Coral reefs routinely host a quarter of the ocean’s biodiversity, and at some point more than half of fish species spend time on a reef. Those fish go on to feed hundreds of millions of people, but back at the foundation of the food chain, corals are facing mass mortality, according to presenters at the EarthxOceans Conference, and could go extinct in this century.
Corals live in an intimate symbiotic relationship with microscopic algae that, like all plants, convert sunlight and carbon dioxide into sugars and oxygen. The algae feed the corals and lend them their vivid colors.
As climate change warms those algae, they produce more oxygen, explained Charlie Veron, a marine biologist with the International Society for Reef Studies. “With corals, as with everything else, there reaches a point where there is too much oxygen.”
When corals detect toxic oxygen levels, they eject the algae from their tissues, turning them white in a process called bleaching. Bleached corals have also lost their food supply. Unless temperatures return to normal within weeks, the corals will starve and b break down, until all that remains is rubble.
“This (rapid warming) hasn’t happened in millions of years, and so there’s no adaptation to what the corals are doing,” Veron said. Half the world’s corals have already perished. “We can’t do anything about that other than stop warming the oceans and that means stopping climate change.”
But it’s already too late to save corals from warming without more immediate interventions.
“Normally conservationists would solve the underlying issue, climate, before beginning restoration,” said Tom Moore, the coral-reef restoration manager for the Florida Keys Marine Sanctuary. “If we waited to start restoration until after we dealt with climate change, we would likely be left with nothing to restore.”
Veron hopes to grow each coral species in aquaria, not unlike the Svalbard Global Seed Vault, so the ocean can be repopulated after warming is reversed.
Moore has already seen some local success restoring reefs using corals raised in nurseries. “In the same way that we can repopulate forests by taking clippings from trees, we can cut one coral up into thousands of pieces,” he said.
Humans can’t restore all the world’s reefs this way, however, because the task is too vast for a species that can work underwater only a few hours per day. So the U.S. National Oceanic and Atmospheric Administration hopes to develop robot divers to repair reefs using artificial intelligence.
Other scientists are fighting for corals on other fronts. Marine biologist Erika Woolsey, CEO of The Hydrous, educates humans with virtual tours of coral reefs and 3D-printed models of living corals that, like the real thing, turn white in warm water.
Coral ecologist Helen Fox and the Allen Coral Atlas are mapping the world’s coral reefs to monitor their health. “It’s hard to save what you don’t know where it is,” she said.
Peter Mumby, chief scientist for the Great Barrier Reef Foundation, works to identify and protect coral reefs most crucial to the spread of coral zygotes. He also suggests cooling the ocean by brightening the clouds above it.
But climate change isn’t the only threat corals face from human activity, warned Dr. Robert Richmond, director of the Kewalo Marine Lab in Hawaii. Richmond has been training local scientists in coastal communities to promote practices that protect coral. In Palau, for example, farmers moved taro fields inland, away from rising seas, and prevented agricultural sediment from reaching and smothering corals.
Corals can be saved, Richmond said, by “doing things like protecting sediment discharges from getting into the ocean, controlling the kinds of toxic substances that get into the water and ensuring that there are fish there to provide the ecological services.”
Individuals can help prevent climate change, Fox said, by making lifestyle changes that reduce carbon emissions, like flying less, eating less meat, conserving energy and agitating for systemic change. “I really think that’s what it’s going to take to get coral reefs thriving again.”
Written by: Jeff McMahon