Climate change already at work, say reef scientists

Bleached Coral Reef A warming climate is already affecting coral reefs in ways that could "fundamentally change what reefs look like in the future". That was the conclusion of the International Coral Reef Symposium, which took place in Cairns, Queensland, Australia  in July. The event, held every four years, attracted representatives from some 80 countries, with "international scientists, policy-makers, managers and conservationists to present the latest findings on coral-reef science and management". "The research and findings presented at ICRS 2012 are fundamental in informing international and national policies and the sustainable use of coral reefs globally," said the organiser. Topics for discussion included links between climate change, coral-bleaching and ocean acidification; sustaining coral fisheries worldwide; the effectiveness of marine protected areas; and the social and economic benefits of coral-reef management. A number of panellists summarised findings. "Tropical coral-reef waters are already significantly warmer than they were and the rate of warming is accelerating," said Janice Lough, of the Australian Institute of Marine Science. "With or without drastic curtailment of greenhouse gas emissions we are facing, for the foreseeable future, changes in the physical environment of present-day coral reefs." Over the past century global temperatures have warmed by 0.7°C and those of the surface tropical oceans by 0.5°C, she said. This had already resulted in widespread coral-bleaching events and outbreaks of coral diseases. Current projections indicated that the tropical oceans could be 1-3°C warmer by the end of this century. Jeremy Jackson, Senior Scientist Emeritus at the USA¹s Smithsonian Institution, said that reefs globally had already seen severe declines over several decades. In the Caribbean, 75-85% of coral cover had been lost in the past 35 years, while the Great Barrier Reef, the world's best-protected reef eco-system, had seen a 50% decline in coral cover in the past 50 years. Climate change was also causing increased droughts, agricultural failure and sea-level rise. "That means what's good for reefs is also critically important for peoples the future of coral reefs isn't a marine version of tree-hugging but a central problem for humanity," he said. John Pandolfi of the University of Queensland explained how the responses of different types of corals to warming and ocean acidification are not universal. Some had a chance of survival; others would die. Reefs already damaged by human activity, including overfishing and land pollution, would face a tougher challenge. "There will be winners and losers in climate change and ocean acidification, but reefs will demonstrably change and, for most people's idea of what reefs are, not for the better," he said. Philip Munday of James Cook University, covered fish populations. Impacts, which are already occurring, were reduced coral cover and less habitat structure for fish. "That will mean fewer species and lower fish abundance," he said. "Some species will fare better than others. For example, fish that eat coral will be more severely impacted, but overall we can expect a decline in fish numbers." Some fish seemed able to adjust to temperatures changes, he said, while increased carbon dioxide levels could, over time, affect fish behaviour, leading to reduced survival. Tests on fish in tanks had shown that higher CO2 levels caused neurological changes that reduced ability to avoid predators, due to a reduced sense of smell and an increased tendency to stray further from protective reef areas. At the symposium's end, 2600 of the "world's top marine researchers" released their Consensus Statement on Climate Change and Coral Reefs, calling for a worldwide effort to overcome growing threats to coral eco-systems and the livelihoods of the millions who depend on them for food, income and storm protection. "There is a window of opportunity for the world to act on climate change ­ but it is closing rapidly," said Prof Terry Hughes, convener of the symposium. Video:   These items appear in the September issue of Diver. Special Offer: download the DIVER APP for FREE! Already available for Apple iPhone, iPad and iPod Touch devices via iTunes, the Free DIVER App offer has now been extended to Android mobile phones and tablets - and you can download a FREE taster issue too!

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