Fisheries capture has plateaued, creating ever-greater reliance on aquaculture to feed growing populations. Aquaculture volumes now exceed those of capture fisheries globally1,2, with China dominating production through major land-use change; more than half of Chinese freshwater aquaculture systems have been converted from paddy fields1,3. 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.

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This work was supported by grants from the Chinese Academy of Sciences (XDB15020100), Natural Science Foundation of Jiangsu Province (BK20151056), National Natural Science Foundation of China (41501274 and 41471077) and Special Fund for Forest Scientific Research in the Public Welfare (201404210). H.K. is grateful to the NRF (2016R1D1A1A02937049) and KFS (2017096A001719BB01).

Author information

Author notes

    • Sunghyun Kim

    Present address: Smithsonian Environmental Research Center, Edgewater, MD, USA

  1. These authors contributed equally: Junji Yuan, Jian Xiang.


  1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China

    • Junji Yuan
    • , Jian Xiang
    • , Deyan Liu
    • , Tiehu He
    • , Sunghyun Kim
    • , Yongxin Lin
    •  & Weixin Ding
  2. School of Civil and Environmental Engineering, Yonsei University, Seoul, Republic of Korea

    • Hojeong Kang
  3. University of Chinese Academy of Sciences, Beijing, China

    • Tiehu He
  4. School of Natural Sciences, Bangor University, Bangor, UK

    • Chris Freeman


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W.D., J.Y. and D.L. designed the study. J.X. led the GHG fluxes and auxiliary measurements, with support from T.H., S.K. and Y.L. Site selection and set-up was carried out by J.Y. and D.L. H.K. and C.F. were the key international collaborators during this research. The manuscript was drafted by J.Y., H.K., W.D. and C.F., with all authors contributing to the final version.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Chris Freeman or Weixin Ding.

Supplementary information

  1. Supplementary information

    Supplementary Figures 1–3, Supplementary Tables 1–6 and Supplementary References.

  2. Supplementary Table 5

    Summary of measured rates of CH4 and N2O emission, emission factor of applied N (EFN) and yield-based N2O emission factor (EFY) in global inland freshwater aquaculture systems.

  3. Supplementary Table 7

    Dataset containing fluxes of CH4, N2O and CO2 measured in paddy fields and crab aquaculture ponds.

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