Prioritising catchment agricultural management practice change through marine risk assessment in the Great Barrier Reef

The iconic Great Barrier Reef (GBR) in Australia faces continuing and increasing threats from human activities including climate change, agricultural pollution and large scale port development pollution. The current degradation of many GBR ecosystems including, for example, reduction in coral cover and seagrass health and severely reduced dugong populations are linked to declining water quality in the GBR. Suspended sediment, nutrients and pesticides loads discharged to the GBR from agricultural and coastal development have increased greatly in the last 150 years. These pollutants disperse into the GBR during high flow river discharge and damage GBR ecosystems including coral reefs and seagrass meadows. Reef Plan, the joint Australian and Queensland Governments program to address land-sourced pollution, provides funding to farmers, matched by the farmers themselves, for improved management practices to reduce pollution. A requirement of a cost effective program of this type is the ability to prioritise where and how such funding should be applied in the GBR Catchment. We have developed and applied a risk assessment method to inform investment prioritisation and guide policy makers and catchment managers on the key land-based pollutants of greatest risk to the health of GBR coral reefs and seagrass meadows. The risk assessment uses a Multi Criteria Analysis approach with qualitative and semi-quantitative information on the influence of individual rivers in the 6 natural resource management (NRM) regions on coral reefs and seagrass meadows. Relative risk was estimated from the habitat areas (coral reefs and seagrass) exposed to defined pollutant thresholds (observed or modelled) and this was combined with river pollutant load information to develop priorities for regional management areas within the GBR Catchment. The assessment showed distinct differences between NRM regions and between catchments within the regions in terms of potential impact from each pollutant and for coral reefs and seagrass meadows. The results, in conjunction with information on pollutant generation from dominant land uses in the GBR Catchment, are used to inform investment priorities both between and within NRM regions