Environmental challenges in a near-pristine mangrove estuary facing rapid urban and industrial development: Darwin Harbour, Northern Australia

Abstract

The tropical, macro-tidal estuary of Darwin Harbour is in near-pristine condition and supports a rich biodiversity. However, urban and industrial development pressures are increasing in many parts of the catchment. This challenges us to improve our understanding of how the harbour’s ecosystem responds to environmental threats and how best to optimise future development while preserving valuable ecosystem services. Here, we synthesise our current knowledge of several environmental aspects of the harbour and its catchment.The intertidal zone and its abundant mangrove forests account for a major proportion of primary productivity in Darwin Harbour. These areas also play a key role in preserving water quality by intercepting catchment-derived pollutants and they substantially influence the movement of sediment through the estuary. Darwin Harbour mangroves generally remain in healthy condition with extensive areas of highly biodiverse habitats near urban and industrial developments.The future health of Darwin Harbour depends substantially on the protection of the mangrove estate against further pressures from coastal land clearing, catchment derived pollutants and accelerated sedimentation from runoff and dredging. Rapid sea level rise (currently ≈8 mm/year) is a further significant threat to the stratified floristic assemblages and specialised invertebrate fauna typical of Darwin Harbour mangrove forests. These threats require development of new sensitive harbour-wide monitoring techniques to provide early warning of the excess accumulation of stressors and disruption to ecosystem functioning.