Wednesday, July 25, 2007

New online voice on coral reefs and climate change

Ove Hoegh-Guldberg's new blog Climate Shifts is a welcome addition to the online coverage of climate change and coral reefs. Ove is one of the world's top experts on the subject; his 1999 paper on climate change and coral bleaching (in the Aussie journal Marine and Freshwater Research) helped bring the problem to the attention of the public and other scientists, myself included.

The comments after recent post on the ridiculous documentary "The Great Barrier Reef Swindle" (not to be confused with the equally ridiculous "The Great Global Warming Swindle", how about the great title swindle?) reflects the contentious debate with the coral reef science community on the right way to discuss the existential threat climate change appears to pose to many of the world's reefs. Some experts think we're fixing the place settings on the Titanic, so to speak, by not screaming about the climate change threat more. Others disagree.

Our friend Caspar Henderson in the UK picked out the astute comment from Charles Sheppard, who literally wrote the book on Indian Ocean corals. I'll do the same:

I think the media (and some simple scientists it seems!) can’t grasp the difference between species extinction (as in Dodo, Sabre-Tooth Tiger etc) and ecological extinction (as in the system is too broken to work any more). One remaining oak tree in a clear-felled mud-scape is not species extinction of the oak, but the forest doesn't do foresty things any more.

I have recently returned (again) from a very heat stressed region of the coral reef world - Arabian/Persian Gulf - and dived for many hours on once rich reefs. I saw a live coral at intervals of perhaps 20 or 50 metres apart, the rest being dead. That is zero coral cover to the nearest whole number, but it is still not species-extinct. You would need to measure cover to about 0.0001% to register a positive number there. But then, to how many decimal places do we need to measure ‘dead’? Answer: to many, if you are looking to confirm species extinction, but none at all if you want to determine whether you still have a reef.


Caspar Henderson said...

It looks as if the official final draft paper from IPCC Fourth Assessment Report Working Group 2 came up with a form of language allowing for the possibility that corals could adapt to 3 C rise or even more (see The IPCC drafts, 12 April 07). So it looks as if the official line carefully ignores the likelihood that reefs as such would (almost certainly?) be pretty much eliminated long before then, and places a centre stage the possible adaptation/ survival of (something like) 0.0001%. Such a line would be useful for governments, and others, if they wanted to mislead and/or divert attention from the gravity of the situation. Or am I wrong?

Simon Donner said...

Here's the text from the Summary for Policymakers to which Caspar refers:

"Corals are vulnerable to thermal stress and have low adaptive capacity. Increases in sea surface temperature of about 1 to 3°C are projected to result in more frequent coral bleaching events and widespread mortality, unless there is thermal adaptation or acclimatisation by corals."

It does seems to imply that thermal adaptation or acclimation could counteract 1-3 C of warming. There's evidence that some corals may be recover faster from bleaching, suffer less mortality, or possibly adapt through symbiont shuffling, but there's no specific evidence supporting adaptation or acclimatisation of up to 3 C. (important to remember what we call "adaptation" is not a panacea; even if possible, not every species could adapt at the same rate, etc.)

I could forgive the loose wording in the SPM if it were not for the 3 C limit. I was one of the reviewers of the coral reef sections of the WGII report, from which the SPM was drawn, and I don't recall any specific mention of 3°C, nor any literature sources to specifically support it.

Nevertheless, as I've argued before, rather than get caught up in the geopolitics of the IPCC summary for policymakers, we should celebrate the fact that the full reports have cobbled together and thoroughly reviewed all the science on these issues. I don't think governments could effectively use this bit of SPM language to "promote" a different agenda, because there are too many people watching, and ready to hold their government's feet to the fire.