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:


Oceans Turning Acidic at Fastest Rate in 300 Million Years

According to recent reports from the Journal Science, the world’s oceans are becoming acidic faster than at any time in the past 300 million years.

Increased levels of carbon dioxide, now at 394 ppm, are causing the world’s oceans to grow more acidic. A 2010 study from the scientific journal Nature showed that the oceans were becoming acidic at a rate ten times faster than at any time in the last 55 million years. Now, the new study shows that ocean acidity is growing at a rate most current sea creatures have never experienced.

The Science study collected data from sediment cores in order to gain information on past ocean acidity. The lead researcher, Bärbel Hönisch, a paleoceanographer at Columbia University’s Lamont-Doherty Earth Observatory, noted that past spikes in ocean acidity resulted in major losses of marine species. Barbel seemed concerned about species key to fishing and tourism saying “if industrial carbon emissions continue at the current pace, we may lose organisms we care about—coral reefs, oysters, salmon.”

Acidification causes stress to ocean creatures that build shells out of calcium, which the increasing acidity dissolves. This threatens creatures who serve as food and habitat builders for many ocean species. Of prime concern is the threat to ocean reef systems. Corals build their reefs out of calcium carbonate and rising levels of atmospheric CO2 put stress on these key species. It is estimated that more than a million species rely on ocean reefs for habitat. Stress to and loss of reefs would put most, if not all, of these creatures at extreme risk of extinction. Ocean researchers believe that it will not be possible for any corals to survive if CO2 levels reach 600-650 ppm. But current levels are already causing stress.

A combination of rapidly warming oceans, spiking ocean acidification, and reduced oxygen levels are creating a situation where an ocean mass extinction is inevitable if carbon dioxide emissions don’t stop soon. Since more than 1 billion people are fed by the world’s oceans, it is important to dramatically reduce these emissions soon.


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