Briefing Sheet: Hedgerows

The environmental value of hedgerows is now well recognised, but media reports often allude to their loss across the countryside, with the impression that this is both ongoing and also the cause of wildlife declines. This briefing sheet explores the importance of hedgerows to the landscape and its wildlife, earlier losses, and current trends in the UK, along with the impact of hedgerow management.

Background

Hedgerows play an important role within the UK countryside. Traditionally they were used to mark boundaries and keep livestock contained. More recently, it is recognised that hedges have the added benefits of regulating different environmental aspects including water, pollution, and erosion. Hedges, along with the banks they are sometimes found on, can reduce flooding by regulating the flow of water1. Due to their deep roots, hedgerows can remove water quicker than crops, easing issues that may occur with excess water1, with the added benefit of controlling erosion by acting as a barrier from water run-off, especially in hilly areas1,2. They can protect fields from wind, reducing both water loss from the field and soil erosion1,3.. They act as a barrier to reduce the number of fertilisers and pesticides that enter nearby areas of water and contribute to carbon storage1.

Hedgerows are important for farmland wildlife. They provide a variety of resources for species that benefit crops, including shelter for predators of crop pests and food for bees and other insects that pollinate crops3. They are especially vital for wintering birds1. This importance resulted in the UK Biodiversity Action Plan (BAP) identifying ancient and species-rich hedgerows as a priority habitat which led to legislation to restrict their removal. In 1997, the Hedgerows Regulations were created under the Environment Act 19951.

Hedge and hedgerow are two different terms. Hedges are the woody elements of a field boundary. A hedgerow also includes the vegetation, along with the ditch and bank. The term “hedge” can also be used to describe linear strips of woody vegetation such as shrubs and lines of trees4. There are five key elements of hedgerows, these are trees, shrubs, hedge base, field margin and ditches.

After the Second World War, farmers were encouraged by government policy to remove hedgerows to make farming more efficient and increase food production. There were financial incentives to increase field size by removing hedges to allow for larger machinery5,6. However, some farmers found the hedge provided a useful boundary for soil type changes and that, once removed, the different soil types now in the same field presented a challenge when sowing crops. Now, there are policies to encourage hedgerow growth, restoration and management5, and the 1990s saw numbers stabilise and even start to increase7. Since 1993, the environment stewardship scheme has included hedge planting options, where public money was invested to replace and plant new hedgerows.

Hedgerow stats

According to The Countryside Survey 2007, there is an estimated 477,000km of managed hedgerows in Great Britain. This was a decrease from the previous estimate in 1998 of 508,000km. However, a large proportion of these were previously managed hedges that have deteriorated to become lines of trees and relict hedges, as shown in figure 17. The total number of woody linear features have remained relatively stable8 (figure 2), demonstrating that this apparent loss is actually more of a reduction in management intensity8.

Figure 1: The changes in the length of “managed” hedges and lines of tree and relict hedges between 1984 and 2007 in Great Britain, taken from the 2007 Countryside Survey UK Headline Messages9.

In his 2016 book, John Wright estimated there were 700,000km of hedgerows in 20077. Thisfigure refers to “Total Woody Linear Features”8, which includes managed hedgerows but also other classes of hedge such as relict hedges, both those that are either part of a boundary (114,000km[JB1] [EH2] ) or no longer part of a boundary (114,000km)7.

Within the Countryside Survey, hedges are classed as a “a line of woody vegetation that has been subject to management so that the trees no longer take their natural shape8.” However, Wright says that although relict hedges do not take the obvious form of a hedge, and are not as useful for agriculture, they still hold biological interest and should be included7.

Figure 2: The changes in different features of hedgerows, including the total Woody Linear features, in Great Britain between 1984 and 20078.

The loss of managed hedges appears to have slowed by the late-1990s, likely due to the law introduced in 1997[JB3] [EH4] . The Countryside Survey collected data on hedgerows in 1978, 1984, 1990 and 19936. These surveys estimated that the length of managed hedgerows had reduced 23% between 1984 and 19906. This was due to changes in management leading to hedgerows that tend to be more overgrown, with an increased number of different species. In 1990, there was also a decrease in how connected the hedges were compared to previous years, which is an important factor for species movement6.

