Current status of greenhouse gas emissions from aquaculture in China

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Aquaculture and mariculture are becoming an increasingly important source of food supply in many countries and regions. However, with the expansion of aquaculture and mariculture comes increasing emissions of greenhouse gases (GHG) which contribute to global warming and climate change. China leads the world in aquaculture and mariculture production, but there are no studies that systematically assess China's overall carbon footprint from these industries. This study quantified GHG emissions from aquaculture and mariculture by four source phases (feed, energy use, nitrous oxide and fertilizers), and then analyzed the carbon footprint of each of these phases for GHG production of nine major species groups over the past ten years to show the spatial distribution of GHG emissions from aquaculture and mariculture in China. Our results showed that the production of feed materials contributed most to the GHG emissions and found that crop energy use, crop land use changes (LUC), fertilizer production, crop nitrous oxide production and rice methane production were the main sources of feed emissions. The total GHG emissions of the nine species groups were 112 ​Mt (109 ​kg) CO2e, the nine species accounting for approximately 86% of aquaculture and mariculture production. GHG emissions of cyprinids had the highest contribution at 47%. Spatial analysis based on our study showed Guangdong, Hubei, Jiangsu and Shandong had the highest GHG emissions of all the provinces in this study, and they accounted for approximately 46% of all emissions. The regional Gross Domestic Product (GDP) was significantly positively correlated with GHG emissions in every province, with a correlation coefficient higher than 0.6. Our results showed for the first time the relationship between the relative production by species composition and spatial distribution of GHG emissions from aquaculture and mariculture in China. Our findings provide the scientific basis for reduction of GHG emissions within a broader context of expanding aquaculture in the future.