Document ID: chunk:federal_register_of_legislation:F2017L00641:body:0:p25
Version: federal_register_of_legislation:F2017L00641
Segment Type: other
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Character Range: 79300–82258

to marine turtles in Australia, noting the current management in place to address the threat.
Threats are listed in order of priority based on the number of stocks found to be at 'high' or 'very high' risk through the threat prioritisation assessment process (Section 4.4), which takes into account existing mitigation.

4.1 Description of threats

4A Climate change and variability
Climate change is of particular concern to marine turtles because it is likely to have impacts across their entire range and at all life stages. Climate change is expected to cause changes in dispersal patterns, food webs, species range, primary sex ratios, habitat availability, reproductive success and survivorship[69, 83, 96]. Impacts will differ based on the ability of a stock to adapt to changes in suitable nesting beaches and food availability.
Predicted increases in sand temperature may result in changed sex ratios or decreased hatching success[70, 95, 212, 217, 260]. Changes to water temperature may affect ocean circulation and dispersal patterns, timing of breeding, as well as result in coral bleaching and seagrass die off, which may affect turtle foraging[69].
Green and hawksbill turtles in the Arabian Gulf have shown adaptations to high ambient water temperatures[186] and a genetic mechanism has been found in loggerhead turtles that may allow embryos to develop tolerance to higher sand temperatures[216]. Increasing loggerhead and green turtle nesting is being recorded in New South Wales each year (Crocetti, pers. comm. 2016). It is possible that marine turtles may be nesting further south in response to climate change impacts. These findings indicate the possibility that given sufficient time and availability of suitable habitat, those species of marine turtle that nest in summer may be able to behaviourally adapt to changing temperatures[186] by changing the timing of nesting or moving to beaches at higher latitudes. Winter nesting turtles cannot shift to a cooler time of year and may only be able to adapt by shifting their nesting southwards[212]. However, sea level rise and associated risk of nests flooding may complicate hatchling success, as the magnitude of sea level rise is expected to be greater at more southerly latitudes, particularly for Western Australia[25].
Increased frequency of extreme weather events may lead to reduced or altered nesting habitat, and increased egg mortality through inundation or scouring[67]. These issues have been identified as a particularly threatening process for the northern Great Barrier Reef green turtle stock (including Raine Island)[70]. Increased frequency and intensity of heavy rain events, also means an increase in the risk of extreme flooding events[61], which can exacerbate the mobilisation of sediment and chemicals into the marine environment.
Changes to ocean circulation patterns and altered marine food webs will have substantial impacts on turtles during multiple phases