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Insights to beachcast management on Gotland, Sweden

An Industrial Ecology perspective on waste-resource ambiguity

Time: Fri 2023-12-01 13.00

Location: F3 (Flodis), Lindstedtsvägen 26 & 28, Stockholm

Video link:

Language: English

Subject area: Industrial Ecology

Doctoral student: Hanna Nathaniel , Vatten- och miljöteknik

Opponent: Tekn.dr Johanna Spångberg, Sveriges lantbruksuniversitet (SLU), Uppsala

Supervisor: Docent Fredrik Gröndahl, Vatten- och miljöteknik; Dr Daniel Franzén, Vatten- och miljöteknik; Sofia Lingegård, Vatten- och miljöteknik

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QC 20231110


Beachcast or beach wrack, washed-up algae and seaweed, used to be a highly sought-after agricultural resource (fertiliser and soil conditioner) in coastal communities around the world before being replaced by chemical fertilisers, but considering the talks of a circular bio-economy – can we reintroduce it? 

Since the abandonment of beachcast in agriculture, the amount of beachcast has significantly increased as an effect of eutrophication caused by the use of chemical fertiliser, and the material is commonly considered waste. Meanwhile, soils have degraded and need the multiple positive effects on agroecosystems that beachcast could provide. So, while harvesting the biomass serves to remedy the adverse ecosystem effects on marine ecosystems (from excessive organic material, i.e. macroalgae blooms), beachcast could potentially contribute to more sustainable food production.

Sadly, it is not simple. This potentially symbiotic process infers uncertainties regarding soil cadmium accumulation, coastal ecosystem effects, and other challenges - and despite multiple studies and attempts at a waste-to-resource conversion of beachcast, the challenges remain unsolved, and a novel take on the topic seems necessary.

On Gotland, Sweden, with a historical tradition of using beachcast in agriculture, a modern governance system for management has emerged from a national policy subsidising beachcast harvesting, which has partly come to connect the marine and agricultural domains, among other actors. In this case, beachcast harvesting is subsidised as a measure to curb eutrophication and reduce the detrimental effects of excessive beachcast, a phenomenon present in the Baltic Sea and many other coastal regions worldwide that are caused by an accelerating nutrient accumulation at sea and sediment stocks. So, by further applying beachcast as a fertiliser in agriculture and horticulture, a practical example of a regional land-marine nutrient loop could be created to make beachcast management more sustainable. However, multiple challenges need to be addressed. 

This thesis and case study of Gotland, Sweden, presents an illustrative example of contemporary beachcast governance and management that provides knowledge and insights to support policy development and more sustainable beachcast management practices. insights for policy that can support the development of more sustainable management practices. This is done by using semi-structured interviews to understand the beachcast governance and management practices based on stakeholder perceptions (Paper I), performing a cost-benefit analysis of beach-cast harvest to assess the economics of closing land-marine nutrient loops in the Baltic Sea region (Paper II), conducting a cultivation experiment to predict future trends in soil cadmium concentration from applying beachcast as fertiliser (Paper III), and mapping regional variations in chemical composition of fresh and composted beachcast to consider future treatments (Paper IV). 

The results show that to overcome the challenges and achieve more sustainable practices, the following measures and considerations are essential: further supporting continued experimentation and monitoring of marine ecosystems to handle the harvest-hesitation caused by the uncertainties associated with marine ecosystem effects; sampling of composted material and careful agricultural use to remedy the waste-resource ambiguity associated with Cd contamination; and a continued subsidy and cross-sectoral collaborations to abide managerial and financial responsibility for beachcast activity.   

In this in-depth and transdisciplinary case study with a mixed-methods approach, the findings point to a theoretical and practical incongruity In seeking a waste-to-resource conversion of beachcast, which indicates that beachcast cannot compete with commercially viable products in today's intensive agricultural regime. Instead, agroecology, an alternative pathway according to FAO, appears to be a more promising context for beachcast to be acknowledged and receive the necessary investment to resolve its ambiguous resource status.