Guarding the Great Barrier Reef

By July 23, 2012Climate Change, Other

In early June a UNESCO report expressed concern about port developments in Queensland that might threaten the Reef. That was followed by a conference of scientists in Cairns in mid July which said that the Reef was in great danger from climate change. Oh, and port development, shipping, ocean acidification, tourism, population growth, agriculture — you name it. The threats were dutifully reported in the media, because of the Reef’s status as an Australian ‘icon’ and our standard-bearer on the World Heritage List.

My long memory tells me that it was the Crown of Thorns starfish that was the first of the many ‘threats’ we now hear about, and that was in the early 1960s. We were told then that the reef would die, and both the Queensland and Commonwealth Governments put money into finding out more about the starfish and what to do about it. It is a widespread organism, found across the Pacific and the Indian Oceans, and infestations seem to come and go. The starfish doesn’t in fact kill the coral, and after infestations the infected reef recovers quite quickly.

But more to the point, the way we hear about the Reef is always as a threatened jewel. I doubt that most people have any real conception of what the Great Barrier Reef is, even those, like me, who have visited sites on it many times. It is, first of all, an enormous ‘structure’, 2,000 kilometres long, containing over 3,000 reefs and several hundred islands. Hardly any of it is regularly inspected or even visited. Most of it is well away from the coast, out toward the fringing reef at the edge of the continental shelf, and there is no great population centre anywhere near it.

Wikipedia will tell you that anthropogenic global warming is the Reef’s great enemy, and that coral bleaching caused by elevated sea temperatures will become an annual event. It hasn’t done so yet, and a likely cause is a combination of winds and currents keeping warm water in place. In any case, the coral reefs near Papua New Guinea flourish in water that is a couple of degrees warmer than that in the southern parts of the Reef. And the threat caused by rising sea-levels is the silliest I’ve heard: corals grow, and you can see how much lower the sea-level was if you dive down a little on the edge of any reef. The sea has risen 120 metres since the end of the last ice age, and corals have coped by growing upwards. They would strongly dislike a lowering of the seas!

It is much the same with the other scares. All of them are possible, but none of them is as yet real. ‘Ocean acidification’, for example, is a scary way of saying that the seas may have become, on average, a little more alkaline over the past couple of decades. But we really don’t know, and the ph levels of the sea vary horizontally and vertically. Yes, ships come to grief in the Reef (forgive the rhyme), and more than 1500 have done so since Europeans began sailing there. Yes, oil has spilled (not much of it). But as we saw in the Caribbean, oil is seen as a food by other organisms, and they break it down quickly. It may or may not be true that the seas are becoming appreciably warmer — at the moment I think it is an open question.

Yes, nutrients wash down the rivers, and so do pesticides, and so does soil and debris after floods. The Reef seems to take it all in its stride. Storms damage bit of it, as does bleaching, as do the starfish. But it is a giant system, and nothing yet seems to have occurred on a system-wide basis.

Let u by all means keep a watchful eye on it, but it would be pleasant if we heard  bit less of  ‘imminent threats’, and a bit more of what is pristine and unspoiled in the Great Barrier Reef.There is a lot of that.


Join the discussion 4 Comments

  • Dave Barnes says:

    You say that the Crown of Thorns starfish (Acanthaster planci) does not kill coral. Indeed it does, and large infestations can kill huge areas of coral. The starfish feeds by everting its stomach over the surface of coral colonies and digesting the living tissue.

    Points seldom mentioned by your so called guardians are (1) the GBR survived the mediaeval warm period when temperatures were higher than today; indeed there are corals alive today that were living at the end of that warm period (which last circa 900-1300 AD) and (2) only 20,000 years ago there was no GBR, only a series of low wooded hills that were the remains of an ealier reef dating from around 125,000 years ago

    [Does A.planci kill coral? According to Wikipedia’s entry on the starfish (not always a reliable source, I agree) ‘the starfish preys on coral by digesting the surface of living tissue from the coral skeletons. These skeletons persist, together with the mass of coralline algae that is essential for reef integrity…’ Regeneration will occur in time. Further, ‘Some ecologists suggest that the starfish has an important and active role in maintaining coral reef biodiversity, driving ecological succession. Before overpopulation became a significant issue, crown-of-thorns prevented fast-growing coral from overpowering the slower growing coral varieties.’ I’m going to find a more authoritative source. DA]

    [Later: Harriott and Fisk’s 1987 Technical Paper for the GBRMPA says that devastation by A. planci is restored within 10 and 50 years, according to the types of corals that had been ‘eaten’.]

    • Dave Barnes says:

      The fact remains that the Crown of Thorns starfish kills coral and leaves behind dead skeleton. The living tissue of corals covers only the surface of colonies. The biggest colonies on the GBR are around 10 m high, even so, the tissue only occupies the outer 5-10 mm of such colonies.

  • Colin Davidson says:


    The hottest waters in the world are the Red Sea and the Arabian Gulf. No shortage of coral in those seas.

    Just off the coast of New Guinea are some CO2 bubblers. The sea nearby is much less alkaline than the rest of the ocean, around 7.8 or so. The waters are very warm. The ecological result? PROFUSION. Masses of sea grass. Healthy growing coral. Plenty of crustaceans.

    In short, while scientific models and modellers, and some experimenters say differently, the real-world experiments confirm that the Reef is safe from both warmer water and increased dissolved CO2.

    As Dave Barnes implies, the real threat to coral reefs is COLD.

  • […] I’ve written about the reef before, and it is not the real subject of this essay. But without the fuss about the reef there would be no story. And this is it. James Cook University has a Professor of Physics called Peter Ridd, who has, among other things, written sensibly about peer review and about quality assurance in science. He is a marine geophysicist who think that stories about the imminent death of the reef  are fanciful. In May this year he pooh-poohed claims by two other JCU staff about the state of the reef. Let the Cairns Post tell the story (in part). […]

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