Marine Science, Coastal Dynamics and Management

Coasts worldwide are ravaged by major storms. Planning on exposed coasts requires an understanding of the impacts of previous storm events. The approach taken for storm protection in this project was to re-establish native dune ecosystems with their inherent ability to withstand and recover from storms, rather than to construct a rigid engineered seawall. The May-June 1974 storms on the Australian east coast provided an impact benchmark for the likely "1 in 100-year events" for the Magenta Shores project. The calculated storm bite on previously mined Magenta beach dunes was up to 300m3 of sand per linear meter. Mineral sand mining resulted in highly erodible loose quartz sand, 'stabilized' by the South African Chrysanthemoides monilifera subsp. rotundata (bitou bush). These highly degraded coastal ecosystems were on irregular landforms with a reduced occurrence of soil binding fungi and associated native host plants. Regular monitoring showed that colonization occurred in stages, with increases in diversity dependent on the ongoing removal of dense bitou seedlings. The primary colonizing species Spinifex sericeus and development of a fungal network were essential for secondary colonizing species Acacia longifolia subsp. sophorae. Within three years, native species dominated the stabilized dune ecosystems. The dune shape depended on establishing the prostrate primary colonizer Spinifex, and maintaining the shape and sand volume was dependent on the sand grain-trapping mechanisms of the fungal hyphae and their host plants. Overall, the project demonstrated the importance of mimicking natural processes–by allowing windblown sand to form crests and swales parallel to the beach; creating protected fibrous coastal tea-tree windrow microenvironments; burying Spinifex seedheads in the moist sand layer for primary colonization of the reconstructed dune and establishing primary colonizing native vegetation cover and associated fungal hyphae.