グレートバリアリーフ、一部で過去最悪のサンゴ死滅率

【シドニーＡＦＰ＝時事】オーストラリアのグレートバリアリーフの一部で、観測史上最悪のサンゴの死が確認された。同国の研究機関が１９日、発表した。研究者らは、調査対象外の部分でも同様の事態が発生しているのではないかと懸念している。（写真は、グレートバリアリーフのリザード島周辺で、白化して死んだサンゴ）
　オーストラリア海洋科学研究所によると、１２のサンゴ礁を調査した結果、死滅率は最大で７２％に上っていた。これは、夏の大規模な白化現象、二つのサイクロン、洪水が原因だという。
　同研究所によると、グレートバリアリーフ北部では、造礁サンゴの約３分の１が死滅している所もあった。政府の監視が始まって３９年の間でサンゴが「最も大きく減少した年」となった。
　世界最大の生きた構造物としばしば称されるグレートバリアリーフは、２３００キロメートルにわたる熱帯サンゴの広がりで、驚異的な生物多様性を持つ。
　しかし、繰り返される大規模な白化現象が観光の目玉であるこのサンゴ礁の魅力を奪い、かつて鮮やかだったサンゴを病的な白色に変えてしまっている。
　今年は、過去８年間で５回目の大規模な白化がすでに確認されている。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2024/11/19-19:07）

Parts of the Great Barrer Reef have suffered the highest coral mortality on record, Australian research showed Tuesday, with scientists fearing the rest of it has suffered a similar fate.
The Australian Institute of Marine Science said surveys of 12 reefs found up to 72 percent coral mortality, thanks to a summer of mass bleaching, two cyclones, and flooding.
In one northern section of the reef, about a third of hard coral had died, the largest annual decline in 39 years of government monitoring, the agency said.
Often dubbed the world's largest living structure, the Great Barrier Reef is a 2,300 kilometre (1,400-mile) expanse of tropical corals that house a stunning array of biodiversity.
But repeated mass bleaching events have threatened to rob the tourist drawcard of its wonder, turning banks of once-vibrant corals into a sickly shade of white.
Bleaching occurs when water temperatures rise and the coral expels microscopic algae, known as zooxanthellae, to survive.
If high temperatures persist, the coral can eventually turn white and die.
This year had already been confirmed as the fifth mass bleaching on the reef in the past eight years.
But this latest survey also found a rapid growing type of coral -- known as acropora -- had suffered the highest rate of death.
This coral is quick to grow, but one of the first to bleach.
- 'Worst fears' -
Lead researcher Mike Emslie told public broadcaster ABC the past summer was one of the most severe events across the Great Barrier Reef, with heat stress levels surpassing previous events.
These are serious impacts. These are serious losses, he said.
WWF-Australia's head of oceans Richard Leck said the initial surveys confirmed his worst fears.
The Great Barrier Reef can bounce back but there are limits to its resilience, he said.
It can't get repeatedly hammered like this. We are fast approaching a tipping point.
Leck added the area surveyed was relatively small and feared that when the full report was released next year similar levels of mortality would be observed.
He said that it reinforced Australia's need to commit to stronger emission reduction targets of at least 90 percent below 2005 levels by 2035 and move away from fossil fuels.
The country is one of the world's largest gas and coal exporters and has only recently set targets to become carbon neutral.