Elsevier

Biological Conservation

Volume 186, June 2015, Pages 187-196
Biological Conservation

Re-structuring hedges: Rejuvenation management can improve the long term quality of hedgerow habitats for wildlife in the UK

https://doi.org/10.1016/j.biocon.2015.03.002Get rights and content

Highlights

  • Hedgerows benefit wildlife if in good condition with a dense structure.

  • Traditional hedge-laying rejuvenation is quite expensive and not commonly used.

  • A multi-site field experiment tested five rejuvenation methods over three years.

  • Cheaper, modern alternatives improved hedge structure and berry provision.

  • Conservation hedging could double the length of hedgerow that is rejuvenated.

Abstract

Hedgerows provide key wildlife habitat in intensive agricultural landscapes, but are declining in length and structural condition due to a lack of rejuvenation management, neglect and over-frequent trimming with mechanised flails. Here, we test cheaper, alternative methods to traditional hedge laying methods using a multi-site manipulative field experiment. In the first quantitative test of new approaches to hedge rejuvenation management, hedge regrowth, structure, berry provision for over-wintering wildlife and cost of rejuvenation were assessed in response to five methods, for three years following rejuvenation. Three ‘laying’ methods and coppicing were effective at improving hedgerow condition by stimulating basal regrowth, thus increasing the density of woody material at the base and reducing gap size. The pros and cons of coppicing are discussed in relation to its impact on different wildlife groups, and it is recommended in limited circumstances. Differences between the three ‘laying’ methods reduced over time, so a cheaper conservation hedging method is recommended as an alternative to traditional hedge laying. This new approach to hedge management offers the potential to restore twice the length of hedgerow currently rejuvenated under agri-environment schemes.

Introduction

Hedgerows play a significant conservation role within otherwise intensively managed landscapes through the provision of habitat, food and refuges for a wide range of plant and animal species (Wilson, 1979, Fuller et al., 1995, Dover and Sparks, 2000, Merckx and Berwaerts, 2010). In addition, hedgerows support ecosystem services such as pollination (Morandin and Kremen, 2013) and pest control (Morandin et al., 2014), and may act as a dispersal network in future adaptation to climate change (Lawton et al., 2010). Hedges are protected by legislation in some European countries (Baudry et al., 2000) and designated a priority habitat for conservation under the EU Biodiversity Strategy (JNCC, 2012). In several European countries, including England, agri-environment schemes (AES) provide incentives for sensitive management of hedgerows (Fuentes-Montemayor et al., 2011, Natural England, 2013a, Natural England, 2013b), while in the UK the 1997 Hedgerow Regulation limits the removal of hedges. Despite these measures 6.2% of hedgerow length was lost in the UK over the decade to 2007, mainly due to under-managed hedges turning into “relict hedgerows” or lines of trees (Carey et al., 2008). In addition, in 2007 only 48% of UK hedges were considered as being in ‘good condition’, which includes having few vertical gaps, a minimum height of 1 m and width of 1.5 m (Carey et al., 2008). The stock of hedges in north-west Europe is also deteriorating in quality as a habitat for wildlife due to the modern practice of managing hedges with mechanical flail cutters once every 1–3 years as the main form of management (Brooks, 1975, Reif et al., 2001). This has been driven by the high cost of traditional hedge management such as hedge laying, a shortage of labour on farms and the loss of traditional management skills.

The structural condition of a hedgerow has a strong effect on its value as a habitat for wildlife, with several groups showing a positive association with a dense woody hedge structure, consisting of many vegetation layers and few gaps. For example, hedges with a dense shrub layer are more likely to support shade-loving perennial plant species used by bees (Hannon and Sisk, 2009); those with many layers of vegetation are associated with a high diversity of invertebrates (Maudsley, 2000); the number of gaps in a hedge is negatively associated with abundance of bank voles (Clethrionomys glareolus Schreber; Gelling et al., 2007) and yellow-necked mice (Apodemus flavicollis; Kotzageorgis and Mason, 1997); and the vulnerability of bird nests to predation increases in structurally simple, more open hedges (Fuller et al., 1995). The size of a hedge can also affect its conservation value, as width has been shown to be the main determinant of the diversity and abundance of hedgerow understory plant communities (Roy and de Blois, 2008), the occurrence of ten farmland bird species is positively associated with the width of hedgerows (Hinsley and Bellamy, 2000, Whittingham et al., 2009) and the species richness of Carabid and Staphylinid beetles is greatest on hedges with a tall, wide continuous canopy (Griffiths et al., 2007).

