00:00Australian authorities say the Great Barrier Reef has seen its greatest annual loss of life
00:05coral across most of its expanse in four decades of record.
00:10Australian Institute of Marine Science said in its annual survey on Wednesday that due to
00:15increasing coral cover since 2017, the coral deaths, caused mainly by bleaching last year
00:22associated with climate change, have left the area of living coral across the iconic
00:28reef system close to its long-term average. The change underscores a new level of volatility
00:34on the UNESCO World Heritage Site. Mike Emsley heads the Tropical Marine Research Agency's
00:41long-term monitoring program. He said the live coral cover measured in 2024
00:47was the largest recorded in 39 years of surveys.
00:53Australian Institute of Marine Science's long-term monitoring program has just released
00:57our annual report for our 39th year of monitoring the Great Barrier Reef and what we've found has
01:04been substantial impacts from the 2024 mass coral bleaching event. We divide the Great Barrier Reef
01:13into three regions, the north, the centre and the south and what we've found was the highest annual
01:20decline in live coral cover that we've recorded in our monitoring program in both the northern
01:26and the southern Great Barrier Reef. There were still losses in the central Great Barrier Reef but
01:32it was somewhat less than the other two regions at only 14%. So the northern underwent a loss of about
01:40a quarter of the live coral cover and the southern Great Barrier Reef was almost a third. So these are
01:45substantial impacts and evidence that the increasing frequency of coral bleaching
01:51is really starting to have detrimental effects on the Great Barrier Reef.
01:59The losses from such a high base of coral cover had partially cushioned the serious climate impacts on
02:05the world's largest reef ecosystem which covers 344,000 square kilometres off the northeast Australian coast.
02:16The climate change is the number one cause of these mass coral bleaching events. There is a direct
02:21link between the increases of global greenhouse emissions, rising temperatures, sea surface temperatures
02:29that lead to these heat stress events and mass coral bleaching.
02:36Emsaly's agency divides the Great Barrier Reef, which extension 1500 kilometres along the Queensland state
02:44coast, into three similarly sized regions, northern, central, and southern. Living coral cover shrunk by
02:53almost a third in the south in a year, a quarter in the north, and by 14% in the central region.
03:03So in recent years we have seen increases in the amount of live coral cover on the Great Barrier Reef.
03:09It has recovered from a previous bleaching event which finished in 2017. We saw increases through to
03:192024 where we recorded the highest levels of coral cover in the 39 years of monitoring.
03:26And because we came off such a high base, this has somewhat cushioned the impact of the 2024 bleaching
03:35and coral cover has declined to about near the long-term average. However, this isn't to underscore the
03:43seriousness of the impacts. While there's still a lot of coral cover out there, these are record declines
03:49that we have seen in any one year of monitoring. Corals can recover from bleaching. It does take months
03:58for that to happen. They reabsorb the little, tiny algae and start to recover. But it doesn't impose all
04:06these indirect effects on them. So they'll have slower growth. Because of record global heat in 2023 and 2024,
04:15the world is still going through its biggest and fourth ever recorded mass coral bleaching event on
04:21record, with heat stress hurting nearly 84% of the world's coral reef area, including the Great Barrier Reef,
04:28according to the United States National Oceanic and Atmospheric Administration's Coral Reef Watch.
04:36So far at least 83 countries have been impacted.
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