Scientific publications

Wetlands restoration researchers - publication

Authors: Emilie Gios, Erik Verbruggen, Joachim Audet, Rachel Burns, Klaus Butterbach‑Bahl, Mikk Espenberg, Christian Fritz, Stephan Glatzel, Gerald Jurasinski, Tuula Larmola, Ülo Mander, Claudia Nielsen, Andres F. Rodriguez, Clemens Scheer, Dominik Zak, Hanna M. Silvennoinen

Summary: Restoration of drained peatlands through rewetting has recently emerged as a prevailing strategy to mitigate excessive greenhouse gas emissions and re-establish the vital carbon sequestration capacity of peatlands. Rewetting can help to restore vegetation communities and biodiversity, while still allowing for extensive agricultural management such as paludiculture. Below ground processes governing carbon fluxes and greenhouse gas dynamics are mediated by a complex network of microbial communities and processes. Our understanding of this complexity and its multi-factorial controls in rewetted peatlands is limited. Here, we summarize the research regarding the role of soil microbial communities and functions in driving carbon and nutrient cycling in rewetted peatlands including the use of molecular biology techniques in understanding biogeochemical processes linked to greenhouse gas fluxes. We emphasize that rapidly advancing molecular biology approaches, such as high-throughput sequencing, are powerful tools helping to elucidate the dynamics of key biogeochemical processes when combined with isotope tracing and greenhouse gas measuring techniques. Insights gained from the gathered studies can help inform efficient monitoring practices for rewetted peatlands and the development of climate-smart restoration and management strategies.

Authors: Gabrielle R. Quadra, Sannimari Käärmelahti, Christian Fritz, Ralph J. M. Temmink

Summary: Peat is interesting; it is very wet and made from old plants and animals breaking down very slowly. Even though peatlands are just 3% of the land, they lock away 30% of Earth’s carbon. But sometimes people mess things up by draining the peatlands and digging up the peat, which releases carbon into the atmosphere and contributes to the warming of our planet. But do not worry; we can save the day! We can put water back in the peatlands to bring them back to life so they can lock carbon again. Sphagnum—the Latin name of a peat moss—is the hero here! This special moss can support peat formation and be used for gardening and growing food. Ready to help save peatlands and protect the planet? Keep reading!

Authors: Benjamin Bodirsky, Felicitas Beier, Florian Humpenöder, Debbora Leip, Michael Crawford, David Chen, Patrick von Jeetze, Marco Springmann, et. al

Summary: The current global food system has detrimental outcomes for global health, environmental conditions and social inclusion. A coherent vision of a desirable food system can guide a sustainable food system transformation and help to structure political processes and private decisions by quantifying potential benefits, facilitating debates about co-benefits and trade-offs, and identifying key measures for desirable change. Such a transformation requires integrating measures targeting human diets, livelihoods, biosphere integrity, and agricultural management. Here, we apply a global food and land system modeling framework to quantify the impacts of 23 food system measures by 2050. Our multi-criteria assessment shows that a food system transformation can improve outcomes for health, the environment, social inclusion, and the economy. All individual measures come with trade-offs, particularly those targeting agricultural management, while few trade-offs and multiple co-benefits are linked to dietary change measures. By combining measures in packages, trade-offs can be reduced and co-benefits enhanced. We show that a sustainable food system also requires a transformation of the overall economy to stop global warming, reduce absolute poverty, and create alternative employment options. Within the context of a cross-sectoral sustainable development pathway, the food system transformation improves 14 of our 15 outcome indicators.

Authors:Aram Kalhori, Christian Wille, Pia Gottschalk, Zhan Li, Josh Hashemi, Karl Kemper & Torsten Sachs

Summary: Rewetting drained peatlands is recognized as a leading and effective natural solution to curb greenhouse gas emissions. However, rewetting creates novel ecosystems whose emission behaviors are not adequately captured by currently used emission factors. These emission factors are applied immediately after rewetting, thus do not reflect the temporal dynamics of greenhouse gas emissions during the period wherein there is a transition to a rewetted steady-state. Here, we provide long-term data showing a mismatch between actual emissions and default emission factors and revealing the temporal patterns of annual carbon dioxide and methane fluxes in a rewetted peatland site in northeastern Germany. We show that site-level annual emissions of carbon dioxide and methane approach the IPCC default emission factors and those suggested for the German national inventory report only between 13 to 16 years after rewetting. Over the entire study period, we observed a source-to-sink transition of annual carbon dioxide fluxes with a decreasing trend of −0.36 t CO2-C ha−1 yr−1 and a decrease in annual methane emissions of −23.6 kg CH4 ha−1 yr−1. Our results indicate that emission factors should represent the temporally dynamic nature of peatlands post-rewetting and consider the effect of site characteristics to better estimate associated annual emissions.

