JUANA SUMMERS, HOST:
Scientists say Australia's Great Barrier Reef is suffering another mass bleaching. That is when corals turn ghostly white due to heat, and it's becoming more common as the climate warms, as NPR's Lauren Sommer reports.
LAUREN SOMMER, BYLINE: Even though it's autumn in Australia, the water around the Great Barrier Reef has been as much as seven degrees hotter than average in the past few weeks. So scientists have been watching the reef closely, flying over it in small planes. From the air, they can see some corals are bright white. David Wachenfeld is chief scientist of Australia's Great Barrier Reef Marine Park Authority.
DAVID WACHENFELD: This assessment of bleaching at multiple reefs confirms a mass coral bleaching event on the reef.
SOMMER: Corals turn white when they're stressed because they lose their roommates, the tiny marine algae that live in corals. Those algae make most of the corals' food. But bleaching doesn't mean the corals are dead yet.
WACHENFELD: If the water temperature decreases, bleached corals can recover from this stress.
SOMMER: But temperatures haven't cooled down yet. And this is the fourth mass bleaching on the reef in the past seven years.
EMILY DARLING: What jumps out at me is the frequency of these events. There's just been no recovery window for the corals.
SOMMER: Emily Darling is with the Wildlife Conservation Society. She says these bleaching events are becoming more common as the climate gets hotter. And without time to recover, coral reefs are at risk of disappearing, harming those ecosystems and the people who depend on them.
DARLING: We need to really learn from these bleaching events. We need to change business as usual. We need to take action on climate change.
SOMMER: That means cutting carbon emissions, she says, as well as protecting coral reefs in pockets of cooler water. Those refuges may be some of the few places that corals can survive. Lauren Sommer, NPR News.
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