Research

The regulatory functions of peatlands in water and element cycles, their ecosystem services, and their role in biodiversity conservation have increasingly become the focus of scientific and public debate; particularly in the course of climate change and more frequent occurrence of droughts and heat waves. Peatlands are efficient sinks of atmospheric carbon (C), and store an estimated 30% of the global soil C pool on only ~ 3% of the global land surface.

Across Europe, however, vast areas of peatlands have been degraded or destroyed, mainly by drainage, peat extraction or agricultural cultivation. In particular, ombrotrophic peatlands are severely affected. Consequently, degraded peatlands have turned from sinks into sources of atmospheric C, which pivots to restoring ecosystem functions to mitigate climate warming. High emissions of carbon dioxide (CO2) from drained or altered peatlands significantly contribute to European greenhouse gas budgets. The depth of the aerated peat layer largely determines CO2 emissions.

In this context, restoration is an efficient emission mitigation tool, yet successful restoration of peatlands is challenging and consensus is lacking: decay under oxic conditions leaves peat decomposed, decreasing its water holding capacity, up to a state of hydrophobicity. Due to a patchy understanding of physicochemical and biological processes of restoring peat, restoration often focuses to reinstate pre-degradation hydrological conditions, after which the system is left to natural succession. While water levels close to the surface reduce CO2 emissions 8, restoration of peatland vegetation, likely holds the key to recreate C sinks and peatlands with only low methane (CH4) emissions. Nutritionally imbalanced sites may have increased CH4 emissions, but maintain their C sink function and net negative radiative forcing at modest nutrient loadings, but turn into strong CO2 and/or CH4 sources in case of degradation and higher nutrient enrichment.

Peatlands, also restored peatlands, are increasingly prone to climate extremes, such as drought, with longlasting effects on both plant and soil communities and thus on C cycling. Unveiling past tipping points is a prerequisite for an understanding of how individual species and entire ecosystems respond to future climate changes. We have shown that plant community composition strongly converges at a water level of ~12 cm, indicating a community-level tipping-point 15. A similar water level was recently suggested to be a prerequisite for restoring the C sink function. As many peatlands currently operate under water levels near to this tipping point, inter-annual variability in precipitation and air temperature may determine whether (semi-)natural peatlands contribute to climate warming or mitigation of climate change. Functional transitions in peatland ecosystems depend on this critical hydrological threshold that determines long-term vegetation changes and resulting C fluxes. The advances in understanding the nonlinear nature of ecosystem responses to drought and in developing a mechanistic understanding of tipping points that are provided by palaeoecological analyses could provide a hydrological baseline for restoration.

Current difficulties and limitations in peatland restoration hinge on the lack of data and models on indicators of ecosystem conditions, such as on the spatio-temporal dynamics and budgets of gas fluxes, biodiversity, or hydrology. Peat degradation alters the water holding capacity and reduces the potential to buffer variations in water availability, constraining rewetting and restoration of ecosystem functioning.

Swindles et al. highlighted the effects of drought in peatlands all over Europe as a consequence of climate change and human impacts over the last 300 years. While we understand the effects of drought, the extent to which drought (incl. drainage) effects on peatland processes are reversible is poorly understood although essential for peatland restoration. Interdisciplinary approaches are needed to restore and preserve degraded peatlands in the long term and to re-establish bog vegetation as a key to initiate peat formation and to avoid high methane (CH4) emissions after rewetting.

Methodologies have been proposed to derive greenhouse gas budgets under drained or semi-natural conditions, both from chamber based approaches and Eddy Covariance techniques. However, trade-offs and synergies between greenhouse gas budgets, plant diversity and microbial activity, and land-use forms or management options in the context of conservation and restoration have to be evaluated. Remote sensing or satellite imagery-based approaches could provide new tools to monitor vegetation and/or hydrological conditions or to model greenhouse gas exchange. This will help to define priority areas and actions, and identify ecological and socio-economic drivers.

To address these research deficiencies, we intend to study seven sites in the nemoral zone of central Europe regarding their historic development (reference conditions, past resilience, C accumulation), current conditions (vegetation, hydrology, C-stocks, CO2 and CH4 exchange), and potential development (degradability, drought resilience, prospective C-budgets and CO2 and CH4 fluxes). We will focus on CO2 and CH4, as N2O was of minor importance at sites comparable to restoration sites under study in ReVersal, i.e., at sites with a high potential for successful restoration 13. We aim to develop remote sensing and satellite imagery based tools for monitoring and evaluation of restored peatlands. The chosen sites span a gradient of different water and nutrient availability and are situated in locations that are to a varying degree affected by the observed increasing frequency of droughts in Europe.
 

