Bleached Coral Reefs Bounce Back

Bleached and dying coral reefs are often held up as proof that global warming is laying waste to Earth's ecosystems. Now come reports that a number of reefs around the world are being brought back from the dead by dedicated oceanographers and conservationists. “The results are more than just promising; they are beautiful,” says Baruch Rinkevich, a marine biologist at the National Institute of Oceanography in Haifa, Israel. But how can these reefs recover in the face on ongoing global warming? Either global warming has reversed course or the bleaching of reefs wasn't due to global warming in the first place.

In Jamaica, the Philippines, Japan, Singapore, Thailand, and Zanzibar people are busy rebuilding reefs that have seen better days. Mineo Okamoto, a specialist in marine assessment techniques at Tokyo University of Marine Science and Technology, has been working to restore Sekisei Lagoon in Japan's Okinawa prefecture. Back in 1993 this remote coral lagoon was in pristine condition but, according to a report in Science, “Okamoto sensed that change was coming from global warming, with its threat of more-frequent bleaching events, and rising ocean acidification, which is caused by the uptake of carbon dioxide from the atmosphere and weakens corals.”

In 1997 and 1998 an El Niño followed by a La Niña warmed the eastern Pacific to the point that the algae that live symbiotically with coral deserted their hosts. Without the zooxanthellae algae to provide nutrients coral colonies starved and bleached out. The 1997-98 El Niño event, which lasted for over a year, also produced record-high sea surface temperatures throughout the Indian and western Pacific oceans, which caused some of the most extensive coral bleaching ever seen. The bleaching event killed an estimated 16% of corals worldwide (see “Warmer Waters More Deadly to Coral Reefs Than Pollution”).


Bleached coral. Photo OAR/National Undersea Research Program.

Sekisei Lagoon's northern edge was hit hard. But the interior and southern rim suffered only minimal damage, which enabled coral to recolonize bleached sections without human intervention. To help the damage portions of the lagoon recover, Okamoto has been placing grooved ceramic disks in locations where they can serve as shelter for coral larvae when the reef corals spawn. Once the immature coral starts growing on the disks, they are used to recolonize damaged portions of the reef. Around the world similar efforts at reef restoration are underway with promising results (see “Bringing Coral Reefs Back From the Living Dead”).

While we can all applaud the efforts of conservationists like Okamoto, something seems out of place here. According to the climate change crowd, global warming was supposed to be an unremitting march to destruction—an ever warming climate bringing with it scorched lands and ravaged oceans. How is it that more than a decade after the big bleach-out in 1998 the reefs are recovering, many on their own (see “Heat-resistant Corals Ignore Climate Change Threats”). The article in Science directly blames human activity, sediment and El Niño for the coral's plight, with references to global warming tacked on at the beginning and the end. This leads to the conclusion that global warming is mentioned more out of reflex or political correctness than any true causal relationship.

Since the publication of a paper in the Journal of Geophysical Research, which found that the El Niño-Southern Oscillation (ENSO) is a key indicator of global atmospheric temperatures, more and more scientists are questioning the IPCC global warming dogma. Chris de Freitas, a climate scientist at the University of Auckland, John McLean, of Applied Science Consultants in Victoria, and Bob Carter, from the Marine Geophysical Laboratory at James Cook University, found that combining the ENSO with the effects of sporadic volcanic eruptions accounted for 80% of recorded global temperature change in recent decades. CO2 and other anthropogenic global warming forcings become bit players on the global scale.


ENSO temperature variation, note the spike around 1998.

“The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely” says corresponding author de Freitas. Those who study coral directly attribute the bleaching of reefs to ENSO moderated temperature changes, so why throw in a reference to global warming? Perhaps to garner more research funding or to curry favor with the climate change establishment.

Why do ecologists and conservationists always blame humanity for any change in the environment, particularly destructive change? It is because they have a myopic view of nature, believing it to be static and unchanging. The only way to explain disruptive change in their world view is to blame humanity. But that is not how nature works. To quote from Dr. Roy Spencer:

They can not conceive of nature changing all by itself, even though evidence of that change is all around us. Like the more activist environmentalists, their romantic view of a peaceful, serene natural world ignores the stark reality that most animals on the Earth are perpetually locked in a life-or-death struggle for existence. The balances that form in nature are not harmonious, but unsteady and contentious stalemates.

