A threat to cod is a threat to humans
For centuries, Atlantic cod has been a commercially important food source across its entire habitat, which spans from North America, Greenland and Iceland to Great Britain and the Nordic countries. “When human activities pose a threat to the cod, we are in a way threatening ourselves,” says Professor Nils Chr. Stenseth.
For centuries, Atlantic cod has been a commercially important food source across its entire habitat, which spans from North America, Greenland and Iceland to Great Britain and the Nordic countries.
Cod fisheries in the Nordic region have been taking place at least since the Stone Age, so there was major cause for concern when several cod stocks collapsed in the 1990s. Some stocks are recovering, but Atlantic cod is still labelled as vulnerable on the International Union for Conservation of Nature’s Red List of Threatened Species.
Professor Nils Chr. Stenseth at the University of Oslo’s Department of Biosciences has led a number of research projects focusing on cod. He points out that when we are studying the cod, we are actually also studying the human race.
Humans are changing the world
– Many biologists and other scientists, myself included, believe we are now entering a new geological epoch, which we call the Anthropocene (from the Greek anthropos = human). This epoch is characterised by extensive changes around the globe brought about by human activity, and cod are one of the victims of this development, theorises Stenseth.
He heads both NorMER, which is a Nordic Centre of Excellence, as well as CEES, which is a Norwegian Centre of Excellence at the University of Oslo. He is worried that cod is not the only species to be threatened by man-made changes to the environment: Humans might be next.
– To be able to sustain human life in the Anthropocene, we need answers to three fundamental questions: How do species – including humans – adapt to the Anthropocene? How should humans adapt to the Anthropocene in order to sustainably co-evolve with the biosphere? And finally, which social transformations are needed to facilitate a sustainable co-evolution? NorMER aims to address all three of these topics. Most of our attention thus far has been devoted to the first topic, but now we are taking action to also address the latter two.
Fisheries have caused cod to adapt
Atlantic cod is an example of a species that has been changed by human activity in a way that ultimately may be to our own detriment. For example, NorMER-affiliated doctoral fellow Anne Maria Eikeset demonstrated in 2009 that the practices of Norwegian fishermen have had an effect on the evolution of cod stocks.
The fishermen’s nets targeted the largest cod, the individuals that would fetch the highest price, while smaller cod were able to escape and reproduce. Being small became a survival advantage, and now the cod population is dominated by smaller individuals that become sexually mature earlier – and have less economic value. In the long run, fishermen would probably have earned more by fishing less.
Researchers at the NorMER centre have also shown that the cod whose habitat is the southern tip of Greenland are not just one large stock, but actually four genetically distinct stocks that exist in relative isolation from one another and should be managed separately. This is valuable knowledge for the resource management authorities seeking to restore Greenland cod to their historic highs.
– The best-known Nordic cod stock, skrei, spend years growing large in the Barents Sea, and then they return to Lofoten or other coastal areas to spawn,” explains Professor Stenseth. “But there are also stocks of cod that remain in one fjord throughout their life cycle, and these have developed certain genetic differences as they have evolved separately from other stocks. We have carried out projects, some of them before the NorMER centre was launched, to study how various cod stocks respond differently to climatic variations.
– It turns out that the climate-related increases in water temperature have led to a weakening of the southern coastal cod stocks, while the increased temperatures farther north have had a positive effect.
This can be explained in part by the fact that cod thrive best in cool waters. The optimal summer temperature range for cod growth is 13–15°C, and the fish that live out in the open sea can simply swim northwards to seek cooler waters. The cod stocks that by nature remain in one coastal area, however, grow more slowly due to their now-warmer habitats.
Is climate masking resource management?
Professor Stenseth points out that the NorMER centre produces three kinds of results.
– We have trained a number of doctoral research fellows and post-doctoral researchers, we have published a long list of scientific articles, and we have built up a knowledge platform for the marine resource management authorities. The latter is a good example of how biology can have important applications for societal development.
In recent years, cod fishing has once again become viable off the coast of Northern Norway. While the management authorities believe this has been made possible through proper management regimes. Professor Stenseth is not so sure.
– At the same time as management measures have been adapted, the climate has also been changing in a way that has proved advantageous for the northern cod stocks. No one knows which of these factors is actually more important. Perhaps it’s the case that both factors have contributed positively, but it’s also possible that climate change is making poor management look good.
A taste for Nordic cooperation
NorMER was a time-limited research project which is now approaching its end. Professor Stenseth is particularly proud of the extensive cross-disciplinary and Nordic cooperation that has been conducted.
– We have, for instance, sent Norwegian ecologists to Finland to learn about economics, and Finnish economists have come to Norway to learn about ecology. One result was an article on how changes in the marine environment may affect the ability to reach international agreements for fisheries management. The researchers warned that it becomes particularly difficult to achieve effective agreements when the natural resource base changes rapidly.
– When I look back on all we’ve achieved,” continues Professor Stenseth, “there is no doubt that this Nordic cooperation is a win-win situation. Every partner has benefitted scientifically from the cooperation, and it has raised our international profile in both Europe and the US. Activities under NorMER are drawing to a close, but I am sure the CEES centre and other future Norwegian Centres of Excellence in the coming years will incorporate a great deal of Nordic cooperation on their marine activities.”
- CEES - Centre for Ecological and Evolutionary synthesis
- NorMER: Nordic Centre for Research on Marine Ecosystems and Resources under Climate Change
- The Top-level Research Initiative - A Nordic Climate Reseach programme
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