The environmental website Grist posted a sad, damning story on Friday, Jan. 5 about coral bleaching–one of many harbingers of the environmental disaster known as climate change. The story, which discusses a new paper published in the journal Science, concludes that coral bleaching events (caused when the ocean gets too warm, which causes the coral to expel the symbiotic algae that they rely on) around the world are happening so quickly these days that reefs lack sufficient time to recover, which leads to mass die-offs.
“With the time transpiring between bleaching events shortened by a factor of five, there isn’t adequate time for the ecosystems to recover,” Grist reported. “Even the fastest-growing corals that survive a major bleaching event need about 10 years to regain their health. These damaging events are now occurring more quickly virtually eliminates any serious chance of large-scale recovery on a global scale. Huge portions of the world’s reefs face almost certain death–and that loss will reverberate beyond earth’s oceans.”
This isn’t hyperbole. In fact, the paper–which lists Terry P. Hughes and 24 other researchers as authors and is titled “Spatial and temporal patterns of mass bleaching of corals in the Anthropocene”–is every bit as alarmist. Here’s a very brief excerpt, from the paper’s abstract:
“We analyzed bleaching records at 100 globally distributed reef locations from 1980 to 2016. The median return time between pairs of severe bleaching events has diminished steadily since 1980 and is now only 6 years,” states the paper. “As global warming has progressed, tropical sea surface temperatures are warmer now during current La Niña conditions than they were during El Niño events three decades ago. Consequently, as we transition to the Anthropocene, coral bleaching is occurring more frequently in all El Niño–Southern Oscillation phases, increasing the likelihood of annual bleaching in the coming decades.”
To find out how this study squares with what researchers in Hawaii know, I asked the University of Hawaii’s Hawaii Institute of Marine Biology–which has long studied coral reefs and bleaching events.
“We have not had enough widespread bleaching events to make the determination of whether the frequency or intensity has increased,” said Dr. Ku`ulei Rodgers, the Institute’s Coral Reef Ecology Lab Principal Investigator, told me in a Jan. 5 email. “The main Hawaiian Islands (MHI) did not see the first widespread bleaching event until 1996. This was followed by bleaching events in the Northwestern Hawaiian Islands in 2002 and 2004 that did not affect the MHIs. We did not have another major bleaching event until 2014 and 2015 which affected the entire archipelago. Statistically these few data time periods are not enough to determine whether or not the frequency has increased in Hawai‘i as they have been able to do on a global scale. Regional differences are strikingly different throughout the world.”
Rodgers also referred me to a Dec. 8, 2017 study she co-wrote (along with Keisha Bahr and Paul Jokeil) that was published in the journal Frontiers in Marine Science. The paper, titled “Impact of Three Bleaching Events on the Reef Resiliency of Kane‘ohe Bay, Hawai‘i,” states that while bleaching events “have been increasing in frequency and severity worldwide,” there has been “extensive variation” in the three relatively recent bleaching events in Hawaii.
“Bleaching prevalence was observed to decrease in certain reef areas across events, suggesting some acclimation and/or resilience, but possible increase susceptibility to mortality,” states that paper. “Long-term monitoring sites show a similar temporal pattern of coral mortality and decline in coral cover, but revealed some reefs remained relatively un-impacted by consecutive high temperature events.”
Clearly, more research is needed, though Rodgers said the Science study makes it pretty clear what’s headed our way.
“The Hughes et al paper that just came out gives a good indicator of what Hawaii will experience in the near future,” Rodgers said. “Their predictions for the frequencies of bleaching events for the Pacific will most likely hold true for the Hawaiian Islands. This is because they base their findings on a large, robust dataset.”
Click here to read the 2017 Kaneohe coral bleaching study by Bahr, Rodgers and Jokeil.
Photo of bleached coral: NOAA/Bernardo Vargas-Angel