Economic Modelling of Dryland Salinity in Western Australia

The clearing of land for agricultural purposes in the low rainfall areas of south-west Western Australia has resulted in soluble salts being transported from upslope recharge areas, through groundwater flows, to downslope discharge areas. Dryland salinity is not confined to individual properties. It may disperse among properties and catchments and is thus a common property problem. In an attempt to model the effect of natural resource utilisation and the divergence between private and socially optimal rates of land degradation resulting from the exploitation of common resources, a dynamic optimisation model of soil salinity has been developed. The objective of soil conservation models may not necessarily be to stop future degradation in its entirety, but to ensure that all resources are applied to their highest value combination of end uses, both currently and in the future (Morris et al, 1988). The model is also used to examine the steady-state solution to optimal control. In the case of dryland salinity, a steady-state equilibrium occurs when the hydrological balance is in equilibrium. Salinisation of dryland areas has been caused predominantly by the removal of high water-using, deep-rooted native forest, and its replacement with shallow-rooted annual crops and pastures. Agricultural expansion in the low rainfall areas of south-west Western Australia has modified the natural water balance, thereby affecting the volume and flow of surface and ground water. The resultant change in the hydrological balance of the soil brings rising water tables and stored salts to the surface, and evaporation causes these salts to be left behind

Environmental indicators for Australian cities: report on the 1997 national State of Environment study on human settlement indicators

State of the Environment Australia 1996 (SOEAC, 1996) represents the most comprehensive attempt, to date, of reporting on the condition of Australia's natural and built environments. Human Settlements (Newman et al., 1996) was selected as the first substantive chapter in this 500 page report in part because human settlements constitute a significant 'environment' in their own right as well as impacting pervasively upon Australia's natural environment (as represented by the atmosphere, land resources, biodiversity, inland waters, estuaries and marine). This dual characteristic of human settlements is reflected in the set of environmental indicators being developed as part of the present phase of the SOE Reporting process (Newton et al., 1998). In the 1996 Report, Australia's urban, rural and remote settlements were each examined separately in the context of their own characteristic 'environmental' pressures, states and responses (P-S-R). In the present phase of SOE reporting, a set of key and core indicators of human settlements are being sought that represent P-S-R at a range of spatial scales in the urban hierarchy. In this paper we explore the underpinning concepts, frameworks and models that are being employed in developing environmental indicators for human settlements in contemporary Australia. An over-arching concern is that indicators reflect a thorough understanding of the systems they are to monitor. In this regard, the extended metabolism model acts as a highly useful conceptual representation of human settlements, in that it is both descriptive-identifying the primary domain areas of urban systems such as energy, transport, housing, etc., which key indicators are developed-and normative-specifying desired directions for future urban development