Methane emissions only negligibly reduce the ecosystem service value of wetlands and rice paddies in the mature Ganges Delta

Wetland provides a wide range of ecosystem services with immense value. However, methane (CH4) emissions adversely affect ecosystem services, and it requires fixation cost. The objective of the present study was to estimate CH4 emissions and ecosystem services value (ESV) and how much the fixation cost of CH4 reduces the ESV. Since rice cultivation is a very common practice here, the paddy fields were also incorporated in this study. CH4 flux and satellite data were employed for estimating the emissions with the help of two-factor (temperature and water availability) model. Global coefficients of ecosystem service value (ESV) that is defined as the monetary valuation of materialistic and non-materialistic services were adapted for estimating the ecosystem service of the CH4 emitting sources. Results show that during the boro season (pre-monsoon summer paddy cultivation season), average monthly emissions of paddy fields are equal to the wetlands which are 0.16 t/km2. During amon season (monsoon paddy cultivation season), this emissions is 0.7 t/km2 and 0.53 t/km2, respectively, from wetlands and paddy fields. Both wetlands and paddy fields emit a greater amount of CH4 during amon season than boro season. Behind this seasonal variation, water availability in terms of precipitation-evaporation ratio plays a more vital role than temperature. Total estimated ESV is 928.51 million US$, and CH4 fixation cost is 6.64 million US$ which is only 0.71% to total ESV. So, considering such huge net ESV, emphasis on wetland conservation and restoration are necessary.