Vulnerability of sea turtle nesting grounds to climate change

Given the potential vulnerability of sea turtles to climate change, a growing number of studies are predicting how various climatic processes will affect their nesting grounds. However, these studies are limited by scale, because they predict how a single climatic process will affect sea turtles but processes are likely to occur simultaneously and cause cumulative effects. This study addresses the need for a structured approach to investigate how multiple climatic processes may affect a turtle population. Here, we use a vulnerability assessment framework to assess the cumulative impact of various climatic processes on the nesting grounds used by the northern Great Barrier Reef (nGBR) green turtle population. Further, we manipulate the variables from this framework to allow users to investigate how mitigating different climatic processes individually or simultaneously can influence the vulnerability of the nesting grounds. Our assessment indicates that nesting grounds closer to the equator, such as Bramble Cay and Milman Island, are the most vulnerable to climate change. In the short-term (by 2030), sea level rise will cause the most impact on the nesting grounds used by the nGBR green turtle population. However, in the longer term, by 2070 sand temperatures will reach levels above the upper transient range and the upper thermal threshold and cause relatively more impact on the nGBR green turtle population. Thus, in the long term, a reduction of impacts from sea-level rise may not be sufficient, as rookeries will start to experience high vulnerability values from increased temperature. Thus, in the long term, reducing the threats from increased temperature may provide a greater return in conservation investment than mitigating the impacts from other climatic processes. Indeed, our results indicate that if the impacts from increased temperature are mitigated, the vulnerability values of almost all rookeries will be reduced to low levels.