GREAT BARRIER REEF
// Outlook Report 2014
changes to groundwater and weed infestations.189 In areas where ecological function of freshwater wetlands is good, water quality and coastal habitats tend to be in better condition than where it is lost or modified.214 As the accuracy of mapping of wetlands improves, estimates of their extent and loss are refined, especially for infrequently inundated wetlands on highly developed coastal floodplains. In some coastal floodplain basins (for example the Barron, Kolan and Johnstone rivers) up to 80 per cent of freshwater wetlands have been lost.189 The rate of wetland loss has slowed in recent years.189
3.5.3 Forested floodplains
Freshwater wetlands capture and recycle nutrients
Forested floodplains help slow, capture and recycle nutrients and sediments and are important nursery areas for many species with connections to the Great Barrier Reef.189 Forested floodplains also protect the soil surface from the erosive forces of rain.189 Since European settlement, the area of forested floodplain has been reduced by nearly 50 per cent across the catchment.189 The largest loss is in the Fitzroy basin which is estimated to have lost 6638 square kilometres of forested floodplains. Much of its remaining 12,700 square kilometres extent is grazed.189 The habitat has been affected by clearing and land modification, changes to overland and groundwater flows, weed and pest invasion, water extraction and reduced connectivity.189
The area of forested floodplain has been halved and much of it is grazed.
3.5.4 Heath and shrublands
Heath and shrublands help slow the overland flow of water; prevent erosion; recycle nutrients and sediments; and are important as buffers on steep coastal hill slopes.189 Approximately 94 per cent of the heath and shrublands in the catchment remains intact, with about 78 per cent protected in national parks, conservation areas and state forests.189 Almost 70 per cent of the current total area of heath and shrublands occurs in the Cape York region.189
3.5.5 Grass and sedgelands
Grass and sedgeland habitats occur throughout the catchment. They are typically composed of perennial native grasses with no canopy of trees. The habitat is used for feeding and roosting by migratory birds; helps slow the overland flow of water; and captures nutrients and sediments.189 Little modification has occurred in the Cape York region.189 The greatest loss has been in the Burdekin and Fitzroy regions where more than 40 and 60 per cent, respectively, of the habitat has been lost. Coastal grasslands have been extensively modified for agricultural production or urban settlements, particularly in the Burdekin and Fitzroy regions.189
Grasslands and sedgelands have been modified extensively in southern catchments, especially close to the coast.
3.5.6 Woodlands and forests
Woodlands and forests regulate sediment and nutrient supply to the Great Barrier Reef and reduce flooding by slowing the overland flow of water.189 They also indirectly influence the ecosystem through their contributions to the hydrological cycle, for example evapotranspiration, cloud formation and rainfall generation.189 The extent of woodlands and forests varies throughout the catchment. There have been significant losses of woodland habitats in the Burdekin and Fitzroy regions and an average loss of 39 per cent throughout the catchment.189 It is estimated that the total loss of forests and woodlands since European settlement is 134,754 square kilometres.189 Forests in the Cape York and the Wet Tropics regions have remained largely intact. The loss of woody vegetation is thought to be due mainly to clearing for agriculture and, to a much lesser extent, urban development.189