News of Interest.TV

A Reexamination of Climate Change Issues

Coral Reefs are Not Endangered Due to Global Warming

 updated April 14, 2010

 Aerial view of Great Barrier Reef, Australia.
Aerial view of Great Barrier Reef, Australia.

When the 1998 El Niño raised the temperatures of the waters in the Pacific Ocean, it caused widespread ”bleaching” of coral reefs, which is shown to be a natural response to temperature changes of water in scientific studies. The resulting change in the appearance of corals around the world was enough for many to proclaim that the world’s corals were "dying off en mass" due to global warming, despite the fact that corals have lived through hundreds of relatively recent historical cycles of glacial periods interspersed with warm periods, as well as higher acid concentrations in the water and sea level rise of as much as 400 feet.

Note a 2001 United Nations press release falsely claiming that the 1998 El Nino caused a loss of 90% of the corals in some parts of the Indian Ocean:

”.. It includes new information on the impacts of global warming and coral bleaching, including the El Niño event in 1998 that caused the loss of 90 per cent of the corals in some parts of the Indian Ocean, representing 5% of the world’s reef area. Much of this damage passed almost unnoticed by the world’s policy-makers. Marine scientists point out that had such levels of damage occur in terrestrial environments they would have caused a major public outcry.”

Claims of Coral Dying due to ”Bleaching”

The Book ”Unstoppable Global Warming— Every 1,500 Years” explains numerous scientific studies showing that ”bleaching” coral is an entirely natural occurrence for adapting to temperature changes of the surrounding water— through the coral expelling the current algea associated with it in order to accumulate new strains of algea with are better suited for the newer temperature of water. Studies cited include ”The Acquisition of Exogenous Algal Symbionts by an Octocoral After Bleaching" by Cynthia L. Lewis and Mary Alice Coffroth. Following is an excerpt from the book:

The claim that higher temperatures will kill off the world’s corals is irresistible to global warming activists. They understand the emotional appeal of the reefs and their bright-colored fishes. Greenpeace, perhaps predictably, has been quick to play this card:

”The Philippine coral reefs, among the most diverse and largest in the world, may not be around for long. ... On the last day of the symposium [at Bali] the environmental group Greenpeace released a new coral reef study showing that, because of the global warming, the Pacific Ocean could lose most of its coral reefs by the end of the current century.” (385)

The only problem with the ”disappearing coral” theory is that it is false. Corals date back 450 million years, and most of today’s coral species date back at least 200 million years. Just in the last two million years, coral reefs have been through at least seventeen glacial periods, interspersed with their warm interglacial periods. These glacial-interglacial shifts imposed repeated dramatic temperature changes, along with sea level changes as drastic as four hundred feet.

Temperatures across the Pacific change sharply with the El Nino-Southern Oscillation (ENSO)-which causes a major Pacific temperature change every four to seven years. The 1998 El Nino boosted sea surface temperatures all over the Pacific, causing massive coral bleaching, especially in the Indian Ocean. That’s when Mark Spalding, supposedly a coral expert, claimed that the vast majority of the corals had died out. (386) Bleaching is a part of corals’ strategy for adapting to their almost-constant temperature changes. (387)

Ross J. Jones of Australia’s Queensland University reported coral bleaching on a portion of the Great Barrier Reef just after average daily sea temperatures rose by 2.5 degrees Celsius in eight days. (388) However, Canada’s D.R. Kobluk and M.A. Lysenko found severe coral bleaching in the Caribbean after the water temperature declined 3 degrees Celsius in eighteen hours. (389)

New studies tell us that bleaching is the coral system’s way of dealing with sudden temperature changes. Cynthia Lewis and Mary Alice Coffroth of the University of Buffalo deliberately triggered bleaching in some coral colonies. In response, the colonies ejected 99 percent of their symbiotic algae friends. The researchers then exposed the bleached coral to a rare variety of algae that wasn’t in the coral colonies at the beginning of the experiment. Sure enough, within a few weeks, the corals had substantially restocked their algae shelves, and about half included the new marker algae. Later, the marker variety was displaced from several of the coral colonies by more effective algae strains-indicating that corals pick the best partners for the new conditions from the wide variety of algae floating in their part of the ocean. (390)

