Aims of this survey
The need for this survey was triggered by observations of severe erosion and rangeland degradation in the West Kimberley up to 1970. The survey was planned to:
- define the extent, location and severity of erosion and pasture degradation in each land system
- map the land systems and pasture lands
- report for each station the land systems, pasture lands, erosion, pasture condition, optimum and recommended carrying capacities, and regeneration needs in terms of livestock control and rangeland management practices
- formulate rangeland condition guides for pasture lands in each land system to define:
- optimum condition of soil and vegetation
- types of erosion and pasture composition trends likely on pasture lands at different condition levels
- the carrying capacity of each pasture land at different condition levels.
Survey area and inventory summary
The West Kimberley region of Western Australia was surveyed in 1972 by A Kubicki, LC Short, DG Wilcox and AL Payne and the results were published in 1979 as Technical bulletin 42 A report on erosion and range condition in the West Kimberley area of Western Australia.
The survey covered about 89 600 square kilometres (km²) in the catchments of the Fitzroy, Lennard, Meda and May rivers.
The survey found that the worst-affected pasture lands were:
- frontage grass and black soil plain pastures closely associated with the major rivers
- frontage grass and ribbon grass pastures of drainage floors, plains and valleys
- white grass/bundle bundle pastures of valleys with basaltic red earth soils in the east and north-east of the survey area
- short grass pastures of undulating interfluves and alluvial drainage floors in the central and eastern parts of the survey area.
The survey report provides condition statements – for the time of the survey – for the whole survey area and for each land system. Pasture condition and soil condition were assessed at points throughout the survey area.
The survey found that:
- nearly 20% (17 500km²) of the survey area was in good rangeland condition – this country consisted mainly of poorly accessible land systems and systems supporting low quality spinifex pastures
- nearly 51% (45 400km²) of the area was in fair rangeland condition
- nearly 30% (26 700km²) of the area was in poor rangeland condition – pastures were degraded to poor or very poor condition and moderate and severe erosion was widespread
- the worst areas of degradation and erosion were on the most valuable pasture lands.
The report recommended that about 6920km² of poor condition rangeland be removed from the area being grazed, within 3 years, to prevent irreversible degradation.