Long-term changes of coral reef habitats in two islands with and without residents in outer Spermonde Archipelago, South Sulawesi revealed by satellite remote sensing


by: Nurjannah Nurdin, Khairul Amri , Dwia Aries Tina Pulubuhu, Chair Rani, M. Akbar AS, Teruhisa Komatsu


Spermonde Archipelago in South Sulawesi has been facing human impacts on a coral reef ecosystem providing important ecosystem services. It is important to identify damages of a coral reef ecosystem by human impacts to mitigate the adverse effects and to realize sustainable development of tropical islands. Remote sensing is a very practical tool to analyze spatial and temporal changes in coastal habitats through historical archives of satellite images. Multi-spectral images obtained with LANDSAT MSS, TM, ETM and OLI sensors from 1972 to 2016 were analyzed with unsupervised classification method for extracting coral reef habitats in Gondongbali (GI) and Pamanggangang Islands (PI) with and without residents, respectively, to compare human impacts on a coral reef ecosystem around the two islands. Overall accuracies of classification of six habitats, live coral, dead coral with algae, rubble, seagrass, sand and mix bottom, for GI and PI were 83.4% and 84.0%, respectively. The overall accuracies allow the unsupervised application for mapping coral reef habitats. A temporal change of live coral area showed a decreasing tendency with a speed of about 1%/yr of 1972 in both islands since 1972. Its speed of GI was slightly greater than that of PI. Decreased areas of live coral changed to dead coral with algae, rubble and mix bottom. The seagrass habitat in GI showed a stepwise increase from 1972 to 2016, suggesting influence of nutrients discharge from land into the lagoon.

Keywords: coral reef ecosystem, human impact, spatio-temporal change, remote sensing, landsat