The Great Barrier Reef (GBR) is a valuable natural asset that provides $6 billion per annum to the Australian economy and supports more than 50,000 jobs, primarily in tourism. It’s an irreplaceable resource, a national and international icon and it is slowly declining.
In the past 50 years more than half of the coral coverage has disappeared, and the number of sharks, dugongs and turtles today is a small fraction of only a few decades ago. Increasing fishing pressure has made it harder to catch a decent-sized fish. Three major outbreaks of crown-of-thorns starfish have swept along the GBR since the 1960s, and a fourth is underway. In 1998 and again in 2002, global warming caused mass coral bleaching along the length of the Reef leading to further loss of corals. Since 2000, fewer than half of the individual reefs comprising the Great Barrier Reef have more than 10% coral cover, compared to an average of close to 40% in the 1960s.
The good news is we know why these changes are occurring, and more importantly, how to fix them.
First, we need to recognise and manage the links between activities on land and the health of the Great Barrier Reef. Changes on land following the arrival of Europeans and their livestock, and from land clearing and the development of fertilised cropping (e.g. sugarcane and bananas) have all increased the inflow of sediment and nutrients onto near-shore habitats. Annual growth bands, similar to tree rings records, from Porites coral skeletons show a five to 10-fold increase in the delivery of sediments after 1870, when human settlement and land-use practices rapidly changed.
Recent water-quality data from regional catchments, combined with information on land-use change, provide a second strand of evidence that the amounts of sediment, nutrients and pesticides flowing into the sea from rivers are far higher now than in pre-European times. Sediment loads have increased by five to 10-fold, while total phosphorus and total nitrogen is up to 10- and five-times higher, respectively.
During floods, satellite imagery shows that river plumes and associated phytoplankton blooms can cross the GBR lagoon into the Coral Sea, transporting dissolved matter to inner, middle and even outer reefs. For the first time in the history of the GBR, biologically active concentrations of agricultural pesticides and herbicides have been measured up to 60km offshore during wet seasons when rivers are running strongly. This all matters, because runoff from river catchments and dredging for access to ports is smothering coastal reefs and seagrass beds with sediment. Added nutrients during floods promote blooms of phytoplankton, the food of juvenile crown-of-thorns starfish, leading to population explosions of adult starfish. The growing incidence of coral and fish diseases is also directly linked to water quality decline on the GBR.
Second, we need to acknowledge the importance of fish, including top predators like sharks, and herbivores that control blooms of seaweed, for the functioning of ecosystems. No-take ‘green’ marine reserves are effective tools for rebuilding depleted fish stocks, repairing distorted foodwebs, and for helping to build the resilience of the reef in anticipation of future bouts of bleaching from inevitable climate change. In 2004, the Great Barrier Reef was rezoned in a decisive response that increased the number of green zones from five to 33% of the marine park. Today, green zones have twice as many fish and they export larvae to the surrounding seascape, helping to sustain ongoing commercial and recreational fishing.
Third is the elephant in the room: climate change. There are no climate sceptics among the coral reef science or reef management communities – we have been measuring impacts of climate change on reefs since the 1980s. This month, in an unprecedented move, more than 3,000 reef scientists from 80 countries endorsed a Consensus Statement on Climate Change and Coral Reefs, during the 12th International Coral Reef Symposium in Cairns. The statement calls for a worldwide effort to overcome the threats to coral ecosystems and to the livelihoods of millions of people who depend on them.
In this country, contemporary policies have so far demonstrably failed to address coral bleaching or disease, to prevent outbreaks of crown-of-thorns starfish, or, as yet, to significantly improve water quality. Australia’s greenhouse gas emissions continue to rise, even as we export most of our carbon footprint overseas. If the goal is to avoid dangerous climate change, where is the plan for Queensland to transition away from an unsustainable coal and gas industry? The success of management of the GBR marine park today is constrained by the conflict of interest between income from mining royalties to Queensland and the Commonwealth governments versus their joint responsibilities to Australians to ensure the reef is not slowly destroyed.
We cannot climate-proof the reef by establishing marine parks. Without direct global action to minimise greenhouse gas emissions, such as the new Commonwealth tax on carbon pollution, the Great Barrier Reef will continue to decline. Already, the mix of coral species is changing as temperatures rise, in favour of those that are more resistant to bleaching. Logically, the state of Queensland should be leading the charge to wean the world off coal and protect the 50,000 jobs and $6 billion annual income from the reef. Instead, successive state governments have shirked their responsibilities for stewardship of the Great Barrier Reef by continuing the rapid expansion of coalmines and coal ports along the Queensland coast. The Commonwealth has been complicit in damaging the reef by allowing unprecedented amounts of dredging within the Great Barrier Reef World Heritage Area.
Earlier this year, UNESCO voiced its growing concerns over the declining World Heritage Values of the Great Barrier Reef. In particular, they called for a moratorium on building any new coal ports along the Queensland coast, and raised the spectre of adding the Great Barrier Reef to the World Heritage Areas in Danger List. If this happens, it would be a disaster for Australia’s tourism industry. In the 21st century, it is morally reprehensible to entertain proposals for new coalmines in Australia. As the richest coral reef nation in the world, surely we have the scientific knowledge and the resources to do better?
12th International Coral Reef Symposium
ARC Centre of Excellence for Coral Reef Studies