POPULATION STUDY AND REASSESSMENT OF CONSERVATION STATUS OF AN ENDEMIC DIPTEROCARP, Hopea bilitonensis

Abstract

Hopea bilitonensis is a rare, endemic Dipterocarp species in the Malesian Region. It has a disjunct distribution pattern, where main populations occur on the sandy soils of Bangka Belitung Islands of Indonesia and some on limestone forest in Perak, Peninsular Malaysia. Current global status of this species based on the IUCN Red List is Critically Endangered (CR) A1c+2c, B1+2c (1998) whilst in Malaysia it is assessed as CR A4c, B1ab(iii) (2010). A reassessment of the conservation status of this species is needed to provide the most current population status and its extinction risk, especially in Indonesia using the IUCN Red List Categories and Criteria version 3.1. This study was conducted to survey and assess the current populations of this species in Belitung Island where most population occurred and subsequently to recommend its current conservation status. The species is in fact still common in the island, stretching along the main roads and surrounding forests. Using the purposive sampling method, we developed a total of 16 plots of 20x20m each in 10 different locations across the Belitung Island. A total of 730 individuals were found with stem diameter at breast height ranged from 2cm to more than 30cm. For global reassessment, based on the current distribution and herbarium records, the calculated extent of occurrence (EOO) is 108,128.642km2, whilst the area of occupancy (AOO) is 84 km2. However, the species clearly has a restricted distribution and is facing high threats due to frequent timber harvesting and continuing decline of the EOO and AOO. The species extinction risk was then assessed by using five quantitative criteria of the IUCN. Therefore, we propose H. bilitonensis category is considered to be Endangered (EN) based on A2c, B2ab(i,ii,iii,iv,v) and C2a(i) criteria.