New Study Shows How to Design Marine Farms to Mitigate Climate Change

Today, in partnership with the University of Adelaide, a new study, Climate-Friendly Seafood: The Potential for Emissions Reduction and Carbon Capture in Marine Aquaculture, which describes the actions marine farmers can take to be influential in reducing impacts of climate change, was published in BioScience. The study shares positive news for farmers. The study looked at the major sources of greenhouse gas emissions and carbon sinks in the farming process of marine fish, macroalgae and bivalve, and then produced recommendations on how to mitigate those emissions and facilitate carbon sequestration in the marine environment.

Fish farms were found to be generally the highest emitting of the species groups assessed though some, such as Atlantic salmon, can be produced with GHG emissions comparable to or only marginally higher than some mollusk farming. But environmental emissions associated with fish farming, which can occur through impacts to critical “blue carbon” habitats from waste and nutrient enrichment or physical disturbance, were found to be an under-reported source that could conservatively equate for up to 16 percent of total global aquaculture emissions. The study also finds that seaweed culture may be the best opportunity for carbon sequestration in the marine aquaculture sector, however the fate of the end product is key for achieving positive carbon outcomes. To be sequestered, seaweed farms must act as carbon “donors” by depositing fragments into the deep sea or in nearshore environments and the carbon stored long term, or by contributing to land-based sequestration through use in bioproducts to improve soil health.

The findings build on an increasing body of work illustrating the potential climate value of seafood. Previous studies have established that mariculture products can offer a more ‘climate-friendly’, high-protein food source because they can have lower greenhouse gas emission footprints than equivalent products farmed on land. Climate-Friendly Seafood takes those findings a step further by outlining six principles for the industry and government to develop and maintain zero or even net-negative-emissions processes on a larger scale.

“We’ve used the results of our analysis to carve out clear, climate-friendly principles for the marine farming industry and governments,” said Dr. Alice Jones, Industry Research Fellow at the School of Biological Sciences, University of Adelaide, and lead author of the study.

For fish farming operations, the most critical practices to avoid emissions include improvements in feed efficiency and utilization, transitioning use of diesel fuels to renewable alternatives, and improved siting of operations to eliminate impacts to blue carbon habitats and subsequent environmental emissions. Despite the increasing interest in seaweed for its climate benefits, for seaweed aquaculture to be an effective source of carbon sequestration, siting of the farm is also critical alongside utilization of seaweed in climate-friendly products, such as bio-plastics. If this combination of practices can be achieved it will provide opportunities for offsetting such that production could potentially result in negative carbon emissions.

For the consumer, the study shows that eating an increased proportion of farmed bivalves and seaweed could be a climate-change mitigating measure. Unlike other sources of protein, researchers are continually finding that bivalves and seaweed have little or no emissions associated with the “upstream” phase of farm production—that is, feeding them. On-farm emissions are almost solely due to the fuel and infrastructure (tanks, nets) needed to raise the animals, and “downstream” emissions are associated with getting products packages and shipped to the grocery or retail store. Buyers can take a critical step in reducing emissions by being conscious of where their seafood comes from, to cut the need for packaging, refrigeration and transportation.

“Addressing climate change requires all hands on deck, and food production has historically accounted for a major share of global greenhouse gas emissions,” said Robert Jones, Global Lead for Aquaculture at The Nature Conservancy a co-author of the study. “We are calling on the aquaculture sector to further its commitment to join the fight to address climate change. This study shows aquaculture has a major role to play and provides a road map for implementation.”

If put in practice, these principles would make significant and immediate progress in the development of climate-friendly mariculture practices and emissions reduction outcomes in production of fish, seaweed and bivalves, and beyond. “If these principles are adopted, this study could be game-changing for not just marine applications, but other types of food production as well,” said Heidi Alleway, Global Aquaculture Scientist at The Nature Conservancy and a lead co-author. “We see an opportunity, here, to shape aquaculture to be at the forefront of addressing climate change impacts from food production.”