The end of Coral This map is a harbinger of a major change…

The end of Coral

This map is a harbinger of a major change about to happen to our planet, driven by humans. The 2015-2016 year hosted the strongest El Niño event on record, an event that was a disaster for coral reefs around the world. This map shows coral reefs around the world that were bleached in that event – red dots show places where >30% of reefs suffered bleaching events, orange dots are <30% but still noticeable bleaching, and only the blue dots avoided a bleaching event in that year. According to the results of a newly published global survey, this massive, global bleaching event was just one of many that have happened since 1980 – a rapid shift in the oceans that is threatening the existence of coral reefs entirely.

Coral are symbiotic organisms – they have 2 parts: photosynthetic algae that produce food and an animal that produces a hard skeleton that protects the algae. This symbiosis only works when conditions are right for each species; if ocean waters get too hot, the algae will overproduce certain chemicals, creating an environment that is toxic for the other part of the coral. In this case, the coral will expel the algae, leaving behind only the white, limestone shell of the coral. This type of event is called a “coral bleaching” as all the color departs the reef.

Coral bleaching events don’t need to be fatal; if conditions return to normal, eventually the algae will return and the reef will survive. However, it’s not healthy for the reef even if the reef does survive – bleaching events make reefs more prone to disease or attack by predators. Imagine a human who suffered a serious injury – if that injury was followed by another injury before there was time to recover from the first, that human is in much more jeopardy than would happen from either injury. Most reefs need 10-20 years to fully recover from a bleaching event.

Prior to 1980, coral bleaching events happened, but they were almost always local events driven by local weather patterns. A 2010 analysis of 150 years of a large reef in Honduras found that prior to 1998, there were 0 cases of coral bleaching that simultaneously affected the entire coral 400 kilometer long reef off the coast of Honduras over the last 150 years.

The new study conducted a global survey of recorded coral bleaching events and found that, on average, prior to 1980 most reefs would suffer local coral bleaching events 1 time every 25 years or so. That’s plenty of time for a reef to recover. However, globally that rate has been dropping dramatically and in the past few years, statistically, we’re down to 1 bleaching event every 5.9 years. This is not enough time for reefs to recover in-between events, and on its own that is putting coral health in jeopardy.

This pattern is not a local pattern. They surveyed 100 coral reefs in every basin around the world and 94 of them have had at least 1 severe, reef-wide bleaching event since 1980. There’s no clustering, it’s happening everywhere. During the 1998 El Niño, 74% of these reefs suffered a severe bleaching, during the 2016 El Niño 75% did. Many other reefs were bleached in a 3rd global bleaching event during a weaker 2010 El Niño – cutting the time between serious coral bleaching events to far less than the recovery time.

So far, the dominant pattern in these bleaching events is the vastly stronger El Niño events we are witnessing as the planet warms. El Niño events are associated with higher average ocean temperatures across much of the planet, and those ocean temperatures are the trigger for the super-bleaching events we have seen so far. Unfortunately, that is not the only part of the story.

Ocean temperatures have been rising globally even in years that don’t have an El Niño. The year 2017, for example, was the 2nd warmest year in recorded history dating back to the 1800s and most likely much longer. Even without an El Niño event, there were coral reefs that suffered serious bleaching events.

For the last 35 years, severe El Niño events were required to push reefs over the edge into a bleaching event. But, as the oceans are warming, the chance of a bleaching event hitting any reef in a given year is rising at 3.9% per year. Right now, the El Niño cycle is dominating bleaching events, but the odds of a bleaching event in any given year are going up at a comparable rate, and soon there isn’t going to be any major, healthy reef system left in the world. At the current rate, by 2050, most reefs will suffer major bleaching events every year. They won’t live that long.

Literally hundreds of millions of people rely on coral reefs to live. They provide shelter for fish that people eat, they regulate ocean chemistry, they build structures that absorb wave energy and protect coastlines. This is a looming disaster for the world – what will we do with a few hundred million people who lose their food supply and livelihood? The scientists who wrote the paper are in the press, as seen below, begging for people to pay attention to this issue and hoping that humans will try serious efforts to protect reefs – whether they be establishing artificial reefs or far more serious efforts to limit climate change due to greenhouse gases.

Without the kind of action that so far, humanity has been unwilling to take, we are going to lose coral reefs in the next 30 years. I’m skeptical that anyone will do what is necessary to prove me wrong.

-JBB

Image credit and original paper:

http://science.sciencemag.org/content/359/6371/80

2010 paper on Honduran reef:

http://bit.ly/2lZjNk0

Press reports:

http://bit.ly/2E8uyIi

http://bit.ly/2EehVM1