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Carbon Dioxide and Methane Fluxes from a Tropical Freshwater Wetland Under Natural and Rice Paddy Conditions: Implications for Climate Change Mitigation

Abstract

We investigated the impact of converting a natural tropical freshwater wetland in Uganda into a rice paddy wetland on climate change mitigation, by comparing carbon dioxide (CO2) and methane (CH4) fluxes from the natural section (under different vegetation communities dominated by Cyperus papyrus, Typha latifolia and Phragmites mauritianus) and from a rice paddy section, during the dry and wet seasons. CO2 fluxes (mg C m− 2 h− 1) from the rice paddy section during the dry and wet seasons were 1045.4 ± 46.6 (mean ± SE) and 804.4 ± 50.2 respectively, significantly higher (p < 0.05) than those obtained from all the three vegetation communities of the natural section. However, CH4 fluxes (mg C m− 2 h− 1) from the rice paddy section during the dry and wet seasons were 2.1 ± 0.4 and 5.1 ± 0.5 respectively, significantly lower (p < 0.05) than those observed from all the vegetation communities of the natural section. Considering total carbon emission, it was observed that whereas conversion of natural tropical freshwater wetlands into rice paddies may limit CH4 emission, it compromises climate change mitigation efforts by increasing total carbon emission, that could make rice paddy wetlands net carbon sources. Fluxes of CO2 and CH4 from the wetland were mainly influenced by water level. Further, we estimated that rice paddy wetlands currently emit only 0.72 and 0.14 % of the total annual CO2 and CH4 respectively, emitted from Uganda’s wetland soils due to their low spatial coverage. However, we predict that future emission of both gases from Uganda’s wetlands will mainly originate from rice paddy wetlands due to their rapid expansion rate.

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Acknowledgements

Financial support for this study was provided by the African Centre of Excellence for Water Management (ACEWM), under the World Bank’s African Centres of Excellence (ACE II) Project. Additional funding was provided by the University of Natural Resources and Life Sciences (BOKU), Vienna, Austria through Mag. Gerold Winkler and Prof. Thomas Hein. We appreciate the local community members neighbouring Naigombwa wetland for the good hospitality and support during field sampling. More thanks go to the Department of Environmental Management, Makerere University for offering laboratory and working space, and to Mr. Enock Kajubi for mapping the study area. Lastly, we thank Mr. Peter Mutua at the International Livestock Research Institute, Nairobi, Kenya for the technical assistance during the analysis of gas samples.

Funding

This work was supported by the African Centre of Excellence for Water Management (ACEWM) (Grant No. ACEWM/GSR/9813/10), under the World Bank’s African Centres of Excellence (ACE II) Project.

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The study was conceptualized and designed by DW and FK. DW carried out data collection and analysis, and wrote the first draft manuscript. FK, TF and TH reviewed, edited and contributed to the discussion of the manuscript. Funding acquisition was by TF and TH. The study was supervised by FK, TF and TH. All authors read and approved the final manuscript.

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Correspondence to David Were.

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Were, D., Kansiime, F., Fetahi, T. et al. Carbon Dioxide and Methane Fluxes from a Tropical Freshwater Wetland Under Natural and Rice Paddy Conditions: Implications for Climate Change Mitigation. Wetlands 41, 52 (2021). https://doi.org/10.1007/s13157-021-01451-4

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  • DOI: https://doi.org/10.1007/s13157-021-01451-4

Keywords

  • Greenhouse gases
  • Rice paddy
  • Uganda
  • Vegetation community
  • Wetland conversion