Old and new observations on coastal changes of Jakarta Bay: an example of trends in urban stress on coastal environments

Since the author surveyed the coastal environment of Jakarta Bay in the 1950s, rapid urbanization has affected both the alluvial plain that borders the bay and the coral reefs in it. The urban stress factors are diverse and include baywater pollution, the use of beach sand and coral debris for construction, the implementation of major engineering works (harbour extension, storage lake), intensified fishing and tourism and, within the Jakarta connurbation, groundwater extraction resulting in land subsidence of as much as 4-5 cm/year. Natural stress factors also have occurred and relate to an anomalous behavior of the InterTropical Convergence Zone (ITCZ), resulting in very low precipitation and relatively strong northerly and easterly winds during the 1960s and 1970s. The coastal environment was unable to absorb the combined stress factors and substantial change and deterioration thus resulted. The causative factors are weighed and an outlook for the future is given.