Fish fingers and cod and chips are under a far greater threat from carbon emissions than previously thought, according to a recent study that has grave implications for food security.
The North Atlantic cod stock in the Barents Sea is likely to first rise and then crash, possibly to almost zero before the end of the century if climate change isn’t addressed, says the scientific paper, published by the Arctic Monitoring and Assessment Programme.
The grim forecast is based on the most comprehensive study to date of the effects of climate change on cod, which – for the first time – takes into account ocean acidification as well as warming.
It found larvae mortality rates were 75% higher when exposed to the combined pressures of the two factors – both of which are caused by emissions – than to heating alone. As a result, fish numbers, catches and revenues will decline faster than previously estimated.
The Barents Sea, which is in the Arctic, is a major source of seafood nutrition for northern Europe. Along with Iceland, it is a key source of cod imports into the UK, which has over-fished its own waters. More Atlantic fish are migrating into this region as a result of global warming.
But this ocean has the highest level of acidification in the world because cold water absorbs more carbon dioxide, which changes its pH level. It is also the ocean that is experiencing the fastest rates of heating. While the global average is a rise of 1.1C since the start of the industrial revolution, the coastal breeding grounds of the cod in the Barents Sea have experienced a temperature increase of 3.5C.
Unless the warming trend is controlled, the stocks will see a boom and then a bust.
A temperature rise of up to 4.5C is beneficial to the cod. By this time, catches are projected to be worth 255 million Norwegian kroner per year (£23m). But after this point, the larvae rapidly start to die off. At 6C of warming (less than 3C for the rest of the world), they completely disappear.
Even if nations keep to their Paris commitments, which is currently not the case, global temperatures are on course to rise above 3C, which would mean well over 6C for the Barents Sea.
The numbers, which were released on the fringes of this week’s Arctic Frontiers conference in Tromsø this week, may yet prove an under-assessment of the risk because oxygen depletion – another side-effect of man-made climate change – is not accounted for.
“We are trying to show the magnitude of risk and it looks very significant,” said Martina Stiasny, one of the co-authors. “This is one of the most important fish stocks in the world. It will be a problem for food security.”
Responding to the findings, the Norwegian environment minister, Ola Elvestuen, said the study showed the need for urgent cuts in emissions. “The first task is to stop this happening. This is one more piece of news that shows the need for urgency. We must work to stay within 1.5C. We need to move forward really fast.”