Some 70 percent of coral reefs across the globe have been affected by bleaching—which NOAA said is the most obvious visual indication of climate change in the marine environment. Coral reefs are typically vibrantly colored by photosynthetic algae called zooxanthellae—which provides the reef with food and oxygen. But exposure to carbon dioxide is causing water temperatures to rise, and algae cannot surive in these warmer waters. As they die off, the coral deteriorate and lose their color, a phenomenon known as bleaching. The widespread occurrence of bleaching throughout much of the world is alarming not only because it could be the result of human-caused climate change but also because it precedes the disappearance of the reefs—and the life they support—altogether.
NOAA experts said bleaching was happening to American reefs at an alarmingly rapid pace.
“I’m concerned because we could very well see bleaching return to Florida, parts of the Caribbean and Hawaii,” Mark Eakin, a coral reef specialist at NOAA, told The Guardian. “It won’t be as severe as 2015 but we’ve now moved into a general pattern where warmer than normal temperatures are the new normal. U.S. reefs have taken a severe beating. We are looking at the loss or at least severe degradation of most reefs in the coming decades.”
Australia’s Great Barrier Reef has garnered the most attention after two-thirds of the 1,400-mile reef suffered from bleaching in 2016. However, experts said American coral reefs near Hawaii, Florida, Guam and Puerto Rico may soon be subject to severe bleaching and could all die off in a matter of years if water temperatures continue to rise.
“As of May 2017, the ongoing global coral bleaching event continues to be the longest, most widespread, and most damaging on record. It has affected more reefs than any previous global bleaching event and has been worse in some locales (e.g., Great Barrier Reef, Kiribati, Jarvis Island),” according to the NOAA report.
In 2014 and 2015, some 90 percent of coral reefs in Hawaii alone were suffering from bleaching. Even after the state established strict no-fishing zones and environmental protections, 47 percent of corals near Oahu were found to be affected by bleaching and almost 10 percent were nearly dead, according to a Hanauma Bay nature preserve survey.
Georgia Tech oceanographer Kim Cobb told The Guardian U.S. reefs won’t be sustainable in another 100 years at the current rate of global warming.
“The idea we will sustain reefs in the U.S. 100 years from now is pure imagination, at the current rate it will be just 20 or 30 years. It’s just a question of time,” she said. “The overall health of reefs will be severely compromised by the midpoint of the century and we are already seeing the first steps in that process.”
Reef bleaching doesn’t just negatively impact the zooxanthellae covering coral but also the fish communities that depend on the coral for their survival.
There are millions of different species that live in and near coral reefs. However, rising water temperature has led to the threatening of 22 coral species while three have been listed on the Endangered Species Act. There also is a number of fish that could face extinction as their natural coral reef habitats continue to disintegrate, including butterfly fish, spiny lobsters, whale sharks, hawksbill sea turtles and various species of whales and dolphins.
According to Cobb, bleaching of U.S. reefs may “undercut the resilience of these ecosystems” as soon as 2040.