Rapid growth in greenhouse gas emissions from the adoption of industrial-scale aquaculture

Fisheries capture has plateaued, creating ever-greater reliance on aquaculture to feed growing populations. Aquaculture volumes now exceed those of capture fisheries globally^1,2, with China dominating production through major land-use change; more than half of Chinese freshwater aquaculture systems have been converted from paddy fields^1,3. However, the greenhouse gas implications of this expansion have yet to be effectively quantified. Here, we measure year-round methane (CH₄), nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from paddy fields and new, extensively managed crab aquaculture ponds. The conversion increased associated global warming potentials from 8.15 ± 0.43 to 28.0 ± 4.1 MgCO₂eq ha⁻¹, primarily due to increased CH₄ emissions. After compiling a worldwide database of different freshwater aquaculture systems, the top 21 producers were estimated to release 6.04 ± 1.17 TgCH₄ and 36.7 ± 6.1 GgN₂O in 2014. We found that 80.3% of the total CH₄ emitted originated in shallow earthen aquaculture systems, with far lower emissions from intensified systems with continuous aeration⁴. We therefore propose that greater adoption of aerated systems is urgently required to address globally significant rises in CH₄ emissions from the conversion of paddy fields to aquaculture.