Regional Ecological Risk Assessment for Australia's Tropical Rivers: Application of the Relative Risk Model

ABSTRACT

The Relative Risk Model (RRM) was used to undertake a spatially explicit regional ecological risk assessment at a continental scale for the 1.1 million km² Northern Tropical Rivers (NTR) region of Australia, and at a catchment scale for the Daly River, Northern Territory. The NTR RRM assessed risks of 18 threats to three aquatic habitats and four ecological assessment endpoints across 51 catchments, while the Daly River RRM assessed risks of 17 threats to three aquatic habitats and five ecological assessment endpoints across 18 sub-catchments. The three most significant current threats to the aquatic ecological assets for the NTR region were cattle grazing on native vegetation, feral pigs, and unmanaged fire, and those for the Daly River catchment were cattle grazing on native vegetation, transport/communications infrastructure, and land clearing. Climate change and associated sea-level rise are emerging problems that threaten to cause much greater impacts than currently exist. The uncertainties associated with both scales of assessment were considerable and are discussed. Despite the uncertainties the RRM was found to be a robust method for assessing and prioritising the risks of multiple threats to multiple assets and is a useful screening tool for decision-makers in prioritizing research and/or management actions.

Key Words:

• ecological
• risk
• assessment
• tropical
• rivers
• relative risk model

ACKNOWLEDGMENTS

This project was funded under Land and Water Australia's Tropical Rivers Program. We thank Prof. Wayne Landis (Western Washington University) and Dr. Keith Hayes (CSIRO Mathematical and Information Sciences) for providing valuable comments on work related to this article. Andrew Edwards from Bushfires, NT, provided the fire data analysis. Ian Lancaster, Dr. Peter Whitehead, Peter Jolly, Dave Howe, Ian Smith, John Gilmour, Chris Wicks and Fergal O’Gara (NT Government), Dr. Stuart Blanch (NT Environment Centre), Assoc. Prof. Michael Douglas (Charles Darwin University) provided input into the Daly River conceptual model development. Dave Howe, Chris Wicks, and Fergal O’Gara (NT Government), Dr. Stuart Blanch (NT Environment Centre), and Matt Daniel (Greening Australia) provided expert opinion for the stakeholder interval analysis. We also thank the many stakeholders who attended consultations in Derby (WA) and Richmond (Qld), and Damian Shepherd (Western Australia Department of Agriculture and Food), Brad Moore (Department of the Environment, Water Heritage and the Arts), and Rosemary Niehus (Queensland Herbarium) for providing spatial data.