March 7, 2011 / 9:41 AM / 6 years ago

Great Barrier Reef storm damage severe but patchy

<p>A satellite image obtained from the U.S. Naval Research Laboratory shows Cyclone Yasi making landfall in Queensland, Australia, late February 2, 2011.U.S. Naval Research Laboratory/Marine Meteorological Division/Handout</p>

SYDNEY (Reuters Life!) - Powerful cyclone Yasi caused patchy but severe damage to Australia's famed Great Barrier Reef when it tore through last month, with some areas little more than rubble, scientists said Monday.

But while pockets of centuries-old coral was destroyed and recovery may take decades, most of the damage was confined to areas with so little tourism that many of the reef sites don't even have names, with major areas spared.

The assessment, carried out by the Great Barrier Reef Marine Authority (GBRMPA) and Queensland Parks and Wildlife Service, surveyed 36 reefs or some 300 km (186 miles) of the 2,400 km-long reef that makes up the popular tourist site, which contributes billions of dollars to Australia's economy annually.

"There were some reefs that were very severely damaged, in some of those areas there was hardly a coral left alive and big places of coral rubble and broken plates that had been ripped off the reef," said Paul Marshall, GBRMPA assessment co-ordinator.

"That was pretty heart-wrenching, to see just how some of these areas have been affected. Some of these areas were coral gardens I knew quite well and now they're just reduced to rubble."

Yasi was rated a maximum-strength category five storm and was roughly the size of Italy.

While corals known as "bommies" or coral heads are generally more robust, Marshall said that during the course of the survey they came across broken bommies, some up to 4 meters (13 ft 1.4 in) wide, lying on the ocean bed.

"You start to imagine the force that must have been happening underwater," he said.

The good news was that damage was quite patchy, with neighboring reefs and coral structures in some cases remaining relatively unscathed, which will help foster rebuilding of the severely damaged areas.

Signs of recovery should start to emerge in about five years, but it will take more than 20 years to get good coral cover and some damage to the reef may take quite a lot longer to repair, Marshall added.

He and his colleagues were also concerned about the potential impact from the devastating Queensland flooding that came in the months before Yasi, with toxic, pesticide-laden sediment carried out to the reefs stressing or damaging the fragile coral.

Though tourist areas near places such as Cairns escaped damage despite Yasi passing through them, a much larger threat remains due to global warming, which could lead to further devastating cyclones such as Yasi and the massive 2009 Cyclone Hamish, which had gusts of up to 295 km (183 miles) an hour.

"If you look at the track of the last five major cyclones for the Great Barrier reef you do see a fair bit of overlap -- all affect similar areas, so some of these reefs have copped a 'triple whammy' from cyclones in the last couple of years," Marshall said.

"With climate change the whole regime of disturbance is going to change, so we're very concerned these cumulative effect of disturbance after disturbance."

The Great Barrier Reef (GBR) contains an abundance of marine life and comprises of over 2,000 individual reef systems and coral cays as well as hundreds of picturesque tropical islands.

It contributes A$5.4 billion to the Australian economy every year from fishing, recreational use and tourism.

Editing by Elaine Lies

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