Lewis and Coffroth say this is a healthy demonstration of flexibility in coral colonies. They say coral systems have the flexibility to establish new associations with algae strains from the whole environmental pool and that is ”a mechanism for resilience in the face of environmental change.” (391)

In the same June 2004 issue of Science, Angela Little of Australia’s Cook University and Madeline van Oppen of Australia’s Institute of Marine Science echoed the findings of Lewis and Coffroth. They attached titles to various parts of the Great Barrier Reef in Australia and studied the algae recruited by the juvenile corals that grew on them. They found that the young corals were likely to try any algae— ”a potentially adaptive trait.” (392)

Eco-activists and biologists who claim global warming is killing corals are wrong-again. Science has returned its verdict on corals and global warming: No Link.


(385) Report from the 9th International Coral Reef Conference, Bali, 23 June 2003.

(386) Samanta Sen, ”Disappearing Coral Reefs Also a Human Loss,” Interpress News Service, September 13, 2001.

(387) Jeff Hecht, ”Corals Adapt to Cope With Global Warming”, August 11, 2004.

(388) R. J. Jones et al., ”Changes in Zooxanthellar Densities and Chlorophyll Concentrations in Corals During and After a Bleaching Event,” Marine Ecology Progress Series 158 (1997): 51-59.

(389) D. R. Kobluk and M.A. Lysenko, ”Ring Bleaching in Southern Caribbean Agaricia Agaricites During Rapid Water Cooling,” Bulletin of Marine Science 54 (1994): 142-50.

(390) C. L. Lewis and M.A. Coffroth, ”The Acquisition of Exogenous Algal Symbionts by an Octocoral After Bleaching,” Science 304 (2004): 1490-491.

(391) Ibid.

(392) A. F. Little et al., ”Flexibility in Algal Endosymbioses Shapes Growth in Reef Corals,” Science 305 (2004): 1492-94; Kobluk and Lysenko, ”Ring Bleaching in Southern Caribbean Agaricia Agaricites During Rapid Water Cooling,” 142-50.

Claims of Reductions in Coral Calcification due to Global Warming

Global warming researcher Steven McIntyre has published an article on his website showing the results of his examination of a widely publicized study by Glenn De’ath et al which claims a recent ”unprecedented” decline of coral calcification since 400 years ago. In his article, McIntyre explains that when the data from the study is graphed in a raw ”unsmoothed” fashion, much of the trends which had been reported essentially vanish, with the calcification rate seeming to actually slowly be increasing except for brief periods of downward spikes which may even be due only to missing data.

Claims About Ocean Acid Levels Rising due to Global Warming

As arguments of a warming ocean having an adverse effect on marine life have been shown to be false, the debate is now being attempted to be shifted to the ocean becoming more ”acidic” ( or rather, less ”basic” ) due to the sea absorbing more CO2, thus adversely effecting ”calcifying” marine life such as coral reefs and shellfish. However, an article on the website entitled ”The Ocean Acidification Fiction” explains the results of recently published scientific papers by Liu et al., and Pelejero et al. showing that current ocean acidification is not unusual, unnatural, or unprecedented.

A Million Websites Claim a Danger to Coral from the Effects of Global Warming

As many as a million websites including from numerous major mainstream news sources have accumulated during the past decade making claims of coral endangerment due to global warming, especially during the heyday of the global warming fears and during the ”bleached coral” episode in the years after 1998, and recent extreme articles are continuing to crop up to attempt to create support for the upcoming Convention on Climate Change.

While some dangers do exist for coral reefs such as ”blast fishing” and toxic pollution, global warming is certainly not among the legitimate dangers.

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