Demise of Madagascar's once great barrier reef : changes in coral reef conditions over 40 years

Abstract

In the 1960s and 1970s the biology and geology of the Grand Rcif of Tular, (now Toliara) in southwestern Madagascar, was thoroughly studied and reported. Toliara is the largest city in the south of the country, and the Grand Rcif offshore provides both artisanal fisheries and coastal protection to the growing regional capital. Substantial research on the comparatively pristine reef was described in a volume of Atoll Research Bulletin in 1978. Since then, published scientific study of this reef has been largely lacking. The present study compares the condition of the Grand Rcif of circa 40 years ago, with that seen in a brief resurvey undertaken in 2008, on transects corresponding to some of those documented previously. The trend has been of severe degradation; hard coral cover on the fore-reef slopes has declined substantially, and there has been a near total loss of the "architectural species" in particular. Coral has been replaced to great extent by fleshy algae. Observations also indicate severe decline on the broad reef flat, back reef and lagoon areas. Perhaps most seriously for the local fisheries and human communities, is that the fore reef is almost depleted in reef fish today.