The present living structure of the Great Barrier Reef has experienced four bleachings in 19 years. Bleaching occurs when water temperatures increase and the coral expels the algae living within it, draining its colour. It is the world’s largest coral reef system and is more than 8,000 years old, however its time seems to be running out. It has been called Australia’s National Treasure and a once-in-a-lifetime experience for tourists, and now, probably for a different reason.
A study, conducted by the ARC Center of Excellence for Coral Reef Studies, was released in March detailing the extent of the damage to the Great Barrier Reef during recurrent bleachings in 1998, 2002, and 2016. More recent data from the 2017 survey shows that the reef is still in the midst of another bleaching event.
The reef’s condition may not be terminal yet according to the Director of the ARC Center, but coral grows as little as 0.1 inches a year and even the fastest growing corals can take a decade to recover to full health. The last two bleachings occurred only 12 months apart, offering no chance of recovery for the corals that were damaged in 2016.
Corals achieve their luminescent color through algae, with which they have a symbiotic relationship. Coral provides algae shelter and compounds for photosynthesis. On the other hand, the algae helps coral remove waste, and also gives coral the oxygen and carbohydrates they produce from photosynthesis. Algae leaves the coral to fend for itself when stressed due to various factors like warming water, extra-bright sunlight, and changes in salinity. The coral turns white or “bleached.” Algae could return when the water cools down, but if that doesn’t happen, then the coral simply dies.
The study, which collected data through aerial and water surveys, has shocking numbers regarding these coral deaths. In 1998 and 2002, about ten per cent of the reef surveyed had severe bleaching. In 2016, 90 per cent had been affected by bleaching with 50 per cent of the reef experiencing severe bleaching.
The study also shows that reefs are not adapting to warming waters. Reefs bleached before still bleached as badly the next time it occurred.
The global prognosis for reefs is poor as well, with experts noting that reefs as we know them will not return to their pre-bleaching structures with bleaching becoming a global phenomenon. Up to 70 per cent of the world’s coral reefs may be lost by 2050.
Experts have concluded that bleaching happens because of climate change. Mass bleaching was first discovered in the latter half of the 20th century, which coincides with the detectable warming of the Earth’s climate due to greenhouse gases. Before then, bleaching was only a localized event that tended to happen during extreme low tide.
The study had even worse news in terms of local intervention strategies. Local management of coral reef fisheries do not seem to offer much, if any, resistance to recurrent severe bleaching events. Hundreds of individual reefs are still bleached on the northern Great Barrier Reef regardless of whether they are no-entry, no-fishing, or open-to-fishing. Still, continued protection of fish stocks and water quality may provide better prospects for recovery, but that is all dependent on the frequency of these severe bleachings occurring because of climate change.
According to the study, it seems like action toward reducing global warming is the only thing that can save coral reefs, which make up only one per cent of undersea ecosystems but shelter 25 per cent of marine species. They also protect shorelines and support different industries like fishing, medicine, and tourism.
The earth and mankind stands to lose a lot by letting coral reefs die out. Even if drastic actions are taken to reduce global warming worldwide, we will still have caused extensive, and possibly irreparable damage. The only question is how much of these coral reefs and the rest of the ecosystem will we have left when humanity decides to stop neglecting them.