As with many things, although total hedgerow length may be stable or even increasing, quality is at least as important, or perhaps more so, than quantity. For hedgerows, quality is determined by the types of trees and shrubs within the hedge that create the habitats.

In August 2020, the People’s Trust for Endangered Species (PTES) launched a new national survey, the Great British Hedgerow Survey, which was featured in BBC Countryfile. The survey is aimed at landowners, wildlife groups and anyone who is interested to perform health checks on hedgerows and get advice on what type of management is required to help them thrive. These results will help gather data on the national status of British hedges.

Hedgerow Management

Management has the most impact on the number and variety of tree and shrub species in the hedgerows. Originally it was thought shorter hedges, around 2m tall, would prevent ground plants suffering from too much shade10. However, this has been contradicted by studies showing taller and wider hedges provide greater structural diversity, containing more floral species that can be beneficial to butterflies10. Denser, well-connected hedges are more favourable for small mammals, such as dormice, and their predators. Variety is also required to support a range of different mammals and birds as each will have a preference, for example bats prefer trees due to hibernation space10. Maintaining the ground flora at the hedge-bottom will help smaller mammals by providing extra food and cover from predators.

The Farming and Wildlife Advisory Group (FWAG) recommend cutting hedgerows every other year as this is beneficial for both wildlife and the farmer, cutting down on time spent and cost10–12. Spreading cutting across two years has been shown to help insects, birds and mammals while increasing flowering for bees10–12. Avoiding certain key times of year for wildlife is important. Bird nesting occurs in the spring to early summer, fruit begins to form in the autumn and small birds and mammals consume those in the winter. Both September and February cuts were shown to reduce the number of berries on woody shrubs. However, berries on non-woody species, like blackberries, reacted more positively to cutting in February13. Although autumn cutting may remove fruit, cutting in late winter could increase berry production in the summer13. Overall, evidence indicates that autumn cutting is more favourable than cutting in late winter. Furthermore, rotational cutting and allowing areas of hedges to be left uncut before hedge laying will help maximise conservation13.  It is important to note, it is now illegal to cut hedges between the 1st March to 31st August so that birds can nest, and fruit can be produced14. Cutting can resume on the 1st September14.

New hedgerows should be well planned so more than one species is used, creating that much needed diversity. They should also be connected to other areas of semi-natural habitat, for example using similar plants or trees to others in the area in order to help new colonies of species develop within the hedgerows10. It is important to maintain a balance between what is good for birds and what is good for insects.

Hedgerow protection:

Hedgerows have been protected since 1st June 1997 by the Hedgerows Regulations 1997, made under Section 97 of the Environment Act 1995. A countryside hedgerow is protected if it meets a certain criterion based on length, location, and importance. If a hedgerow is more than 20m long with gaps of 20m or less within its length or if it is under 20m but joins another hedge, it is protected14. Hedgerows are protected if they are on or next to14:

  • Land used for agriculture or forestry
  • Land used for breeding or keeping horses, ponies, or donkeys
  • Common land
  • Village greens
  • Sites of special specific interest
  • Protected European sites for conservation or a protected area
  • Local or national nature reserve
  • Land belonging to the state

Hedgerows that mark the boundaries of private gardens are not protected.

A hedgerow is considered important if it is at least 30 years old and meets one of the specific conditions listed on the government website.

To remove a hedgerow, it must be less than 30 years old and you need to be the owner. All hedgerow removal needs to be discussed with local planning authorities to make sure it is legal, who will either give permission for removal or state it must remain14.

Land Use

How the surrounding land is used has an impact on the diversity of the hedgerow, especially the hedge-bottom. Using herbicides at the bottom of the hedge will affect the plants but also the insects living there. Herbicides, fertilisers, and insecticides used on crops can drift into the hedgerow, killing off some plants and could lead to lower numbers of insects1,15. Instead, buffer strips can be introduced to help wildlife, as part of field margin management. These can include sowing wildflower seeds or leaving wider grassy strips between the hedgerow and crop15. A gradual transition from hedge to a farmed field will help with insect diversity. Creating a strip of undisturbed herbaceous plants next to the hedge can be an added benefit to bees. Other features such as banks, walls and ditches near hedgerows can help insects and small mammals. In areas with grazing livestock, fences including electric ones, are used to protect the hedge base from grazing, but also to allow for their restoration10. In 2006, it became an offence under the Common Agricultural Policy’s cross-compliance requirements to cultivate, spray or fertilise within 2m of the centre of a hedge.

