The Great Barrier Reef is one of the most beautiful natural wonders on the planet. But rising global temperatures due to greenhouse gas emissions have damaged large parts of the reef. According to a research paper published Wednesday in the journal Nature, the coral cover on the Great Barrier Reef has declined from 28% to just 13% in the last 27 years.

The Great Barrier Reef
steinchen / Pixabay

50% of the Great Barrier Reef ‘extremely’ bleached

Researchers led by Terry P. Hughes of James Cook University in Australia conducted a series of aerial and underwater surveys. Data showed that the heatwave last summer that pushed temperatures in the country to record levels caused the most widespread and damaging coral bleaching on record. Hughes and his colleagues found that nearly 50% of the reef had been “extremely” bleached and 91% showed some signs of bleaching.

Scientists were not expecting this level of damage for another 30 years. The last year’s disaster was the third mass bleaching of reefs since 1998. Researchers suspect that the fourth one is already underway. Surveys showed that about 67% of corals along a 500-mile area north of the city of Cairns had died. The central and southern sections that managed to survive are bleaching now.

What is coral bleaching?

The Great Barrier Reef is one of the world’s largest living structures. Corals generally require warm water to flourish. But they are incredibly sensitive to excess heat. According to the New York Times, even a 2-3 degrees Fahrenheit rise in temperatures could kill them. Coral bleaching occurs when an increase in ocean temperatures causes the corals to expel the photosynthetic algae. It causes the coral reef to turn white and bleach. The bleached corals stand a chance to recover if the temperature drops and the algae recolonize them.

Coral bleaching is the direct result of global warming. Sean Connolly, the co-author of the study, told CNN that the frequency and severity of bleaching events give slow-growing corals little chance to recover. If the coral reefs die, we would lose some of the richest and most colorful life forms in the ocean. According to the United Nations, coral reefs serve as nurseries for about 25% of the world’s fish.

The impact on humans

The livelihood of 275 million people around the world is linked to the reefs. Reef fish are the primary source of protein for millions of people. The loss of coral reefs could disturb our food supply and lead to a humanitarian crisis. Scientists estimate that the Great Barrier Reef contributes an estimated $3.7 billion to the Australian economy through tourism and fishing.

Terry Hughes said in a statement that global warming is not a future threat. It has been happening for almost two decades on the Great Barrier Reef. The ocean temperatures have increased by at least 1.5 degrees Fahrenheit since the late 19th century. Last year, the El Nino warmed the planet to record levels, making 2016 the hottest year on record since 1880.