Our main objective is to develop a spatio-temporally explicit indicator framework for peatland restoration success across peatland sites affected by drainage and/or extraction. To this end, we will (i) examine biological and biogeochemical conditions, and fluxes of CO2 and CH4 to mechanistically understand C budgets and effects of water and nutrient availability, (ii) explore changes in biodiversity along degradation and restoration trajectories under past, current and future climatic and socio-economic conditions, (iii) evaluate uncertainties of conservation and restoration approaches for adaptive management strategies including trade-offs between goals, (iv) develop remote-sensing based models to assess degradation indicators in space and time to facilitate knowledge integration and transfer, and (v) assess the transferability of these models across landscapes to provide cost‐effective, reliable and long-term monitoring prospects.

Our methodology will invoke a step-change in the conservation and restoration of peatlands. Restoration success will be determined at two levels: (i) the restoration of hydrology with the appropriate water quality and water table levels and (ii) the restoration of plant and microbial biodiversity with their respective functions in C and nutrient cycling. Only a combination of both restoration levels will underpin successful restoration of peatland C dynamics, i.e., of the carbon sink function. If these levels can only partly be met, trade-offs have to be made between functions: e.g. a preservation of existing C pools at the expense of limited biodiversity and/or transiently elevated methane emissions in case of too wet or nutritionally imbalanced conditions.

To understand the range and relationships between biological and biophysical processes, we need to step beyond single site studies, and foster research across sites and scales, including (semi-) natural reference sites. An evaluation of degraded and restored sites needs to include (i) palaeoecological data to understand past succession and hydrology over periods of past changing climate and land-use; (ii) indicators of peat decomposition and hydrological and nutritional status; (iii) indices of biodiversity in vegetation and microbial communities, and (iv) robust estimates of the C and greenhouse gas budgets. We hypothesize:

1. From palaeoecological data, optimum hydrological conditions for peat growth, resilience toenvironmental changes as occurred in the past, vegetation, and C accumulation rates can be inferred asa basis to set restoration targets and trade-offs.
2.  Water availability, aerated peat depth, and indicators of peat quality, nutritional status, plant biodiversity,and microbial diversity determine the trajectories of restoration and target levels:
   (a) only a re-establishment of the bog hydrology, vegetation, and a diverse microbial community under low or moderate nutrient availability will create a greenhouse gas sink.
   (b) if one of the target levels (hydrology or biodiversity) cannot be met, trade-offs between theecosystem functions have to be made at the expense of a positive greenhouse gas budget
3. Ongoing climate change and more frequent occurrence of heat waves and droughts pose a threat toefforts of restoration of bog vegetation, limiting the potential carbon sink strength of peatlands.

Whilst significant advances have been made in the study of peatland restoration and in effects of water table depths on CO2 and CH4 fluxes, we take a cross-disciplinary approach that links paleoecology, community ecology, hydrology, biogeochemistry and remote sensing. This will provide novel tools to understand main drivers of successful peatland restoration in the light of ongoing global change. Notably, in the nemoral zone, peatlands experience high levels of anthropogenic pressures: nitrogen pollution, increases in temperature, changes in hydrological conditions, and changes in water quality. Drought, heat waves and other disturbances are predicted to occur more frequent. We thus need efficient tools to evaluate degradation, restoration, and trade-offs between restoration targets, in particular for nemoral peatlands. Such a proposed multidisciplinary and international approach has been rarely addressed in peatland restoration.
 

The project objectives will target representative peatland ecosystems in the nemoral zone from Western (Netherlands, Northwest Germany) to Eastern (Poland), and Northern (Southern-Sweden) to Southern (Austria) Europe. The sites are affected by various degradation factors including drainage, climate change, intensive land-use or different management techniques, and different approaches for restoration have been (partly) applied. However, all sites feature signs of potential restoration success and are thus representative of sites with highest priority for restoration. Core sites will be Kusowo Bagno (POL) and Pürgschachen Moor (AUT), further sites are Amtsvenn and Vechtaer Moor (GER), Fochteloër Veen (NLD), Pichlmeier Moor (AUT), and Store Mosse (SWE).

