Sarah Clarke ABC Net 12 Jun 10;
ELIZABETH JACKSON: After facing what appeared to be a gloomy outlook, there's finally some good news for the Great Barrier Reef.
After a hot summer, and a series of heatwaves last year, scientists say late monsoonal conditions protected much of the coral from a major bleaching event.
But a new study shows mortality in the world's tropical oceans is increasing, and as bleaching becomes more common, corals simply aren't getting enough time to recover.
Our environment reporter Sarah Clarke travelled to the Great Barrier Reef for this report.
SARAH CLARKE: 2009 may have been the second warmest year on record, ending the hottest decade in a century, but that heat didn't translate to ocean temperatures, with a trough delivering last minute respite for much of Australia's oceans.
Ray Berkelmans is from the Australian Institute of Marine Science.
RAY BERKELMANS: Thankfully, just around Christmas time the active monsoon trough started and that persisted for just about most of the summer.
So together with high cloud cover and strong winds, that kept us from getting warm conditions for most of the summers.
SARAH CLARKE: Those cooler conditions chilled the ocean, protecting much of the Great Barrier Reef. There was some mild bleaching recorded in the southern region but the worst was further north.
Ove Hoegh-Guldberg is from the University of Queensland.
OVE HOEGH-GULDBERG: Right up in northern Australia, you know, in the Torres Strait region you had extremely warm weather for a very long period of time; that pushed sea temperatures above the long term summer maximum by several degrees, and of course that's what drove bleaching.
SARAH CLARKE: Bleaching occurs when coral's stress in unusually warmer waters. The worst events in Australia were recorded in 1998 and 2002. Some parts of the Great Barrier Reef have since recovered, but there has been some coral mortality.
And a study by John Bruno from the University of North Carolina now shows between one and two per cent of the world's tropical corals are being lost each year.
JOHN BRUNO: Well Sarah, we've seen coral reefs degrading over the last three or four decades. So we don't have a lot of data from the late 60s and the early 70s, but we're quite sure things started really taking off in the early to mid 80s.
So our best guess is that we've lot about half of the world's living coral cover over the last three or four decades.
SARAH CLARKE: That's combined with new research which suggests that it can take some corals up to 18 months to recover. And as bleaching events become more common, some species won't have enough time to rebuild.
And that translates to a grim outlook for unique places like the Great Barrier Reef, according to Ove Hoegh-Guldberg from the University of Queensland.
OVE HOEGH-GULDBERG: Now, you can never say from one season to the next that the next year is going to be a mass bleaching event, but what we're seeing is that that overall risk is increasing over time as the temperature goes up.
You don't have to be a mathematical genius to work out that, you know, 30 to 40 years from now we've lost most of the coral that we have here today, and that's why a lot of us are very concerned.
ELIZABETH JACKSON: Ove Hoegh-Guldberg from the University of Queensland ending that report from Sarah Clarke.
