After five years of sampling, it was allowed to harvest kelp in the south of Nordland this summer. – Trawling is currently sustainable, say the researchers. Nevertheless, trawling can have major consequences for marine life. Kelp forests contain their own ecosystem and are a “nursery” for fish fry. Home to many species, the bog forest can look desolate. But it is in many ways similar to the forests we have on land. Thousands of species hide, eat and live between the trunks of the big tarn. Nevertheless, we trawl for kelp in several places in Norway today. Inside the kelp forest, you can find up to 100,000 crustaceans, brush fields and fish within every single square metre. Photo: NIVA – How does trawling for seaweed affect the ecosystem? – In Norway we currently harvest between 150-170,000 tonnes. But there are as many as 30 million tonnes of kelp along the coast. You can therefore say that the withdrawal is negligible. – Locally, the effects can be greater. Kjell Magnus Norderhaug from the Institute of Marine Research says so. Together with Henning Steen, he has led research on the effects of kelp trawling along the Norwegian coast for several decades. Among other places outside the world heritage site at Vega in Nordland, the kelp forest has now returned. Photo: Helge Lyngmoe / news Nevertheless, it is not entirely correct to say that there is no effect of trawling. – We have carried out research and monitoring where we found effects in everything from algae to predatory fish at the top of the food chain, says Norderhaug. – In the trawl streets where trawling takes place, trawling has an effect on all levels of the ecosystem. This also applies in the kelp forest around the trawl street itself, even though three quarters of the kelp forest remained where the researchers had researched. Hardy species of kelp in berry picking Larger ones live on the outer reefs and islets. There, the kelp is exposed to natural uprooting all the time. Nevertheless, he grows back quickly after a storm. – The trawler is like a berry picker that is pulled after the trawler. He hooks up the large tree crowns, explains Norderhaug. – Below them there is an undergrowth of kelp plants that shoot up when the big ones are trawled. The kelp forest has slowly but surely grown back, after the forest disappeared from Trøndelag far into Russia in the mid-70s. Hordes of sea urchins left the seabed as a marine desert for nearly 50 years. The researchers have taken video underwater, dived to collect kelp and small animals, in addition to catching fish and crabs with video and fishing. Photo: Elisabeth Økland / Trefadder The researchers have taken underwater video, collected kelp and caught fish and crabs with fishing nets. Monitoring shows that it takes longer for the rest of the ecosystem to return. – The kelp is already back after about three to four years, but then it’s a fairly poor ecosystem, says Norderhaug. The researchers now believe that there is a low risk that kelp harvesting will affect the occurrence of green or red sea urchins. Photo: Erling Svensen / Havforskingsinstituttet In order for, for example, algae to grow back, it takes longer. It can take over six years. These are the places where all small animals live. They are again food for fish, seabirds and marine mammals. – We would never recommend harvesting if the condition of the kelp forest was not good. In addition, kelp harvesting is regulated more strictly in Nordland than in the rest of the country, says the researcher. No cap on trawling To determine whether kelp trawling is viable, the researchers point to three factors: How big the effect is where it is trawled. How much of the kelp forest is trawled, and how much is left standing. How long the kelp and the ecosystem spend to recover after trawling. Where do you trawl today? Today you trawl for kelp from Rogaland to the south of Nordland. There, most areas have a harvest cycle of five years. But in some places it may be necessary to have a longer rest period. Nordland county is divided into 40 harvest fields. Half of the field has a harvest cycle of ten years, the rest can be harvested every five years. But even if there are some limits on where one trawls, there is still no limit to how much. Nina Dehnhard from the Norwegian Institute of Natural Sciences reacts to that. – I see this as very critical. Kelp forest acts as a carbon store and thus helps to mitigate the effects of climate warming. In addition to the fact that it is an important grazing area for many species of both fish and seabirds. Dehnhard says the kelp forest is an important grazing habitat for several species of seabirds, such as terns, cormorants, great cormorants and eiders. – It is a habitat that is particularly important in these times when we have both a climate and a biodiversity crisis. Photo: Knut-Sverre Horn – 63 percent of Norwegian seabird species are on the red list. What we need now is management of the Norwegian sea area based on ecosystems. She adds: – The opening of kelp trawling in the south of Nordland is the opposite. Truls Gulowsen, leader of the Nature Conservation Association, believes that the kelp forest can be compared to the forest above water: – If you look at biomass, a new forest plant field looks the same as an old one. But life on land makes a difference, so does life in the sea. Photo: Tor Bjarne Christensen The head of the Norwegian Nature Conservation Association, Truls Gulowsen, is also skeptical about opening up more to kelp trawling. – We are fundamentally skeptical of kelp trawling and are very afraid of whether there would be a development where this increases in scope with today’s missing cap, he says. – Expanding to new areas that are in the process of recovering from a serious situation does not seem smart. Especially when we need to limit the footprint. Trawling opens the door to a new industry The Directorate of Fisheries has not replied to news about whether they are considering putting a cap on kelp trawling. But on their website they write that in relation to the total quantity of larger fish that grow along the Norwegian coast, the autumn quantity constitutes a very small part, approximately 0.3 per cent. Stortare makes up about 80 percent of the total macroalgae biomass along the Norwegian coast, and it is mainly this species that forms the kelp forest. Photo: Erling Svensen / Marine Research Institute – By comparison, it is estimated that around 40 per cent are grazed by sea urchins, and that around 10-15 per cent of the kelp plants are naturally pulled loose each year, writes the Norwegian Directorate of Fisheries. They also point out that an alternative to natural harvesting is to grow larger ones. Today, fish farming accounts for the largest discharges of nitrogen and phosphorus along the Norwegian coast. Gulowsen agrees that kelp is a fantastic resource, and an exciting business opportunity. More than 300 species of algae and animals have been observed attached to the plants in the kelp forest, and more than 100,000 individuals of small animals can be attached to a single large kelp. Photo: Mikkel Stokke But he thinks it prevents a possible livelihood, when you can take care of the kelp forests as you like. – As long as brutal harvesting of an important habitat is allowed, it will almost always win over the possibility of establishing something new, says Gulowsen. – If you had cultivated kelp, it would instead have been a subsidy to the ocean’s production. Recommends demarcations The researchers at the Institute of Marine Research are also reserved. Now there is only one major player trawling for kelp. It is most likely that more will come on the scene as time goes by who will compete for the resources. – We have recommended calculating the resources per harvest field so that the Norwegian Directorate of Fisheries can consider setting limits on extraction in the harvest field, depending on how large the resources are in each field, says Norderhaug. The kelp-eating green sea urchin is a cold-water species. Climate change has therefore made sea urchins less prominent. Nevertheless, small, large ones are more exposed than the large ones in the kelp forest to sea urchin attacks. Photo: Lars Korvald Nevertheless, he points out that even if there are worse growing conditions for fish fry for a period when trawling for kelp, it is primarily fishing that affects the fish population. – There is also something good about harvesting low in the food chain. 100 kg of kelp can become 10–20 kg of small animals. 10–20 percent of these can again be eaten by larger fish. We can therefore harvest more if we harvest low in the food chain.
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This is what the kelp forest looked like after trawling – The researchers think it is tentatively sustainable – news Nordland
