Declining rice methane emissions in China due to decreased and displaced rice cropping

The renewed surge in atmospheric methane (CH₄) growth since 2020 has necessitated a critical re-examination of anthropogenic sources. Rice cultivation plays a pivotal role in global food security but is also a substantial source of anthropogenic methane (~8–10%). However, quantifying its contribution to the recent surge in atmospheric methane remains uncertain due to the spatiotemporal heterogeneity of methanogenesis and inconsistencies in official agricultural statistics.

Here, by integrating a continuous remote sensing-based dataset of China’s rice agricultural systems with refined pixel-based emission factors that account for localized cropping intensity, we reveal that rice methane emissions declined from 9.41 Tg yr^-1 in 2000 to 3.61 Tg yr^-1 in 2022, a reduction of 61.6% in China. This steep downward trend (0.36 Tg CH₄ yr^-1) stands in stark contrast to the flat or slightly increasing trends reported by previous statistical inventories. We demonstrate that this trend is dominated by a "north-south offset", where emission reductions from shrinking southern double rice systems outweigh the increases from expanding northern single rice systems.

These findings highlight that rice emission inventories relying on statistical data likely overestimate methane emission of rice agricultural systems by overlooking shifts in rice cropping pattern. Crucially, our refined 1-km resolution spatially explicit map of rice methane emissions offers a robust prior to constrain top-down satellite inversions. This framework also provides a transferable pathway for other main rice-growing countries to refine their estimation methods and better understanding of emission responses to structural changes in agricultural systems.