It should be noted that this data is now somwhat dated!
Soil degradation refers to any deterioration in the natural physical, chemical
or biological properties of a soil, and is a function of soil texture, soil
fabric, soil fauna and mineral and organic matter content. Soil degradation
reflects the unsuitability of a land-use / management practice on a particular
soil type, and manifests itself as soil erosion (eg. loss of the topsoil),
compaction a causing loss of water holding capacity and permeability changes,
acidification, salinisation, etc.
This issue is particularly relevant to property scale planning and management,
but off-site impacts can also be significant. Soil degradation is sensitive to
catchment scale changes, particularly where the change is direct.
The soil properties that affect land management, as identified within the
Atlas of Australian Soils, have been rated according to their potential to
degrade under the land-uses practiced upon them. The land-use data has been
rated by intensity into 10 classes. Both ratings are based on expert opinion.
The two rating systems have been combined spatially to produce a land-use
practice-soil vulnerability surface, which has been re-classified into 5
classes ranging from low soil degradation hazard (nature conservation areas
and/or soils having negligible physical and chemical limitations) through to
high hazard (i.e. high intensity land-uses on highly vulnerable soils). The
quality and reliability of data is limited by the coarseness of the soils
mapping and the difficulties of defining soil classes over vast areas of
inherently heterogeneous soil mosaics.
Soil degradation hazard is an issue in many parts of the mid Murray-Darling
Basin (Murrumbidgee, Murray-Riverina, Avoca and Loddon River basins) because
of limy, powdery soils. This can cause poor crop response, and leave bare
erodible ground. The biophysical impacts include loss of topsoil nutrients and
organic matter. This results in vegetation re-establishment difficulties and
the loss of biodiversity.
In Queensland, the main soil management concerns are on the central to
northern coast and correspond with sulphidic, waterlogged and sodic soils
(Burdekin, Don, Haughton, Fitzroy, Calliope, Boyne and Ross Rivers).
Engineering works associated with land development and other kinds of
disturbance, including drainage, cultivation and irrigation, have caused the
sulphidic soils to be oxidised, causing sulphuric acid release to waterways.
In these areas, sodic soils readily disperse and erode, causing turbid
streams. In South Australia the catchment with the poorest rating is the
Myponga River catchment. In Victoria the Barwon, Moorabool and Werribee River
basins have poor ratings. In Western Australia the catchments with poor
ratings are the Esperance Coast, Frankland, Blackwood, Avon, Moore-Hill, Yarra
Yarra Lakes and Murchison River basins.
Data are available as:
- continental maps at 5km (0.05 deg) cell resolution for the ILZ;
- spatial averages over CRES defined catchments (CRES, 2000) in the ILZ;
- spatial averages over the AWRC river basins in the ILZ.
See further metadata for more detail.
