The Australian Government’s top Great Barrier Reef scientist says a third mass bleaching event in five years is a clear signal the marine wonder is “calling for urgent help” on climate change.

One quarter of the Great Barrier Reef suffered severe bleaching this summer in the most widespread outbreak ever witnessed, according to analysis of aerial surveys of more than 1,000 individual reefs released last week.

David Wachenfeld, chief scientist at the Great Barrier Reef Marine Park Authority, told Guardian Australia, “My greatest fear is that people will lose hope for the reef. Without hope there’s no action. People need to see these bleaching events. They are clear signals the Great Barrier Reef is calling for urgent help and for us to do everything we can.”

Terry Hughes, director of the Center of Excellence for Coral Reef Studies at James Cook University, surveyed 1,036 reefs from a plane over nine days in late March. The marine park authority also had an observer on the flights. Hughes has released maps showing severe levels of bleaching occurred in 2020 in all three sections of the reef - northern, central and southern — the first time this has happened since mass bleaching was first seen in 1998.

Some 25 percent of the reefs were severely bleached — meaning that more than 60 percent of the corals on each reef had bleached.

Hughes said previous observations had shown that bleaching at that extent leads to “high levels of mortality” of corals.

The Great Barrier Reef has experienced five mass bleaching events - in 1998, 2002, 2016, 2017 and 2020 - all caused by rising ocean temperatures driven by global warming.

In February the reef was subjected to its hottest sea surface temperatures since records began in 1900.

Some scientists fear that rising levels of heat being taken up by the ocean have pushed tropical reefs to a tipping point at which many locations bleach almost annually.

Measures to improve the resilience of the reef include improving water quality, controlling outbreaks of coral-eating starfish, and research and development to improve the heat tolerance of corals. “None of that is a substitute for strong action on emissions,” Wachenfeld said. “Dealing with the climate problem is the underpinning for everything else to work.”

Words to Learn 相关词汇

【漂白】 bleach cause something to become white or much lighter by a chemical process or by exposure to sunlight

【临界点】tipping point the point at which a series of small changes or incidents becomes significant enough to cause a larger, more important change

澳大利亚政府大堡礁研究的权威科学家表示，五年内大堡礁发生第三次大规模白化现象，这是大堡礁这一海洋奇迹“呼吁紧急援助”应对气候变化的明确信号。

根据上周发布的一项对1000多个独立珊瑚礁的航空调查分析，今年夏天，在有史以来暴发最广泛的白化现象中，大堡礁四分之一的区域出现了严重白化。

大堡礁海洋公园管理局首席科学家大卫▪瓦肯菲尔德告诉《卫报》澳大利亚版说：“我最担心的是人们会对大堡礁失去希望。没有希望就没有行动。”

“人们需要看到这些白化现象。这是大堡礁正在呼吁我们紧急帮助、竭尽所能的明确信号。”

3月下旬，詹姆斯库克大学卓越珊瑚礁研究中心主任特里▪休斯在9天的时间里，从飞机上对1036个珊瑚礁进行了调查。海岸公园管理局也派出了一名观察员。

休斯发布的地图显示，在2020年，大堡礁北部、中部和南部三个部分都出现了严重的白化现象，这是自1998年首次发现大规模白化现象以来首次出现这种情况。大约25%的珊瑚礁严重白化，这意味着每个珊瑚礁上超过60%的珊瑚已经白化。休斯说，先前的观察显示这种程度的白化会导致珊瑚的“高死亡率”。

1998年、2002年、2016年、2017年和2020年，大堡礁共经历了五次大规模的白化，都是由全球变暖导致的海洋温度上升造成的。

今年2月，大堡礁遭遇了自1900年有记录以来最高的海平面温度。

一些科学家担心，海洋吸收的热量不断上升，将热带珊瑚礁推向了一个临界点，许多地方几乎每年都在白化。

改善珊瑚礁复原力的措施包括改善水质、控制食珊瑚海星的爆发，以及研究如何改善珊瑚的耐热性。

瓦肯菲尔德说：“所有这些都不能替代对排放采取强有力的行动。解决气候问题是其他一切措施有效的基础。”

(chinadaily.com.cn)