Citation: Devereux, E.J.,(2025), “Introduction to Hedgerows: Biodiversity Belts” , EcoFoodDev, https://www.ecofooddev.com/introduction-to-hedgerows-biodiversity-belts/

If you live in Ireland or the UK, you will be more than familiar with the rows of hedgerows reinforcing our country roads, and dividing the landscape into patchworks of differing colours and functions. Further afield, Europe contains well-defined networks of hedgerows in such regions as the central Pyrenees, while hedge-demarcated agricultural landscapes, generally referred to as bocage, occur throughout Western Europe, particularly in France and Galicia (north-west Spain). Beyond Europe, hedgerows are present in Africa, China, Ecuador, Bolivia, and North America, all with varying purposes and characteristic species of flora and fauna (Baudry et al., 2000).

Hedgerows are increasingly recognised as being reservoirs of essential biodiversity and providing numerous, critical ecosystem functions or services. Hedgerow biodiversity is particularly gaining recognition in mainstream agricultural science and research in terms of nature-based approaches to sustainable agriculture. The preservation of hedgerow biodiversity is acknowledged as being beneficial from an environment and climate perspective (for example their importance for carbon sequestration and storage), and also from a future agricultural sustainability and ecosystem service delivery point of view.

Agricultural landscapes rich in biodiversity are essential for several reasons. Farmland biodiversity provides multiple functions, from securing increased crop yield (and hence increased/stable food production) as well as safeguarding farm incomes. Hedgerows are key sources of this biodiversity.  

Hedgerow Biodiversity Loss

Unfortunately, while intensification of agriculture in the EU over the last number of decades has boosted yield, food quality, and food security, it has done so through increased mechanization and increased use of fertilisers and pesticides. This has resulted in a stark reduction of farmland biodiversity. Further to this, ill-fitting agricultural policy instruments, and inappropriate planning laws, have also resulted in the startling loss of hedgerows across the agricultural landscape.

To begin to address these issues, to afford hedgerows their appropriate significance, and to develop the protections and incentives needed to fully realise the benefits and potential of hedgerows, we first need to more fully understand and quantify their character. Quantifying and investigating the simultaneous, multiple services provided by farmland hedgerows (as shelter for livestock, for pest control, boosting soil health, reducing runoff, for carbon capture and storage, as genetic reservoirs for crop research, reducing farmer dependency on chemical inputs etc.) will be essential in the move towards a fully sustainable farming future. Quantification of the assets in our hedgerows will also be vital to ensure that these sustainable farming measures are economically viable for the farmer.  

Irish Hedgerows: Function and Significance

The hedgerows of Ireland are unique habitats with long histories. The landscape is characterized by an intricate network of dense hedges which have evolved over centuries. They boast an enviable array of floral and faunal species and hold a special place in Irish cultural identity. They also offer a window into past land management activities, and prior vegetative biodiversity, providing potential banks of genetic information beneficial for present and future crop production. However, I have detected a gap in the research in the form of hedgerow biodiversity quantification. It is my belief that to protect the biodiversity of our hedgerows, we should build as comprehensive a picture as possible of what we are trying to protect. Hence, this project aims to begin to contribute to building that picture, by conducting hedgerow analysis beginning on my family farm in Ireland.

What are hedgerows?

Hedgerows are linear features vegetation found primarily in rural, agricultural settings. Their structure typically consists of:

• a strip of woody species of scrubby trees, or a line of trees (heights and density vary as each hedgerow is unique and subject to the local environment as well as historical management practices);
• underscrub (shrub/scrub), which usually consists of dense, ungrazed, or lightly grazed Bramble (Rubus sp.) and other species such as Raspberry (Rubus idaeus);
• in Ireland, gorse/furze (Ulex europaeus) tends to dominate upland hedgerows and hedgerows on acidic/peat/heath landscapes;
• a base layer, which can be colonised by tall grasses and weeds such as, for example, Rumex sp., or Bracken (Pteridium sp.), which can grow tall and dense and dominate the vegetation, and other tall ferns (Averis, 2013);
• There is also commonly an associated grassy margin.

