MTSRF Synthesis Report A Synthesis of Climate Change and Coastal Science to Support Adaptation in the Communities of the Torres Strait Stephanie J. Duce, Kevin E. Parnell, Scott G. Smithers and Karen E. McNamara School of Earth and Environmental Sciences, James Cook University Supported by the Australian Government’s Marine and Tropical Sciences Research Facility Project 1.3.1 Traditional knowledge systems and climate change in the Torres Strait © James Cook University ISBN 978-1-921359-53-8 This report should be cited as: Duce, S.J., Parnell, K.E., Smithers, S.G. and McNamara, K.E. (2010) A Synthesis of Climate Change and Coastal Science to Support Adaptation in the Communities of the Torres Strait. Synthesis Report prepared for the Marine and Tropical Sciences Research Facility (MTSRF). Reef & Rainforest Research Centre Limited, Cairns (64pp.). Published by the Reef and Rainforest Research Centre on behalf of the Australian Government’s Marine and Tropical Sciences Research Facility. The Australian Government’s Marine and Tropical Sciences Research Facility (MTSRF) supports world-class, public good research. The MTSRF is a major initiative of the Australian Government, designed to ensure that Australia’s environmental challenges are addressed in an innovative, collaborative and sustainable way. The MTSRF investment is managed by the Department of the Environment, Water, Heritage and the Arts (DEWHA), and is supplemented by substantial cash and in-kind investments from research providers and interested third parties. The Reef and Rainforest Research Centre Limited (RRRC) is contracted by DEWHA to provide program management and communications services for the MTSRF. This publication is copyright. 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This report is available for download from the Reef and Rainforest Research Centre Limited website: http://www.rrrc.org.au/publications/synthesis_products.html Cover photographs courtesy of Rebecca Clear and David Hanslow (TSRA) and Mariana Fuentes (JCU) Report prepared June 2010 Published by the RRRC November 2010 Climate Change and Coastal Science in the Torres Strait: Synthesis Executive Summary This report provides a synthesis of research on climate change and coastal science in the Torres Strait, and has been produced for the Australian Government’s Marine and Tropical Sciences Research Facility (MTSRF). It identifies and summarises work to date on reef evolution, hydrodynamics and sedimentary environments throughout the Torres Strait. It describes the island dynamics at Boigu, Saibai, Masig, Poruma, Warraber and Iama Islands. Numerous studies relating to climatic change are reviewed and the most relevant regional predictions for climate change in the Torres Strait are presented. The potential physical and ecological impacts of these changes in the Torres Strait are also identified. Adaptation and mitigation measures are suggested and their outcomes and consequences are evaluated. The key principles from sustainable land use plans on the islands are summarised and knowledge gaps in the fields of both coastal and climatic science are identified to guide future research. The most important factor influencing the hydrodynamics of the islands of the Torres Strait is the seasonally reversing wind regime, characterised by dominant southeasterlies for nine months of the year (March to November) and northwesterlies over the summer months (November to March). The tidal regime through the Torres Strait is complex and is also fundamental to the morphodynamics of the islands. Surge events are characterised by an elevation of mean water level caused by pressure and wind set up, often resulting from storms some distance away. Such events occur in the Torres Strait and are responsible for much of the geomorphic work performed on the island beaches. Summaries of island dynamics are described for those locations at which data are available, and the areas vulnerable to coastal erosion and inundation are identified. Climate change is expected to result in the warming of average air and ocean temperatures, average global sea level rise, ocean acidification and regional changes to wind and precipitation patterns and extreme weather events. It was recognised that the exact nature and rates of these changes remain uncertain particularly at regional and local scales. In Torres Strait the best available estimates suggest that local air temperatures will increase by 1-4°C and sea surface temperatures by up to 3°C by the year 2070. Sea level rise of up to one metre is also projected to occur by the year 2100. Other changes in regional climatic conditions predicted include a ten percent increase in downwards radiation, between 0.8 and 13% increase in wet season rainfall, between 3.9 and 23% decrease in dry season rainfall, and a 16% increase in evapotranspiration by the year 2070. Wind speed is expected to increase by between two and five percent by 2030, accompanied by uncertain changes to wind direction trends. Ecological impacts on the health of coral reef and seagrass communities, as well as species of concern including turtles and dugongs, in the Torres Strait are predicted to result from these climatic changes. These impacts include increased coral bleaching events, a temperature induced decline in turtle hatchling survival and an imbalance in the gender of hatchlings. The most concerning immediate physical impacts likely to result from these climatic changes relate to inundation affecting island infrastructure, vegetation and water sources and coastal erosion threatening infrastructure and sites of cultural significance. The exact nature of these impacts will vary from island to island. In some cases, sea level rise could potentially increase the transport of sediment from reef flats to islands, causing them to grow. However, in general, these impacts will decrease the amount of viable land on islands and, unless managed well, will cause decline in the quality of life for the communities of Torres Strait. Relocation to higher ground must be planned and the potential relocation of some communities must be considered. This report identifies numerous adaptation and mitigation measures, including hard and soft engineered works, which can minimise these physical impacts and even improve island condition. These must be considered on an island by island basis to ensure they are successful and that the negative consequences are understood, minimised and acceptable to the communities. i Duce et al. Contents Executive Summary ................................................................................................................ i List of Figures ........................................................................................................................ iii List of Tables ......................................................................................................................... iii Acronyms and Abbreviations Used In This Report ................................................................. iv Acknowledgements ................................................................................................................ v 1. Introduction ................................................................................................................... 1 1.1 The Torres Strait ....................................................................................................... 1 2. Synthesis of Coastal Science in Torres Strait ............................................................. 4 2.1 Reef Evolution and Human History ........................................................................... 4 2.2 Hydrodynamics ......................................................................................................... 4 2.2.1 Tidal Regime ................................................................................................. 6 2.2.2 Currents ........................................................................................................ 8 2.2.3 Waves ......................................................................................................... 10 2.2.4 Surge Events ............................................................................................... 11 2.3 Sedimentary Environment ....................................................................................... 12 2.4 Island Dynamics ..................................................................................................... 13 2.4.1 Boigu ........................................................................................................... 14 2.4.2 Saibai .......................................................................................................... 15 2.4.3 Masig .........................................................................................................