An aerial survey of the Great Barrier Reef shows coral bleaching is sweeping across the area off the east of Australia for the third time in five years. Bleaching has struck all three regions of the world’s largest coral reef system and is more widespread than ever.
The air surveys of 1,036 reefs in the past two weeks found bleached coral in the northern, central and southern areas.
As summers grow hotter and hotter, it does not need an El Nino event to trigger mass bleaching at the scale of the Great Barrier Reef.
Of the five events that the word has seen so far, only 1998 and 2016 occurred during El Nino conditions.
El Nino is a climate pattern that starts with a band of warm ocean water in the central and east-central Pacific around the equator and affects global weather.
Great Barrier Reef
- The Great Barrier Reef is made up of 2,900 separate reefs and 900 islands.
- It is unable to recover because there is not enough time between bleaching events.
- The first example of back-to-back bleaching — in the consecutive summers of 2016 and 2017 has already happened.
- The number of reefs spared from bleaching is shrinking as it becomes more widespread.
- Underwater surveys will be carried out later in the year to assess the extent of damage.
- Ocean temperatures over the next month will be crucial to how the reef recovers from heat-induced bleaching.
- So this still is a critical time for the reef and it is the weather conditions over the next two to four weeks that will determine the final outcome.
Ocean temperatures across most of the reef were 0.5 to 1.5 degrees Celsius (0.9 to 2.7 degrees Fahrenheit) above the March average.
In parts of the marine park in the south close to shore that avoided the ravages of previous bleachings, ocean temperatures were 2 to 3 degrees Celsius (3.6 to 5.4 degrees Fahrenheit) above average.
The authority had received 250 reports of sightings of bleached coral due to elevated ocean temperatures during an unusually hot February. The 345,400-square kilometer (133,360-square mile) World Heritage-listed colorful coral network has been devastated by four coral bleaching events since 1998. The most deadly were the most recent, in those consecutive summers of 2016 and 2017.