Project 1.4.1

Vulnerability of sea turtles to climate change

Project Leader: Dr Mark Hamann, JCU

A vulnerability assessment framework was developed and used to assess the cumulative impact of various climatic processes on the nesting grounds used by the northern Great Barrier Reef (nGBR) and Torres Strait green turtle population. The variables from this framework were manipulated to investigate how mitigating different climatic processes individually or simultaneously influenced the vulnerability of the nesting grounds. The results indicate that nesting grounds closer to the equator - such as Bramble Cay and Milman Island - are the most vulnerable to climate change. In the shortterm (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 thermal threshold for egg development, 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 increasing susceptibility to increased temperature. Therefore, reducing the threats from increased temperature may provide a greater longterm return on conservation investment than mitigating the impacts from other climatic processes. These results indicate that mitigation of the impacts of increased temperature on rookeries will reduce the vulnerability of almost all nGBR and Torres Strait rookeries from high to low.


Geomorphological studies at Raine Island

Project Leader: Dr Mark Hamann, JCU

Raine Island, in the northern Great Barrier Reef Marine Park, is the world’s largest remaining green turtle rookery. However, declines in numbers of nesting turtles have been observed. In response to concerns that this could be related to apparent changes in the island’s beach morphology, this MTSRF-funded project reconstructed a 40-year shoreline history using both historical data and modern 3D terrain modeling. Over this time period swale-width has decreased at a linear rate of ~-0.30 m/yr to the northeast, accreting at a rate of 0.54 m/yr to the southwest. The most accurate estimates of volumetric change over the past 9 years are a net sediment budget gain of ~45,200 m3, predominantly (55%) to the north and northwest, while over the past 40 years, net sediment gain (~14,000 m3) has been reduced by episodes of erosion to the northeast, southeast and west. Southwest Raine Island has experienced the bulk of net sand accumulation (~40 m3). In effect, the island appears to be undergoing both a slow change in shape and a slow east-to-west migration. Significant episodes of accretion and erosion to the west appear to coincide with periods of strong El Niño and La Niña respectively. This study has provided a useful initial stage in modelling shoreline behaviour, response to climate change, and potential ecological vulnerabilities and management implications at Raine Island.


Participatory monitoring of turtle ecology and nesting success in the Torres Strait

Project Leader: Dr Mark Hamann, JCU

Nesting beach studies undertaken by the Queensland Government indicate that the northern Great Barrier Reef turtle population is showing early warning signs of decline. Torres Strait islanders are one of the major stakeholders in the management of these populations, because of their strong cultural associations and links with turtles. To both improve scientific understanding such that it can inform management initiatives, and also to raise awareness among Torres Strait islanders about turtles and their research and monitoring, MTSRF-funded researchers involved Islanders from several communities in the collection of marine turtle population demographic data, and trained local people about turtle monitoring techniques. The data showed that shallow water reef flats are important habitats for juvenile green and hawksbill turtles; recruitment of juvenile turtles into the Torres Strait is low (~2%); green turtle fibropapilloma is an emerging issue; and that there are migratory links between turtle populations in the northern Great Barrier Reef and Torres Strait. Researchers also investigated Islanders’ thoughts and aspirations regarding marine turtle management. They considered community-based management processes to be important, especially the application of cultural norms to achieve compliance and enforcement within the community, and consensus-based decision-making with regard to the use of more formal management rules. The need for cooperation with other communities and stakeholders across scales was also recognised, particularly with regard to enforcement. The outcomes suggest that co-management will be a more appropriate approach than either community-based management or ecosystem-based management for green turtles in the Torres Strait.





Project 1.4.1(e) UQ Parra, G. et al. (2009) Feeding habits of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific humpback dolphins (Sousa chinensis)

Little information exists on the feeding habits of Australian Snubfin (Orcaella heinsohni) and Indo-Pacific humpback dolphins (Sousa chinensis). In this study, University of Queensland researchers provide quantitative analyses of the diet of both dolphin species in Queensland waters, based on the examination of stomachs collected from stranded and bycaught animals between 1970 and 2008. Snubfin and humpback dolphins appear to be opportunistic-generalist feeders, eating a wide variety of fish and cephalopods associated with coastal-estuarine waters.


Report Series No. 5 - Marsh, H., Hodgson, A., Lawler, I., Grech, A. and Delean, S. (2008) Condition, status and trends and projected futures of the dugong in the Northern Great Barrier Reef and Torres Strait; including identification and evaluation of the key threats and evaluation of available management options to improve its status


Project 1.4.1 Marsh, H. et al. (2007) Northern Great Barrier Reef & Torres Strait Final Report

This report provides the first synopsis of the distribution and abundance of the dugong on the remote coast of Queensland from Cooktown north including Torres Strait.