Rejuvenation management, whereby new growth is stimulated at the base of a hedgerow, is necessary periodically to prevent hedgerows from losing their dense woody structure and becoming sparse and gappy (Croxton et al., 2004). Laying is a traditional form of hedge management found in several European countries (France, Germany, Ireland, Belgium and The Netherlands; Tenbergen, 2001; McAdam, 1994; Müller, 2013), and was particularly prevalent in the UK prior to the mechanisation of farm management (Croxton et al., 2004). Hedge laying involves manual cutting and removal of woody material from the hedge in an approximately 40 year cycle. Over the centuries, different parts of the UK, Germany and The Netherlands have developed their own distinctive styles of hedge laying, all based on the same basic theory (Müller, 2013). Within the UK, the most widespread is known as ‘Bullock’ or ‘Midland’ style hedge laying which developed in the traditional beef-rearing counties of lowland England to create robust, livestock-proof barriers (Brooks, 1975). Stems are partially severed at their base and layed over horizontally between stakes to encourage new vertical growth near the base of the hedge while up to a third of the volume of the hedge is removed (Brooks, 1975). The original aim was to create a livestock-proof barrier, rejuvenate the hedge by encouraging new growth from the base and help to improve the overall structure and strength. Importantly, hedge laying reduced the vigour of the hedge and enabled it to be managed in intervening years by hand cutting (Brooks, 1975). In recent years, hedge laying has been encouraged to maintain traditional country skills and to create aesthetically pleasing screens to fields and gardens. It is also recognised that hedge laying creates structural heterogeneity and improves the shelter provided for wildlife, particularly nesting birds and invertebrate species (McAdam et al., 1996).

Another rejuvenation method traditionally used across Europe is coppicing (Reif et al., 2001, Deckers et al., 2004), whereby the stems are cut through close to ground level and most of the above-ground part of the hedge removed to encourage growth at the base of the hedgerow. In the mid 20th century approximately half of hedgerows were layed or coppiced in the UK (Croxton et al., 2004), while by 2007 just 2% of hedges surveyed as part of the UK Countryside Survey had been layed or coppiced in the previous 3–5 years (data accessed at http://www.countrysidesurvey.org.uk/), which over a 40 year rotation equates to 16–27% of hedges being rejuvenated. Similar reductions in traditional hedgerow rejuvenation methods have occurred elsewhere in Europe (Reif et al., 2001).

The type of rejuvenation management applied to a hedge can affect the rate of subsequent regrowth (Croxton et al., 2004), hedgerow structure and thus its habitat value for wildlife (Hinsley and Bellamy, 2000). The provision of berries for over-wintering birds and small mammals is the main motivation for some of the hedgerow management options in English AES (Sparks and Croxton, 2007) and can be affected by hedgerow rejuvenation. Hedge laying resulted in hedges containing a greater diversity of invertebrate orders compared with unmanaged controls two years after rejuvenation, while hedges that had been coppiced and replanted with hawthorn did not differ from controls (McAdam et al., 1994). The method of rejuvenation used can also have a long-term effect on hedgerow plant communities; the species richness of understorey plant species that indicate high conservation value of a hedge was reduced over 70 years in coppiced hedges, while those that were layed had a slight increase in species richness (Staley et al., 2013).

Hedgerow rejuvenation is incentivised within English AES to a limited extent. English AES have a two-tier structure. Land owners with a Higher Level Stewardship agreement (HLS) may receive capital grants for hedge-laying or coppicing and replanting, but entry into HLS is restricted to target farmland of high conservation value (Natural England, 2013b). The Entry Level Stewardship (ELS) AES is open to all English landowners and can include grants for hedgerow rejuvenation, but these are limited to a maximum of 200 m of hedgerow over 5 years per ELS agreement (Natural England, 2013a). Between 2005 and 2014, 1268 km of hedgerow were layed or coppiced under English AES (Emily Ledder, pers. comm.), just 0.32% of the total hedgerow length estimated in 2007 at 402,000 kms in England (Carey et al., 2008). This is equivalent to 1.6% of English hedges being rejuvenated under AES over a 40 year rotation.

