A delicate balance
Australia’s arid and semi-arid grasslands are home to an economically very important form of extensive livestock farming. The distinctive feature of the climate in these regions is the short rainy season followed by a long dry season and it is the availability of water and vegetation that determines the size of herds. The grasslands are also fragile and overgrazing always brings the risk of land degradation. This is why it is important for the livestock farmers to keep a close eye on the condition of their pastures and to adapt management practices where and when necessary. Is it preferable, for example, to allow the cattle to graze freely over large areas of grassland or to rotate them in smaller confi ned pastures? However, it is not easy to assess the condition of the grasslands. Recent vegetation maps are non-existent, the livestock farms are huge, and the grasslands are in a state of imbalance. The very irregular rainfall also results in wide short-term variations in vegetation cover that can conceal the longer term deterioration of the grasslands, symptoms of which are the appearance of bare earth and a shift from perennial to annual grass varieties. It is therefore important to differentiate changes in the grasslands that are the result of grazing from natural changes in the vegetation. Earth observation can help in this.