A STUDY OF PLANT-SPECIES - EXTINCTION IN SINGAPORE - LESSONS FOR THE CONSERVATION OF TROPICAL BIODIVERSITY

The native vascular plant flora of the Republic of Singapore has suffe red the extinction of 594 out of a total 2277 species. These represent local, not global, species extinctions. Coastal habitats, including m angroves, have lost 39% of their species, while inland forest have las t 29%. Epiphytic species (62% loss) appear particularly prone to extin ction, which is reflected in a similar disposition exhibited by the Or chidaceae. Deforestation and disturbance have been the main cause of p lant species extinction in Singapore. The rich mangrove epiphyte flora has been totally exterminated, and a number of tree species are reduc ed to populations of a few mature individuals. Many more species conti nue to survive than the species-area relationship would predict given the 99.8% loss of primary forest. This is interpreted as a result of t he failure of equilibrium to be achieved yet in the remnant forest fra gments, even after more than a century of isolation. Singapore's secon dary forests appear to accrete plant diversity very slowly, even if co ntiguous with primary forest areas. We conclude that remnant fragments of primary tropical forest, even of very small size, can play a major role in the conservation of tropical biodiversity. The patterns of ex tinction observed in Singapore indicate that coastal and estuarine sit es are in greatest demand for development and therefore must be given high priority for conservation despite their somewhat lower biodiversi ty. Epiphyte and orchid diversity appear to be very good indicators of the degree of disturbance suffered by a habitat in the humid tropics.