Trouble on the range

The rangelands are a mix of ecosystems occupying more than 75 per cent of Western Australia and may be defined as areas where the growing season is too short or variable to sustain intensive agriculture. About half of these lands are used for grazing sheep and cattle. Conditions are harsh. The climate is characterised by long periods of little or no rainfall, followed by torrential downpours and floods. The soils of the rangelands are shallow and infertile, and this, in combination with the arid conditions, results in a sparsely vegetated, fragile environment. These environments are affected by various forms of land degradation.

The pastoral industry, the major land user of the rangelands, is considered to be the prime contributor to this degradation. Other causes are the decline of traditional Aboriginal practices, and the mining industry.

Vegetation decline

Initially, extensive clearing by landholders of the natural vegetation was the main cause of land degradation. This is turn created other environmental problems such as loss of biodiversity, salinity, water logging, acidification and eutrophication. Where there is serious vegetation decline, wind and water erosion occur. Loss of habitat and general ecosystem degeneration usually follows.

Ungrazed areas are not immune from such changes in their vegetation. In the absence of local burning practices by Aborigines, wildfires have contributed to the extinction of many small marsupials this century. Direct costs in terms of lost production total about $44 million a year.

What causes vegetation decline?

Vegetation decline, and the accompanying erosion, is mainly caused by overgrazing by domestic stock, often made worse by additional grazing pressure from other animals. On the Nullarbor Plain, rabbits contribute significantly to overgrazing; in the Gascoyne and Murchison districts, kangaroos; and in the Kimberley, feral donkeys have had a similar effect. Feral goats are an additional problem in the Gascoyne and Murchison.

Insects are also important as consumers of arid vegetation. Termites are capable of eating as much vegetation as a commercial cattle herd. When trees and shrubs are lost from areas, the impact of termites can add to the rate of vegetation degradation. Periodic plagues of caterpillars and grasshoppers also have severe local effects.

Bushfires occur naturally and are essential in maintaining many types of grassland ecosystems in the rangelands. They are rare and can be dangerous in other types of country, such as mulga or bluebush shrublands.

Rangeland regeneration

Restoration of rangelands is difficult for several reasons:

• areas under regeneration may go without rainfall for many months;
• huge areas are involved;


• fencing is costly;


• income to be gained from rehabilitation per unit area is low;
  mechanical treatments are expensive; and


• seeding is expensive.

Proper management plays an important role in rangelands regeneration. Key strategies includes planning the placement of stock watering points so that damage is minimised; locating fences along natural boundaries; and most important of all, adopting appropriate stocking policies. This may mean complete destocking in some areas and strict control of stocking rates in most other areas.

Grazing pressure by native (and especially feral) herbivores also needs to be controlled by effective fencing. Solar powered electric fences are increasingly being employed in this way. Station managers are advised and encouraged to adopt conservative stocking regimes over regenerated areas.

Monitoring the range

Plant inventory surveys and monitoring allow decision making on the basis of scientific data. The surveys map and catalogue plant resources and give an indication of their present state. From this information, appropriate stocking rates are recommended. Permanent monitoring sites allow land managers to assess trends in species growth and composition.

What about the kangaroos?

Kangaroos and feral goats, camels, donkeys and wild horses can limit regeneration even after the removal of domestic stock. In rangeland areas in need of special protection from kangaroos, the Department of Conservation and Land Management monitors the population. Culling of excess kangaroo populations is possible by obtaining a special shooting licence from the department. A quota is stipulated in the State kangaroo management program.

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