Jane Chambers

Large areas of the Australian continent are currently affected by secondary (anthropogenic) salinisation. In some parts of Western Australia, particularly the ‘wheatbelt’ region which lies between the 600 and 350 mm rainfall isohyets, salinisation, primarily as a result of land clearing and the associated rise in saline watertables, has been occurring for over a century (Hatton et al. 2003, Figure 1). As a consequence, very few freshwater systems remain in this region, and in order to manage the changing landscape, a key question facing natural resource managers is which physicochemical or ecological thresholds have most importance in the change from saline to hypersaline conditions? Knowing this will allow these systems to be managed so that further losses of ecological function and biodiversity can be prevented. This chapter considers the broad ecosystem changes that occur when salinity rises in waterbodies with salinities ranging from hyposaline to hypersaline (see Box 1).The research question explored in this chapter is ‘do well-defined thresholds exist that signal a change in ecosystem structure and function when moving from saline to hypersaline ecosystems?’

This review deals with the establishment of wetlands on land affected by mining, but it is useful to recall that the mining industry may have an impact in a number of ways, including direct impacts on existing wetlands, for example, physical obliteration, altered groundwater contours, heavy metal contamination, and eutrophication (nutrient enrichment and its consequences). Our emphasis is not so much on these impacts, or on techniques to rehabilitate wetlands after such disturbance, but on creating wetlands as a form of rehabilitation of mined lands rather than returning them to agricultural or forest production. However, some of these impacts leave a heritage that must be taken into account when attempting to create wetlands in a landscape affected by mining.