Abstract
Farm dams are significant methane (CH 4 ) sources in agricultural landscapes. Fencing them to limit livestock access reduces organic matter and nutrient inputs, thereby limiting CH 4 emissions. However, existing studies on the benefits of fencing are constrained by short durations, omission of ebullitive fluxes, limited spatial and temporal coverage, and small sample sizes. Here, we report a large‐scale, multi‐season assessment of total CH 4 (diffusive + ebullitive) and carbon dioxide (CO 2 ) fluxes from fenced and unfenced farm dams, along key environmental drivers. We monitored 113 farm dams in temperate mainland south‐eastern Australia over 2 years, amounting to 39,552 and 45,408 hourly observations of total CH 4 and CO 2 fluxes, respectively. We integrated field‐measured emissions with Sentinel‐2 indices, topo‐climate variables, and geostatistical models to identify flux drivers, quantify temperature sensitivity, and spatially extrapolate mitigation potential across Local Government Authorities (LGAs). We found that fencing reduced CH 4 fluxes by 66%–82% across seasons while also significantly lowering the temperature sensitivity of CH 4 fluxes, slowing the exponential rise in emissions under warming conditions. Specifically, CH 4 fluxes in fenced dams increased by 71% per 10°C warming ( Q 10 = 1.71, E M = 0.4 eV), compared to unfenced dams increasing by 275% ( Q 10 = 3.75, E M = 0.98 eV). CH 4 fluxes were driven by temperature, rainfall, and hydrological proxies (Modified Normalized Difference Water Index, MNDWI; Floating Algae Index, FAI), while CO 2 fluxes responded to rainfall and Normalized Difference Water Index (NDWI). Extrapolating our findings across the study area (~526,296 km 2 ), fencing all farm dams could cut CH 4 fluxes by 1.16–1.35 kt year −1 . By combining high‐resolution emission data with scalable management strategies, this study offers a framework to improve greenhouse gas inventories and guide targeted climate mitigation in agriculture.