Document ID: chunk:federal_register_of_legislation:F2023L00138:front:0:p14
Version: federal_register_of_legislation:F2023L00138
Segment Type: other
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Character Range: 36569–39699

which has experienced reduced rainfall over the past few decades. The Western Australian Australasian Bittern Recovery Plan identifies climate change (i.e. changes in precipitation and evaporation rates) as one of the primary threatening process to Australasian Bittern populations (Pickering 2013, DBCA 2018). A drying climate reduces the peak water level and peak area of wetting in wetlands, which effectively reduces the quality and quantity of breeding wetlands and drought refuges available. Seasonal wetlands are also experiencing reduced inundation periods, increasing the risk of wildfire at these sites.

   In the Murray–Darling Basin a major concern is an increased frequency and intensity of droughts which is likely to exacerbate the already extreme fluctuations in wetland habitat availability combined with seasonal shifts in rainfall. In dry periods there is also less water available for rice farming, which supports around 59 per cent of the national population, and greater pressure on rice farmers to use water-saving agronomy or switch to alternative crops like cotton (Herring et al. 2019a).

2.2.4     Reduced water quality
             Reduced water quality due to increased salinity, acidification, siltation and pollution is having an ongoing impact on the species' habitat. In the wheatbelt of inland south western Australia, historical clearing of extensive natural woodlands for crops and sheep farming has led to rising water tables which has increased salt levels on and near the land surface, including in wetlands and waterways. Salinisation of wetlands can alter the vegetation and faunal characteristics at a site, resulting in wetlands that no longer meet the ecological requirements of Australasian Bittern. Salinisation has impacted hundreds of inland and south-eastern coastal swamps and has excluded the Australasian Bittern from former inland locations (Jaensch 2004). For example, Yarnup Swamp in the Muir–Unicup wetlands has not been used by the Australasian Bittern since the mid-1980s because of its high salinity. Since Cobertup East Swamp in the Muir-Unicup wetlands became acidified in 2005, Australasian Bittern has no longer been recorded at this swamp (Pickering 2013).

             Siltation in waterways occurs due to reduced vegetation cover in catchments resulting from human landuse. At the mouth of the Snowy River, Victoria, siltation has caused the back flow of saline water which has destroyed the species' reed-bed habitat in Lake Corringle in Victoria. Consequently, the Australasian Bittern is no longer found at this location (Birds Australia 2009).

             In the Murray–Darling Basin salinity is a major problem causing extensive degradation in some areas (Kingsford 2000). Elevated salinity could also negatively affect Australasian Bittern prey sources, such as invertebrates.

             The regulation of river flows has the potential to reduce water quality by excessively raising or lowering water temperatures, reducing dissolved oxygen levels and increasing nutrient and contaminant loads (Kingsford 2000). These changes can result from altered