Impacts of rehabilitating degraded lands on soil health, pastures, runoff, erosion, nutrient and sediment movement. Part IV: The Kimberley rehabilitation programs and lessons for the Great Barrier Reef catchments

Abstract

There were extensive areas of bare, eroded and scalded soils and clay pans, all D-condition land, on the properties of Ord, Turner, Fox Rivers and parts of Flora Valley, Elvire, and Ruby Stations in the Ord River catchment covering some 46,700 km2. Some of these properties were eventually resumed and amalgamated by the Government as the Ord River Regeneration Reserve (ORRR). The aim was to reduce sedimentation of Lake Argyle on the Ord River, which was built for irrigation of down-stream flood plain areas from Kununurra. Government ownership allowed full control for new fencing, artificial water points and cattle management, so all grazing was prevented, with the removal of cattle, donkeys, and camels. On-ground mechanical disturbance and seeding with predominantly Cenchrus spp. and Aerva javanica, began in the early 1960s to revegetate these eroded plains. Artificial water sources were closed to reduce potential grazing influences, although there are water holes present in major rivers, most of the area has no grazing to the present. Marsupials are confined to a limited distance from natural water holes in creeks and rivers. The ORRR is now rehabilitated by Cenchrus species pastures, with C. setiger being a dominant grass, and it is managed by the WA Department of Parks and Wildlife. The original native pasture species have not become dominant at this time. Any feral animal grazing and cattle incursions from neighbours are managed and animals may be shot. The undulating to flat, D-condition country was successfully rehabilitated over some four decades by aggressive mechanical disturbance, sowing well adapted tropical exotic pasture grass and forb species, total grazing control, and a run of consecutive above average rainfall seasons. There are similar issues and many lessons from this rehabilitation program that are relevant for rehabilitating degraded landscapes in the grazing lands of reef catchments in Queensland.