Are Coral Reefs Dying?

Over recent months a number of news stories and scientific studies have reported that coral reefs are in widespread global decline from human impacts and in particular from global warming. That reefs in many areas are being adversely affected by local human populations is observable. How serious this is and what portion of reefs are seriously affected is however much less clear and probably to some extent exaggerated.
     Coral reefs in one form or another have been around for some 500 million years and even some present day reefs have histories going back over 50 million years. This is an incredibly long span of time. Our own evolution from ape to modern human has been a long slow process but still it has taken place in only about 5 million years. Most present day genera of corals have histories going back tens of millions of years and several first appear in the Cretaceous period around 100 million years ago.  Eocene fossils of many types of fishes   and other reef creatures from 50 million years ago are very similar, often even indistinguishable from, present day species.
     During much of their existence reefs have flourished in a world that was more tropical than it is now. The bleaching events that are being widely touted as threatening reefs with extinction generally involve water temperatures only a degree or two above normal. It is difficult to believe that reef communities have persisted for so long within a degree or two of their extinction when in fact during much of that time the Earth was warmer than at present. So, what is going on?
     Since the beginnings of recorded history predictions off imminent catastrophe have been a perennial feature of humanity. Despite a track record of near total failure such predictions never seem to lose their appeal, neither to would be prophets nor to an audience willing to believe them.
     Science, despite it’s attempt at skeptical rationality, is no exception. Proclaiming serious problems results in attention, recognition and research funds. It also generates fads of interest in, and acceptance of the reality of, the claimed problems. In the 1950s and 60s the marine science community was promoting their endeavor with the promise of untold food and minerals from the sea. This promoted a lot of funding but little return. Then in the 70s and 80s environmental concerns began to be widely recognized and the failed promises of loot and plunder from the sea were quickly dropped for concerns over saving them. This too required lots of money for research but didn’t entail the inconvenient necessity of delivering anything. Success could always be claimed whenever no real problem eventuates and if it does that only indicates the necessity for more funding.
     Despite the muddle of misinformation, exaggeration, promotion and herd following it is undeniable we live in a finite world and it cannot sustain growing human impacts forever. One of the biggest difficulties we face is distinguishing reality amid a confusing welter of imagination, beliefs and misinformation. Failing to do so presents us with an impossibly large range of “problems”, misdirects effort,  impedes sensible use of resources, and generates increased demand elsewhere.  What we don't get from one place we make up for in another.
     With regard to the condition of reefs here are some facts to consider:
     In the entire world, throughout history, there has only ever been one reef species that has been exterminated by humans, this was the Caribbean monk seal.
     Although clearly associated with higher than normal water temperatures, coral bleaching regularly occurs at temperatures that are below what the same corals tolerate in other areas. Recent research has revealed that a number of different species of algal cell live in association with corals and these algae have differing temperature tolerance. The number and kind of algae can vary seasonally in the same coral colony and they differ in different areas. This explains how the same coral in one place can tolerate temperatures that cause bleaching in another and  indicates an as yet un-assessed degree of ability to adjust to different temperatures.
     Whether or not the recently observed bleaching is unprecedented is not known. Extensive surveys of central Pacific reefs in the Early 1970s found some reefs with shallow water corals mostly dead but in place. This was assumed then to be due to Crown-of-Thorns starfish infestations but it now seems more probable that a severe bleaching event may have been the cause. A study just published using isotopic analysis of age and temperatures from corals in the eastern central Pacific has found that the strongest (i.e. highest temperature) El Niño event for the past 1000 years was in the 1600s.
     So too, a generally ignored effect of global warming would of necessity be a latitudinal expansion of the oceanic region available to corals.
     The Great Barrier Reef of Australia with its nearly 350,000 Km² of reef and lagoon area makes up about 30% of the world’s total reef area.   It is also among the most pristine of reef areas. Distance, weather and a relatively small population mean most of the GBR is rarely even visited . Of the 2900 reefs in the complex only a few dozen are regularly used for tourism and the total annual fish harvest of 17 Kg per Km² is less than 1% of what reefs elsewhere commonly sustain. The total commercial and recreational reef fish harvest for the Barrier Reef currently only comes to some 6000 metric tons annually. This is similar the what the Florida Keys produces from less than 1% of that area of reef and lagoon.  It is also less than half of Australia’s own production of farmed salmon from a few bays in Tasmania. Elsewhere in the remote vastness of the Pacific and Indian Oceans there are many many reefs in healthy condition.
     Even in S.E. Asia, East Africa, and the Caribbean where reefs are most heavily impacted many healthy reefs still remain and are the mainstays of a multi-billion dollar global recreational dive industry. Dive tourism has not only made healthy reefs an important economic asset but also assures that any significant deterioration will not go unnoticed.
     Although the situation is never be as good as we might like it is seldom as bad as we may fear. Neither complacency nor despair is warranted but a healthy level of skepticism is, especially when mass media and “expert” opinion is involved.

 Walter Starck