Mangrove forests of the Wakatobi National Park

Within the Wakatobi National Park, small areas of mangrove forest develop on shorelines where there is limited input of freshwater and terrigenous sediment. These conditions permit the development of fringing reefs and seagrass meadows close to the mangroves so there is considerable ecological connectivity between these three ecosystems. The Wakatobi mangrove forests are unusual because they develop on shorelines with shallow calcium carbonate-rich sediments with areas of raised fossil coral that constrain tidal water circulation and limit the development of mangrove roots. They lack the deep, fine-grained sediments typical of large mangrove areas in deltaic systems. The seaward edge of these forests is dominated by Rhizophora stylosa with a straggling growth-form and a low canopy. The forest in the inner (landward) part of some Wakatobi mangrove forests is more diverse with straight-stemmed trees and a canopy that can be over 25m high. Substantial quantities of large-diameter fallen wood are found with these forests, particularly in the more landward part of the forest where a mean of 102m(3) ha(-1) of fallen large woody debris was measured. Wood on the seaward side of the mangrove forests is processed by wood boring bivalves of the family Teredinidae, but wood on the landward side is subject to termite and basidiomycete degradation. The main uses of mangrove forest products in the WNP are firewood from Rhizophora stylosa, fish fence poles from Bruguiera gymnorhiza and sawlogs from Rhizophora apiculata. Nypa palm leaves are used to make roofing shingles. The impact of extraction of forest products in the WNP is locally severe, but generally limited. The use of mobile sawmills threatens forests of tall trees on Kaledupa. Protection of mangrove ecosystems should focus on these older forests and on regulating firewood cutting so that cut trees are not prevented from coppicing and ecosystem services from harvested areas are largely retained.