Nature visits all manner of destruction on its creations: floods, hurricanes, forest fires, tsunami, and mud slides caused by torrential rains. And these are just the most common, add earthquakes, volcanoes, ice ages and the occasional rogue asteroid. Change happens in nature, often violently, for without desolation there can be no renewal, no empty niches for new species to evolve into. Hardship is nature's perpetual gift to every living thing.

Yes, temperature can and does cause coral bleaching, but that doesn't imply global warming. If science wants something that can plausibly be blamed on increased atmospheric carbon dioxide, acidification seems a more likely contributing factor. No doubt other human activity also harms the notoriously sensitive coral reefs as well. But think about this for a moment—coral became the primary builders of ocean reefs sometime after the Permian-Triassic Extinction event some 251 million years ago. Since then they have weathered a number of other lesser extinctions and episodes of rapid global warming. Ice ages and warm periods have come and gone and the coral reefs remain.

In fact, Paul Blanchon et al. have published important new research on “Rapid sea-level rise and reef back-stepping at the close of the last interglacial highstand” the journal Nature. Investigating ancient coral beds in the northeast Yucatán peninsula, Mexico, researchers claim to have documented a period of rapid sea-level rise—a catastrophic increase of more than 5 centimeters per year over a 50-year stretch. This occurred around 121,000 years ago during the Eemian interglacial, the warm period before the last glacial onslaught. The sudden increase in sea-level resulted in the death of the existing reef because the sea rose too fast for the coral to build their foundation up toward the surface. Once the sea-level stabilized again, the same group of corals established a new reef farther inland and 10 feet higher in elevation, a process known to geologists as backstepping.

The Eemian was some 2°C warmer than current global temperatures and clearly coral managed to avoid extinction under those conditions. In the larger scheme of things, coral is able to roll with the changes, adapting to new conditions, something mankind should take note of. This is not to say that any individual coral or reef is immortal, clearly they are not. Though some researchers may refuse to believe that nature would harm the creatures they love, the periodic devastation of reef ecosystems is just another part of nature's cruel cycles. As an outcome of global warming, bleached coral is a red herring.

Be safe, enjoy the interglacial and stay skeptical.


help save the reefs.

A better debate than gun control?

I am researching the topic of coral reef destruction to assist my daughter's school critical writing project. It seems that college-educated adults only really delve into the academic literature around a contemporary topic when it is chosen as a school assignment by their children. Anyway, my compliments to you for a comprehensive online platform that addresses the arguments against blaming natural processes on various aspects of human activity.

The gun control debate is strangely similar to that of Carbon Dioxide regulation in that it hinges on solving destructive events (like coral bleaching or school killing rampages) by limiting free enterprise (like emission control equipment or background checks). The only difference is that the United States has never passed a Constitutional Amendment declaring that the right of nature to defend itself shall not be infringed. Maybe we should?

More on Reef Resilience

For more scientific evidence of the resilience of coral reefs see “Ravaged Reefs Rebound.” Looks like corals as a group are not as fragile as some of the eco-alarmist types would have us believe.

De Feitas paper

While generally agreeing with most of this post I find the reference to the de Freitas paper misleading. Sure 80% of the variation in temperature in recent decades is related to ENSO, volcanoes etc, but this is the big squiggles on a timeplot of temperature. The slow background rise in average temps is related to the other 20%. I'm not saying it is co2 but it must be something.

It must be something...

As a follow on to my earlier reply below, I would suggest reading “Earth's Climate Follows The Sun's UV Groove.” There is growing evidence that variation in the Sun's output of UV light drives atmospheric circulation in ways previously unsuspected. Both decadal and centennial variation in climate can be explained via this mechanism, so when you say “it must be something” I would suggest looking up—the answer was overhead all along.

Could it be...

You say that the slow background rise in global temperature must be due to something and you are correct. Consider that we are still in the midst of an interglacial warm period and that previous such periods have topped out with Arctic temperatures 2-4°C higher than today. While each interglacial is different, what we are seeing is neither surprising nor unprecedented. I have never denied that Earth is warming. I am, however, highly skeptical that the rise in temperature is caused primarily by human CO2 emissions.

