Whatever happened to dryland salinity? A review of the Australian salinity agenda; management for sustainable productivity and climate change effects.
In the not too distant past, dryland salinity in Australia was considered to be one of the nation's greatest environmental concerns. All States were involved, with significant amounts of public money being spent on the issue. Statements referring to it as an "awakening monster from the deep" and "the creeping white death", publicised on Federal websites such as the Australian Academy of Sciences and CSIRO, indicated the level of national concern. The causes have been attributed to an excess of water in the landscape, mobilising deep ancient salinity stores and bringing previously dormant salts to the surface. Dryland salinity is listed as being a 'threatening process' to biodiversity, killing native fauna and flora and apparently favouring exotic species, despite Australia being one of the naturally saltiest places on earth. The research reported here in upland catchments of NSW challenges these views, the generally accepted model of the processes driving secondary dryland salinity in most uplands of the Murray Darling Basin is at odds with field observations. Holistic biotic and abiotic measurements taken in grassy woodlands exhibiting various degrees of increased salinisation, to investigate the fundamental processes operating within and between the regolith and surface/subterranean biota, show that elevated salinity levels are a localised, soil surface process associated with vegetation/soil degradation and subsequent increased soil evaporation rates. No cause-effect relationship was established linking increased salinity levels to native fauna or flora mortality. Many native species flourish in such environments, as can be expected, having co-evolved with salty and sodic soils. The results have implications for appropriate salinity mapping, modelling and management activities. This includes the issue of a warming climate regime and the likelihood of increasing soil surface evaporation rates, hence, increased salinisation associated with soil and vegetation degradation.