Bea Maas

beamaas@gmx.at

PDF der Diplomarbeit im Hochschulschriften-Service der Universität Wien


Six years of habitat modification in a tropical rainforest margin of Indonesia do not affect bird diversity but endemic forest species

Studies on temporal changes of tropical bird communities as response to habitat modification are rare. To evaluate the sustainability of current land-use practices, we quantified changes in bird assemblages at the forest margin of Lore Lindu National Park, Central Sulawesi for a period of six years. Therefore, standardized bird counts were conducted in the years 2001/2002 and 2008 at 15 census points representing natural forest, secondary forest, agroforestry system and openland sites. Although overall species richness remained nearly identical, different species groups were affected unequally by habitat modification within the forest margin landscape. The mostly endemic forest species declined in abundance (72.0 % of forest species) and were counted at a smaller number of census points in 2008 (81.8 %). In contrast, 81.8 % of the solely widespread open-land birds became more abundant and 63.6 % of the species were recorded at al larger number of census points. Hence, recent human activities in the forest margin ecotone negatively affected species of high conservation value and contributed to the ongoing process of biotic homogenization. Species richness turned out to be a poor indicator of habitat change, and our results underline the importance of considering species identities. Small-scale disturbance and land-use change at the margin of Lore Lindu National Park had surprising negative impacts on bird community structure and endangered species, but not overall biodiversity, even within few years. Biotic homogenization as result of habitat conversion and modification is a global phenomenon. The winners, such as in our study, are widespread open land species, while the losers are endemic forest birds. Further monitoring of temporal changes of biodiversity is an important precondition to adequately valuate effects of human activities on species assemblages within sensitive transition zones such as forest margin areas, which are particularly exposed to anthropogenic disturbance.

The research was carried out in collaboration with the German-Indonesian research program STORMA (The Stability of Rainforest Margins in Indonesia; www.storma.de).