How have our hedgerows evolved?

The history of hedgerows is essential to understanding their significance. As mentioned, hedgerows provide a variety of functions, including boundary marking, windbreaks, livestock shelter, and a range of ecological and agricultural functions such as landscape connectivity and carbon sequestration – and have done so throughout history, long before modern, intensive agriculture.

Hedgerows as we might recognise them today originated mainly due to planting, but also by spontaneous natural colonisation of woody species along historical field boundaries and linear feature types (such as earthen banks or stone walls), and occasionally as remnants following woodland clearance for agricultural land (Forman and Baudry, 1984; Rackham, 1997).

Whilst historically the main function of hedges was for agricultural land enclosure, they were also managed as a source of wood, fuel, and food, with many hedges containing abundant fruit species such as apple (Malus sp.), plum (Prunus domestica) and raspberry/blackberry. Such species were essential throughout Irish history as subsistence often depended on foraging, hunting, and fishing. Hedgerows also served as historic townland or parish boundary markers, and as archives of cultural and archaeological history. I will delve into the history, archaeology and evolution of hedgerows, and their cultural heritage significance, in future blog posts.

Hedgerow Ecosystem Services

Ecosystem services are the benefits that nature provides to human beings, by means of resources and subsistence, and cultural landscapes/well-being. They are the direct and indirect contributions that ecosystems provide for human quality of life (Bert et al., 2017; Dainese et al., 2017; Montgomery et al., 2020). Hedgerows are recognised as providing essential ecosystem services, such as:

• Provisioning Services (i.e., food and fuel).
• Regulation Services (i.e., air quality, climate moderation, water quality, soil erosion control, disease management, pest control and pollination).
• Cultural Services (i.e., aesthetic value, educational and recreational).
• and Support Services (i.e., soil formation, photosynthesis, and nutrient cycling).

Hedgerows contribute to the aesthetic appeal and sense of place in the landscape, and importantly offer vital habitat provision, acting as refugia and corridors for biodiversity. The variety of hedgerow types in terms of height, width, shape, and species-mix promotes diversity in flora and fauna. Many of the hedgerows of Ireland contain tree species of a mixed broadleaved variety, reflecting the remnants of woodland that once covered the island (Teagasc, 2017). At the landscape level, hedgerows play significant roles in controlling physical, chemical, and biological fluxes. They serve as windbreaks and control water runoff, erosion, and nutrient cycles. I will delve deeply into these services in future blog posts.

The role of hedgerows in sustainable agriculture and tillage-based systems

Sustainable agriculture ensures present and future generations’ needs are met while safeguarding the environment, economy, and society. Key principles involve responsible resource management, economic viability, and social equity. These practices enhance soil, water, and biodiversity health, bolster economic returns, and ensure fairness. Sustainable agriculture encompasses environmentally, economically, and socially sustainable approaches, aiming for holistic farm productivity and minimal environmental impact (Brodt et al., 2011).

In this context, functional ecology and carbon sequestration in hedgerows synergistically benefit sustainable agriculture by boosting biodiversity, storing carbon, fostering soil health, undertaking biotic regulation, aiding natural pest control, serving as corridors for commuting and foraging of various fauna and avifauna, and offering agricultural and economic multifunctionality (Brodt et al., 2011). These benefits align with sustainable agriculture by reducing the need for synthetic inputs, improving soil fertility, promoting gene flow, and capturing carbon to mitigate climate change (Precigout et al., 2022; Staley at al., 2023).

Sustainable soil

Hedgerows serve as natural barriers that help prevent soil erosion and protect valuable topsoil in tillage-based farming. They do this by acting as physical obstacles against wind and water, hence reducing erosive forces. The extensive root systems of hedgerow plants stabilize the soil and maintain soil structure. Hedgerows also act as sediment traps, capturing soil particles carried by wind or water. Furthermore, they help retain nutrients in the soil, contributing to soil fertility (Holden et al., 2019).

