Global Warming, Storms, Starfish Take Out Half of Great Barrier Reef

According to a new paper published in the Proceedings of the National Academy of Sciences and to a report published in the Washington Post, Australia’s Great Barrier Reef has lost more than 50% of its coral since 1985.

The report showed that coral coverage had dropped from 28 percent to 13.8 percent during the period studied. Though the study took stock of years from 1985 to 2012, it found that most of the damage, about two thirds, had occurred since 1998.

Primary drivers for damage were global warming and industrial agriculture. Abnormally powerful cyclones slammed the reef in the decades of the 2000s and 2010s, causing severe losses. Furthermore, instances of coral bleaching, when hot waters cause corals to weaken or die off, multiplied during the period of record showing greater frequency after 1998. Both coral bleaching and increased numbers of powerful cyclones were likely global-warming related. But the third impact, an exploding population of reef devouring starfish, was spurred by agricultural run-off in Australia. The starfish, which can feed on nutrients in the run-off, multiplied to cover large sections of reef and devoured vast volumes of reef-building algae.

Though it may be possible for Australia to reign in some of its Agricultural run-off, it is unlikely that it will be able to reduce instances of coral bleaching and increasingly damaging storms without partnering with countries around the world to drastically cut greenhouse gas emissions.

Recent studies have shown that corals suffer from a combined threat of bleaching in the south and ocean acidification in the north. Overall, under current greenhouse gas emissions regimes, it is expected that most corals will be dead by around 2060 and about 500-600 ppm CO2. In fact, this combination of heating and ocean acidification is causing major stresses to many life forms in the ocean and risks not only a massive die-off among corals, but among millions of ocean animal species including the fish that many countries and humans depend on for food and livelihoods.

Below is a comparison of the potential for bleaching events during the 2030s and 2050s provided by NOAA:

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