Marine forests dropping off the edge

21 11 2011

This is probably a little late in terms of breaking news, but it’s good fodder for a blog post nonetheless.

I’ve done several posts now on the value (and threats) of marine macroalgae (seaweeds) – the last one hinted that a major paper was imminent regarding the fate of one of the world’s most important centres of macroalgae diversity in response to our rapidly changing climate: southern Australia.

Well, that paper has now come out in the eminent journal Current Biology headed by that crazy Aussie-Viking phycologist, Dr. Thomas Wernberg (byline here: Thomas was just awarded an Australian Research Council Future Fellowship and deserves many congratulations – not least for which the audacity to wear yellow budgie smugglers in public).

Entitled simply “Seaweed communities in retreat from ocean warming“, the short paper belies a hell of a lot of work examining over 60 years of herbarium records indicating MASSIVE shifts in the macroalgae community southwards on both the east and west coasts of Australia (see some media spots here). What do I mean by ‘massive’? Well, about 300 species on average (52 examined in most detail) shifted about 200 km south on the east coast (where warming has been most pronounced), and about 50 km south on the west coast.

I can almost hear the bilious and factually depauperate murmurings in response – ‘Who cares…, etc. ?’. Well, we all should. Seaweeds are the architectural pillars of marine biodiversity – without them, you get fewer fish, fewer coral reefs and, well, a pretty empty and barren ocean. Even ultra-conservative, anti-environmental arseholes might understand that.

The killer in all this isn’t so much the shifting ranges of these species per se, it’s that species can only shift so far before falling off the edge of the continental shelf. Some back-of-the-envelope estimates we made in the paper indicate that up to 25 % of Australia’s essential and amazing macroalgae diversity could literally run out of places to hide from the heat in southern Australia by 2100. If the water becomes too warm, there will simply be no more available coastal shelf on which to grow after the southerly march is exhausted. They can’t just pack up and move to Antarctica (at least, not over a few decades or centuries). Extinction is far more likely.

Of course, we have no idea about local adaptation (physiological or evolutionary), but I wouldn’t bet that most of these species can evolve entirely new physiologies in time.

So, another bad-news story from us – say ‘goodbye’ to a lot of essential marine plant life over the coming decades. <Sigh>.

CJA Bradshaw


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