Kelp farming – possible environmental effects, synergies and conflicts with other interests in the coastal zone

Summary

Larger areas are available at sea than on land, and the growth rate of macroalgae (seaweed and kelp) exceeds that of terrestrial plants. An increase in food and raw material production by means of seaweed and kelp can therefore contribute to solve some of the tasks the world is facing in view of a globally growing population. Seaweeds and kelp have been utilized commercially in Norway for decades, mainly through harvesting of naturally growing resources. The first commercial license for kelp cultivation in Norway came in 2014. Since then, the number of licenses has increased markedly. With its long coastline, Norway has a unique opportunity to succeed with commercial kelp industry, but for the last 10-15 years there has been an increased competition for areas in the coastal zone, with various and partly contradictory interests and considerations. Generally, an increased focus on environmental effects is on the political agenda, and understanding the impact of kelp cultivation on coastal marine ecosystems is of essence, both regarding the water masses and the seabed ecosystems. As of today, we are restricted to consider potential environmental impact of kelp cultivation based on a general understanding of the natural ecosystems, as understanding of the impact of kelp cultivation on natural ecosystems are very limited, even internationally. The aim of this report has been to increase the knowledge on the potential positive and negative effects of kelp cultivation on the marine environment and to discuss synergies and conflicts with other interests in the coastal zone. Essentially, cultivation of kelp is significantly different from fish aquaculture, as no feed, fertilizers or other substances is added to the water masses to promote cultivation of kelp. However, kelp cultivation requires large surface areas. This is important for coastal managers and planners to know in order to facilitate adaptive management strategies. Kelp absorbs nutrients and CO2 from the water, releasing organic matter and oxygen, as well as exporting dissolved organic matter. At minor kelp farms, one can reasonably assume that these processes correspond to what is taking place in the natural kelp forests along the coast. With more intensive cultivation, kelp can contribute to increased competition for nutrients, as well as contribute with a significant amount of organic matter, which may contribute positively to increased biological wealth or negatively to increased eutrophication. The large areas required for intensive kelp cultivation seem to be a challenge for planning and management. In this report, we have summarized the current issues the industry is facing today regarding possible interactions between kelp cultivation and area use in the coastal zone. As kelp cultivation is a developing and fast-growing industry it is essential that the industry develops in close connectivity with research and environmental management efforts. Thus, we here argue for applying an adaptive management strategy regarding kelp aquaculture. This means that management needs to be adjusted regularly as the industry develops and the scientific knowledge grows. Cooperation between research, management and business actors is essential to ensure a future business development in a sustainable manner.