A review of intensified land use effects on the ecosystems of Botany Bay and its rivers, Georges River and Cooks River, in southern Sydney, Australia

The effects of land use intensification on waterways in Sydney’s Botany Bay catchment were reviewed. Land use effects have been more extensively studied in the catchment than in most other regions and a compilation of the knowledge gained is useful for informing management, particularly as land use pressures in the region are accelerating. Two and a half centuries ago, Botany Bay was earmarked for initial European settlement in Australia, but the colonists preferred nearby Sydney Harbour. This decision provided a brief reprieve from intense development. However, colonial residents soon spread into the catchment, as well as using it for Sydney’s most polluting industries, with wastes often discharged directly to waterways. Industrial wastes became more controlled from the 1970s, but by that time the catchment’s landscape was severely altered and legacy pollutants had accumulated in benthic sediments. Today, the vast majority (i.e. > 85%) of waterborne pollutants are discharged in urban stormwater. Pollutants have been shown to exert a range of detrimental effects on ecosystems in freshwater tributaries and the estuary. Also, construction, land reclamation and dredging have directly removed large areas of natural aquatic habitat. Formerly productive commercial fisheries have been lost from the estuary. However, waterways across the Botany Bay catchment continue to support a range of valued recreational uses. With the local population bound to increase rapidly over the next half of a century and beyond, the future state of waterways in the region will depend upon trade-offs between valued uses.