Authors: Sannimari A. Käärmelahti, Christian Fritz, Gabrielle R. Quadra, Maider Erize Gardoki, Greta Gaudig, Matthias Krebs & Ralph J. M. Temmink 

Summary: Rewetting drained agricultural peatlands aids in restoring their original ecosystem functions, including carbon storage and sustaining unique biodiversity. 30–60 cm of topsoil removal (TSR) before rewetting for Sphagnum establishment is a common practice to reduce nutrient concentrations and greenhouse gas emissions, and increase water conductivity. However, the topsoil is carbon-dense and preservation in situ would be favorable from a climate-mitigation perspective. The effect of reduced TSR on Sphagnum establishment and nutrient dynamics on degraded and rewetted raised bogs remains to be elucidated. We conducted a two-year field experiment under Sphagnum paludiculture management with three TSR depths: no-removal (TSR0), 5–10 cm (TSR5), and 30 cm (TSR30) removal. We tested the effects of TSR on Sphagnum establishment and performance, nutrient dynamics, and hotspot methane emissions. After two years, TSR5 produced similar Sphagnum biomass as TSR30, while vascular plant biomass was highest in TSR0. All capitula nitrogen (N > 12 mg/g) indicated N-saturation. Phosphorus (P) was not limiting (N/P < 30), but a potential potassium (K) limitation was observed in year one (N/K > 3). In TSR0, ammonium concentrations were > 150 µmol/l in year one, but decreased by 80% in year two. P-concentrations remained high (c. 100 µmol/l) at TSR0 and TSR5, and remained low at TSR30. TSR30 and TSR5 reduced hotspot methane emissions relative to TSR0. We conclude that all TSR practices have their own advantages and disadvantages with respect to Sphagnum growth, nutrient availability and vegetation development. While TSR5 may be the most suitable for paludiculture, its applicability for restoration purposes remains to be elucidated. Setting prioritized targets when selecting the optimal TSR with peatland rewetting is pivotal.

Authors:  Lisanne Hendriks, Stefan Weideveld, Christian Fritz, Tatiana Stepina, Ralf C. H. Aben, Ngum E. Fung, Sarian Kosten

Summary: Greenhouse gas (GHG) emissions from drained peatlands have been studied extensively. Considerably less attention has been paid to the emissions from the ditches used to drain peatlands. High within-ditch GHG production and lateral inflow of GHGs may lead to ditches emitting considerable amounts of GHGs on the landscape scale.We quantified annual emissions of ebullitive and diffusive methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) in 10 drainage ditches in intensively used temperate peatlands used for dairy farming, in The Netherlands. Additionally, we assessed water and sediment quality to determine proxies for emissions via the two emission pathways.The mean annual emissions from the studied ditches varied between 3.57 and 60.1 g CO2-eq. m−2 day−1 (based on a global warming potential over a 100-year timeframe), where CO2 contributed on average 43% (ranging between 1.9 and 22.0 g CO2 m−2 day−1) and diffusive CH4 contributed 16% (0.1–16.5 g CO2-eq. m−2 day−1) to the total GHG emission. Ebullition of CH4 made up nearly half of the total GHG emission (40%, 1.3–40.9 g CO2-eq. m−2 day−1). N2O emissions were mostly low. CO2 emissions were higher in winter months, while CH4 ebullition was higher during spring and summer. Diffusive CH4 emissions did not show a seasonal pattern.The mean emission factor, the estimate of average emissions per unit area (EF), for CH4 was 2144 kg CH4 ha−1 year−1, which is two times higher than the tier 1 EF reported by the IPCC (with underrepresented ebullition data), underlining the high variability of ditch emissions.Ditch emissions were also higher than the EF used for the surrounding drained peatlands indicating that ditch emissions can be important on the landscape scale and should be considered to be included in national greenhouse gas reporting.

