At the 12th International Coral Reef Symposium recently held in Cairns, Australia, it was announced that more than 2500 marine researchers and managers from around the world have signed a new Consensus Statement on Climate Change and Coral Reefs, which calls on all governments to ensure the future of earth’s coral reefs via two different approaches. One of these courses of action calls for improved local protection of coral reefs from land-based sources of pollution, sedimentation and overfishing, which is both laudable and needed. The other approach calls for global action to reduce emissions of carbon dioxide, which is notlaudable because it is not needed.
The writers of the Consensus Statement begin to make their case for its strident calls to action by noting that “approximately 25-30% of the world’s coral reefs are already severely degraded by local impacts from land and by over-harvesting,” which is easily proven. But they go on to add that the warming of the world’s oceans over the past century or so, plus its slight CO2-induced acidification, have resulted in “unprecedented coral bleaching and mortality events,” which statement cannot be proven.
All that we do know is that if there truly has been a recent unprecedented increase in coral bleaching and mortality events, it has occurred within the combinatorial context of (1) the local impacts mentioned in the Consensus Statement and (2) the global impacts of the concomitant increase in the air’s CO2 concentration, which is known to be promoting the movement of the world’s oceans towards a state of mild acidification (which is still a long ways off), but which is merely believed (and that only by some) to be responsible for the lion’s share of the warming of the seas over the past century or so, based on the output of mathematical models of climate (which are always improving, but which never quite attain to the level of predictive correctness their creators would like them to achieve).
Now the Consensus Statement says it is the warming of the world’s oceans that has “resulted in unprecedented coral bleaching and mortality events.” But this contention cannot be proven in the broadest sense. It is true that in some cases periodic extreme warmth may indeed have been the proximate cause of coral demise; but it may well be the case that, in the absence of man’s many local affronts to reef environments, the coral bleaching and mortality events of the recent past would not have occurred. Put another way, if the local impacts mentioned in the Consensus Statement had not been building up over the years, decades and even centuries, it is possible, if not likely, that the heat events that sometimes kill corals nowadays may not have been able to do so if the corals had not been severely weakened by mankind’s historical and continuing deleterious affronts to their watery environs.
An important empirical fact that argues in behalf of this proposition is the fact that coral species that are being negatively affected by periods of high temperature in our day and age successfully lived through both equally warm and sometimes warmer periods in ages past (i.e., the Medieval and Roman Warm Periods, as well as the much warmer and considerably longer Holocene Climatic Optimum). Therefore, it is our belief that if the many local assaults of humanity upon today’s coral reefs and their watery environments could be gradually reversed and ultimately halted, we might possibly never see another case of coral bleaching due to either high temperatures or ocean acidification.
Of course, such a dramatic reversal of anthropogenic behavior will likely never occur; but by doing our best to reverse what damages have already been done, and by discouraging the types of local activities that caused those damages, we will come much closer to achieving the goal we all would like to reach than we ever will by trying to drastically diminish anthropogenic CO2 emissions, which are actually helpful to many of the inhabitants of both aquatic and terrestrial environments, as may readily be ascertained by perusing the wealth of substantiating materials we have archived under a wide array of pertinent topics that are identified in our website’s Subject Index.
Sherwood, Keith and Craig Idso