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

Abstract

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 having been converted from paddy fields 1,3. However, the greenhouse gas (GHG) implications of this expansion have yet to be effectively quantified. Here we measure year-round methane (CH 4), nitrous oxide (N 2 O) and carbon dioxide (CO 2) emissions from paddy fields and new, extensively managed crab aquaculture ponds. The conversion increased associated global warming potentials (GWP) from 8.15 ± 0.43 to 28.0 ± 4.1 Mg CO 2 eq ha-1 , primarily due to increased CH 4 emission. After compiling a worldwide database of different freshwater aquaculture systems, the top 21 producers were estimated to release 6.04 ± 1.17 Tg CH 4 and 36.7 ± 6.1 Gg N 2 O in 2014. We found that 80.3% of total CH 4 emitted originated in shallow earthen aquaculture systems, with far lower emissions from intensified systems with continuous aeration 4. We therefore propose greater adoption of aerated systems is urgently required to address globally significant rises in CH 4 emission from the conversion of paddy fields to aquaculture.

On the Causes and Consequences of Recent Trends in Atmospheric Methane

“…freshwater emissions are separate from wetlands. Not yet included are probably minor emissions from glacial systems (other than permafrost soils) [22], terrestrial aquaculture [23] and breakdown of plastics in the environment [24]. In the GCP TD budget, at least half of the emissions are anthropogenic:~34% (BU 26%) of total from agriculture,1 9% (BU 16%) from fossil fuels, plus contributions from biomass and biofuel burning.…”

Large Fine‐Scale Spatiotemporal Variations of CH4 Diffusive Fluxes From Shrimp Aquaculture Ponds Affected by Organic Matter Supply and Aeration in Southeast China

“…Furthermore, the accurate estimate of the regional and global CH 4 budgets remains challenging also because of the overlooked role of small ponds (Holgerson, ; Holgerson & Raymond, ). As an important part of the global small ponds, some recent studies have suggested that aquaculture ponds can be indispensable CH 4 emission sources (Chen et al, ; Hu et al, ; Wu et al, ; P. Yang et al, ; Yuan et al, ). Although some efforts have been made on characterizing CH 4 fluxes in aquaculture ponds, the number of field records of CH 4 emissions from aquaculture ponds remains very scarce as compared to those from other aquatic systems (e.g., lakes and reservoirs; Yang et al, ).…”

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

“…Aquaculture production is dominated by China's fish and crab ponds. Yuan et al () found a tripling of the CH 4 emissions per hectare per year when operating a fishpond instead of a rice paddy field. This finding contradicts Liu et al (), which calculated EFs from aquaculture to be half as large as those from rice paddy fields.…”