Authors: Ralph J. M. Temmink , Bjorn J. M. Robroek, Gijs van Dijk,
Adam H. W. Koks, Sannimari A. Käärmelahti, Alexandra Barthelmes,
Martin J. Wassen, Rafael Ziegler, Magdalena N. Steele, Wim Giesen,
Hans Joosten, Christian Fritz, Leon P. M. Lamers, Alfons J. P. Smolders

Summary: Peatlands are among the world’s most carbondense ecosystems and hotspots of carbon storage. Although peatland drainage causes strong carbon emissions, land subsidence, fires and biodiversity loss, drainage-based agriculture and forestry on peatland is still expanding on a global scale. To maintain and restore their vital carbon sequestration and storage function and to reach the goals of the Paris Agreement, rewetting and restoration of all drained and degraded peatlands is urgently required. However, socio-economic conditions and hydrological constraints hitherto prevent rewetting and restoration on large scale, which calls for rethinking landscape use. We here argue that creating integrated wetscapes (wet peatland landscapes), including nature preserve cores, buffer zones and paludiculture areas (for wet productive land use), will enable sustainable and complementary land-use functions on the landscape level. As such, transforming landscapes into wetscapes presents an inevitable, novel, ecologically and socio-economically sound alternative for drainagebased peatland use.

Authors: Gabrielle R. Quadra, Coline C.F. Boonman, Renske J.E. Vroom, Alfons J.P. Smolders, Jeroen J.M. Geurts, Ralf C.H. Aben, Ralph J.M. Temmink, Stefan T.J. Weideveld, Christian Fritz 

Summary: Topsoil removal (TSR) is a management option performed before rewetting drained agricultural peatlands to reduce greenhouse gas (GHG) emissions and remove nutrients. Currently, its common practice to remove 30 to 60 cm of topsoil, which is labor-intensive, costly, and highly disruptive. However, optimal TSR depth for mitigating carbon emissions from rewetted peat soils has neither been determined nor linked to soil biogeochemical factors driving carbon emissions. We performed two mesocosm experiments to address this. In experiment 1, we removed the topsoil of two contrasting drained peat soils before rewetting (i.e., extensively managed, acid peat and intensively managed, near-neutral peat) with a 5 cm interval up to 25 cm TSR. In experiment 2, we combined TSR with the presence and absence of Typha latifolia on intensively managed, near-neutral peat soil. The experiments ran for 22 and three months, respectively, in which we measured carbon dioxide (CO2) and methane (CH4) emissions and porewater chemistry. Our experiments reveal that (i) 5 cm TSR greatly reduced CH4 and CO2 emissions irrespective of peat nutrient status during the 22-month experiment, and (ii) the presence of T. latifolia further reduced CH4 emissions during the 3-month experiment. Specifically, CH4 emissions were six to 10-times lower with 5 cm TSR compared to 0 cm TSR. Peak CH4 emissions occurred after three months with 0 cm TSR and strongly decreased thereafter. Random forest analyses highlighted that variation in CH4 emissions could mainly be explained by cumulative root biomass and porewater alkalinity. Furthermore, 5 cm TSR reduced porewater values of pH, alkalinity, CH4, and ammonium. The effectiveness of TSR in preventing the build-up of phosphorus, iron, and sulfur in porewater was site-specific. Our results show that only 5 to 10 cm TSR may already effectively prevent the adverse effects of rewetting former agriculturally peatlands by reducing undesirable CH4 emissions and avoiding nutrient release. Further, we argue that target setting and site-specific assessments are crucial to optimize the amount of TSR to reduce carbon emissions while minimizing disturbance and costs.


Authors: C. K. Nielsen, L. Elsgaard, U. Jørgensen, P. E. Lærke

Summary: In view of climate considerations regarding the management of peatlands, there is a need to assess whether rewetting can mitigate greenhouse gas (GHG) emissions, and notably how site-specific soil-geochemistry will influence differences in emission magnitudes. However, there are inconsistent results regarding the correlation of soil properties with heterotrophic respiration (Rh) of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from bare peat. In this study, we determined 1) soil-, and site-specific geochemical components as drivers for emissions from Rh on five Danish fens and bogs, and 2) emission magnitudes under drained and rewetted conditions. For this, a mesocosm experiment was performed under equal exposure to climatic conditions and water table depths controlled to either -40 cm, or -5 cm. For the drained soils, we found that annual cumulative emissions, accounting for all three gases, were dominated by CO2, contributing with, on average, 99 % to a varying global warming potential (GWP) of 12.2–16.9 t CO2eq ha−1 yr−1. Rewetting lowered annual cumulative emissions from Rh by 3.2–5.1 t CO2eq ha−1 yr−1 for fens and bogs, respectively, despite a high variability of site-specific CH4 emissions, contributing with 0.3–3.4 t CO2 ha−1 yr−1 to the GWP. Overall, analyses using generalized additive models (GAM) showed that emission magnitudes were well explained by geochemical variables. Under drained conditions, significant soil-specific predictor variables for CO2 flux magnitudes were pH, phosphorus (P), and the soil substrate’s relative water holding capacity (WHC). When rewetted, CO2 and CH4 emissions from Rh were affected by pH, WHC, as well as contents of P, total carbon and nitrogen. In conclusion, our results found the highest GHG reduction on fen peatlands, further highlighting that peat nutrient status and acidity, and the potential availability of alternative electron acceptors, might be used as proxies for prioritising peatland areas for GHG mitigation efforts by rewetting.

