Effect of water presence consistency on balance between CH4 emission and CO2 sequestration in floodplain wetland

Abstract

Current study attempts to comprehend the complex interplay between wetland hydrological regime and balance between Methane (CH₄) emission and Carbon dioxide (CO₂) sequestration in the rain fed floodplain wetlands. A mapping of wetland was done based on consistency of water presence using water presence frequency (WPF) of ten years (2013–2022). Ground truth validation ensured the accuracy of the wetland mapping. To obtain an estimation of spatial balance, satellite image-based estimation was adopted. In this task, first, annual gross CH₄ emission and CO₂ sequestration were estimated separately by the estimation of seasonal emission and cycle-wise sequestration. The masses of gross annual emission and sequestration were then compared to determine net balance of gas regulation. The study also considered the atomic mass balance of carbon and the global warming potential (GWP) to standardize the greenhouse effects of these gases. The yearly total emission and sequestration were estimated 0.3 × 10³ ton and 82.2 × 10³ ton. Overall the wetland contributed positively in this balance by absorbing 81.9 × 10³ ton surplus amount of CO₂. As a result of such a surplus amount of CO₂ sequestration, if the global warming potentiality (GWP) of the emitted CH₄ is considered, then also the yearly sequestration remains surplus by 72.8 × 10³ ton. This amount saves 7.3 million USD of fixation cost per year. In terms of atomic mass of C, yearly 22.2 × 10³ ton was additionally sequestrated in wetland. This balance was investigated to have negatively associated with water presence consistency of the wetland. The water presence frequency (WPF) which portrays the consistency of water presence in the wetland, exhibited coefficient of correlation (r) value −0.5 with yearly balance CH₄ emission and CO₂ sequestration, indicating a negative association. This association of WPF was respectively positive and negative with CH₄ emission and CO₂ sequestration. Since the peripheral parts of wetland are often left behind from the focus of wetland restoration program and face massive encroachment. The present findings signify the vital role of hydrologically poor peripheral wetland parts in the balance and suggest to put emphasis on the conservation these parts for immense ecological and environmental importance.