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Many wetlands have been drained due to urbanization, agriculture, forestry or other purposes, which has resulted in a loss of their ecosystem services. To protect receiving waters and to achieve services such as flood control and storm water quality mitigation, new wetlands are created in urbanized areas. However, our knowledge of greenhouse gas exchange in newly created wetlands in urban areas is currently limited. In this paper we present measurements carried out at a created urban wetland in Southern Finland in the boreal climate. We conducted measurements of ecosystem CO2 flux and CH4 flux (FCH4) at the created storm water wetland Gateway in Nummela, Vihti, Southern Finland, using the eddy covariance (EC) technique. The measurements were commenced the fourth year after construction and lasted for 1 full year and two subsequent growing seasons. Besides ecosystem-scale fluxes measured by the EC tower, the diffusive CO2 and CH4 fluxes from the open-water areas (FwCO2 and FwCH4, respectively) were modelled based on measurements of CO2 and CH4 concentration in the water. Fluxes from the vegetated areas were estimated by applying a simple mixing model using the above-mentioned fluxes and the footprint-weighted fractional area. The half-hourly footprint-weighted contribution of diffusive fluxes from open water ranged from 0 % to 25.5 % in 2013. The annual net ecosystem exchange (NEE) of the studied wetland was 8.0 g C-CO2 m−2 yr−1, with the 95 % confidence interval between −18.9 and 34.9 g C-CO2 m−2 yr−1, and FCH4 was 3.9 g C-CH4 m−2 yr−1, with the 95 % confidence interval between 3.75 and 4.07 g C-CH4 m−2 yr−1. The ecosystem sequestered CO2 during summer months (June–August), while the rest of the year it was a CO2 source. CH4 displayed strong seasonal dynamics, higher in summer and lower in winter, with a sporadic emission episode in the end of May 2013. Both CH4 and CO2 fluxes, especially those obtained from vegetated areas, exhibited strong diurnal cycles during summer with synchronized peaks around noon. The annual FwCO2 was 297.5 g C-CO2 m−2 yr−1 and FwCH4 was 1.73 g C-CH4 m−2 yr−1. The peak diffusive CH4 flux was 137.6 nmol C-CH4 m−2 s−1, which was synchronized with the FCH4. Overall, during the monitored time period, the established storm water wetland had a climate-warming effect with 0.263 kg CO2-eq m−2 yr−1 of which 89 % was contributed by CH4. The radiative forcing of the open-water areas exceeded that of the vegetation areas (1.194 and 0.111 kg CO2-eq m−2 yr−1, respectively), which implies that, when considering solely the climate impact of a created wetland over a 100-year horizon, it would be more beneficial to design and establish wetlands with large patches of emergent vegetation and to limit the areas of open water to the minimum necessitated by other desired ecosystem services.

Drained peatlands are a large emission source and a shift to paludiculture (rewetting and cultivation of wet-tolerant plants) is emerging as a potential emission reduction measure. Paludiculture can potentially results in emission savings from direct emissions, product substitution and carbon storage, but the whole life cycle climate impacts are rarely studied. In this study, we evaluated two paludiculture product systems (cattail (Typha) construction board and common reed (Phragmites) horticultural vermicompost) with cradle-to-grave life cycle assessment (LCA) applied global sensitivity analysis to identify, which parts of the product system would need more research and product development to ensure net emission savings. Based on the results, both product systems result in much lower emissions than current agricultural land use and may be net greenhouse gas sinks (average − 6.0 tCO2eq ha−1 for cattail board; −3.0 tCO2eq ha−1 for reed growing media). The uncertainty in the product life cycle is concentrated to a few key processes: the direct CO2 and CH4 emissions from paludiculture, construction board additives, and CH4 emissions from vermicomposting reed. Further research to these would minimize the uncertainty and help in maximizing the climate mitigation potential of paludiculture derived products. Highlights • Paludiculture reduces emissions from agricultural peatlands. • Paludiculture products can store carbon and substitute emission intensive products. • Benefits can be increased by identifying high emission process stages in production. • Life cycle assessment can help in guiding process development.

