A new journal from the Nature Publishing Group (publishers of Nature, Nature Neuroscience, and other favorites of mine) has just started a journal about climate change, and to my delight they feature a story about climate change and Atlantic cod, an old love of mine from my time on the Gulf of Maine.
Atlantic cod, Gadus callarius Linneaus, by Goode, from the magnificent Bigelow and Schroeder, Fishes of the Gulf of Maine, 1953, the best field guide I’ve ever read, now online.
Cod aren’t doing terribly well, because of overfishing and decimation of inshore spawning stocks, though some pockets still produce nice numbers of this lovely fish. The Nature Climate Change story gives a heads-up to a study about how cod fared in previous climate change cycles. This is a hot topic, as many fishermen and scientists wonder whether warming seas have already contributed to the cod’s decline so far or might inhibit its recovery. The new study finds that previous large swings in climate have cut cod populations back by as much as a fifth, knocking it down but not out. But the authors don’t seem optimistic on how well they’ll fare in this one.
Having read a few of these papers, I gather that the jury is still out on how much climate change will complicate the cod’s future.
The Natural Environment Research Center actually writes it up more cleanly than the Nature Climate Change story does:
The new findings, published online today (14 November 2007) in Proceedings of the Royal Society B, show that natural climate change has previously reduced the range of cod to around a fifth of present-day values. Despite this, cod continued to populate both sides of the North Atlantic.
The researchers used a computer model and DNA techniques to estimate where cod could be found in the ice age, when colder temperatures and lower sea-levels caused the extinction of some populations and the isolation of others. ….
Professor Bigg [the lead researcher] said “This research shows that cod populations have been able to survive in periods of extreme climatic change, demonstrating a considerable resilience. However this does not necessarily mean that cod will show the same resilience to the effects of future climatic changes due to global warming.”
Yet another story, this one from the Telegraph and titled “Climate change joins fishing as cod threat,” notes that cod don’t do so well in their northernmost ranges:
[The] study by Prof Bigg and colleagues shows that cod “are good at surviving habitat reduction, except in the northern half of their range. With regard to future climate change, it is clear that the acceptable habitat will retreat poleward significantly as temperatures warm,” [Bigg] says.
“It is not unlikely that acceptable conditions for spawning will disappear from much of the North Atlantic to become restricted to the Arctic.”
Cod is currently not found there, apart from the Barents Sea, and so there is the question of whether the currently depleted species is able to colonise new areas faster than its old habitat is lost, says Prof Bigg.
Yet another paper, meanwhile, by Mieszkowska, Sim, and Hawkins [pdf download], concluded that climate change might already be adding pressure to North Sea cod. The jury will doubtless be out on this one a while. But it raises more worries both about what climate change may do to cod — and about the difficulty of predicting how different species will fare as things warm up.