Whether conversion of mangrove forest to rice cropland is environmentally and economically viable?

- CH4 emission was significantly higher from rice paddy than the mangrove sediment.
- N2O emission was significantly higher from mangrove sediment than rice paddy.
- Conversion of mangroves to rice paddy ecosystem enhances carbon equivalent emission of the system.
- Market value of products from the mangrove is higher than that of the rice paddy.
- Mangrove area has incurred large economic loss due to conversion to the rice paddy.

The diverse habitat of the mangrove ecosystems all over the globe are under continuous threat of conversion for immediate and/or short-term economic benefits. Nonetheless, the emission of climatically relevant greenhouse gases increases with the disturbance of the mangrove sediment −this might undermine the credible reservoir of carbon within the sediment. This article attempts to estimate the environmental (carbon emission) and economic consequences of converting mangrove to cropland (especially rice paddy) based on field-scale study at three different sites (Khola, Gupti and Damra) within the Bhitarkanika mangrove for two consecutive years. The study suggests that the cumulative methane (CH4) emission was significantly higher from the rice paddy (211.3 kg ha−1) compared to the mangrove sediment (50.8 kg ha−1), while the average nitrous oxide (N2O) emission was significantly higher from the later (2.1 kg ha−1). Multivariate statistical analysis suggests that the land use was the prime controlling factor for variation in CH4 and N2O emission. Total carbon equivalent emission (CEETOT) from the rice paddy was significantly higher than mangrove during the study period. The study suggests that the economic value of the mangrove ecosystem was several folds higher than that of the rice paddy. The CEETOT of the Bhitarkanika mangrove has increased approximately 212 Gg over last few decades due to the conversion of the mangrove area to the rice paddy. Such studies are imperative in developing effective regional climate change adaptation strategies. The study advocates urgent need to educate and aware people about the benefits of the mangrove compared to the cropland.