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The future of coral reefs, if any

December 14th, 2007

A report in the Australian summarises an article in Science, stating that coral reefs are unlikely to survive the next few decades. The meeting I went to in Cairns had a marginally more optimistic view. If we can drastically reduce other pressures such as overfishing and nutrient pollution, reefs might be sufficiently resilient to recover from bleaching events and other consequences of global warming.

All of these pressures act cumulatively. Bleaching kills corals, excess nutrients encourage the growth of algae which prevent new corals from establishing themselves and overfishing removes herbivores that eat the algae. A big reduction in nutrient and fishing pressure might offset the more frequent occurrence of bleaching events.

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  1. Ikonoclast
    December 14th, 2007 at 09:19 | #1

    I note from the Australian article that Kevin Rudd “told the UN’s Bali climate change conference that global warming was threatening Australian natural wonders such as the Great Barrier Reef, Kakadu National Park and rainforests, killing rivers and exposing people to more frequent and ferocious bushfires.”

    The only serious approach when he comes home is to declare a National Climate and Environmental Summit with a view to declaring a National Climate and Environmental Emergency with 12 months. There is no point waiting for other countries. In fact they might benefit from the example and follow suit.

    All relevant parties need to come to the summit. It would comprise leaders of all governments national and state, a panel of top scientists in all appropriate fields, a panel of top economists with an even spread of viewpoints, business and union reprsentatives and community and indigenous representatives.

    Some sort of committee or panel system would be needed with each group creating its own report first and then sending their top representatives to higher convocations or assemblies with their report. Feed it through like that up to a top executive committee of inner cabinet and other key figures.

    The plan ought to be to reach a carbon neutral economy in one generation. (About 25 to 30 years). Nothing less will suffice. If this takes massive national projects to build a suite of alternative energy solutions for base load power then so be it. It can be done. We need to get cracking.

    Failure to do this will cost far more than doing it. No sustaining environment eqauls no economy equals no people.

  2. Ikonoclast
    December 14th, 2007 at 09:21 | #2

    Oops, I meant “Failure to do this will cost far more than not doing it.”

  3. BilB
    December 14th, 2007 at 11:51 | #3

    Comment/Question.

    Are there any projections on the effect to the Barrier Reef of rapid sea level rise. Will the addition of a metre of water level above the reef work to reduce the bleaching with increased water flows? and if this happens will the increased water flow volume also have an effect on nutrient deposition rates?

  4. Peter Pan
    December 14th, 2007 at 12:12 | #4

    I believe the major factor is Carbon Dioxide itself and not the secondary effect of atmospheric warming. Once atmospheric CO2 reaches 450 ppm, the dissolved CO2 is supposed to make the oceans so acidic that coral cannot form their skeleton. And at higher level existing reefs start to disolve. We are currently around 370 ppm and this is increasing at 1 to 2 ppm per year.

    Of course the forecasts are the results from models and I don’t know how much we can trust them. (No much I suspect!). Anyway, if this modelling can be trusted the Great Barrier Reef will start to dissolve in another 30 odd years regardless of other factors such as bleaching and nutrient load.

  5. December 14th, 2007 at 12:20 | #5

    some one put a ribbon on the bell, we must deliver it to the cat with our earnest prayers to wear. messenger must be good at curtsy, or forelock tugging(certificate required).

    or, we could gather in front of parliament and shake our fists.

    but i think i’ll just watch the world go down the drain. it’s the custom of the country.

  6. ks
    December 14th, 2007 at 13:43 | #6

    Peter Pan, two points:

    1). The acidity caused by the dissolved CO2 of the ocean, will be more aggressive as the temperature rises. Therefore, as the temperature rises this will eventually cause the ocean to rise. This is being seen now by the raising of the sea levels caused by the warming of the ocean.

    2). I would not be so doubting of these models. These models are conservative and cautious as they are peer reviewed and open to the critical eye. This has ensured that the scientists doing this research must be as open and honest as possible. Can the same be said of the propriety models used in many professions that escape this criticism?

  7. Peter Wood
    December 15th, 2007 at 21:14 | #7

    The issue of Science that the newspaper article referred to has some news articles and a good review article by a total of 17 authors:

    Coral Reefs Under Rapid Climate Change and Ocean Acidification
    O. Hoegh-Guldberg, P. J. Mumby, A. J. Hooten, R. S. Steneck, P. Greenfield, E. Gomez, C. D. Harvell, P. F. Sale, A. J. Edwards, K. Caldeira, N. Knowlton, C. M. Eakin, R. Iglesias-Prieto, N. Muthiga, R. H. Bradbury, A. Dubi, and M. E. Hatziolos
    Science 14 December 2007: 1737-1742.

    Unfortunately the article is paywalled so you might need to be at a university to access it. The article mentioned two thresholds beyond which things could get quite bad. One involved temperature and was at around 2 degrees C above current levels. The other involved ocean acidity (depenedent of CO2 levels, temperature is more depenedent on CO2-equivalent levels, which of course is highly dependent on CO2 levels). Ocean acidity was measured as a carbonate ion concentration threshold – as acidity increases, positively charged hydrogen ions increase, which decreases the concentration of carbonate ions. When carbonate ion concentrations get below 200 micromols per kilogram, things get bad. This occurs at around 480 ppm CO2 in the atmosphere.

    Increased grazing by herbivores such as parrotfish seems to help coral reefs and decreased sediment and nutrients from river runoff seems to help.

    I think that the impact of river runoff could be decreased by regulating or decreasing cattle grazing (perhaps by including agriculture in an emissions trading scheme). Because agriculture is responsible for around 16% of emissions (more in the short term, because of methane), good climate change policies in this sector would both mitigate climate change through reducing emissions and provide adaptation through decreasing the impact of climate change on coral reefs.

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