grass roots Sudden Heat Wave in Our Seas Poses Threat of Fishery Collapse

SCIENTISTS who study climate change are in the habit of warning that even a one degree C change in a century is a very big deal. That has certainly been their message over the last two or three decades.

We in the British Isles have also tended to believe that the most dramatic effects of global heating will be felt thousands of miles away, maybe on low lying islands, such as Tuvalu, in the Pacific Ocean.

So, it is a real shock to read, without much warning, that sea water temperatures around the UK and Ireland have jumped this year by up to 4 degrees C above average. That is not just a guestimate. It carries the authoritative stamp of the Met Office.

And a team From Bangor University have added helpful context regarding exceptional warmth around our shores. “Marine heat waves”, they have said, “are classified as prolonged periods of anomalously high sea surface temperature”, when compared to the long-term average for the time of year.

Writing a few weeks ago, they stated “…thanks to measurements made by satellites orbiting the earth, we know that, in some areas around the UK, surface water temperatures are 4 to 5 degrees C above normal for midJune.”

“So what?” you may say, “Won’t that just mean more enjoyment for sea swimmers, as they frolic in almost Mediterranean warmth around our shores?”

As a veteran killjoy and merchant of doom, I prefer to look at the downsides of such a dramatic apparent change in our climate. What about the impact on fisheries, for instance? In my quest for evidence, I didn’t have to look too far.

Over in the States, a very helpful scientist call Chris Free had already done most of the analysis for me! Now Chris Free is clearly a brilliant person, not least because he’s been thinking along the same lines as me!

He’s also been working with top-flight climate scientists, at the US National Oceanic and Atmospheric Administration, and at Rutgers University in New Jersey.

What Chris Free and these other brainy people have done is to correlate sea temperatures with the productivity of fisheries, over many years and in a wide variety of places around the world. They have found that, while fish catches in some areas have risen with higher sea temperatures, in most cases catches have gone down as the seas have got warmer.

But get this! Some regions, says Free, “have been hit especially hard.” And he zeroes in on our patch of northern Europe. As seas have warmed, he says, the North Sea which has large commercial fisheries, and the seas of east Asia, which support some of the fastestgrowing human populations, have experienced the loss of up to a third of their fish.

He reports that the North Sea, with large fisheries for species like Atlantic cod, haddock, and herring, has experienced a 35% loss in sustainable catch potential in less than a hundred years.

That has put me in mind of the great Grand Banks fisheries collapse off the Maritime Provinces of Canada in the 1980s and 90s. When I mentioned this to my friend Kathleen in Ontario, she retorted at once, “But that was caused by over-fishing!”

Not to be deflected, I quickly began to sift through more information from my hot US source. After a bit of flannelling and a glance at the review of worldwide fishery collapses by Chris Free, I countered as follows…

“Areas,” I said, “with a history of overfishing, such as Atlantic cod in the Irish and North Seas, were among the most vulnerable.” I wish I spoke so cogently all the time! (Thanks for letting me crib from your work Chris! I will buy you a beer next time I pass by the Rutgers campus in New Jersey!)

But why and how will more warmth in the sea hit the fish? On this point, it’s the scientists at Bangor University who come to my aid. They point out that, “…those stratified seas on the continental shelf around Britain and Ireland are some of the most biologically productive on the planet.”

“They have long been an important area for fishing cod, haddock, mackerel and other species.” Those fish eat smaller fish and crustaceans which in turn feed on plankton. And, to cut a long story short, the plankton are badly disrupted and depleted by the higher temperatures! Or, as a brief headline by the Bangor University team puts it, “Fish may go hungry!”

OK! Thank goodness for the academic boffins of Bangor and Rutgers! What they’re hinting at, in brief, is, “Get down to the fish and chip shop quickly, before a collapse in fish stocks sends prices rocketing, or, worse still, sees the whole fish and chip industry go under!”

Julian O’Halloran