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Johanna Stadmark

Johanna Stadmark


Johanna Stadmark

Nitrogen retention versus methane emission: Environmental benefits and risks of large-scale wetland creation


  • Geraldine Thiere
  • Johanna Stadmark
  • Stefan E.B. Weisner

Summary, in English

Coastal eutrophication by nutrient fluxes from agricultural land to marine recipients is presently com- bated by measures such as the implementation of watershed-scale wetland creation programs aimed at nitrogen removal. Such created agricultural wetlands – termed ‘nitrogen farming wetlands’ (NFWs) – receive nitrogen (N) loads predominantly as nitrate, facilitating N removal by denitrification. However, the conversion of agricultural soils into waterlogged wetland area is likely to increase climate gas emissions, particularly methane (CH4). There is thus a need to evaluate the benefits and risks of wetland creation at a large, watershed-scale.

Here we investigate N retention and CH4 emission originating from watershed-scale wetland creation in South Sweden, the relation between both processes, and how CH4 emission depends on individual wetland parameters. We combine data from intensively studied reference wetlands with an extensive wetland survey to predict N retention and CH4 emission with simple models, to estimate the overall process rates (large-scale effects) as well as spatial variation among individual NFWs.

We show that watershed-scale wetland creation serves targeted environmental objectives (N reten- tion), and that CH4 emission is comparably low. Environmental benefit and risk of individual wetlands were not correlated, and may thus be managed independently. High cover of aquatic plants was the most important wetland property that suppressed CH4 net production, potentially facilitating N retention simultaneously. Further, differences between wetlands in water temperature and wetland age seemed to contribute to differences in CH4 net production. The nationally planned wetland creation (12,000 ha) could make a significant contribution to the targeted reduction of N fluxes (up to 27% of the Swedish environmental objective), at an environmental risk equaling 0.04% of the national anthropogenic climate gas emission.


  • Division aquatic ecology
  • Department of Biology

Publishing year







Ecological Engineering: the Journal of Ecotechnology





Document type

Journal article




  • Ecology




  • ISSN: 1872-6992