Sustainable water

Hedgerows are significant contributors to water retention and runoff reduction, effectively managing the impact of heavy rainfall and ensuring water availability. They achieve this through multiple means intercepting rainfall to reduce surface runoff, facilitating water infiltration into the soil by enhancing its structure, acting as water storage areas, reducing soil erosion through their physical presence, and promoting overall water availability by maintaining soil health and reducing nutrient loss. Hedgerows offer a comprehensive approach to enhancing water management, mitigating flooding risks, and maintaining the health of agricultural lands (Merot, 1999).

Other sustainable agriculture benefits of hedgerows

As already discussed, hedgerows play a multifaceted and pivotal role in advancing sustainable agriculture, with their benefits spanning diverse areas. Biodiversity enhancement is a fundamental trait, as hedgerows foster a wealth of organisms crucial for natural pest control and pollination. In the face of climate change, hedgerows exhibit promising potential for carbon sequestration, contributing to the reduction of greenhouse gas emissions within agricultural landscapes. Beyond this, hedgerows create microclimates, offering shelter to crops, livestock, and beneficial insects, especially in open tillage systems. Their role in pest management is vital; hedgerows serve as refugia (shelter or sanctuary) for natural predators, reducing reliance on chemical pesticides. Additionally, these ecological corridors act as vital habitats and forage sources for pollinators, benefiting both crop yield and quality. By promoting reduced tillage practices and enhancing soil health, hedgerows enhance agroecosystem resilience.

In the next blog post I will investigate the archaeology of Irish hedgerows, and their development from the Neolithic to the present day.

References

Averis, B., 2013. Plants and Habitats: An introduction to common plants and their habitats in Britain and Ireland.

Baudry, J., Bunce, R.G.H. and Burel, F., 2000. Hedgerows: an international perspective on their origin, function and management. Journal of environmental management, 60(1), pp.7-22.

Bert, R., Steven, B., Victoria, N., Paul, P. and Kris, V., 2017. Ecosystem service delivery of agri-environment measures: A synthesis for hedgerows and grass strips on arable land. Agriculture, Ecosystems & Environment, 244, pp.32-51.

Brodt, S., Six, J., Feenstra, G., Ingels, C. and Campbell, D., 2011. Sustainable Agriculture. Nature Education Knowledge 3 (10): 1.

Dainese, M., Montecchiari, S., Sitzia, T., Sigura, M. and Marini, L., 2017. High cover of hedgerows in the landscape supports multiple ecosystem services in M editerranean cereal fields. Journal of Applied Ecology, 54(2), pp.380-388.

Holden, J., Grayson, R.P., Berdeni, D., Bird, S., Chapman, P.J., Edmondson, J.L., Firbank, L.G., Helgason, T., Hodson, M.E., Hunt, S.F.P. and Jones, D.T., 2019. The role of hedgerows in soil functioning within agricultural landscapes. Agriculture, ecosystems & environment, 273, pp.1-12.

Merot, P., 1999. The influence of hedgerow systems on the hydrology of agricultural catchments in a temperate climate. Agronomie, 19(8), pp.655-669.

Montgomery, I., Caruso, T. and Reid, N., 2020. Hedgerows as ecosystems: service delivery, management, and restoration. Annual Review of Ecology, Evolution, and Systematics, 51, pp.81-102.

Précigout, P.A. and Robert, C., 2022. Effects of hedgerows on the preservation of spontaneous biodiversity and the promotion of biotic regulation services in agriculture: towards a more constructive relationships between agriculture and biodiversity. Botany Letters, 169(2), pp.176-204.

Rackham, O., 1997 (reprint 1986). The History of The Countryside. Pheonix Giant, London.

Staley, J.T., Wolton, R. and Norton, L.R., 2023. Improving and expanding hedgerows—Recommendations for a semi‐natural habitat in agricultural landscapes. Ecological Solutions and Evidence, 4(1), p.e12209.

Teagasc. “Hedgerows.” 2017. www.teagasc.ie. Accessed August 1, 2022. https://www.teagasc.ie/environment/biodiversity–countryside/farmland-habitats/hedgerows/