We bring together peatland-related disciplines – paleoecology, hydrology, microbial ecology, applied vegetation sciences, and biogeochemistry – with the latest remote sensing techniques. We investigate compositional, stoichiometric or chemical features of vegetation and solid peat as integrative key features and relate them to diversity patterns, ecosystem processes and land-use. We establish a CO2 and CH4 flux measurement network on core sites, building on available and new data. This enables to examine the influence of different hydrological and plant-ecological or biogeochemical settings on C turnover. We will quantify C fluxes directly or by recent indicator approaches calibrated by campaign-wise chamber flux measurements, and investigate underlying controls. Mathematical simulation models and statistical tools support to characterize system dynamics and to analyze the interaction of processes to predict future peatland development and restoration success. Local measurements serve as input for an upscaling routine which aims at an estimation of key variables in a spatial and temporal explicit way. Very high resolution (VHR) data obtained by unmanned aerial systems (UAS) will be used together with multi-scale and multi-sensor satellite data in different spectral ranges. The remote sensing information will be related to the hydrological, chemical and biological indicators via methods of machine learning. Models will be trained with the objective on the ability of transfer across temporal and spatial scales. Hence, the project aims to develop new methods for assessing indicators of peatland conditions and to make them available to users (environmental managers and authorities). These new methods will significantly increase information on peatland degradation or restoration through the use of innovative AI procedures that go beyond observation-based data.

 

At the research sites in Germany, the Netherlands, Sweden, Austria, and Poland, all research groups are part of a well-established stakeholder dialogue. Together with the peat industry, nature conservationists, water managers, farmers, and administrative bodies, we have been discussing best practices for restoration. ReVersal will inspire this dialogue that has also been fostered by our local partners, addressing inconvenient issues of water supply and realistic restoration pathways given challenging conditions of nutrient loading and water scarcity. To gain in transparency and validation, the pathways will be jointly developed (co-design) and presented and discussed in local workshops in all participating countries to the mentioned stakeholders, contributing to their practice and discussions on peatland governance approaches.

We are in ongoing dialogue e.g. with ECCMC (GER), Naturum information centre (SWE), Natuurmonumenten (NDL), the Wetlands Conservation Centre (POL), and the mire protection associations (AUT). This co-design involves discussing and possibly adapting the Best Practice recommendations according to local conditions. In addition to the local embedding of the results, we will liaise with national (NGOs and ministries) and international partners (IPS, IMCG, Ramsar). On the national level, we will develop communication strategies adapted to the national perception of peat bog restoration and select event and consultation types that are suited for national stakeholders. On the European and global scale, we will present the outcome of our project at side events of global meetings like the Ramsar COP 15 (likely to take place in 2023) and develop and present a policy brief based on the results. These measures will safeguard that the outcome of ReVersal will gain ample international recognition.
 

ReVersal is strongly interlinked with a variety of projects, programmes, networks, agreements and policy frameworks that guide and direct peatland restoration financing, research, and implementation. On a global policy level, these include the UN Sustainable Development Goals, the UN Environmental Assembly 2019 resolution ‘Conservation and sustainable management of peatlands’, the Paris Agreement and its Nationally Determined Contributions (UNFCCC), the Aichi targets and the post 2020 Global Diversity Framework (CBD), the Mitigation of Climate Change in Agriculture Programme (FAO), and the UN Decade of Restoration (2021- 2030). Relevant global non-UN initiatives include the Global Action Plan for Peatlands (Ramsar Convention) and the IUCN 2016 resolution ‘Securing the future for global peatlands’.

Project partners intervene on the global level via their participation in the governance of key peatland/restoration organizations, including the UN-led Global Peatlands Initiative (GPI), the Society of Ecological Restoration, the Society of Wetland Scientists, the International Mire Conservation Group and the International Peatland Society. On the European level, there are key links to EU Regulation 2018/841 on GHG emissions and removals from LULUCF, Council Directive 91/676/EEC on nitrate pollution from agricultural sources, and to the EU Biodiversity Strategy COM/2011/0244. 

Project partners contribute to ongoing peatland restoration and paludiculture research/implementation projects in Austria (e.g. LTER-CWN,16PALUS), Germany (e.g. Aktimoos, Moorbodenmonitoring), Sweden (Life to ad(d)mire – Restoring drained and overgrowing wetlands (LIFE08 NAT/S/000268), and Poland (Wetlands Conservation Centre - https://bagna.pl). Strong links exist to the Greifswald Mire Centre. Extended collaboration is also sought with bog research projects e.g. in the UK (UK Centre for Ecology and Hydrology), other EU countries, and beyond (e.g. Cape Horn International Center and Universidad de Magellanes, Chile; McGill University Montréal, Canada). The project consortium will – via its networks – actively monitor emerging cooperation and funding opportunities to pursue further research.