Date of this Version
Defining and categorizing drought in a quantitative and scientific manner are important national issues for Australian state and Commonwealth governments, landholders, and agribusiness. The challenge for modelers of Australia’s grasslands is to integrate biological models, geographic information systems (GIS), satellite imagery, economics, climatology, and visual high-performance computing into an Internet-deliverable application that can provide easily understood monitoring and prediction advice in near real-time— a national drought alert strategic information system.
Although NOAA satellite-derived imagery has been somewhat useful in the broad-scale spatial assessment of green cover, especially the spatial response of vegetation to rainfall events (Smith, 1994; Dudgeon et al., 1990; Filet et al., 1990), it has inherent limitations in providing a total solution for drought and rangeland monitoring; biomass relationships are not good, tree cover confounds the signal, and a future projection of the current situation is not inherent. Also, the interpretation of the imagery does not usually consider the effects of soil type, vegetation structure, or rangeland “condition.” Similarly, rainfall analyses alone do not necessarily reflect the quantity and quality of pasture available on the ground. In the recent 1991–95 record-breaking drought in Queensland, rainfall analyses did not map the drought-declared southwestern areas of the state as droughted, and, conversely, coastal areas of the state were classed as droughted by rainfall analyses, when there was no community push for their declaration. Measures of rainfall effectiveness expressed as measures of plant biomass are required for drought definition. Improved assessments of the quantity and quality of biomass are needed, as well as consideration of herbivore densities and future climatic scenarios.