Summary
The researchers analyzed greenhouse gas (GHG) emissions in global aquaculture, including emissions from the beginning of production to point of sale, but excluding those post-farm. They assessed emission factors from the production related to various aquatic animal species-groups associated with commercial feed formulations, feed materials, fertilizers, and on-farm energy.
They found that in 2017, global aquaculture contributed to approximately 0.49% of total anthropogenic (human caused) GHG emissions. This is similar to emissions from sheep production, reflecting the lower emissions intensity of aquaculture compared to terrestrial livestock due to factors like the absence of methane emissions and more efficient feed conversion ratios. The emissions closely followed the geographical distribution of aquaculture production, with feed production being a significant contributor to these emissions.
A limitation of the research noted by the authors is the focus on the “cradle to farm-gate” system boundary, excluding emissions from transport, processing, and distribution, which underestimates the full environmental impact of aquaculture. A strength is the extensive scope that accounts for approximately 93% of aquatic animal species in the analysis. Although the authors describe aquaculture as a “biologically efficient” source of animal protein, compared to that coming from land-based animals, they also caution that the rapid expansion of aquaculture could significantly intensify post-farm GHG emissions and highlight aquaculture’s other environmental impacts, such as on water quality and marine biodiversity.
Global aquaculture makes an important contribution to food security directly (by increasing food availability and accessibility) and indirectly (as a driver of economic development). In order to enable sustainable expansion of aquaculture, we need to understand aquaculture’s contribution to global greenhouse gas (GHG) emissions and how it can be mitigated. This study quantifies the global GHG emissions from aquaculture (excluding the farming of aquatic plants), with a focus on using modern, commercial feed formulations for the main species groups and geographic regions. Here we show that global aquaculture accounted for approximately 0.49% of anthropogenic GHG emissions in 2017, which is similar in magnitude to the emissions from sheep production. The modest emissions reflect the low emissions intensity of aquaculture, compared to terrestrial livestock (in particular cattle, sheep and goats), which is due largely to the absence of enteric CH4 in aquaculture, combined with the high fertility and low feed conversion ratios of finfish and shellfish.