Hedgerow Wildlife

Hedgerows provide important habitats and resources for a range of mammals, birds, amphibians and reptiles, insects, and plants. They can also provide a dispersal network for various mammals, reptiles etc, so they can move between different areas safely. Hedgehogs are in decline, especially rural hedgehogs, and hedgerows provide a suitable habitat, improving foraging opportunities and protection from predators16. They also use them to travel across the landscape, connecting hedgehog populations17. Hedgehogs are sensitive to habitat fragmentation and reinstating or repairing hedges can enhance connectivity, helping to improve population numbers16,17. The activity of multiple bat species has been positively linked to hedgerows and linear features, which use them for orientation, foraging and shelter16,18. Width was less important, with bats preferring density, length, and proximity to woodland16. The hazel dormouse is found in hedgerows all year round, rarely leaving the safety the habitat offers. They require dense and overgrown areas which provide good shelter and sufficient food7. Other mammals that have been commonly found in hedgerows include wood mouse, yellow-necked mouse, bank vole, common shrew7,16. Harvest mouse, field vole, pygmy shew and water shrew have been seen on occasion7,16.

The make-up, structure and condition of the hedgerow has a strong effect on the value it has for wildlife. For example, hedges with a dense shrub layer support shade-loving perennials that are favoured by bees and layers of vegetation that are linked to high diversity of invertebrates19. Wider hedgerows have been shown to support more small mammals. Those that have fewer gaps, and a shrub layer are beneficial to dormice, providing good nesting habitats. Gaps in hedges have been linked to lower numbers of bank voles and yellow-necked mice19 as hedgerows are important for their dispersal to nearby woodland17. Hedgerows are important for many different bird species, especially songbirds. If hedges are more open, this can leave bird nests vulnerable to predation. The size of the hedge is also important19. Higher hedges are preferred by robin, song-thrush, willow warbler, long-tailed tit, great tit and chaffinch7,20. However, yellowhammer and linnet tend to prefer shorter hedges7,20. Wider hedges have been associated with wren, robin, blackbird, lesser whitethroat, yellowhammer, and blue tits. Most of these birds prefer woody features in hedges, with numbers increasing when there are up to eight species of woody plants7,20. Diversity within the hedgerow is important, with large basal areas, many tree species, some dead timber, scrub habitats and overgrown areas increasing the number and diversity of birds21. Allowing hedges to grow to different heights will encourage a range of different birds, with a minimum height of 1.2-1.4 meters recommended by the RSPB7.

Summary

Hedgerows are important, not just agriculturally for boundaries, crop management, water control and defence. They also have ecological importance, they support wildlife and insects, and can help with climate change and mitigate pollution. The key to a successful hedgerow is management and the plants found within. Hedgerows themselves may not be declining but managed ones are, replaced by remains that may be less useful agriculturally, yet still have biological significance. Hedgerows are a priority habitat and should be protected but they must be kept in good condition, repaired, and maintained.

Addendum: 21 December 2020

An error was made when this article was initially published regarding dates for cutting hedges. This has now been corrected within the article, the correct text is as follows:

It is important to note, it is now illegal to cut hedges between the 1st March to 31st August so that birds can nest, and fruit can be produced. Cutting can resume on the 1st September.

References

1. (2019). The Ecology of Hedgerows and Field Margins. (ed. Dover, J.W.) Routledge. Abington.

2. Thomas, Z., Molenat, J., Caubel, V., Grimaldi, C. & Merot, P. (2008). Simulating soil-water movement under a hedgerow surrounding a bottomland reveals the importance of transpiration in water balance. Hydrological Processes, 22:577585.

