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 1092 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.