The environmental problem

During the last 10 years cattle exports from northern Australia to South East Asia have increased. This has resulted in increased pressure on the tropical rangelands. In order to achieve sustainable use of these rangelands a better understanding of their ecology, structure and functioning, is required (Ludwig et al., 1999).

Grazing cattle 21kb

Background and significance of the study

Trees and perennial grasses in the tropical north of Australia rely on being able to capture and store water and nutrients during the wet season for their growth and survival in the dry season. In the Kidman Springs area the median rainfall is about 640mm, largely in summer.

If plants are unable to capture and store water and nutrients they become stressed, especially in the late dry season, which results in increased plant mortality, particularly amongst those plants which are susceptible to grazing and fire.

The loss of plants can also have a knock on effect in terms of a loss of diversity of species of fauna that depend on these plants for their survival.

Vegetation patches are important for capturing and conserving these water and nutrient resources. Grass clumps form traps for water and nutrients flowing in to the landscape.

Where landscapes have lost vegetation patches they have a reduced capacity to capture and store scarce resources. Overgrazing can result in loss of patches and subsequent soil erosion.

Cattle tend to focus grazing and trampling near to watering points, so a watering point is used in this study as a surrogate for a gradient in grazing pressure (Ludwig et al., 1999).