3. Holland, J. (2019). Contribution of hedgerows to biological control. In: Ecology of Hedgerows and Field Margins: 123146. (ed. Dover, J.W.) Routledge.

4. Maskell, L.C., Norton, L.R., Smart, S.M., Carey, P.D., Murphy, J., Chamberlain, P.M., Wood, C.M., Bunce, R.G.H. & Barr, C.J. (2008). CS Technical Report No 1/07. Field Mapping Handbook, 1143.

5. Fry, G.L.. (1991). Conservation in agricultural ecosystems. In: The Scientific Management of Temperate Communities for Conservation: 415443. (eds. Spellerberg, I.., Goldsmith, F.B. & Morris, M.G.) Blackwell Science. Oxford.

6. Barr, C.J. & Gillespie, M.K. (2000). Estimating hedgerow length and pattern characteristics in Great Britain using Countryside Survey data. Journal of Environmental Management, 60:2332.

7. Wright, J. (2017). A Natural History of the Hedgerow and ditches, dykes and dry stone walls. Profile Books LTD. London.

8. Centre for Ecology & Hydrology, England, N. & Peacock, G. (2007). 5. Boundary and Linear Features Broad Habitat. Countryside Survey: UK Results from 2007, 7083.

9. Carey, P.D., Wallis, S.M., Emmett, B., Maskell, L.C., Murphy, J., Norton, L.R., Simpson, I.C. & Smart, S.M. (2008). Countryside Survey: UK Headline Messages from 2007.

10. Department for Environment Food and Rural Affairs. (2004). Hedgerow management and wildlife review: further update, edit and publication. Final report BD2108.

11. Woodland Trust. Wood Wise Hedgerows and Hedgerow Trees. 9.

12. RSPB. Farmers and hedgerow management. Available at: https://www.rspb.org.uk/our-work/conservation/conservation-and-sustainability/advice/conservation-land-management-advice/farm-hedges/farmers-and-hedgerow-management/.

13. Maudsley, M.J., West, T.M., Rowcliffe, H.R. & Marshall, E.J.P. (2000). The impacts of hedge management on wildlife: preliminary results for plants and insects. Aspects of Applied Biology, 389396.

14. CXCS. (2020). Hedge Cutting Dates. Available at: https://www.cxcs.co.uk/hedge-cutting-dates/. (Accessed: 21st December 2020)

15. Natural England & Department for Environment Food and Rural Affairs. (2019). Countryside hedgerows: protection and management. GOV.UK: Available at: https://www.gov.uk/guidance/countryside-hedgerows-regulation-and-management. (Accessed: 8th September 2020)

16. Holland, J. & Ellis, S. (2008). Beneficials on farmland : identification and management guidelines. 24.

17. Feber, R.E., Johnson, P.J., Gelling, M. & Macdonald, D.W. (2019). Ecology and Conservation of Mammals. In: The Ecology of hedgerows and Field Margins: 233249. (ed. Dover, J.) Routledge. Abington.

18. Moorhouse, T.P., Palmer, S.C.F., Travis, J.M.J. & Macdonald, D.W. (2014). Hugging the hedges: Might agri-environment manipulations affect landscape permeability for hedgehogs? Biological Conservation, 176:109116.

19. Verboom, B. & Huitema, H. (1997). The importance of linear landscape elements for the pipistrelle Pipistrellus pipistrellus and the serotine bat Eptesicus serotinus. Landscape Ecology, 12:117125.

20. Staley, J.T., Amy, S.R., Adams, N.P., Chapman, R.E., Peyton, J.M. & Pywell, R.F. (2015). Re-structuring hedges: Rejuvenation management can improve the long term quality of hedgerow habitats for wildlife in the UK. Biological Conservation, 186:187196.

21. Green, R.E., Osborne, P.E. & Sears, E.J. (1994). The Distribution of Passerine Birds in Hedgerows During the Breeding Season in Relation to Characteristics of the Hedgerow and Adjacent Farmland. Journal of Applied Ecology, 31:677692.

22. Osborne, P. (1984). Bird Numbers and Habitat Characteristics in Farmland Hedgerows. Journal of Applied Ecology, 21:6382.

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