Sadly, pollution and warming don't help coral health

While I agree that ecosystems are hardly stable, it is evident that coral reefs are in trouble and at least part of the blame lies on us. We published work in PLoS One last year (Carilli et al. 2009, PLoS One 4(7): e6324. doi:10.1371/journal.pone.0006324) that showed that the 1998 el Nino affected about 90+% of one of the major reef-building corals in the Mesoamerican reef tract. Coral growth rate plummeted and remained low, even in the least polluted parts of the reef for about 3 years before snapping back. Unfortunately, corals in areas more affected by human pollution, fishing, and sediment runoff had not recovered by 2006-2007 when we completed our field work suggesting that pollution exacerbates the effects of warming. We also noted that bleaching in the Caribbean only starts in 1987 suggesting that impacts on the reef have been getting worse. Indeed, we saw no coral die-offs or changes in growth in the 150 years before this. It is worthwhile being a skeptic, but the evidence is strong that there have been negative directional changes in reef health over the last century. Global warming, which is expected to make the sudden extreme warming of el Ninos more intense and perhaps more frequent, is bad news for corals.

Coral: tougher than usually portrayed

Finding no coral bleaching over the past 150 years is hardly a conclusive finding. Climate has varied significantly since corals became the dominant reef builders in the ocean. I do not deny that human activity can and has damaged reefs—pollution and direct physical destruction has ravaged many ocean environments. However, I do not accept that variations in temperature and pH of an equal or greater magnitude than today have not occurred in the past.

As the collection of climate data has improved, it has become obvious that temperature variation caused by the El Niño/La Niña cycle and other decade scale osculations dwarfs any warming trend due to human activity. One of the points of the paper I reviewed was that many corals are more resilient than the insanely fragile creatures usually portrayed by ecologists. Any life form that over specializes to the point where it cannot tolerate a few degrees of temperature change or other variation in its environment has evolved itself into extinction.

And, as the long, brutal record of life on Earth shows, nature periodically cleans house, clearing away the over specialized to make way for new forms of life. Since coral is still around after several hundred million years and a number of notable extinction events, they must not be as delicate as generally thought. As a scuba diver, I am glad that they are tougher than assumed.

Happy Days for Chachi

The 100 million people who depend on coral reefs for nutrition will be glad to hear this. They need only wait a few hundred or thousand years until new reefs (might) form. Unless, of course, they don't if the seas are still too polluted, like today in the Carribean with its miles of dead fancorals

Ocean temperatures have risen

Ocean temperatures have risen and fell countless times throughout geological history. Coral existed when the earth was way warmer and way colder then it is now, suggesting they are capable of adapting to an ever changing climate.

Using their recovery to downplay the current worldwide climate change is pseudoscience.

Shouting "Global Warming" in a crowded ocean.

Most certainly, the recovery of coral is not scientific proof that the world isn't warming. Neither is pointing to episodes of coral bleaching proof that we face ecological disaster because of anthropogenic greenhouse gas emissions. No more than a hot year or a cold year, a dry year or a wet year, is proof of long term climate change.

The problem with the whole

The problem with the whole “planet is warming” vs. “planet is fine” debate is that people don’t realize that Earth’s climate in inherently unstable with or without Human intervention. The last 10,000 years for example have been the most stable in the past 2,000,000 according to the geological record.

With or without human intervention… the climate WILL dramatically change again. There is no question about this scientific fact and it has nothing to do with mankind. When it does happens we will see catastrophic changes in weather patterns, massive flooding, unimaginable drought and mass die offs of multiple species-- That, or a big freeze that would come with a new ice age.

Yes, the world will eventually recover as it always has before. However, the next time that it happens will be the first time that mankind will have to deal with it as a worldwide civilization of 7 Billion people and counting.

In regards to population

Off topic, but you will be relieved to hear the Earth's population is said to peak at only 8 billion, not 9 as previously expected. Due to the catastrophic drops in birth rates and an ageing population, the world's population will begin to decline in a few years. Rest assured.