Courting Disaster: Is Widespread Coral Bleaching Imminent?
By Joseph Vukovich, Staff Contributor
Although they are less visible to humans than their terrestrial counterparts, oceanic ecosystems harbor an enormous amount of biodiversity. This is particularly true for coral reefs, which are frequently described as the “rainforests of the sea.” At least one scientist has stated that, because coral reefs are more biodiverse than rainforests, it would be more appropriate to call rainforests the coral reefs of the land.
In 2014, scientists discovered that a significant portion of the heat generated by global warming had been absorbed by the earth’s oceans, and that the oceans were warming more than had been previously appreciated.
“This has a large number of implications for the environment (e.g., weather patterns, fishery health, ice melting, etc.), but it poses a particularly strong threat to the health of coral reefs.”
To understand why, a brief explanation of the fundamentals of coral reefs is necessary. Healthy coral reefs have a symbiotic relationship with small algae called zooxanthellae. Zooxanthellae absorb nutrients, some of which are shared with their coral hosts. In addition to being a great source of food, these algae provide coral with its characteristic brilliant colors.
Warmer oceans present a threat to this relationship. The relationship can only be maintained within a narrow temperature range, so “when water warms above normal levels, corals tend to expel their algal lifeline.” The subsequent loss of color is what gives this process its name – coral bleaching. Of course, it is not a mere cosmetic change.
“The coral also loses an important source of food and becomes more susceptible to disease.”
It is possible for coral to recover by reestablishing the symbiotic relationship, but even then the coral may remain more fragile than it was before.
So, given the increased warming of the planet’s oceans, what are the implications for coral reefs? Past examples of bleaching events can help answer this question.
In 1998, there was an unusually strong El Nino event, causing global ocean temperatures to be higher than usual. The effect on coral reefs was substantial. Sixteen percent of the world’s reefs were lost that year alone. In some areas the effects were even worse. Near the Seychelles, El Nino interacted with regional weather effects to produce a particularly strong effect. The result was a bleaching of 90% of the coral in the Inner Seychelles region.
The 1998 El Nino effect was unusually strong. Could this mean that such a global bleaching is unlikely to reoccur? Unfortunately, probably not. As previously mentioned, scientists now have a greater understanding of the extent to which oceans have been warming. According to C. Mark Eakin, a scientist at the National Oceanic and Atmospheric Administration’s (“NOAA”) Coral Reef Watch program, it would not take nearly as large of an El Nino event to wreak havoc on coral reefs. Eakin points to the fact that, while it was not as strong as the 1998 bleaching, there was another global bleaching event in 2010 that was not driven by a large El Nino event the way the 1998 bleaching was.
Scientists are divided about whether or not 2015 will result in another bleaching event. Some, like Eakin, point to NOAA’s ocean temperature data as evidence that this may indeed be the case. Others point out that local weather conditions could potentially reduce the stress on reefs. It is important to highlight the fairly narrow range of disagreement here.
“They are not disagreeing about the fundamental mechanics of coral bleaching, or whether a global event could theoretically occur. They are disagreeing about whether one will happen this year.”
Even if Eakin ends up being incorrect about his forecast for this year, there is hardly room for celebration. As global temperatures continue to increase, global bleaching events become more likely (e.g., there’s less need for a “push” from a strong El Nino event), and the events will come more and more quickly. Although, as mentioned above, reefs can theoretically recover from a bleaching event, they grow very slowly. Repeated stresses in the form of bleaching events may push reefs beyond their capacity to recover.
While the threat to coral reefs, and the ecosystems they inhabit, is indeed severe, in some sense this information hardly changes anything. Scientists have agreed for some time that global warming is real, that human activity is having a large impact on it, and that the price of inaction is severe. In this way, the threat to coral reefs and oceanic ecosystems is nothing more than another in a long list of potential catastrophes with a common solution – addressing mankind’s reckless emission of carbon dioxide into the atmosphere.