Introduction

Hedgerows constitute vital semi-natural habitats that provide essential resources and refuge for a wide range of plant and animal species. However, agricultural intensification has led to widespread hedgerow removal and soil degradation, diminishing farmland biodiversity and reducing soil organic carbon (SOC) stocks, resulting in a substantial carbon (C) debt in agricultural soils.

To address the ecological consequences of habitat loss, conservation policies increasingly promote hedgerow planting and rejuvenation. The existing SOC deficit also presents an opportunity for hedgerows to sequester additional carbon by removing atmospheric carbon dioxide (CO₂) and storing it in soil. Consequently, SOC sequestration through hedgerow planting and rejuvenation represents an integral component of climate mitigation strategies and large-scale ecosystem restoration initiatives.

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Policy Context and Expansion Targets

Recent policy reports highlight the crucial role of hedgerows in mitigating climate change and enhancing biodiversity within agricultural landscapes. The UK Committee on Climate Change (CCC) proposed increasing hedgerow length by 40% (~190,000 km across Great Britain) to achieve net zero emissions by 2050. In contrast, Natural England’s Favourable Conservation Status report recommended a 60% expansion to maximise biodiversity benefits.

Land managers can achieve these targets through several ‘hedgerow actions’, including:

• Planting new hedgerows to establish additional habitat;

• Filling gaps with shrubs to form continuous hedgerow networks;

• Rejuvenating existing hedges through hedge-laying or coppicing;

• Allowing hedgerows to grow taller and wider; and

• Encouraging individual trees within hedgerows to mature.

These management practices support both structural integrity and ecological function, reinforcing hedgerows as key components of sustainable agricultural systems.

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Hedgerow Condition and Biodiversity

The 2007 Countryside Survey revealed that over half of England’s hedgerows were in poor structural condition. In contrast, structurally diverse and well-maintained hedgerows are likely to support greater species richness and abundance across multiple taxa. Despite this, substantial knowledge gaps remain regarding how hedgerow structure, woody species composition, age, and landscape context influence the diversity of plants growing at the hedge base, particularly woodland specialists.

Our recent study demonstrated that hedgerow age (time since planting) governs SOC accumulation until it reaches a plateau at approximately 40 years. Using sequestration rates derived from 40-year-old hedgerows, we estimated that a 40% increase in total hedgerow length across England could remove approximately 10.53 Tg CO₂ from the atmosphere over 40 years through combined biomass and soil carbon storage.

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Reducing Uncertainty and Improving Estimates

To reduce the uncertainty associated with national-scale SOC estimates, it is essential to account for the influence of multiple environmental and management variables. Soil type, climate, woody species composition, and hedgerow structural condition all significantly affect carbon sequestration potential. Integrating these factors into predictive models will improve accuracy and help target restoration efforts for maximum ecological and carbon benefits.

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Future Research and Policy Implications

A comprehensive understanding of how hedgerow composition, structure, soil type, climate, and landscape context interact to influence biodiversity and carbon storage is urgently needed. This knowledge will clarify whether different hedgerow management actions produce trade-offs or synergies between biodiversity enhancement and carbon sequestration.

Such insights are critical to:

1. Determine the contribution of hedgerow expansion to achieving the UK’s net-zero and biodiversity objectives; and

2. Inform the ongoing development and implementation of national agri-environment and payment for ecosystem services (PES) schemes.

By strengthening the scientific evidence base, policymakers and land managers can optimise hedgerow management strategies to simultaneously address biodiversity loss and climate change mitigation.

Photos of typical hedgerows in the UK

Aim and Objectives

Project Aim

The primary aim of this project is to assess the potential contribution of hedgerow expansion to mitigating biodiversity loss and climate change. The project will adopt an integrated, multi-method approach that combines:
(i) analysis of existing national datasets on hedgerow extent and associated plant communities;
(ii) collection of new field data; and
(iii) upscaling of findings through advanced data analysis and modelling.

Specific Objectives

1. Assess temporal changes in hedgerow plant communities
   Evaluate how hedgerows across different farming systems (e.g., arable versus grassland) and regions differ in their temporal changes in plant communities between 2007 and 2023. Determine whether these differences are driven by woody species composition, structural condition, and hedgerow age, while accounting for other landscape factors such as the extent of surrounding semi-natural habitat.

2. Quantify carbon stocks and sequestration drivers
   Investigate how hedgerow carbon stocks and sequestration rates (in both biomass and soil) vary with structural condition and woody species composition relative to soil type.

3. Monitor early-stage ecological and soil organic carbon dynamics in new hedgerows
   Determine how plant community composition and soil properties change during the first ten years after hedgerow establishment, and assess how these dynamics differ across farming systems.

4. Estimate current national hedgerow natural capital
   Quantify the present-day plant diversity and carbon stocks of the existing hedgerow network across England, thereby establishing a baseline measure of hedgerow natural capital.

5. Model future expansion scenarios and trade-offs
   Simulate a range of hedgerow expansion scenarios to evaluate their potential impacts on biodiversity enhancement and climate change mitigation. Identify potential trade-offs and synergies between these outcomes to inform future policy and management decisions.

Training

The successful candidate will develop a comprehensive set of research skills, including experimental design, field sampling, statistical analysis and modelling, data interpretation, academic writing, and oral presentation. The project will provide training in field health and safety procedures and in the use of field equipment.

In addition, the student will deepen their understanding of:
(i) plant identification;
(ii) the processes governing carbon cycling and storage in hedgerow biomass and soils; and
(iii) hedgerow management practices.

The student will receive ongoing support through a comprehensive Postgraduate Research (PGR) skills training programme provided by the NERC Doctoral Training Network (DTN) and the University of Leeds. These include courses in statistical analysis, academic and grant writing, and research impact development.

Supervision will involve regular meetings with all supervisors to provide academic guidance and project support. The student will also participate in various research groups within the School of Geography and across the University of Leeds, including the Priestley International Centre for Climate, an interdisciplinary research hub delivering evidence-based climate solutions, and the Global Food and Environment Institute, which advances sustainable food and environmental systems.

Student Profile

The ideal candidate will demonstrate a strong interest in environmental issues and hold a solid academic background in one or more of the following disciplines: physical geography, environmental science, ecology, biology, soil science, or a closely related field.

Experience in fieldwork, plant identification, and statistical modelling is desirable but not essential, as the PhD programme will provide full training in these areas. The project will particularly suit a student who is motivated, methodical, and eager to apply interdisciplinary approaches to address pressing challenges in biodiversity conservation and climate change mitigation.

References

Biffi S, Chapman PJ, Grayson RP, Ziv G. 2022. Soil carbon sequestration potential of planting hedgerows in agricultural landscapes. Journal of Environmental Management, 307

Biffi S, Chapman PJ, Grayson RP, Ziv G. 2023. Planting hedgerows: Biomass carbon sequestration and contribution towards net-zero targets. Science of the Total Environment, 892

Carey, P.D., Wallis, S., Chamberlain, P.M., Cooper, A., Emmett, B.A., Maskell, L.C., McCann, T., Murphy, J., Norton, L.R., Reynolds, B., Scott, W.A., Simpson, I.C., Smart, S.M. & Ullyett, J.M. (2008) Countryside Survey: UK Results from 2007. NERC/Centre for Ecology & Hydrology, Lancaster, UK. https://countrysidesurvey.org.uk/content/uk-results-2007

Staley, J. T., R. Wolton, and LR. Norton. 2023. Improving and expanding hedgerows—Recommendations for a semi-natural habitat in agricultural landscapes. Ecological Solutions and Evidence 4:e12209. https://doi.org/10.1002/2688-8319.12209