Are the reefs dying?
RAMYA KANNAN
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As latest research confirms the effect of climate change on the coral reefs of the Great Barrier Reef, Australia is gearing to deal with the threat to its greatest natural resource.
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The Great Barrier Reef, which stretches over 2300 km along the Queensland coast, is not only home to corals but also to a host of other marine organisms including over 1500 species of fish, 4000 species of molluscs, 24 species of sea birds that live a nd breed on islands, mammals such as whales, dolphins, and the endangered dugong.
Photo: AP
The rare batfish: It can successfully remove the forest of algae that kill the reefs.
A TOURIST surfaces spluttering as water enters his snorkel tube… Pausing to grab some air, he strokes out to the yellow dinghy bobbing on the clear waters of Radical Bay, off Townsville in Queensland.
Pointing to the abundant coral reefs below him, concern etched on the lines of his face, he asks the skipper of his tourist yacht, now in the dinghy, “Those corals out there, are they brown naturally or are they dying?” Skipper Grant Lewis says, “Some of these corals are naturally brown, but sure enough there are those that are dying across the reef. They have been for some years now.”
Grappling with the issue
South of the country, a few days ago, the Fifth World Science Journalists Conference was grappling with the issue of climate change. In one session, John ‘Charlie’ Veron, eminent Coral Reef Researcher with the Australian Institute of Marine Sciences, described as having spent more time under water than above it, is using hyperboles to articulate his agitation: “We are committing the earth to unrivalled destruction… The Great Barrier Reef is dying. We need to pay immediate attention to it. All these things cannot wait.”
If you are on the right wavelength, you can pick up the churning undercurrents of climate change nearly everywhere in Australia: On the radio, television, on a calm seashore, in pubs, among tourists, tour guides, not just with marine researchers and climatologists. Clearly, the continent is concerned about climate change and the far-reaching impact on what it believes is its greatest natural resource — the Great Barrier Reef.
Not without reason though. The coral bleaching survey for 2005-2006, published in May 2006, ( www.gbrmpa.gov.au) conducted by the Great Barrier Reef Marine Park Authority noted: “At the height of summer, sea temperatures were either at or above levels known to cause thermal stress to corals in all regions of the Great Barrier Reef Marine Park, particularly in the far southern area.” There is now worldwide consensus, in the face of evidence, that high sea temperatures — a fallout of climate change — are responsible for the vast coral bleaching.
The report pointed out “At the start of summer, a hot water anomaly developed early and persisted over much of the southern area of the Great Barrier Reef Marine Park. In January… cloud cover over the central and northern Great Barrier Reef Marine Park (led to), cooling water temperatures in this region. However, waters in the southern region continued to warm.”
While low level bleaching (less than 10 per cent) was recorded in Lizard Island, Cairns, Townsville and Whitsunday survey regions, severe bleaching of over 75 per cent was observed in the far southern region. The inshore reefs, around Keppel Islands, were the worst affected, with an average of 84 per cent of corals affected, according to the report.
Scientists studied 34 reefs within the area of the Great Barrier Reef Marine Park, in order to “assess the spatial extent and severity of coral bleaching throughout the Great Barrier Reef Marine Park”. Participants of the BleachWatch programme of the GBRMPA also called in with complaints of bleaching. According to the final report, the surveys were timed to coincide with the peak of the bleaching event, and to document the patterns of bleaching, so as to be able to “interpret the causes and significance of changes in reef condition”.
Substantial bleaching
Paul Marshall, Manager, Climate Change Response Program, Research and Monitoring Co-ordination Unit, says, “Even an increase of 1.5 degrees above the normal maximum temperature is sufficient to bleach corals — when water temperature increases, it kills off the zooxanthellae, the algae that lives in symbiosis with the animal coral and gives it the flamboyant colours.” The hottest years in Australia so far, he says, have been 1998, 2005, 2002, 2003, 2004, in that order.
Marshall has been studying coral bleaching and regeneration since 1998 when a sudden surge in temperatures as a result of El Nino led tosubstantial bleaching. In 1998, he says, 50 per cent of the reefs were bleached as a result of increasing water temperature and, in another episode in 2002, 60 per cent was bleached. Globally, 16 per cent of all reefs were destroyed.
Marshall has reason to be anxious. The 2006 bleaching around Keppel Islands is an indication of how things are going to be in the future. Bleaching does not kill the coral. It will still live and can recover when other zooxanthellae come to live in its midst, but “recovery can take years,” he says. “It could be decades before they are restored to their original glory.” However, if the temperature stress remains, corals die and new formations must settle and grow on the reef for recovery.
Janice Lough, climatologist and principal research Scientist at the Australian Institute of Marine Studies, Townsville, says x-rays of coral slices that show annual density bands, indicate that the corals stopped growing for about a year in 1998 after the warming episode, before they started growing again. Dr. Lough also served on the United Nations Sigma XI Scientific Expert Group on Climate Change, which identified “substantial loss of coral along the Great Barrier Reef” as a result of climate change in its February 2007 report.
