Prioritising Important Plant Areas (IPAs) among the limestone karsts of Perak, Malaysia

The flora of limestone karsts is exceptionally rich, due in particular to the wide array of microhabitats that limestone outcrops support. However, in Peninsular Malaysia limestone outcrops are heavily exploited for the quarry industry, cave temples, leisure venues and the development of geoparks, hence the limestone flora is amongst the most threatened biodiversity in the Peninsula. The 95 limestone karsts in Perak are currently known to support 538 species, representing c. 44.2% of the total limestone flora of Peninsular Malaysia. Of these, 13.2% (71 species) are endemic to the Peninsula of which 10 species are hyper-endemic (i.e. restricted to a single karst), 108 (20%) are threatened with extinction and 6 are considered likely to be Extinct. Typical of limestone in Peninsular Malaysia, a single karst harbours only a fraction of the total limestone flora such that a network of karsts is required to capture maximum plant diversity. Through evaluation of data from field surveys, herbarium specimens and the literature, 27 of the Perak karsts were found to trigger Important Plant Area (IPA) status, i.e. they harbour important populations of threatened species, outstanding botanical richness and/or are important examples of threatened habitats that in Perak include the foothills and limestone forest. Fifteen karsts were identified for priority conservation measures based on Conservation Priority Scores (CPS), a quantitative methodology based on endemic and threatened status. With the addition of two species-rich karst sites, 17 karsts are recommended as the first iteration of the network of priority IPA sites for Perak that together conserve 90% (483 species) of the Perak limestone plant diversity, 93% (66) of the endemic species and 94.4% (102) of the threatened species. CPS is found to be more reliable than using total species richness for assessing conservation importance and we also demonstrate that karst size and isolation are not primary indicators of range-restricted plant diversity. Significant knowledge gaps still exist, with 59 karsts in Perak without botanical surveys, and with many rare species having not been recollected for over 30 years, emphasising the need for further botanical research in these important and threatened landscapes.