Identifying trends in land degradation in non-equilibrium rangelands.
Abstract
The use of changes over time in the pattern of vegetation growth across gradients of differing grazing intensity to identify trends in range condition in arid Australian rangelands is discussed. Grazing intensity was measured indirectly using distance from water. Vegetation growth was derived from remotely sensed vegetation index values before and after large rainfalls. The amount of growth was adjusted for initial vegetation cover to give a standard measure of vegetation response. A vegetation response ratio was derived by comparing areas less than 4 km from water with benchmark areas further away. Systematic changes in this ratio over time indicate a trend. Ratio values from test areas suggested decline, improvement and no change, consistent with recent management history. The method can be applied where the whole area is affected by grazing and relatively pristine benchmarks are unavailable. It could therefore be useful in the semi-arid rangelands where paddocks are smaller than in the arid part of Australia. It is suggested that the method also has possible uses in the rangelands of Africa and the Americas. The method is cheaper and more effective than other techniques and increases the capacity of grazing gradient-based monitoring schemes for arid and semi-arid areas.