The environmental problem
The rangelands that take up about 70% of Australia's land mass are largely used for pastoralism and tourism which both require maintaining natural ecosystem processes. Conditions are often harsh with unpredictable rainfall and infertile soils, making the survival difficult if the natural balance is altered.
More than half of the species of endangered mammals in Australia live in the rangelands along with about a third of its threatened birds, one of the 11 threatened reptile species, and half the throated species of plants (CSIRO, 1996). One third of the mammal species that lived in the rangelands prior to European settlement are now extinct and many are threatened.
One of the many factors causing landscape change in the New England tablelands is disturbance. This can be either natural or human in origin, the result being visible or invisible land transformation.
These landscapes are suffering declines in vegetation patches, which are important for landscape functioning. There are also problems with exotic species, such as introduced predators like foxes and cats, which can kill natives.
Kangaroos are also a problem in some locations because the provision of watering holes, as a result of pastoralism, has caused their populations to increase to unsustainable levels.
Different levels of intensity of grazing affect the composition, richness and abundance of native species as well as the structure and functioning of landscapes. Feral grazers such as rabbits and goats, horses and camels are in competition with native grazing animals and domestic livestock and cause land degradation problems through over grazing.
The study of grazing gradients is one way CSIRO is examining the impact of grazing on the rangelands.
Intensity of grazing tends to drop off as the distance from permanent watering points increases. In areas of uniform vegetation the result is a constant gradient away from the water, but in varied vegetation, grazing gradients can be obscured by animal's preferences for different vegetation types.
To be away from the influence of water dependant grazing stock, it is necessary to go more than 10km away from water. CSIRO have been using GIS and RS to locate good reference and experimental sites so they can survey biodiversity at distances from watering points. RS is used to assess the pattern of the country at each study site. For example, the CSIRO project looking at grazing gradients in the Kidman Springs area of the Victoria River Downs region.
