Plant diversity assessment of karst limestone, a case study of Malaysia’s Batu Caves

Rafidah Abdul Rahman,Ruth Kiew

doi:10.3897/natureconservation.44.60175

Abstract

Batu Caves hill is typical of karst hills in Peninsular Malaysia due to its small size and high biodiversity. It harbours 366 vascular plant species that represent about 25% of the Peninsula’s limestone flora. Five species are endemic to Batu Caves and 23 are threatened species. This high biodiversity is the result of many microhabitats, each with their own assemblages of species. Threats are especially severe as the area of Batu Caves is surrounded by urbanisation that encroaches to the foot of cliffs, is vulnerable to fire, habitat disturbance and, formerly, by quarrying. Assigning a Conservation Importance Score (CIS) to all species is quantitative and accurate, can be implemented rapidly and produces reproducible results. Species with highest CIS are native species of primary vegetation, restricted to limestone substrates, endangered conservation status and, in this case, endemic to Batu Caves. It allows not only species, but microhabitats, sites within a hill and different hills to be compared. By identifying and surveying all microhabitats and focusing on locating endemic and threatened species, maximum biodiversity can be captured. Of the 16 microhabitats identified, the most threatened were the buffer zone, lower levels of steep earth-covered slopes and cave entrances. Application of this method provides a scientific basis for balancing the need to protect microhabitats and sites with the highest CIS, with their multiple uses by various stakeholders, which, at Batu Caves, include the activities of cave temples and eco-recreation. It also provides a scientific quantitative method to compare hills to ensure that those hills with highest CIS are not released for mining.

Highlights

Karst limestone hills throughout SE Asia are under severe threat as the demand for cement and other limestone products (Clements et al 2006) frequently takes precedence over conservation of biodiversity, eco-tourism, recreation, culture and their iconic landscape value (Kiew 1997)
Kiew et al document changes in the flora and note that, for example, half the orchid species (20 species) have not been recently collected and that four species, Polyalthia guabatuensis, Sageretia thea var. malesiana, Sapium insigne and Sauropus macranthus, that grew in the buffer zone that has been almost eliminated, are probably extinct in Malaysia
The Flora of Peninsular Malaysia project is in the process of assessing the conservation status of vascular plants and, to date, about 12% of vascular plant species have been assessed

Summary

Introduction

Karst limestone hills throughout SE Asia are under severe threat as the demand for cement and other limestone products (Clements et al 2006) frequently takes precedence over conservation of biodiversity, eco-tourism, recreation, culture (cave temples) and their iconic landscape value (Kiew 1997). High biodiversity is the result of the many and varied microhabitats, the product of the fine scale topographic heterogeneity of karst hills, stacked on a single karst hill (Kiew 1991) Endemic species, especially those with narrow distributions (Kiew et al 2017) and species restricted to growing on limestone are characteristic of the flora and these are the ones vulnerable to extinction resulting from habitat disturbance and other threats. It is not generally appreciated that plant species are not distributed uniformly over a karst hill, but, on the contrary, the great majority are narrowly distributed in specific microhabitats This misconception led Vermeulen and Whitten (1999) to suggest that, if part of a karst were retained, the rest could be quarried without significant loss of biodiversity. This is clearly not the case and would, if followed, have devastating consequences for plant diversity

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