Dr. Jessica Gephart is an Oceana Science Advisor and an Assistant Professor of Environmental Science at American University in Washington, D.C., where she studies the seafood trade and its impact on food security and environmental conservation. Gephart’s research has also informed Oceana’s Save the Oceans, Feed the World initiative.
Recently, she led a study that compared the environmental impact of various aquatic foods. She and 17 other scientists – including fellow Oceana Science Advisor Dr. Christopher Golden – calculated the greenhouse gas, nitrogen, and phosphorous emissions, as well as the freshwater and land use, of “blue foods.” Blue foods as a category include capture products (or “wild” foods from the ocean and inland waters) and aquaculture products (or farmed fish and shellfish).
In a recent conversation with Oceana, Gephart discussed this paper, which appeared in Nature journal in September as part of the global Blue Food Assessment led by the Stockholm Resilience Center, Stanford University, and EAT.
Oceana: What unanswered questions did you want to address in your Environmental performance of blue foods paper?
Jessica Gephart: Our aim was to fill an important information gap by generating standardized estimates of the environmental performance of aquatic foods, focusing on the major environmental pressures of food systems: greenhouse gas emissions, nitrogen and phosphorus emissions, and land and freshwater use. This allowed us to look at which blue foods were already performing well and identify improvement opportunities.
O: Your study assessed 70% of the world’s blue food production. What accounts for the other 30%?
JG: With over 2,500 different species of aquatic animals and plants caught or cultivated for food around the world, there are many for which there is insufficient data. For example, despite our efforts, we were not able to identify sufficient, representative fuel use data for inland fisheries. We were also unable to include freshwater crustacean aquaculture due to limited data. There are other groups that are included in our analysis, but have few observations compared to global production, such as edible seaweeds and carps. These all represent priority areas for future research.
O: How does your study differ from past research on blue foods?
JG: One thing that sets our study apart from many studies that look at emissions and resource use across the food system is that we include both aquaculture and capture fisheries, and we provide greater species resolution, whereas many past studies either did not include blue foods at all or presented them as “seafood.” Our work therefore provides greater insights across the vast diversity of aquatic food production.
Another major advancement is that we did not simply average the emission and resource use estimates of different studies, but instead extracted the underlying data and ran it through a standardized model. This is because individual studies have different purposes and therefore make modeling decisions that heavily influence the results, often preventing these studies from being able to be compared fairly.
O: Based on your results, what are some of the lowest-impact wild and aquaculture foods on the market, and what makes them so sustainable?
JG: It is important to note that our analysis does not look at final impacts, such as biodiversity loss, but only focuses on major emissions and resource use. For the five stressors considered, capture fisheries use negligible land and water and emit little nitrogen and phosphorus, but result in a range of greenhouse gas emissions.
However, small pelagic fishes, such as sardines, generate lower greenhouse gas emissions than all fed aquaculture groups. Farmed seaweed and bivalves, such as mussels, result in the lowest emissions and resource use of all blue foods, while among farmed finfish and crustaceans, silver and bighead carps have the lowest greenhouse gas, nitrogen, and phosphorus emissions, and salmon and trout use the least water and land.
O: How does wild seafood compare to land-based animal proteins in terms of the environmental impacts you assessed?
JG: We compared blue food performance to industrial chicken performance, as this is often considered the most efficient terrestrial animal-source food. Many blue foods, such as sardines, cods, tunas, salmon, and bivalves, already outperform chicken on these five environmental metrics, on average, with chicken performing similarly to tilapia.
O: What do you want policymakers to take away from this paper?
JG: When steering food production toward greater sustainability, it is not only critical to consider blue foods alongside terrestrial foods, but also to look across the diversity of blue food production. Many seafood systems provide blue foods at relatively low environmental costs, and for others there are opportunities to reduce environmental pressures. For aquaculture, improving feed conversion ratios – that is, the amount of feed required to grow a certain weight of fish – can reduce the emissions of some fed fish by more than half.
Meanwhile, capture fisheries already have negligible freshwater and land use and emit little nitrogen and phosphorus, but there are great opportunities to lower the greenhouse gas emissions by improving management, prioritizing less fuel-intensive gear, and investing in renewable energy for fishing fleets. While this points to a promising role for blue foods in sustainable diets, decisionmakers must consider their local context to ensure sustainable stock management and avoid impacts on aquatic biodiversity.
This interview appeared in the Winter 2021 issue of Oceana Magazine. Read it online here. Header photo by Ferdinand Edralin.