EAPSI: Linking Grazing Management and Gully Erosion to Water Quality in the Great Barrier Reef

Miller Hennessy F, Tucson AZ

Investigators

Abstract

The Great Barrier Reef (GBR) off the coast of Queensland, Australia, is the world's largest and most biodiverse coral reef system, but its health and survival is threatened by a number of external factors. This project aims to investigate one threat--decreased water quality in the GBR lagoon--by linking the impacts of long-term grazing management with sediment export and erosion in the Burdekin Basin. Though the impacts of land-cover on gully erosion have been well documented through small-scale, plot-based experiments, there is little knowledge of the long-term effects of historical grazing management to gully activity and rate of expansion. This research will be conducted in collaboration with Dr. Scott Wilkinson, an expert in gully erosion, at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Canberra, Australia. By comparing historical records and vegetation surveys, this research will provide a quantitative analysis of gully erosion in upland rangelands, aiding CSIRO and the Australian government in the effort to improve water quality and preserve the Great Barrier Reef. Seawater temperature rise, ocean acidification, and decreased water quality in the GBR lagoon are causing considerable degradation and mortality to the GBR. CSIRO attributes 40% of all fine sediment imported to the GBR lagoon to rangeland gully erosion in the catchment basins. Erosion is directly linked to land-cover; studies in the GBR have shown that a 5-15% increase in vegetation cover can reduce sediment erosion by 35-60%, thereby decreasing sediment yield and improving water quality in the GBR lagoon. However, there is little knowledge about the long-term effects of grazing management and gully activity. For specific gully-prone soil types, this project will evaluate the long-term effects of different grazing management and stocking rates on gully stability by comparing historical remote sensing imagery of vegetation cover to surveys of gully stability at 10-20 different properties. This research project aims to provide a quantitative assessment of grazing and erosion and determine criteria to identify zones exceedingly vulnerable to over-proportioned sediment export for priority preventative management. This award, under the East Asia and Pacific Summer Institutes program, supports summer research by a U.S. graduate student and is jointly funded by NSF and the Australian Academy of Science.