The Great Barrier Reef is Turning White. Why Does That Alarm Scientists?

May 12, 2022

Warming sea temperatures threaten to wipe out huge amounts of Australia’s famed Great Barrier Reef, scientists say. The evidence? Bright colors have disappeared from much of the world’s largest coral reef system. 

In fact, experts say, about 90% of the 133,000-square-mile Great Barrier Reef has suffered “bleaching.” That happens when sea temperatures rise. The higher temperatures cause corals to expel algae that the reefs need to live. The reefs then turn white. Bleaching results mostly from climate change. And that’s driven by the release of greenhouse gases. 

This is the sixth “mass bleaching” event on the reef system since 1998, according to Australia’s Climate Council. Three have occurred since 2016, the council said. It called for action to slow climate change. 

“The science is very clear: In order to save the world’s reefs from total destruction, we must dramatically reduce emissions in the 2020s,” the council’s research director said. 

According to the National Oceanic and Atmospheric Association, at least 75% of the world’s tropical coral reefs have suffered bleaching. In 30% of them, the heat killed the coral. 

Coral reefs play a critical role in our ecosystem. They provide habitat and spawning areas for marine life. The reefs also protect thousands of species from predators

Fishers and those who work in tourism also rely on the reefs. That's how they make their living. In addition, reefs provide natural barriers. They protect coastal areas by absorbing the force of waves and storm surges. 

Photo from UNESCO World Heritage Convention.

Question
According to information in the story, what percentage of the world’s tropical coral reefs have suffered bleaching because of warming sea temperatures? (Common Core RI.5.1; RI.6.1)
a. approximately 90%
b. more than 75%
c. less than 50%
d. roughly 30%
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