Due to the widespread, ongoing deterioration in the structure and condition of hedgerows, there is an urgent need to develop cost-effective methods of rejuvenation as an alternative to traditional hedge laying, which result in comparable rates of woody regrowth and dense basal structure. Here, we test the effects of three modern alternative methods of rejuvenation on structure and provision of berries for wildlife and compare them to traditional hedge-laying, coppicing and an unmanaged control, using a large-scale manipulative field experiment. The methods tested included two newly developed, faster alternatives to hedge laying (conservation hedging and wildlife hedging), reshaping with a circular saw (further details below), and coppicing to ground level. We hypothesised that: (1) modern alternatives to traditional hedge laying are cheaper to apply to typical hedgerows in intensively managed landscapes; (2) these alternative methods would have a similar beneficial effect on hedge regrowth and structure; and (3) provision of berries by hedgerows for over-wintering wildlife would initially be most reduced by coppicing compared with other forms of rejuvenation, but that any reduction would be relatively short-term. While our results are directly relevant for AES in England, the widespread prevalence of hedgerow coppicing as a management option across Europe, the traditional use of hedge laying in several European countries and the increasing number of countries implementing AES or other forms of hedgerow management regulation (Baudry et al., 2000, Fuentes-Montemayor et al., 2011) mean that our conclusions also have broader geographical significance.

Section snippets

Field sites and experimental design

Five field sites were used across southern UK. Four of these contained mature hedgerows dominated by hawthorn (Crataegus monogyna Jacq.): Monks Wood, Cambridgeshire (52°24′N 0°14′W), Newbottle Estate, Northamptonshire (52°01′N 1°12′W); Utcoate Grange, Buckinghamshire (51°58′N 0°37′W); Wimpole Hall, Cambridgeshire (52°08′N 0°01′W) The fifth site contained younger mixed species hedges at Crowmarsh Battle, Oxfordshire (51°36′N 1°05W), where hawthorn (C. monogyna) was also the dominant species with

Cost of rejuvenating hedgerows

The cost of applying the traditional hedge laying was approximately twice that of conservation hedging, and three times the cost of wildlife hedging (Table 1). Reshaping with the circular saw was the cheapest rejuvenation method, while the price of coppicing was intermediate between the circular saw and the three hedging/hedge laying techniques. At two of the five sites the coppiced plots had to be fenced to reduce deer browsing the regrowth; this additional cost more than doubled the price of

Discussion

This study is the first quantitative test of new approaches to hedge rejuvenation management. The use of a large-scale manipulative field experiment over three years provides robust evidence for the relative cost of five rejuvenation methods and their effects on the value of hedgerows for wildlife, in terms of hedge structure, regrowth and berry provision. This evidence for the benefits of new, cost-effective methods of hedgerow rejuvenation is urgently needed to halt the decline in hedgerow

Acknowledgements

This research was funded by Defra grant BD2114. We thank Lucy Hulmes, Sarah Hulmes, Jo Savage and Rachel MacDonald for their assistance and patience collecting data, Charles George who extracted gap data from structural images and members of the hedgerow project advisory group for their input.

References (44)

  • J.T. Staley et al.

    Changes in hedgerow floral diversity over 70 years in an English rural landscape, and the impacts of management

    Biol. Conserv.

    (2013)
  • J.T. Staley et al.

    Long-term effects of hedgerow management policies on resource provision for wildlife

    Biol. Conserv.

    (2012)
  • N.R. Bannister et al.

    Hedgerow management: past and present

  • P. Bright et al.

    The Dormouse Conservation Handbook

    (2006)
  • A. Brooks

    Hedging: A Practical Conservation Handbook

    (1975)
  • D. Capizzi et al.

    Effects of habitat fragmentation and forest management on the distribution of the edible dormouse Glis glis

    Acta Theriol.

    (2003)
  • P.D. Carey et al.

    Boundary and linear features

  • M.J. Crawley

    The R Book

    (2007)
  • M.J.W. Dodds

    Mechanical hedge-laying for wildlife, Aylesbury Vale, Buckinghamshire, England

    Conserv. Evid.

    (2005)
  • J.J. Faraway

    Extending the Linear Model with R: Generalised Linear, Mixed Effects and Nonparametric Regression Models

    (2005)
  • D.D. French et al.

    Classification, composition, richness and diversity of British hedgerows

    Appl. Veg. Sci.

    (2001)
  • E. Fuentes-Montemayor et al.

    The effectiveness of agri-environment schemes for the conservation of farmland moths: assessing the importance of a landscape-scale management approach

    J. Appl. Ecol.

    (2011)
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