Executive Summary:
Australia, along with the entire world, faces the tremendous challenge of climate change over the coming decades. Along with its impacts on a wide variety of global ecosystems, climate change has the potential to have long-term impacts on Australia’s Great Barrier Reef (GBR). Among the most serious of these are the phenomenon of coral bleaching (or, more properly, bleaching mortality) and its attendant effects on the reef’s biodiversity.
Reef-building corals are driven by a partnership between corals, and tiny single-celled plants known as dinoflagellates. The dinoflagellates trap solar energy through photosynthesis, providing both organisms with an abundant source of organic carbon and energy. In return, the coral provides inorganic nutrients which act as fertiliser for the dinoflagellates. As a result of this relationship, corals are able to build the huge structures that are typical of coral reefs.
The symbiosis between reef-building corals and their dinoflagellates is extremely vulnerable to environmental stress. A small increase in sea temperature, for example, will destabilise the symbiosis leading to the rapid loss of the brown dinoflagellates from the tissues of the coral. As a result, the corals lose their overall brown colour, with the brilliant white skeleton gleaming through the otherwise transparent tissues of the coral host (hence the term coral bleaching). Prolonged or intense stress will lead to disease and death. With global warming, the latter is becoming the norm, with huge mortalities being recorded across the planet within coral communities.
The long term effects of coral bleaching (in both the Cairns region and the entire GBR) are the focus of this study. Coral bleaching, and related effects of warming, present a serious threat to the future existence of the reef. The Garnaut Climate Change Review (2008) (“the Garnaut Report”) and other recent media commentary has paid particular attention to the issue of the long term survivability of the GBR due to bleaching and there have been growing public concerns about its future.
As noted in a supplementary paper to the Garnaut Report, if atmospheric concentrations of carbon dioxide (CO2) exceed 500 parts per million (ppm) the GBR is likely to experience a massive loss of biodiversity and ecological function. Any semblance of reefs to the coral reefs of the Great Barrier Reef Marine Park today would vanish, with the GBR having a vastly different appearance to that which attracts tourists at present (Hoegh-Guldberg and Hoegh-Guldberg 2008).
This, in turn, raises the issue of how much the nation (and by extension, the world) values a World Heritagelisted natural resource such as the GBR.
