Upland methane sinks under climate change: global patterns, drivers and trends

Well-aerated upland soils serve as a crucial biological sink for atmospheric methane (CH4), playing a key role in mitigating climate change. However, current understanding of how this CH4 sink responds to global climate change remains limited. To address this, we integrated 1,092 observational data points to construct a dataset covering multiple global change factors and used meta-analysis to quantify the response mechanisms of the upland CH4 sink. Results show that warming, reduced precipitation, and elevated carbon dioxide concentrations significantly strengthened the CH4 sink, while increased precipitation and nitrogen addition weakened it. Interactive effects were also observed: low-level nitrogen deposition acted antagonistically with increased precipitation, but synergistically with warming. We subsequently optimized a CH4 oxidation model to explore the global distribution patterns and future trends under different climate scenarios. The current global upland soil CH4 sink is estimated at approximately 37 Tg year-1 and generally shows an increasing temporal trend. Spatially, the sink exhibits heterogeneity: a greater extent of desert areas in the Northern Hemisphere leads to a lower CH4 sink per unit area compared to the Southern Hemisphere. Future spatiotemporal trends of the soil CH4 sink will depend on the climate pathway. Under the Shared Socioeconomic Pathway (SSP) 1-2.6 scenario, the CH4 sink declines over time, whereas under SSP5-8.5, it follows a unimodal trajectory. Variations in the soil CH4 sink also differ across regions. These changes are primarily associated with atmospheric CH4 concentrations under different climate pathways, as well as alterations in soil temperature and moisture resulting from various climate change drivers. These findings underscore the importance of the upland CH4 sink in the global CH4 cycle and significantly advance our understanding of its response mechanisms to climate change.