Post-harvest stages account for more than half of seafood carbon footprint

Abstract Seafood is increasingly important for healthy dietary transitions in modern urban lifestyles. Yet, the patterns of greenhouse gas (GHG) emissions remain poorly understood, which hinders the low-carbon pathways for city-specific seafood supply chains. Here, we constructed a disaggregated supply chain dataset to quantify the GHG footprint of consumption of five major seafood categories across 313 Chinese cities. In 2023, total GHG footprint of Chinese seafood consumption reached 182.6 Mt CO₂-eq (1.5% of the national total emissions), dominated by shellfish (65.7%) and fish (25.1%). Annual per-capita emissions varied from over 1000 kg CO₂-eq/capita in coastal and tourism cities to near zero in many inland cities. Spatially, 79.9% of emissions were concentrated in coastal cities, with the top five cities contributing 27.2%. Most transported seafood (58–88%) was within 200 km, indicating shorter food miles than other food categories. We find that off-farm supply chain stages, which account for 55% of total emissions, are key to retaining seafood's low-carbon advantage over terrestrial protein sources such as chicken and pork. We highlight the need for coordinated strategies to support both sustainable and healthy diets, including efficient mariculture practices in coastal cities and low-carbon cold-chain logistics and feed production in the supply chain.