Mammalian Diversity and Distribution in Human-Altered Tropical Landscapes

Abstract

Habitat loss at the hands of human enterprise continues to drive the global decline in biodiversity. While much attention has been placed on the use of protected areas as a means of conservation, there is an increasing need to understand the capacity of unprotected, human-altered landscapes to provide refugia and connectivity at larger spatial scales. This study evaluates the mammalian diversity that persists under alternative land management regimes and degrees of landscape change in south-central Sumatra, Indonesia. Species occurrence data compiled from extensive field surveys across 1600km2 form the basis for analyses of community composition and speciesspecific responses to the current landscape. Results indicate that species richness declined with increased landscape alteration. The lowest observed species numbers were in areas of industrial scale oil palm production rather than scrub habitats or degraded forest. Endangered mammals that persisted in the wider matrix were extirpated from the oil palm dominated areas. Comparisons between the ecological traits shared by persistent versus locally extirpated species revealed that in the initial stages of landscape change there is the capacity to support large specialist species with slow life histories. As landscape degradation continues to an agricultural matrix only habitat and diet generalists persisted. Tests of species-specific responses to landscape alteration focussed on the occurrence patterns of Sumatran tigers (Panthera tigris sumatrae) and four principal prey species. Measures of human prevalence derived from survey data and a novel application of occupancy estimation techniques, identified significant negative responses to higher levels of landscape development. Satellite derived measures of habitat connectivity and localised landcover degradation found that connectivity to areas of least disturbed forest was more important for reclusive species such as tapir (Tapirus indicus) and red muntjac (Muntiacus muntjak), while the occurrence of the wide-ranging tiger was more strongly influenced by local landcover degradation. The capacity of human altered landscapes to contribute to the conservation of mammalian communities is closely allied to the availability of degraded forests rather than alternative human altered landcovers. Given that these areas of forest are increasingly subject to degradation and conversion, spatial planning and proactive management are required to safeguard these resources.