As the Great Barrier Reef experiences coral bleaching for the second year in a row, scientists say that that the only way to save it is urgent action on climate change.
High water temperatures cause coral bleaching. Corals thrive in the warmer waters of the tropics, but bleaching can occur even with a slight increase in the ideal temperature. Higher temperatures make the zooxanthellae, with which the corals have a symbiotic relationship, excrete toxins. The corals then have to expel the zooxanthellae. However, zooxanthellae nourish both themselves and their coral hosts. These algae also provide the corals with their brilliant colors. Once the algae depart, the corals turn bone-white, hence the term “bleaching”.
Loss of zooxanthellae also means loss of nutrients for the corals.
Scientists have predicted that warming temperatures pose a threat on the survival of the Great Barrier Reef. With the steady rise of global temperatures due to climate change, scientists warned that severely cutting emissions down was crucial. However, global temperatures continued to rise. Now, even a small rise in water temperature can harm the coral reefs.
The Great Barrier Reef is a natural wonder. With an area of about 344,400 square kilometers, it is so large that it can be seen from space. It is also the largest structure built by living organisms. These organisms are coral polyps, which also make up the corals themselves.
The reef is also home to a large amount of diverse marine life. Maintaining diversity is vital to the survival of many living species.
The reef is also a popular tourist destination. More than that, though, it holds a special place in the lives and cultures of Aborginal Australians and Torres Strait Islanders. The reef has provided these groups with important sources of protein throughout their history.
Unfortunately, the reef experienced the worst bleaching on record last year. 85% of the reef system experienced damage. Usually, when waters go back to ideal temperatures, the zooxanthellae return and the corals recover. However, if high temperatures go on for too long, the corals eventually die off. If global temperatures keep rising at the rate they're rising now, many coral reefs all over the world may disappear for good.
A recent study detailed major bleaching events in the Great Barrier Reef. They observed last year's bleaching event as well as other events in 1998 and 2002. In 1998, 48% of the reef underwent bleaching, and 56% in 2002. With 85% of the reef damaged last year, it seems that major bleaching events get worse over time.
The researchers concluded that only urgent and decisive action on climate change will truly save the Great Barrier Reef. Climate change caused the rising temperatures that caused bleaching events. Now, climate change has to significantly slow down so the reef's corals and diverse life can survive. The researchers stress that a global effort to slow global warming is crucial to preventing massive bleaching events from reoccurring.
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