What's the future of the Great Barrier Reef?
by Jeni Bone on 3 Jan 2009
Tourist attraction, livelihood for many, habitat for thousands of species and the source of massive revenue and state pride for Queensland, the Great Barrier Reef is facing the threat of annihilation, given a life expectancy of just 4 more decades, if new evidence is reliable.
The GBR streaches over 1500km along the Queensland coast. Photo courtesy of The Great Barrier Reef Marine Park Authority Great Barrier Reef Marine Park Authority http://www.gbrmpa.gov.au/
A new report claims that the declining growth rate of the Great Barrier Reef's corals indicates it will stop completely by 2050, making way for a less than appealing 'algae reef'.
Scientists from the Australian Institute of Science say the most robust corals on the reef have slowed in growth by more than 14 per cent since the 'tipping point' in 1990.
The decline has been caused by a combination of rising sea surface temperatures and ocean acidification. Calcification refers to how much skeleton the coral forms each year.
When large amounts of carbon dioxide enter the seawater, the resulting chemical change reduces a marine organism's ability to form skeletons and protect itself against the environment. The data suggest that this severe and sudden decline in calcification is unprecedented in at least 400 years.
The group leading the study says that algae will take over the area, small fish will lose their habitat, then the larger fish that eat the small fish will starve. Queensland Premier Anna Bligh said she was worried by increasing scientific evidence of the state of the reef.
The government has announced it will this year begin regulating chemical run-off from farming or agricultural activities into the reef for the first time. 'I know there are not a lot of farmers who are happy with my decision, but we have a special responsibility to look after it, and 2009 will see new laws that will further protect the Great Barrier Reef,' she said.
But other equally credentialed experts are not so sure the current signs are indicators of a dying reef. Some researchers believe the organisms that call the reef home could react to adverse pressures by migrating to cooler waters – meaning that Queensland will one day hand over the tourist attraction to NSW or Victoria!
That may be far off or fantasy, but two things are certain: the Great Barrier Reef is a robust structure that has suffered and survived several episodes of ice ages and global warming and it’s under threat from many forces, most of them man-made. If it’s not the rising atmospheric CO2 levels that are causing oceans to heat up and become more acidic, resulting in corals bleaching, failing to spawn or decomposing with the decrease in pH, it’s effluent and sediments from grazing and urban centres which impact on 90% of the GBR’s catchment area.
The Reef is a 350,000sqkm entity made up of around 3000 individual reefs stretching from Cape York to Bundaberg and containing 350 coral species, making it one of the greatest stores of marine biodiversity in the world.
It’s been inscribed on the World Heritage List, is the only living thing visible from space and it’s worth about $5.1 billion in annual tourism to the economy. But it looks like being a race to slow its degradation or devise a solution to repair it.
Locally, a major step towards preservation was made when in 2005, the Reef Authority increased protection of the Great Barrier Reef from 4.5% to 30% now zoned Marine Park. Ironically, this coincided with the United Nations Environment Programme (UNEP) prediction of the loss of world reefs by the year 2100 would be 30-50% of currently healthy corals.
Retaining and restoring the GBR and reefs the world over is the focus of a diverse group of stakeholders, with collaboration among the CSIRO, the Great Barrier Reef Marine Park Authority (GBRMPA), Australian Institute of Marine Science (AIMS), James Cook University, the University of Queensland, the state and federal governments and industry bodies engaged in fishing and tourism, as well as international experts from Miami to Manila.
Many threats have been identified globally, including shipping, fishing, oil spills, litter, algal invasion and 'exotic pests', but the latest report by AIMS nominates the crown of thorns starfish, cyclones and bleaching as having the most significant impact on the Reef in the 19 years to 2005.
A native inhabitant of the ecosystem, the crown of thorns (COT) is prone to 'outbreaks' as a result of high levels of nutrients in the water and a decline in its predator populations, attributed largely to over-fishing.
Ian Miller from AIMS, who has studied the creature for 15 years, says they are ugly, dangerous and can breed in massive numbers. 'A large female COT can live to eight years old and produce 60 million eggs in a season, breeding for four or five years. These eggs spawn and can achieve a high level of fertilisation. The larvae spread by drifting on currents to the next reef, affecting more than half of the 2,200 km Reef in the past 10 years.'
Today, the majority of reefs from Lizard Island in the north to the Whitsundays are experiencing its third series of outbreaks since the mid-60s. 'During outbreaks, the starfish get hungry and switch to less preferred corals and sponges, attempting to eat massive and important corals. These colonies may be hundreds of years old,' says Miller, adding that reefs affected by the COT can recover relatively quickly, often within seven to 15 years, however, recovery can take much longer if the area has been eroded by other stresses such as water pollution or bleaching.
One short-term solution is to kill them off. GBRMPA issues permits for localised, small-scale control programs at key tourism and research sites which involves injecting them with the biodegradable solution dry acid (sodium bisulphate).
But water quality, specifically a glut of nutrients and other variables like salinity, suspended sediment concentrations, toxicants like pesticides and rising temperatures are proving more challenging.
Monsoon floods carrying sediments, nutrients and toxicants from some 26 major river catchments along the Great Barrier Reef, forming a potent cocktail that can kill or interrupt the fertility cycle of many of the Reef’s inhabitants.
Jon Brodie, Principal Research Scientist at the Australian Centre for
Tropical Freshwater Research at James Cook University, says that while the Reef has always experienced river run-off bringing sediments that smother and turbidity that reduces light availability, modern farming practices are killing the Reef, expelling vast quantities of nitrogen, phosphorus and pesticides into the water.
Queensland’s population growth is not an issue, he asserts, compared to agriculture. 'Water pollution has more to do with cane, cotton and cattle grazing,' Brodie says.
'The Queensland Environmental Protection Act covers industrial and sewerage discharge, but what’s known as ‘diffuse’ discharge, like sediment from grazing land, fertiliser and pesticides from cropping – all much bigger threats – is not under the control of the law.'
Corals and other reef organisms can tolerate variations in water quality, however, when 'critical thresholds' are exceeded, they are adversely impacted. As Brodie explains: 'Other organisms replace coral when fertilizers are present, like the crown of thorns and some seaweeds. When COT are at larval stage, they’re no bigger than a pinhead. They float around and eat micro-algae. When there’s more algae because of an increase of nitrates in the water, more COT larvae survive and eat the Reef.'
In the latest GBRMPA State of the Great Barrier Reef report, pesticides and PCBs (used in a range of industrial applications and electrical transformers) are shown as a cause of reproductive and immunological abnormalities in birds and mammals. Heavy metals like zinc and copper, found in fertilisers, along with arsenic, cadmium and mercury, ingredients in some fungicides, also impact on organism gro
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