In a paper she published with four other scientist researchers in the Bulletin of the Australian Meteorological and Oceanographic Society in June last, Dr. Lough explains, “Coral bleaching is not a new phenomenon due to global
warming. Corals are known to bleach in response to several environmental stresses — low salinity, pollution, unusually high or low water temperatures. In the past, however, coral bleaching only occurred on small space scales. What is new and clearly related to global warming, is an increased frequency since the mid-1970’s of mass coral bleaching events whereby entire reefs are affected.”
The paper also quotes studies by Hoegh-Guldberg and Berkelmans, modelled on future impacts, suggesting that a 1-3º C increase in water temperature in the Great Barrier Reef would result in approximately 80-100 per cent bleaching of reef.
Factors
While warm sea temperature is clearly the causative agent for mass bleaching, marine researchers are also concerned about the increasing acidification of the sea. Explaining, Dr. Lough says this would also be a direct effect of increasing greenhouse gases in on ocean chemistry and its consequences for reefs. This alters the concentrate of carbonate and bicarbonate ions in sea water which corals use to calcify and build skeletons. Weakened skeletons will make corals more susceptible to storm damage and erosion.
Changes in ocean current and rainfall and associated freshwater discharge to reef, pollutant run-offs into the sea, excessive fishing and tourism and coral diseases are all listed among the other causes for coral bleaching and damage. Russel Reichelt, Managing Director, Reef and Rainforest Research Centre, says 10 per cent of the reefs in the Great Barrier Reef area are under risk from sediments, chemicals and fertilizers.
The Great Barrier Reef, which stretches over 2300 km along the Queensland coast, is not only home to corals, but also to a host of other marine organisms including over 1500 species of fish, 4000 species of molluscs, 24 species of sea birds that live and breed on islands, mammals such as whales, dolphins and the endangered dugong. Climate changes will therefore naturally have diverse implications.
It has helped that the Australian Government has been concerned about climate change and its effects on the nation’s most precious natural resource. It has also helped some that the GBR, a UNESCO World Heritage Site since 1981, is the largest protected marine environment in the world. Yet the challenges are many and the debate now is on averting the crisis by controlling and minimising damage.
Recognising the threat to the GBR, the GBRMPA has established a $2 million Climate Change Response Program, along with the Australian Greenhouse Office, to better understand and respond to climate change threats, including coral bleaching. The CCRP will aim to sustain GBR ecosystems and industries and communities that depend on the Great Barrier Reef; and foster supportive policy and networks, as outlined in the May 2006 report.
The CCRP team is currently working on assessing the vulnerability of the GBR to climate changes and also recommend strategies to minimise the impact. The report will be ready by May-June. It will provide a road map for the future and indicate where ‘rezoning’ must be done. The GBRMPA took up ‘zoning’ of the reef in 2004 to protect and conserve areas of the reef from excessive commercial exploitation. Certain areas are off limits for fishing and even collection.
Marshall says rezoning the reef will help protect biodiversity. In addition people have to reduce water pollution and stop over-fishing and overuse. Studies are also on to evaluate the process of natural adaptation. Corals will push the bleaching threshold over a period of time, but the worry is that it might not grow sufficiently to match the galloping pace of climate change.
In addition, as part of the Coral Bleaching Response Plan, the CCRP team monitors water temperature and coral bleaching every summer. Satellite measurements of sea temperature, regional weather forecast and reports from bleachwatch volunteers are logged in periodically. When bleaching is detected, a team is immediately assigned to study the full extent of the bleaching and its ecological impacts.
Also coming up is a Resilience, Risk and Response Atlas to act like a GIS tool on the region, Reichelt says. The Reef and Rainforest Research Centre is also working on Conservation and Sustainable Use, studying status and trends, risks and threats from climate and pests and water quality.
Compelling reason
While focusing on conserving marine systems along the GBR, the Australians have not lost sight of the fact that the aesthetics of the coral reefs is, possibly, the most compelling reason for their preservation. In fact, Marshall concedes that it is the aesthetics that concerns people more. When corals lose colour, it is noticed almost immediately and is directly linked to attracting tourists. “The tourism industry is very sensitive… since it directly affects their prospects.”
Daniel Gschwind, of the Queensland Tourism Industry Council, says tourism has been at the frontline of the battle against climate change in Australia. “The GBR is Australia’s most important tourist asset. It yields up to $2 billion to regional economies,” he says.
According to him, one of the tour operators in the Great Barrier Reef has been testing the feasibility of providing shade to key reef areas to reduce the risk of bleaching, along with scientists. From the industry’s perspective, all tasks — managing assests, operational practices, utilisation of energy and water and development — should promote sustainable use.
As Marshall says, “No matter what we do, reefs are going to be degraded in the future. But if we do nothing, there will be a complete degradation. We have to help coral reefs bounce back after bleaching events.” There are no two ways about that one.
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