Authors: Evaldas Makrickas, Michael Manton, Per Angelstam, Mateusz Grygoruk 

Summary: While traditional forest management systems aim at maximizing timber production, sustainable forest management focuses on the multiple benefits of entire forest landscapes. The latter is now at the top of policy agendas. This calls for learning through evaluation to support the implementation of policies aiming towards multi-functional forest landscapes. The aim of this study is to quantify the economic trade-offs among natural, current, and re-wetted peatland forests using seven indicators, viz. drainage maintenance, rewetting, water retention, wood production, and three types of carbon sequestration as economic indicators. We discuss ways to adapt to and mitigate effect of forest draining on climate change toward securing multi-functional forest landscapes. The cost benefit analysis showed that in a potential natural state, Lithuania’s peatland forests would deliver an economic benefit of ∼€176.1 million annually. In contrast, compared to natural peatland forests, the drainage of peatland forests for wood production has caused a loss of ∼€309 million annually. In comparison, peatland forest rewetting is estimated to increase the economic value by ∼€170 million annually. This study shows that satisfying different ecosystem services is a balancing act, and that a focus on wood production has resulted in net losses when foregone values of water storage and carbon sequestration are considered. Valuation of different sets of ecosystems service benefits and disservices must be assessed, and can be used as a tool towards creating, implementing and monitoring consequences of policies on both sustainability and biodiversity.

Authors: Weier Liu, Christian Fritz, Jasper van Belle, Sanderine Nonhebel

Summary: Majority of Dutch peatlands are drained and used intensively as grasslands for dairy farming. This delivers high productivity but causes severe damage to ecosystem services supply. Peatland rewetting is the best way to reverse the damage, but high water levels do not fit with intensive dairy production. Paludiculture, defined as crop production under wet conditions, provides viable land use alternatives. However, performance of paludiculture is rarely compared to drainage-based agriculture. Here, we compared the performances of six land use options on peatland following a gradient of low, medium, and high water levels, including conventional and organic drainage-based dairy farming, low-input grasslands for grazing and mowing, and high-input paludiculture with reed and Sphagnum cultivation.  Results showed that drainage-based dairy farming systems support high provisioning services but low regulation and maintenance services. Organic farming provides higher climate and nutrient regulation services than its conventional counterpart, but limited overall improvement due to the persistent drainage. Low-intensity grassland and paludiculture systems have high regulation and maintenance services value, but do not supply biomass provisioning comparable to the drainage-based systems. Without capitalizing the co-benefits of regulation and maintenance services, and accounting for the societal costs from ecosystem disservices including greenhouse gas emission and nitrogen pollution, it is not likely that the farmers will be incentivized to change the current farming system towards the wetter alternatives. Sustainable use of peatlands urges fundamental changes in land and water management along with the financial and policy support required.

Authors: S. A. K ̈äärmelahti, R. J. M. Temmink, G. van Dijk, A. Prager, M. Kohl, G. Gaudig, A. H. W. Koks, W. Liu, R. J. E. Vroom, K. Gerwing, C. J. H. Peters, M. Krebs, C. Fritz

Summary: Peatland degradation through drainage and peat extraction have detrimental environmental and societal consequences. Rewetting is an option to restore lost ecosystem functions, such as carbon storage, biodiversity and nutrient sequestration. Peat mosses (Sphagnum) are the most important peat-forming species in bogs. Most Sphagnum species occur in nutrient-poor habitats; however, high growth rates have been reported in artificial nutrient-rich conditions with optimal water supply. Here, we demonstrate the differences in nutrient dynamics of 12 Sphagnum species during their establishment in a 1-year field experiment at a Sphagnum paludiculture area in Germany. Our study shows that slower-growing species (S. papillosum, S. magellancium, S. fuscum, S. rubellum, S. austinii; often forming hummocks) displayed signs of nutrient imbalance. These species accumulated higher amounts of N, P, K and Ca in their capitula, and had an elevated stem N:K quotient (>3). Additionally, this group sequestered less C and K per m2 than the fast and medium-growing species (S. denticulatum, S. fallax, S. riparium, S. fimbriatum, S. squarrosum, S. palustre, S. centrale). We conclude that nutrient dynamics and carbon/nutrient sequestration rates are species-specific. For bog restoration, generating ecosystem services or choosing suitable donor material for Sphagnum paludiculture, it is crucial to consider their compatibility with prevailing environmental conditions. 

