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The research, published in , focuses on Atlantic salmon farming and compares two feed scenarios: one dominated by fishmeal and fish oil, and another primarily composed of plant-based ingredients. While the shift from marine to terrestrial feed sources has been a key strategy in reducing reliance on wild-caught fish, the study reveals that this transition brings its own set of environmental challenges.

To understand the myriad environmental pressures that arise from aquaculture feed, the team used a spatial modelling approach – assessing where the feed came from geographically as well as what type of feed was used – to calculate the cumulative environmental pressures. Their model took into account: greenhouse gas emissions, habitat disturbance, nutrient pollution and freshwater consumption, as well as geopolitical and economic factors which were combined to create a cumulative pressure index (CPI), a measure of impact, allowing for comparison across different feed compositions and sourcing locations.

While it is currently, generally assumed that plant-based fish feed is more sustainable than fish-derived feeds, the findings show that this may not always be the case; the environmental footprint of a feed varies significantly depending on where its ingredients are produced and how they are processed. Additionally, the environmental impact of a feed can vary within its own type where some fish-derived feeds are better than others, the same is also true of plant-based feeds.

For example, soybean production in Brazil was found to generate greenhouse gas emissions more than ten times higher than in the United States, largely due to land use change. Similarly, fishmeal sourced from the Southeast Pacific required significantly more raw fish biomass than that from the Western-central Atlantic, due to differences in species composition and oil yield.

Additionally, the authors noted that geopolitical and economic factors influence how raw materials are chosen, as in the case of Brazilian soybeans; from 2002 to 2010 China was looking to increase foreign investment and Brazil was looking to develop their export markets. This set of mutually beneficial conditions led to an agreement between the two countries that saw Brazilian soybeans imported for Chinese pig-feed despite the negative environmental impact.

The modelling method employed by the researchers also pointed to the potential trade-offs involved in sourcing decisions. For example, avoiding fishmeal from regions with high carbon emissions may inadvertently increase habitat disturbance if alternative sources rely on species with lower yields but higher ecological impact. Similarly, while seafood processing waste is increasingly used in feed production, its environmental benefits depend on the species and region from which it is sourced.

The authors argue that sustainability assessments should move beyond a narrow focus on specific ingredients or singular environmental impacts (such as solely focusing on carbon dioxide production) and instead consider the full feed formulation and its sourcing context. This includes recognising the variability in production practices at subnational levels and supporting best-in-class producers within regions.

The study’s methodology provides a foundation for future research into spatially aware modelling for environmental impacts, such as biodiversity loss and water scarcity. By integrating data on species distribution and sensitivity to environmental pressures, researchers can better understand the localised effects of feed production and inform more robust sourcing strategies.

In time, the model could be further developed to be used by businesses and policymakers to make more informed decisions about the aquaculture industry, as well as being adapted for used in other industries such as the livestock sector.

The researchers acknowledge that implementing responsible sourcing practices is not without challenges, however. They caution against over-reliance on a small number of highly efficient producers, instead encouraging policymakers and industry to support producers who are working to improve their practices. This would diversify the supply chain protecting it from vulnerabilities due to disruptions from extreme weather events or geopolitical tensions, for example.

Ultimately, the research calls for a more nuanced approach to feed sustainability – one that considers not only what ingredients are used, but where and how they are produced. This approach can help aquaculture and livestock industries design sourcing strategies that support environmental goals while maintaining resilience and supply chain integrity.

The full dataset and code used in the analysis are publicly available via the Sustainable Aquafeeds Project GitHub repository, enabling further exploration and application of the findings.