At a Glance

A mass coral bleaching event that has affected the world's reefs for three years is finally easing. About three-quarters of the planet's reefs were damaged or killed. Researchers say despite improvement, the reefs may be barely able to survive during good conditions.

A three-yearmass bleaching event that affected coral reefs worldwide is finally easing, scientists say.

Rising water temperatures left about three-quarters of the world's delicate coral reefsdamaged or killedin what scientists say was the largest coral catastrophe.

The National Oceanic and Atmospheric Administration announced a global bleaching event in May 2014. It was worse than previous global bleaching events in 1998 and 2010.

The forecast damage doesn't look widespread in the Indian Ocean, so the event loses its global scope. Bleaching will still be bad in the Caribbean and Pacific, but it'll be less severe than recent years, said NOAA coral reef watch coordinator C. Mark Eakin.

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Places like Australia's Great Barrier Reef, northwest Hawaii, Guam and parts of the Caribbean have been hit with back-to-back-to-back destruction, Eakin said.

University of Victoria, British Columbia, coral reef scientist Julia Baum plans to travel to Christmas Island in the Pacific where the coral reefs have looked like ghost towns in recent years.

"This is really good news," Baum said. "We've been totally focused on coming out of the carnage of the 2015-2016 El Nino."

While conditions are improving, it's too early to celebrate, said Eakin, adding that the world may be at a new normal where reefs are barely able to survive during good conditions.

Eakin said coral have difficulty surviving water already getting warmer by man-made climate change. Extra heating of the water from a natural El Nino nudges coral conditions over the edge.

About one billion people use coral reefs for fisheries or tourism. Scientists have said that coral reefs are one of the first and most prominent indicators of global warming.

"I don't see how they can take one more hit at this point," Baum said. "They need a reprieve."

MORE ON WEATHER.COM: June 2016 Coral Bleaching on Great Barrier Reef

Before and after image showing coral after undergoing bleaching at Lizard Island on the Great Barrier Reef in March 2016, and the same reef in May 2016 after the coral had died.