How does rising atmospheric CO2 affect marine organisms?

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Health Status of the World's Coral Reefs
Volume 4, Number 37: 12 September 2001

One of the reddest of red flags around which climate alarmists rally these days is the devastation the ongoing rise in the air's CO2 concentration is predicted (by them, of course) to visit on coral reefs (see, for example, our Editorial of 1 January 1999). They are particularly hard on global warming in this regard, which they claim is responsible for the bleaching of corals that has occurred in many parts of the world over the past few years. Several new studies, however, suggest this unfortunate phenomenon is more likely the consequence of a number of other human actions and that it is not in any way related to the historical increase in the atmosphere's CO2 content.

Reporting from the quadrennial North American Paleontological Convention held in Berkeley, California earlier this year, Stokstad (2001) describes the results of some recent studies that bear directly on this subject. Particularly noteworthy are the findings of John Pandolfi of the Smithsonian Institution's National Museum of Natural History, who determined from numerous surveys of fossil reefs on San Andres, Curacao and Barbados that Caribbean reefs have consisted of essentially the same relative mix of coral species for most of the past 220,000 years.

The work of Pandolfi and his associates also revealed that the most prominent of these species -- the Elkhorn coral (Acropora palmata) -- typically comprised approximately 80% of all Caribbean reef corals over this lengthy span of time. Since the early 1970s, however, this historical stalwart of the region has become exceedingly rare; and "once-majestic reefs," as Stokstad puts it, "now are over-grown with algae." Stokstad quotes Richard Aronson of the Dauphin Island Sea Laboratory as saying "this tells you that what we're seeing today is not some random fluctuation." Indeed, he further quotes John Ogden of the University of South Florida as saying that the recent devastation is "a profound change that's unprecedented in recent geologic history," which is the same conclusion drawn by papers described in two of our Journal Reviews: Getting the Baseline Right and The Distant Past is a Key to the Recent Past.

So who or what is responsible for the recent -- and truly "unprecedented" (as far as can reasonably be determined) -- crash in the population of what has historically been the most robust of the Caribbean corals? Could it be what the climate alarmists falsely (see our Editorials of 9 August 2000 and 7 March 2001) call the "unprecedented" global warming of the same period? The questionable correlation is just too tantalizing for those with a strong anti-CO2 bias to resist. That they err in their attribution, however, is evident in comments made by several researchers at the Paleontological Convention, who according to Stokstad note that Caribbean reef community structure "survived the vicissitudes of climate change in the past, such as swings in sea level, temperature, and carbon dioxide levels," which clearly indicates that the reefs' current problems are due to something quite different than CO2-induced global warming.

So what could that something different be? According to Stokstad, Ogden says "it's difficult to lay it [the blame] at the feet of any cause other than humans." We agree; but as noted in the preceding paragraph, the human activities responsible for the devastation cannot include global warming. Further support for this conclusion comes from the papers of Jackson et al. (2001) and Petit et al. (1999). The first of these studies indicates that "large species of branching Acropora corals dominated shallow reefs in the tropical western Atlantic for at least half a million years until the 1980s, when they declined dramatically." The second study indicates that throughout this long period of time, the earth went through several glacial/interglacial cycles for which we have good proxy temperature data, and that the four interglacials that preceded the one in which we now live were all warmer than the current one -- and by an average of more than 2C! Hence, the Acropora corals that have taken such a nosedive in health -- and actual existence -- over the past two decades are clearly able to tolerate temperatures much in excess of those of the present (all else being equal), which may also be less than temperatures experienced during the Medieval Warm Period and the Holocene Climatic Optimum of only one and several thousand years ago, respectively.

In conclusion, there is no question that many of earth's coral reefs, along with numerous other coastal ecosystems, have indeed suffered greatly at the hands of man. The damage, however, has not been wrought by the historical rise in the air's CO2 content, nor by the slight warming of the past century or so, which is nothing more than a natural recovery from the global chill of the Little Ice Age.

To ferret out the real culprit(s) in this detective story, come back next week, when we'll give you our thoughts on the subject. Man is definitely responsible, but not in the ways the climate alarmists would have us believe.

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

Jackson, J.B.C., Kirby, M.X., Berger, W.H., Bjorndal, K.A., Botsford, L.W., Bourque, B.J., Bradbury, R.H., Cooke, R., Erlandson, J., Estes, J.A., Hughes, T.P., Kidwell, S., Lange, C.B., Lenihan, H.S., Pandolfi, J.M., Peterson, C.H., Steneck, R.S., Tegner, M.J. and Warner, R.R. 2001. Historical overfishing and the recent collapse of coastal ecosystems. Science 293: 629-638.

Petit, J.R., Jouzel, J., Raynaud, D., Barkov, N.I., Barnola, J.-M., Basile, I., Bender, M., Chappellaz, J., Davis, M., Delaygue, G., Delmotte, M., Kotlyakov, V.M., Legrand, M., Lipenkov, V.Y., Lorius, C., Pepin, L., Ritz, C., Saltzman, E. and Stievenard, M. 1999. Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica. Nature 399: 429-436.

Stokstad, E. 2001. Humans to blame for coral loss. Science 293: 593.