Overview of adaptive management for multiple biodiversity values at the Western Treatment Plant, Werribee, leading to a pilot nutrient addition study

摘要

Across south-eastern Australia the loss of natural wetlands since European settlement has been substantial such that even constructed waterbodies that provide a measure of habitat for waterbirds can assume importance for their conservation. Melbourne Water operates the Western Treatment Plant (WTP), occupying 10500 ha near Werribee, primarily for the treatment of some 54% of Melbourne's industrial and domestic wastewater. During 1982 the site was included as a component of the Port Phillip Bay (Western Shoreline) and Bellarine Peninsula Ramsar site in recognition of its great importance for waterfowl (Anseriformes and Podicipediformes), shorebirds (Charadriiformes) and wading birds (Ciconiiformes and Gruiformes). The WTP supports other biodiversity values, with a significant population of the nationally Vulnerable Growling Grass Frog Litoria raniformis; a number of threatened species of plant, including the Spiny Rice-flower Pimelea spinescens subsp. spinescens; and two listed vegetation communities: Natural Temperate Grassland of the Victorian Volcanic Plain (Critically Endangered), and Subtropical and Temperate Coastal Saltmarsh (Vulnerable). This paper describes how site managers have endeavoured since 2002 to implement adaptive management to protect and promote the WTP's recognised biodiversitv values during necessary sewage treatment upgrades. Results of management on waterfowl populations are obscured by the effects of the 1997-2009 drought across south-eastern Australia and species' inherent variability in distribution across this vast area. A trial addition of straw to promote waterfowl food in one wetland showed no clear benefits. However, after 12 years of close monitoring of target populations our knowledge is much improved and we believe the site retains the biodiversity values that led to it being listed as a wetland of international importance.