Biodiversity and conservation of river macroinvertebrates on an expanding urban fringe: western Sydney, New South Wales, Australia

Abstract

As in many growing urban areas, the prevention of environmental damage as Sydney spreads westward into the Hawkesbury-Nepean River basin is a major challenge for planners, managers and the local community, We surveyed macroinvertebrates at 45 river and stream sites in April-June 1996, and reviewed data from other sources, in order to assess the issues involved in conservation of the lotic macro invertebrate fauna, Regional richness is high with 443 recorded species and morphospecies, Cluster analysis showed community pattems related mainly to waterway size (separating the Hawkesbury-Nepean River from tributary streams), geology (tributaries on shale or sandstone), tidal intrusion and urbanization (impoverished faunas in urban streams). The ability of genus richness of mites and major insect orders to reflect overall genus richness at a site was limited, and Diptera and Trichoptera appear to have the greatest value as biodiversity predictors. Urban expansion is the major threat to lotic macro invertebrate communities in the region, but agriculture, flow regulation, sand and gravel ex1raction and introduced species have probably also impacted on the fauna, Streams with high conservation value for macroinvertebrates include those few on the Cumberland Plain and surrounding slopes that retain substantial indigenous vegetation in relatively undeveloped catchments. The Hawkesbury-Nepean River sfill harbours a rich faunal community and is also important for conservation, The development of effective strategies for conservation assessment and management is problematic for several reasons, Some species in the region are known to be vulnerable, but the status of most cannot be assessed because of a lack of taxonomic and zoogeographic information, Most "biodiversity indicator" concepts are of dubious value for aquatic macroinvertebrate conservation. A multi-faceted management approach emphasizing subcatchment reserves, riparian restoration and the control of threatening processes is required.