger of extinction due to over-collection by horticulture enthusiasts.
The cave food chain is quite complex but everything ultimately depends on bats for survival. There is no sunlight in caves, so no photosynthesis can take place therefore plants cannot grow. Bats are the only creatures which regularly go outside the cave to feed. A cave without bats generally means no other animals will be found. Bat guano is home and food to a wide range of invertebrates including flies, beetles, bugs, collembola, millipedes, springtails, cockroaches, worms, mites and moths. Some reptiles and amphibians are also well adapted to living in caves. The cave racer, a cave-dwelling snake, is commonly encountered and feeds on bats. Freshwater turtles, such as the Asian leaf turtle, are a common resident in streams flowing through caves.
Services provided by karsts and their biodiversity are less tangible but significant nonetheless. Karsts readily store rain, and apart from maintaining the hydrological integrity of a watershed, they also serve as sources of groundwater for consumption and irrigation. Despite their unique limestone ecosystem and the ecosystem services they provide us, karsts are still being exploited for limestone used in the production of cement and marble products. Apart from quarrying, limestone hills are also vulnerable to other threats such as unsustainable agriculture practices, burning and indiscriminate land clearing, building of temples, especially in Pahang, Perak and Selangor; tourism development such as in Langkawi and Sarawak; and flooding related to hydroelectric dam construction as in Kelantan, Pahang and Terengganu. Logging activities around karsts reduce shade and humidity and endanger sensitive plants; drive away cave-visiting animals such as bats and arthropods that supply organic matter to guano communities; pollute cave streams and kill resident fauna, and diminish bat populations that depend heavily on surrounding forests for foraging area. Although many tropical caves are rich in cave fauna, there seems to be a decline in numbers of species over the years, particularly of bats. Extinctions of at least 18 karst plant species have already been documented in Peninsular Malaysia. Molluscs are also extinction prone as a result of their low vagility, poor tolerance for desiccation, and high degree of site endemism. In Sabah, two site-endemic land snail species (Opisthostoma otostoma and Opisthostoma decrespignyi) are presumed extinct.
Limestone hills take a long time to form, but once gone, they are irreplaceable, and the entire ecosystem gone. If limestone formations and their ecosystems are to survive, there needs to be more awareness about their importance among the public and a long-term strategy for their conservation.