Tuesday, March 13, 2007

The canary and the parrot: dead in the second half of the century, not the first?

Whether it's applied to coral reefs, rainforests or whatever, 'canary in the coalmine' has become one of the most over-used phrases in environmental communications. And in the case of coral reefs one could ask whether a more helpful comparison would be the dead parrot in the Monty Python sketch.

Are vestiges of vivacity just an echo, the last sputtering of a candle (as in "The extinction crisis is over. We lost")? A just published paper seems to contribute to the case that the game is not over for sure:
Under scenarios of future greenhouse gas emissions, mass coral bleaching in the Eastern Caribbean may become a biannual event in 20-30 years. But if corals and their symbionts can adapt by 1 to 1.5 degrees Centigrade, such mass bleaching events may not begin to recur at potentially harmful intervals until the latter half this century. The delay could enable more time to alter the path of greenhouse gas emissions, although the long-term 'committed warming' even after stabilisation of atmospheric CO2 levels may still represent an additional long term threat to corals.
But can temperature average temperature rise be kept to 1 to 1.5 C for the 21st Century? The authors refer B1 SRES, the lowest greenhouse gas emissions scenario entertained by the IPCC, under which atmospheric concentration stabilise at 550pm by 2100. But can B1 really deliver the goods up to 2090 to 2100, and what about beyond that decade? Findings on carbon cycle feedback, among other things, suggest otherwise. (If what I have written here is opaque, see A 21st century greenhouse gas budget?, which tries to join some dots between the IPCC scenarios and its most recent assessment report, AR4. Elsewhere, David Wadhams investigates possible Political corruption of the IPCC report) .

Still, this paper (which is by Simon Donner, Thomas Knutson and Michael Oppenheimer) looks like a valuable corrective to fatalism (or at least uninformed fatalism) with regard to reefs in the Caribbean and elsewhere. Charles Sheppard, who has also modelled reef mortality with higher temperatures (and makes a great giant turtle companion in a photo here) calls it "excellent". Ove Hoegh-Guldberg tells this blog: "The paper by Donner et al is interesting - you only need 1.5°C adaptation in 30 years to survive! I guess that certainly sums up the impossibility of it all!"

In a recent review of Coral by Steve Jones I wrote that the death of the world's coral reefs is not necessarily a done deal. Some leading scientists don't think they have to write the obituary of nature yet. Still, it does look as if coral may soon be pining for the fjords.


Blogger Caspar Henderson said...

By the way, this is the second of two consecutive blog posts referring to work by Simon Donner and colleagues. The is by accident rather than design, although it has to be said that Dr Donner is extremely active, recently fitting in field work with the excellent group Blue Ventures and a valuable paper on Canadian climate change policy (in draft).

12:45 pm  
Blogger Simon Donner said...

A fluke of timing, yes.

I appreaciate the "impossibility" comment. We hope our results help motivate more people in the community to get clearer answers to the question of what if any adaptation is possible (and for what corals), whether it can be maintained or the physiological cost is too high, and what it will all mean for coral and reef fish community structure.

1:42 am  
Blogger linda said...

just to let you know i've been reading your entries little by little since i discovered it :) thanks for taking the time to post all of this informative and fascinating material. i appreciate it!

i've loved the beauty of these animals for some time. when i realized people kept aquariums with corals, anemones, etc., i was, at first, fascinated, and thought i'd like to have one. when i started researching the topic, i realized what a really bad idea this was...and then i started to read much more about the devastation of coral and the reefs. yikes!

1:21 am  

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