A continental landscape framework for systematic conservation planning for Australian rivers and streams

Abstract

Conservation of Australia’s distinctive river ecosystems has lagged behind that of terrestrial and marine environments despite mounting evidence of the destructive effects of human activities. There has been little nationally coordinated conservation activity. A systematic, continent-wide conservation planning approach would ensure limited conservation resources are allocated efficiently and decisions are accountable. This thesis addresses critical gaps in the spatial data required for systematic conservation planning. It describes the development of a stream network and nested catchment reference system to provide the spatial framework. This framework, at a map scale of approximately 1:250,000, supplies planning units for application of reserve design algorithms and determination of priorities for protective management as well as units for reporting conservation evaluation and assessment. The Pfafstetter coding of the catchment units identifies drainage network connectivities allowing them to be readily incorporated into conservation planning procedures. This thesis presents for the first time a comprehensive picture of continent-wide variation in the landscape factors that ultimately control riverine ecosystem patterns and processes. Stream segments, the section of the stream between tributary confluences and the smallest unit in the spatial framework, have been individually characterized and classified at multiple scales using attributes that describe the catchment (and/or sub-catchment) climate, water balance, geology, terrain and vegetation. Segments were clustered according to their similarity in environmental data space so that, unlike ecoregion classifications, groups may be geographically dispersed. The resulting River Environment Types have been found to differentiate significant variation in stream biota (macroinvertebrates and fish) and habitat characteristics. However, classification strength varies widely among types. It is hypothesised that this is due to both classification uncertainty and limitations of the test data. The spatial framework and classifications are the central elements of a continental landscape framework that could be used to support systematic conservation planning and assist the development of a national conservation plan for Australia’s rivers and streams. The framework could also provide the basis for an online information system to serve a broader range of NRM planning and management objectives. The utility of the continental framework has been demonstrated in a review of the National Reserve System (NRS). The review acknowledges some uncertainty in the results due to inaccuracies and limitations of the framework, but nevertheless, concludes that the NRS must be expanded if it is to achieve a comprehensive and adequate protected area system for river ecosystems. This study makes major contributions to spatial analysis methodology. It has developed and applied a new method of drainage analysis applicable to diverse drainage structures at continental scale and recommends enhancements to the internationally adopted Pfafstetter scheme. It also advances understanding of the role for landscape classification and the influence of classification choice on conservation planning outcomes. The development of the continental landscape framework for Australia presents a model and the necessary tools for conservation planning for the rivers and streams of other continents.