This is the declaration of Dr. Paul Hardisty, the Chief Executive Officer of the Australian Institute of Marine Science. Satellites, weather stations, and an in-water autonomous robot are constantly monitoring ocean temperatures. 170 electronic temperature loggers are watching the 350,000 square kilometers reef. An Integrated Marine Observing System underwater glider is observing the waters north-east of Townsville, Australia. And the proof they all bring is disturbing.
In the last weeks, ocean temperatures increased by 1.0 to 2.5 degrees centigrade. It might seem an insignificant number, but that is not what the coral reef feels. Deep there, this tiny growth acts like a torrid day in the middle of August burning the leaves and turning their color to red and yellow. For the coral, the color changes to white. Like in a bleaching process. Today, the coral reef is facing a great threat, and its chances of survival are going down fast.
The coral bleaching event of the Great Barrier Reef
Coral reefs provide shelter to an estimated quarter of all ocean species. The leading cause of coral bleaching is rising water temperatures. As the temperature rises, the levels of CO2 could become too high for coral to survive in as little as 50 years.
Coral bleaching occurs when coral polyps expel algae that live inside their tissues and give the coral its coloration. The algae, called zooxanthellae, provide up to 90% of the coral’s energy. Bleached corals continue to live but begin to starve after bleaching.
Negative environmental conditions, such as abnormally warm or cool temperatures, high light, and even some microbial diseases, can lead to the breakdown of the symbiosis between the coral and the algae. This leads to a lighter or completely white appearance, hence the term “bleached”.
In 2016, bleaching of coral on the Great Barrier Reef killed up to 50% of the reef’s coral. In 2017, the bleaching extended into the central region of the reef. The longest and most destructive coral bleaching event was because of the El Niño that occurred from 2014–2017. During this time, over 70% of the coral reefs around the world have become damaged.
The effects of coral loss
The bleaching leads to diseases and a decline in genetic and species diversity. For humans, the loss threat is hunger, poverty and political instability could be the result of the coral evanescence.
Coral reefs act as a protective barrier for coastlines. It reduces wave impact, which lowers the damage from storms, erosions, and flooding. A lot of money will be lost because of the increased susceptibility to storms. Combined with the lost revenue in tourism, this will result in enormous economic effects.
Reef associated fish populations would also decrease, which affects fishing opportunities. The losses to fisheries from decreased coral cover could be around $49 – $69 billion if human societies continue to emit high levels of greenhouse gases. These economic losses also have important political implications in Southeast Asia and around the Indian Ocean, where the reefs are located. Besides, other ecosystem services will be lost, such as ecotourism.
“If we want to safeguard coral reefs for the future, we also need to begin developing options for intervening on the Great Barrier Reef to help it cope better with climate change, in conjunction with reducing global greenhouse gas emissions,” said Dr. Paul Hardisty.