Water-table management in lowland agricultural peatlands for climate change mitigation

This project provides an exciting and timely opportunity to investigate the practicalities and sustainability of water management in UK agricultural lowland peatlands for climate change mitigation

Introduction: Peatlands are carbon-rich wetlands that occupy just three per cent of the world’s land surface area (12% in the UK) but store a similar amount of carbon to all terrestrial vegetation, as well as supporting unique biodiversity. In their natural state, they can help mitigate climate change by removing carbon dioxide (CO2) from the atmosphere via photosynthesis, and waterlogged conditions mean that when the plants die they do not fully decompose and part of the photosynthesised carbon can be stored for thousands of years. However, many peatlands have been substantially modified by human activity, including drainage for agriculture (Fig 1) and forestry plantations. This drainage results in the release of the equivalent of around 1.5 billion tonnes of CO2 into the atmosphere each year. This equates to three per cent of all global greenhouse gas (GHG) emissions caused by human activities. As a result, crops grown on peat have among the highest production intensities (GHG emissions per crop calorie) in the world. In the UK, agricultural peatlands are the largest land use source of carbon emissions. Nevertheless, peatland drainage and cultivation have contributed greatly to economic development in many areas, including rural communities in parts of the UK. Despite the urgent need to reduce GHG emissions, it is unlikely that these areas could be restored to natural wetlands in time to meet international commitments to achieve net zero GHG emissions by 2050 under the Paris Agreement.

Figure 1. Lowland peat drained for agriculture in (a) the Fens for horticulture and (b) in the Somerset levels for intensive grassland.

A recent study by Evans et al. (2021) showed that every 10 centimetres of reduction in water-table depth could reduce the net warming impact of CO2 and methane (CH4) emissions (100-year global warming potentials) by the equivalent of at least 3 tonnes of CO2 per hectare per year, until water-table depth is less than 30 centimetres. They also analysed the impact of halving current drainage depths in croplands and grasslands on peat, which cover over 250,000 km2 globally, and showed that this could bring significant benefits for climate change mitigation. The study estimates this change in water tables could cut emissions by around 500 million tonnes of CO2 a year, which equates to 1 per cent of all global GHG emissions caused by human activities. However, the means by which water-table depth can be effectively managed at field and/or farm scales and between summer and winter in agricultural peatlands has yet to be determined, and represents a key barrier to mitigating agricultural peatland emissions. The major aim of this project is, therefore, to investigate the practicalities and sustainability of water management in UK agricultural lowland peatlands that will lead to a reduction in GHG emissions but also enable agriculture to continue.

Objectives: In this project, you will work with scientists at the University of Leeds and UK Centre of Ecology and Hydrology to answer some unresolved questions around the practicalities and sustainability of a range of water management techniques in lowland agricultural peatlands. Fieldwork will take place at an instrumented site near Doncaster, which is part of a £5m Greenhouse Gases Removal Demonstrator (GGR-D) project funded by UK Research and Innovation (UKRI).

In particular, according to your particular research interests, the studentship could address the following objectives via a combination of fieldwork and modelling:

  • Investigate methods for managing water levels and transfers within and between fields/farms effectively and their impacts on peatland hydrological function
  • Compare impacts on peatland function of approaches that allow for the storage and release of water from winter to summer
  • Quantify water budgets for wetland crops vs conventional crops
  • Investigate the flood and drought risk associated with different water management options

Potential for high impact outcome: The project will enable significant, timely advancements to be made around the practicalities and sustainability of water management in lowland agricultural peatlands for ecosystem services such as food production, flood control and climate change mitigation. Defra has recently published an England Peat Action Plan: https://www.gov.uk/government/publications/england-peat-action-plan, which outlines an integrated plan for the management, protection and restoration of upland and lowland peatlands, so that they deliver benefits for nature and the climate. The Defra Lowland Agricultural Peat Task Force, and the new England Peat Map (both of which are being advised by members of the supervisory team) are both actively addressing issues related to the characterisation, monitoring and management of lowland peat soils, offering a direct pathway from research to policy impact. A key aim of Defra policy is to extend the useable life of our agricultural lowland peat soils, both to preserve the carbon stored in them and to ensure that profitable agriculture can continue for decades to come. For this to occur, considerably more research is needed on the practicalities of farm, field and landscape-scale water management, in order to support land managers to make the best decisions for their farm business and for the environment. Where effective peatland management can contribute to a reduction in GHG emissions, it is likely to be included in the new Environmental Land Management schemes, currently being developed by Defra and thus the outcomes of this project have the potential to feed into these. The project will produce several outputs, including 3–4 academic publications, and policy briefings.

Training: You will join the River Basin Process and Management Research cluster in the School of Geography, a vibrant group of researchers studying the interactions between water, soil, and vegetation in river basins. You will also become a member of Water@Leeeds providing opportunities for interdisciplinary collaborations with researchers across Leeds. The successful candidate will develop a range of research skills, including experimental design, field sampling, hydrological modelling, statistical analysis and data interpretation, academic writing skills and giving presentations. Training will be provided in field health and safety procedures and the use of field equipment. In addition, the candidate will develop their understanding of (i) peat hydrology, (ii) processes related to the cycling and storage of carbon in peat, and (iii) farm management.

The student will be supported throughout the studentship by a comprehensive PGR skills training programme that focuses on knowledge and intellectual abilities; personal effectiveness; research governance and organisation; and engagement, influence and impact. Training needs will be assessed at the beginning of the project and at key stages throughout the project and the student will be encouraged to participate in the numerous training and development courses that are run within the NERC DTP and the University of Leeds to support PGR students, including statistics training, academic writing skills, grant writing, etc. Supervision will involve regular meetings with all of the supervisors. Through their links to the UKRI Peat GGR Demonstrator project the student will also benefit from involvement with a large team of researchers with expertise ranging from field-based peatland research to economics and social science, providing the opportunity to gain skills across a range of disciplines.

Student profile: The student should have a keen interest in environmental issues with a strong background in one or more of physical geography, earth sciences, soil science, environmental sciences or related discipline.  Strong analytical/statistical/fieldwork skills are desirable but not essential, as full training will be provided during the PhD.

Reference: Evans, C.D., Peacock, M., Baird, A.J., Artz, R., Brown, E., Burden, A., Callaghan, N., Chapman, P.J., Cooper, H. M., Coyle, M., Cumming, A., Dixon, S., Helfter, C., Heppell, C., Holden, J., Gauci, V., Grayson, R.P., Jones, D., Kaduk, J., Levy, P., Matthews, R., McNamara, N., Misselbrook, T., Oakley, S., Page, S., Rayment, M., Ridley, L.M., Stanley, K., Williamson, J., Worrall, F., Morrison, R. (2021) Overriding importance of water table in the greenhouse gas balance of managed peatlands, Nature https://doi.org/10.1038/s41586-021-03523-1