The project identified and quantified the potential greenhouse gas (GHG) emissions benefits of a range of possible mitigation options for agriculturally managed lowland peatlands in England and Wales. The project was funded by Defra as project reference SP1218 and was completed in early-2023.
About the project
The project, funded under Defra's R&D programme, quantified a range of mitigation options for agriculturally managed lowland peatlands in England and Wales.
The project was divided into four primary tasks:
- A desk based assessment of the practical and economic potential of high water table paludiculture management
- A review of the societal impacts of drainage-based lowland peat management
- A field experimental study to quantify the magnitude of emissions reductions that may be achievable by raising water levels within conventional arable systems, together with any potential trade-offs in relation to crop yields, disease risk and soil trafficability
- An evaluation of the economic, environmental, societal and practical costs, benefits, opportunities and barriers associated with altered hydrological management of agricultural peatlands
The aims of the project were to provide Defra, other policymakers and the farming community with best-practice advice on a range of approaches to mitigate GHG emissions from agriculturally used peatlands.
Impacts include:
- Supporting Defra’s 25 year plan to reduce GHG emissions from the agricultural sector,
- Helping to reduce the societal costs of current deep-drained arable systems on peat, and
- Contributing to extending the economic lifetime of farmed organic soils by reducing rates of long-term subsidence and soil loss.
Task 1: Exploring the use of paludiculture
The concept of paludiculture (i.e. the productive use of high-water table peatlands) is not strongly developed in the UK. Apart from periodic reed harvesting at some conservation-managed fens, none of the sites included in this study are under any kind of productive wetland management. Subsequently, the concept has received considerable attention as a potentially sustainable after-use of re-wetted peatlands that could continue to generate economic returns from the land without accompanying CO2 emissions.
Pioneering work led by the Greifswald Mire Centre in Germany has explored a range of paludiculture options including production of biomass for energy generation and building materials (e.g. thatch, insulation), crops, livestock, and Sphagnum moss for use as a peat alternative in horticulture. To date, most UK peat restoration projects have focused primarily on benefits for biodiversity, carbon sequestration and water quality, but the potential role of paludiculture in the adaptive management of UK peatlands has been highlighted in the IUCN Peatland Programme’s recent UK Peatland Strategy (IUCN, 2018). A handful of small-scale field trials are now underway or planned, for example at the Great Fen Project, and in the Norfolk Broads as part of the large EU-funded CANAPE project.
Significant challenges remain for the large-scale implementation of paludiculture in the UK. To address some of these challenges we carried out a comprehensive review of current understanding of the practical, social, economic and environmental constraints on the large-scale adoption of paludiculture in the lowland peats of England and Wales, as well as the potential benefits in relation to climate mitigation, soil preservation (including reduction in subsidence rates) and other environmental outcomes.
The task lead was Barry Mulholland (ADAS).
Task 2: Assessing the societal impacts
Since the original drainage of areas such as the East Anglian Fens and Somerset Levels, exposure of peat to oxidation and compaction has led to a continuous process of land subsidence, often by several meters. With large areas of agricultural peatland now close to or below sea-level, and below the level of embanked river systems, these landscapes can now only be maintained by pumped drainage. In many areas, key infrastructure including roads and railways are also elevated above the surrounding landscape. In some cases, these are still ‘floating’ on peat which continues to subside, leading to deformation which (along with the embankment of roads above drainage ditches) increases accident risk, causes damage to vehicles and increases road maintenance costs. In the Netherlands, the costs of peat subsidence are estimated to be €22 billion, yet no equivalent information for the UK exists. Therefore, we reviewed both UK and international literature on this topic, in order to determine the current state of knowledge regarding the extent of impacts, causes and potential solutions, key uncertainties, data sources and priorities for future assessment.
The task was led by Sue Page (Leicester University).
Task 3: GHG field experiment
In this field experiment we aimed to quantify the mitigation potential of permanently or seasonally raised water levels within arable/horticultural cropland farming systems. Our approach involved creating hydrologically sealed units of peat (’lysimeters’) within a conventionally managed horticultural field, within which we manipulated water levels to a range of different target levels. Using cutting-edge automated measurement technology we monitored the effects of these different water levels on the emissions of CO2 and nitrous oxide, another powerful GHG which is often associated with fertilizer application). At the same time, we measured a range of soil properties such as structural strength (which is important for the operation of farm vehicles), crop yield, and any occurrence of crop pests and diseases. This enabled us to quantify both the ‘benefits’ of raising water levels in terms of reduced GHG emissions and subsidence, and any offsetting ‘costs’ in terms of reduced crop yields or increased costs of farming operations. By better understanding these trade-offs, we were able to identify optimal forms of water management that would help to reduce emissions without adverse effects on the farming economy, or on societally important factors such as food security.
Alongside the experimental work we also maintained our network of ‘flux tower’ measurement sites, which are measuring the emissions and removals of greenhouse gases at a diverse range of cropland, grassland and conservation-managed lowland peat sites in several parts of England and Wales. We also undertook an extensive study of greenhouse gas fluxes across a wider range of sites in order to better understand how these emissions vary across gradients of drainage depth, peat depth and crop type. The results of this work were synthesised and up-scaled to a national level, contributing to the Government’s objective to fully incorporate peatlands in the UK’s National Emissions Inventory.
This task was led by Ross Morrison (UKCEH).
Task 4: Evaluating the benefits
If the mitigation measures identified during the project are to be adopted across the UK’s agricultural peatlands, it is imperative that these mitigation measures are practical, economically viable, legally compliant, acceptable to retailers and socially acceptable to consumers.
Given the UK's European Union exit, there is now an opportunity to revise the farm payment schemes operated under the EU Common Agricultural Policy to support these measures, for example by providing economic incentives which help farmers to deliver mitigation savings. At the same time, it is essential that changes in lowland peat management do not simply displace food production to other parts of the world, which would not only be detrimental to the UK’s economy and food security but could also generate little or no overall emissions reductions if crops that were previously grown on UK lowland peat are instead air-freighted in from overseas. In this task we therefore consulted with a broad range of land-owners and land-managers in order to gain a more holistic understanding of the practical, economic and social issues surrounding the management of lowland peatlands.
To do this we:
- Identified the main practical barriers and opportunities associated with the adoption of peat loss/GHG mitigation strategies by famers.
- Identified the main socioeconomic barriers to the adoption of mitigation strategies.
- Evaluated ecosystem service trade-offs associated with the adoption of mitigation strategies.
- Evaluated the social and environmental impact of different farm-scale mitigation options at the regional scale.
- Identified any barriers in the market supply chain that may prevent adoption.
- Identified how long it will take to implement the mitigation measures.
- Produced a roadmap for mitigating the loss of agricultural peatlands.
This task was led by Davey Jones (Bangor University).