Developing new agricultural practices or improving existing ones in the face of a growing world population is key to limiting food insecurity. Strategies such as seaweed farming are particularly promising as seaweed can be produced extensively whilst also limiting greenhouse gas emissions. Nonetheless, many challenges remain to be addressed before seaweed farming could expand.
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Seaweed farming could meet rising global food demands
The capacity of agriculture to meet future food demands is becoming increasingly limited by the reduced availability of arable land and freshwater. In addition, reducing greenhouse gas emissions to meet the targets of the Paris Agreement while supporting increasing energy and food demands remains challenging.
Moreover, our capacity to achieve the goals of the Convention on Biological Diversity as part of the United Nations (UN) Sustainable Development Goals (SDGs) is limited by habitat degradation currently occurring across ecosystems on land and in oceans. In response, researchers argue that altering current agricultural practices could help limit environmental damage and contribute towards achieving SDGs.
This was the case in a 2021 study by Duarte et al., who presented the case for developing aquaculture as a promising candidate to achieve sustainable development goals. The authors argue that since marine aquaculture is the fastest-growing component of food production (>7% per year), which exceeds the overall growth rates of agriculture (2% per year), aquaculture is proposed to play a critical role in developing the capacity to feed the 9.7 billion people populating Earth by 2050.
Specifically, areas within aquaculture such as seaweed farming could be pivotal to supporting population growth. To date, seaweed aquaculture globally produced 31.8 million tons in 2018 and has a market value of more than USD 11.3 billion. This activity is focused mainly in Asia, with 99.9% of seaweed production occurring in China and Indonesia, but Africa is also increasing its activity of seaweed farming.
The most common seaweed species used for farming are Eucheuma spp., Kappaphycus alvarezii, Gracilaria spp., Saccharina japonica, Undaria pinnatifida, and Sargassum fusiforme. Most of these are species that produce large fronds and occur between the surface and 10 meters deep, to soak as much sunlight as possible.
To date, seaweed farms are gaining popularity. Farmers in Alaska produced more than 112,000 pounds of sugar, ribbon, and bull kelp in 2019. That is a 200 percent increase over the state’s first commercial harvest in 2017. The largest kelp farm in North America is located off from southeastern Alaska.
Challenges to seaweed farming impeding its potential
Despite its documented advantages, a number of issues are challenging the growth of seaweed farming.
This was reviewed by Campbell et al. in 2019 in a paper that discussed why environmental changes are of greatest concern. The authors argue that is because warming facilitates disease outbreaks, alters population genetics, and changes the local physiochemical environment, making seaweed farming particularly unpredictable. For instance, the proliferation of pathogenic microorganisms that deteriorate kelp fronds has been recognized to increase under warmer conditions.
Researchers also mention that whilst current small-scale cultivation projects are considered ‘low risk,’ an expansion of the industry that includes ‘large-scale’ cultivation will need a better understanding of scale-dependent changes in order to balance environmental risks with the benefits that seaweed cultivation projects.
Authors then classify risks with different mitigation options. Those under high risk with few mitigation options include genetic depression of natural algal populations, facilitation of algal diseases, changes to the physical environment through alteration of hydrodynamic regimes, the entanglement of mega-fauna, and depletion of natural nitrogen pools in enclosed water bodies.
Medium impact risks include artificial habitat creation and absorption of light whereas those at low risk include: release of particulate and dissolved organic matter, creation of noise, and pollution and disturbance caused by the addition of cultivation structures.
The researchers, therefore, emphasize the importance of defining the scale of seaweed farming operations. This will help standardize practices and measures to mitigate or adapt operations. Indeed, the variation in cultivation practices currently employed to grow seaweed in Europe makes direct comparisons between sites difficult.
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Future of seaweed farming– socioecological benefits and implications in an era of climate change
With the rise of global temperatures and the acidification of the oceans, seaweed farming is likely to play an increasingly valuable role in the future as a key source of nutrition and to offset the impacts of environmental change.
This was the focal topic of a 2017 study by Carlos Duarte et al., who discussed how seaweed farming could be used to mitigate the effects of climate change. The authors discussed how seaweed aquaculture contributes to climate change adaptation by damping wave energy and protecting shorelines, and by elevating pH and supplying oxygen to the waters, thereby locally reducing the effects of ocean acidification and de-oxygenation.
The scope to expand seaweed aquaculture is, however, limited by the availability of suitable areas and competition for suitable areas with other uses, engineering systems capable of coping with rough conditions offshore, and increasing market demand for seaweed products, among other factors. Despite these limitations, seaweed farming practices can be optimized to maximize climate benefits, which may if economically compensated, improve the income of seaweed farmers.
However, this is not the only benefit associated with seaweed farming. A social study by Larson et al. in 2021 found that seaweed farming benefits Indonesian women and communities on local scales. This was a result of the extra income earned from seaweed, which helped create positive change in terms of transport, housing, basic needs, other needs, and education. The study found no negative changes linked to seaweed farming and there was evidence of increasing life satisfaction throughout villages, both by women from families who are and who are not engaged in farming, indicating positive equity aspects.
Nonetheless, many knowledge gaps remain to be addressed, particularly when delving into finer spatial and temporal scales, which was discussed by Eggerstern and Halling in 2021. The researchers present how knowledge concerning the environmental impacts from farming non-native eucheumatoid haplotypes in the western Indian ocean remains limited despite farming being practiced in this region for several decades.
Addressing knowledge of non-native species and how they affect farming outcomes is of particular interest to the long-term maintenance of operations. This exemplifies the limitations facing seaweed farming, which, despite having a promising future, requires key considerations and further research to elucidate the feasibility and dynamics of seaweed farming within current natural systems.
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- Campbell, I., Macleod, A., Sahlmann, C., et al. (2019). The Environmental Risks Associated With the Development of Seaweed Farming in Europe - Prioritizing Key Knowledge Gaps. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00107
- Duarte, C. M., Bruhn, A., & Krause-Jensen, D. (2021). A seaweed aquaculture imperative to meet global sustainability targets. Nature Sustainability. Published. https://doi.org/10.1038/s41893-021-00773-9
- Eggertsen, M., & Halling, C. (2020a). Knowledge gaps and management recommendations for future paths of sustainable seaweed farming in the Western Indian Ocean. Ambio, 50(1), 60–73. https://doi.org/10.1007/s13280-020-01319-7
- Eggertsen, M., & Halling, C. (2020b). Knowledge gaps and management recommendations for future paths of sustainable seaweed farming in the Western Indian Ocean. Ambio, 50(1), 60–73. https://doi.org/10.1007/s13280-020-01319-7
- Larson, S., Stoeckl, N., Fachry, M. E., et al. (2021). Women’s well-being and household benefits from seaweed farming in Indonesia. Aquaculture, 530, 735711. https://doi.org/10.1016/j.aquaculture.2020.735711