Water table conditions in drained peatlands affect peat decomposition, fluvial carbon and greenhouse gas emissions, and plant growth in oil palm plantations. This study illustrates the spatial heterogeneity of soil moisture profiles in cultivated tropical peat under oil palm plantation and uncultivated secondary forest, using maps. At a study plot under each land use the geographical coordinates of sampling points, tree locations and other features were recorded. Peat soil samples were taken at depths of 0–50 cm, 50–100 cm, 100–150 cm and 150–200 cm, and their moisture contents were determined. Overall, soil moisture content was higher in secondary forest than in oil palm plantation due to land management activities such as drainage and peat compaction in the latter. Significant differences were observed between the topsoil (0–50 cm) and deeper soil layers under both land uses. Soil moisture maps of the study plots interpolated using geographical information system (GIS) software were used to visualise the spatial distributions of moisture content in soil layers at different depths (0–50 cm, 50–100 cm, 100–150 cm, 150–200 cm). Moisture content in the 0–50 cm soil layer appeared to be inversely related to elevation, but the correlation was not statistically significant. On the other hand, there was a significant positive correlation between soil moisture content and the diameters of oil palm trunks. Palm trees with negative growth of trunk diameter were mostly located in subplots which were relatively dry and/or located near drains. The results of this study indicate that soil moisture mapping using GIS could be a useful tool in improving the management of peatland to promote oil palm growth.

Urbanization changes water balance, degrades water quality and disrupts habitats. Wetlands offer storm water volume and flow control, water pollution mitigation, and rich land–water interphase habitats. In the present case study, urban wetlands were designed and implemented to provide multiple functions, including water quality improvement and the establishment of critically endangered clay stream habitat, along a revived urban stream within the Baltic Sea watershed in Southern Finland. The primary water quality concern in the recipient lake is algal bloom controlling and clay particle-carried phosphorus. Wetlands were monitored for functioning over five calendar years. At a wetland monitored for 5 years, herbaceous vegetation was well self-established in the second year, and reached 102 species, of which 97% were native, in the fifth growing season. Successful breeding of amphibians and water birds occurred right after construction. Continuous water quality monitoring over the fourth year at this wetland, with 0.1% area of its watershed, revealed seasonal and event-based differences: for total phosphorus, an annual 10% average with lower removal rates outside, and up to 71% event reductions during the growing season, while highest load reductions occurred during heavy rain and snowmelt events outside the growing season. The created wetlands provided critical habitat and beneficial functions and thus compensated partly for urbanization.

Agricultural and other land uses on ombrotrophic lowland tropical peat swamps typically lead to reduced vegetation biomass and water table drawdown. We review what is known about greenhouse gas (GHG) dynamics in natural and degraded tropical peat systems in south-east Asia, and on this basis consider what can be expected in terms of GHG dynamics under restored conditions. Only limited in situ data are available on the effects of restoration and the consequences for peat carbon (C) dynamics. Hydrological restoration seeks to bring the water table closer to the peat surface and thus re-create near-natural water table conditions, in order to reduce wildfire risk and associated fire impacts on the peat C store, as well as to reduce aerobic peat decomposition rates. However, zero emissions are unlikely to be achieved due to the notable potential for carbon dioxide (CO2) production from anaerobic peat decomposition processes. Increased vegetation cover (ideally woody plants) resulting from restoration will increase shading and reduce peat surface temperatures, and this may in turn reduce aerobic decomposition rates. An increase in litter deposition rate will compensate for C losses by peat decomposition but also increase the supply of labile C, which may prime decomposition, especially in peat enriched with recalcitrant substrates. The response of tropical peatland GHG emissions to peatland restoration will also vary according to previous land use and land use intensity.