Authors: Mark S. Reed, Julia M. McCarthy, Eric A. Jensen, and Hannah Rudman

Summary: There is growing interest in the potential for ecosystem markets to facilitate climate and nature recovery, but there are concerns that poorly designed and operated markets may be used in corporate “greenwashing” and lead to negative unintended consequences for nature and local communities.

This paper:
1. Provides an overview of compliance and voluntary carbon and other ecosystem markets and systematically analyses relevant market actors in the UK, a country with well-developed and rapidly proliferating domestic markets that is actively seeking to increase their integrity;
2. Conducts a comparative analysis of existing national and international principles and synthesises a list of 14 core principles pertaining to the governance, measurement, reporting and verification, and wider benefits of high-integrity ecosystem markets; and
3. Develops an ecosystem markets governance hierarchy, showing the various policy, governance and market mechanisms and infrastructure that are being explored to implement the proposed principles in the UK.

Taken together, the core market principles and governance hierarchy could be used to ensure the development of high-integrity ecosystem markets across the UK and internationally, as national governments around the world attempt to responsibly build and scale these markets.

Authors: Claudia K. Nielsen, Lene Stødkilde, Uffe Jørgensen, Poul Erik Lærke

Summary: Paludiculture can be a tool to incentivise rewetting of agricultural peatlands with the option for biomass utilisation in green protein biorefineries. However, the economic feasibility for green protein paludiculture depends on product maximisation. This study explored the potential of a ratio vegetation index (RVI) model, with inclusion of climatic factors relevant for biomass growth, to predict crude protein (CP) contents in green protein precipitates from biorefining Phalaris arundinacea and Festuca arundinacea cultivated under different management intensities on a wet fen. Assessing yields for two years of cultivation, we found that timing of harvest was a key variable for CP extractability using the biorefinery technique. Biomass and protein yields were similar between management treatments and years, but extractability was enhanced in the dryer of the two years. This study highlighted the potential of an RVI model to predict, under varying climatic conditions, CP contents in the protein precipitate with good model performance (R2 = 0.64, NRMSE = 0.23) and accuracy. In 92 % of occurrences, the model was able to predict statistically similar CP contents compared to measured CP in the protein product, with an average deviation between measured and predicted annual values of 1.7 % across species and management intensities. The findings highlight an option for maximising the overall efficiency of green protein paludiculture by determining the optimal timing of harvest, thereby demonstrating an economic potential to incentivise paludiculture farming.

Authors: Claudia Kalla Nielson and Anton Gårde Thomsen 

Summary: Time domain reflectometry (TDR) measurements of the volumetric water content (θ) of soils are based on the dielectric permittivity (ε), relating ε to θ, using an empirical calibration function. Accurate determination of θ for peaty soils is vital but complicated by the complexity of organic soils and the lack of a general calibration model. Site-specific calibration models were developed to determine θ from TDR measurements for a heterogenous peatland across gradients of peat decomposition and organic carbon (OC) content; derived by soil organic matter conversion. The possibility of predicting OC contents based on the corrected θ (θcor); ε; electrical impedance (Ζ); and a categorical predictor variable was explored. The application of plot-specific and local area calibration models resulted in similar results. Compared to common calibrations, the threshold for accurate determination of θ was at ε = 5; with higher ε underestimating θ by up to 25%. Including the von Post degree of peat humification as a bioindicator, the OC content could be modelled across the area and the full range of θ with an accuracy of ±1.2% for 496 measurements. In conclusion, a strong indication was found for determining OC in peatlands in situ using TDR and a site-specific calibration model for θ together with indices of peat decomposition.

Authors: Coline C.F. Boonman, Tom S. Heuts, Renske J.E.Vroom, Jeroen J.M.Geurts, Christian Fritz

Summary: Nitrogen often stimulates methane production and its release in aquatic ecosystem containing labile carbon. In this experimental work we could show that wetland plants/paludiculture crops efficiently take up nitrogen and showed an overall mitigating effect on methane emissions. Soil biogeochemistry and land-use history was of lesser importance for the 2 soils included in this study. A nice add on of this study is that mesocosm methane fluxes match very well with hectare scale fluxes of similar wetlands (after rewetting). This is extra motivation to conduct mesocosm studies testing methane mitigation techniques that can be applied on the field scale (around the globe).

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