Bat diversity in Vietnamese limestone karst areas and the implications of forest degradation

Limestone karst ecosystems in Southeast Asia and Vietnam are important reservoirs for biodiversity and are currently experiencing habitat loss and degradation due to land use changes and increasing pressure from extractive and tourism industries. Recent reviews indicate that their biodiversity is poorly known and raise doubts about the extent to which karst can maintain its biodiversity in the face of ongoing degradation. We investigated this issue by examining the effects of forest degradation on bat species diversity, composition and abundance. Using mist nets and harp traps, we sampled bat assemblages in karst forests of differing integrity for a total of 240 net nights and 180 harp trap nights, capturing 694 bats representing 36 species and five families. Our results confirm that primary forests in Vietnamese karst are exceptionally important for bat diversity, supporting substantial proportions of the national fauna. Disturbed and heavily degraded karst forests also appear capable of supporting relatively high numbers of bat species at low abundances, but their ability to do so in the longer term is in doubt and requires further research. Our findings of bats in relict forests on karst hillsides and ridgetops provide justification for their protection and raise the possibility that these may provide corridors for the movement of forest-dwelling bats within anthropogenic landscapes. Since the majority of Vietnamese karst landscapes remain unprotected however, the future of their biodiversity remains uncertain.