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Earth's coral reefs could be gone by 2100, research finds

Image: Bleached coral on Australia's Great Barrier Reef near Port Douglas
Bleached coral on Australia's Great Barrier Reef near Port Douglas on Feb. 20, 2017. Copyright Brett Monroe Garner Greenpeace via Reuters file
Copyright Brett Monroe Garner Greenpeace via Reuters file
By Denise Chow with NBC News Tech and Science News
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The bleak outlook forecasts that warming oceans and rising seas could have a devastating impact on ocean ecosystems.


Climate change could wipe out almost all coral reef habitats around the world by 2100, according to research released Monday.

The bleak outlook forecasts that warming oceans and rising seas could have a devastating impact on ocean ecosystems, suggesting that current efforts to restore dying corals will likely encounter difficulties as global warming continues to decimate habitats that could once support healthy reef systems.

"By 2100, it's looking quite grim," Renee Setter, a biogeographer at the University of Hawaii at Mānoa,said in a statement. She presented her findings at the annual Ocean Sciences Meeting, which is being held from Feb. 16 to 21 in San Diego.

Setter and her colleagues simulated ocean environments in which coral reefs currently exist based on projections of sea surface temperature, ocean acidification, wave energy, pollution and fishing practices. They found that by 2100, there will likely be few to zero suitable habitats remaining for corals.

"Honestly, most sites are out," she said in the statement.

The few sites that could support reefs by the end of the century include small portions of Baja, California, and the Red Sea, according to the researchers.

The research shows that corals are most vulnerable to changes in their environment driven by human-caused greenhouse gas emissions. Greenhouse gases, such as carbon dioxide, trap heat in the atmosphere, increasing global surface and ocean temperatures. And when carbon dioxide mixes with ocean water, the resulting chemical reactions make the water more acidic.

This combination of warming seas and ocean acidification is already threatening coral reefs around the world, causing these ecosystems to undergo so-called bleaching events.

Between 2014 and 2017, roughly 75 percent of the world's tropical coral reefs experienced warm conditions that were severe enough to trigger bleaching events, according to the National Oceanic and Atmospheric Administration. And in 2016 and 2017, about half of the coral in Australia's Great Barrier Reef died after record heat triggered mass bleaching.

Coral bleaching occurs as a response to abnormal environmental conditions, such cooler- or warmer-than-usual ocean temperatures, or when oceans become more acidic. When stressed, corals expel tiny photosynthetic algae that live in their tissues, causing these vibrant marine invertebrates to turn completely white.

Bleaching events don't necessarily kill the corals, but the reefs become particularly susceptible to disease, and as oceans continue to warm at an accelerated pace, many reef systems are under siege.

In addition to driving tourism and boosting local economies, coral reefs are an integral part of ocean ecosystems, supporting hundreds — and sometimes thousands — of fish and other marine animals. In a 2017 Deloitte Access Economics report, for instance, the Great Barrier Reef, a designated World Heritage Site, was valued at $56 million.

Beyond climate change, coral reefs are also under threat from illegal fishing, coastal development projects and pollution.

Setter said efforts to clean up pollution in the world's oceans and projects to restore at-risk reefs are essential, but that ocean ecosystems will continue to decline if the root causes of climate change are not addressed.

"Trying to clean up the beaches is great and trying to combat pollution is fantastic. We need to continue those efforts," she said in the statement. "But at the end of the day, fighting climate change is really what we need to be advocating for in order to protect corals and avoid compounded stressors."

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