Towards tracking wetland methane emissions over India using multi-satellite measurements and modeling: part A (natural wetlands)

Abstract Wetlands are the largest natural source of atmospheric methane (CH 4 ), contributing 20%–40% of global emissions. However, significant uncertainties persist in regional CH 4 budgets due to difficulties in accurately mapping wetland extent and reliance on coarse or static wetland datasets, which often miss narrow floodplains and seasonal wetlands. The challenge in wetland mapping is particularly critical in India, where wetlands tend to be small, fragmented, and strongly influenced by the seasonal South Asian monsoon. Sparse observation coverage and inadequate modeling further hinder robust emission quantification for India. This study addresses the above limitation by developing a novel approach to generate a 1 km resolution wetland CH 4 emission database for India. Wetland extent is mapped directly from Sentinel-1 synthetic aperture radar data, Sentinel-2 multi-spectral imagery, and Moderate Resolution Imaging Spectroradiometer (MODIS) indices, providing a fine-scale spatial resolution of 1 km. By applying an inundation factor, we account for seasonal variability and align our model with environmental controls. Integrating wetland extent, heterotrophic respiration, temperature dependence, and precipitation data, we estimate CH 4 emission at a 1 km grid over India. The national natural wetland emissions are estimated as ∼0.5–2.5 Tg CH 4 yr −1 during 2018–2023. Our estimate is higher than those from commonly used global wetland models (∼0.06–0.5 Tg CH 4 yr −1 ), but lower than the estimates from the Global Methane Budget 2000–2017 (∼6.0 Tg CH 4 yr −1 ). By integrating high-resolution remote sensing with regional-specific information tailored to India’s unique monsoon-driven wetland system, our method overcomes the structural limitations of existing wetland models and provides the highly resolved and accurate satellite-constrained distribution of wetland emissions for India. These advancements support adequate representation of Indian wetlands in the global methane budget and improve regional greenhouse gas inventories, atmospheric inversions, and climate impact assessments, supporting more effective implementation of climate and conservation strategies.