The earth is undergoing accelerating climate change that is being driven by rapidly increasing greenhouse gas concentrations. This is changing the conditions under which the earth’s fauna and flora have flourished over the past several million years.  There is now

extensive evidence of changes to the distribution, abundance, and health of earth’s terrestrial and aquatic ecosystems. Species are migrating towards the poles, ecosystems like coral reefs are experiencing increasing stressful conditions and populations of organisms are in decline as a result of a combination of climate change and other anthropogenic impacts.   

The first part of this report reviews the scientific evidence of climate change and details how recent changes in the environment have lead to massive changes in the health of the world’s ecosystems. It then focuses on the special issue of coral reefs, describing first the major changes that have occurred across the world’s reefs and then focusing on the world’s largest coral reef, the Great Barrier Reef. This reef system is the jewel in the crown as far as coral reefs are concerned.  It is also the most pristine and best managed coral reef

ecosystem in the world. However, there are few reasons for complacency as to the increases in stresses over the next 20-40 years. The major influence will come from seas that will be warmer by as much as 2°C.  Calculated thermal stress (based on Degree Heating Months, DHM) will be 3-6 times higher in 2050 than even the worst recent period of thermal stress seen on coral reefs so far. This is likely to result in thermal stress annually that will greatly exceed the stress seen during the worst bleaching events so far (1998 and 2002).

It is important to realise that climate change is not the only factor that has or will change the way reefs look.  While we do not have much control over the rise in sea temperature over the short-term, reducing the factors that are likely to be eroding reef resilience (poor coastal land use and over-fishing) will improve the ability of coral reefs like the Great Barrier Reef to survive the added impacts associated with climate change.   

Change to the health of our ecosystems as a result of climate change is inevitable. Even under the best case scenario, losses of at least 50% of the Reef’s living coral cover are likely to occur by 2050.  How humans will be affected by these changes is still uncharted yet is enormously important. Careful description and definition of the links between physical and chemical changes, biology and the human dimensions of economic and social impacts is central to understanding the economic and social ramifications of climate change. In the last section of Part 1, four sets of futures are developed in order to set the scene for the development of the social and economic perspectives on the expected decline in the natural values of the Great Barrier Reef.