Copyright Material Taylor and Francis

1 INTRODUCTION TO HEDGEROWS AND FIELD MARGINS

John W. Dover

Francis Background and This book is primarily about the ecology of hedgerows, but we have included ‘field margins’ in the title of the book because to understand what happens in hedgerows, it is necessary to consider the influences of the adjacent land use, and these are much more complex than when Ernie Pollard,Taylor Max Hooper and Norman Moore published their seminal work Hedges in 1974 (Pollard et al. 1974). Indeed, in many cases in order to understand what is happening at the local level, it is important to consider the wider landscape-scale issues. Since the publication of Hedges, compul- sory set-aside has come and gone (at least in the EU; Daugbjerg & Swinbank 2011), several classes of pesticide materialhave been developed and been superseded by others (Jeschke et al. 2011), farmland intensification has continued with continuing loss of hedgerows either through removal (Figure 1.1) or lack of management (Carey et al. 2009a), farmland wildlife has significantly declined (Stanton et al. 2018) and responses such as agri-environment schemes have been introduced in an attempt to stem theCopyright losses (Anonymous 2009). In addition, the biodiversity and wider value of hedgerows to farming and society have been increasingly recognised through the concept of ecosystem services (Reid et al. 2005). Hedgerows are given protection in a number of countries (Baudry et al. 2000), though such protection may be partial. In the UK, for example, whilst hedgerows are designated as priority habitat (JNCC 2011), they must exhibit specific characteristics to be eligible for protection, and protection is not available for certain types of hedgerow such as those surrounding curtilages (DOE 1997; Marrington 2010). This chapter briefly introduces readers to the different components of hedgerows and field margins and some important concepts. Succeeding chapters concen- trate on particular issues; in some the emphasis is strictly on one component of the system (such as Chapter 3 on the management of hedges or Chapter 6 on softening 2 John W. Dover

Francis and FIGURE 1.1 Hedge removal in 2009 to enlarge a field for arable production in Warbur- ton, Cheshire, UK. Source: © John W. Dover Taylor the impact of agrochemicals on hedgerows and field margins by modifying their use at crop edges), whilst others consider the ecology of the hedgerow/field margin system as a whole in relation to a particular species or functional group. Unfortu- nately, whilst we cover a numbermaterial of species groups, we do not have space to cover them all so, for example, we do not have a chapter on herptiles (amphibians and reptiles) despite field margins probably being important for them (Reading & Jofre 2009; Carthew et al. 2013; Mendenhall et al. 2014), especially riparian margins (Maisonneuve & Rioux 2001; Prosser et al. 2016), although perhaps not always positively (Joly et al. 2001). Our final chapter introduces a rather ignored topic – urban hedgerows.Copyright As components of urban green infrastructure, hedges deliver valuable ecosystem services, including being components of sustainable urban drainage and capturing particulate air pollution (Dover 2015), but they are also valuable as urban wildlife habitats (Chapter 14).

What is a hedgerow? Strictly, ‘hedge’ and ‘hedgerow’ are different terms – the hedge being the woody component of a field boundary, whilst the hedgerow includes the herbaceous component, the bank and ditch – but this distinction is often ignored and the terms used synonymously (Forman & Baudry 1984). Hedgerows can be found throughout the world including North and South America, Africa, Asia, Australia and Europe Introduction to hedgerows and field margins 3

(Burel 1996; Baudry et al. 2000; Truong & Pease 2001; Breen 2017); unfortunately, the term ‘hedge’ has multiple meanings and varies with geographical location, so in the UK it has been used to describe managed or unmanaged shrubby boundaries, stone walls or turf banks (Pollard et al. 1974; Greaves & Marshall 1987); in northern France hedgerows are typically lines of trees, and the landscape as a whole is termed the ‘bocage’ (Baudry et al. 2000); in Spain, olives are often grown in dense parallel lines and explicitly termed ‘hedgerow orchards’ (Gomez-del-Campo et al. 2017). In over 100 countries, including Thailand, Venezuela, Vietnam, Bangladesh and India, vetiver grass (Vetiveria zizanioides) has been planted densely to produce ‘hedgerows’ which are used in soil and water conservation, and in bioengineering and environmental protection projects (Truong & Pease 2001). In this book, unless otherwise stated, the term ‘hedge’ is used to describe linear strips of managed or unmanaged woody vegetation (shrubs and/or lines of trees, also termed woody linear features, or WLF; Maskell et al. 2008), and other boundary structures are given names that are reasonably descriptive of their morphology, e.g. ‘stone wall’. Müller (2013) provides a classification of the field boundaries of 32Francis European countries that he surveyed; within it he identifies eight general types of woody vegetation (low, medium and high hedges, tree hedges, rows of trees,and single trees and/or shrubs, pollard trees and high pruned trees), over 100 different planting styles of hedge and 135 management styles. A good working definition of a hedge is used in the UK Countryside Survey (Maskell et al. 2008), i.e. to be considered a hedge a WLF should have a minimum length of 20 m andTaylor be no more than 5 m wide at the base; if composed of a line of trees, it should only be one tree wide. Note that this differs somewhat from the definition used by Baudry et al. (2000) who considered that a linear feature could only qualify as a hedgerow if it was managed in some way. Also, using the Countryside Survey definition, linear features wider than 5 m would be considered to be small shelterbelts;material nevertheless such features will probably function in much the same way as narrower structures, and Baudry et al. (2000) note that North American prairie shelterbelts, planted in response to soil erosion that led to the Dust Bowl in the Great Plains (Gardner 2009), are analogous to hedgerows, with many similar features and functions (Guo 2000). Copyright Definitions and components The nomenclature of hedges and field margins is deceptively simple yet contains a few pitfalls. As a result, we have included in this chapter a diagram of an arable field margin to illustrate the various components (Figure 1.2). It is interesting to track the evolution of diagrammatic content over time, as it reflects our increased knowl- edge of the ecology of field margins and the increased emphasis on managing them for biodiversity/ecosystem services rather than simply agricultural production. In Greaves and Marshall (1987), field margins were divided into three main areas: the field boundary, the boundary strip and the crop, with the latter two as fairly uncom- plicated structures. In Marshall and Moonen (2002), the boundary strip became the ‘field margin strip’, a term that embraced a wide range of potential management 4 John W. Dover

Francis

FIGURE 1.2 Diagrammatic representation of an arable fieldand margin to show the various components that may be present (after Greaves and Marshall 1987; Mar- shall and Moonen 2002). The field margin combines the field boundary, such as a hedgerow or green lane, AND any associated boundary strip. Ditches may be located on both sides of a field boundary (and would be considered to be part of theTaylor boundary) and also found either side of the track inside a green lane. WR = wheel ruts typically made by farm vehicles. The field boundary in the diagram is a hedgerow (i.e. the hedge [shrubs/trees] + associated raised vegetated bank); other common boundary features include dry stone walls, grass banks (baulks) or strips, windbreaks, and woodmaterial edges. The boundary strip is typically composed of a sown grass strip, buffer or other agri-environment strip often sown with a mix of species e.g. for pollinators or for game cover. ‘ss’ = sterile strip: an area of bare ground created either by use of a broad-spectrum herbicide or by mechanical means (rotovation). The crop margin/headland may be modified by changing agrochemical inputs to allow the growth of broad- Copyrightleaved plants (whilst controlling most grass species) within the crop to create ‘Conservation Headlands’.

options, and the crop now contained the term ‘conservation headland’ at its edge. In Figure 1.2, whilst I have not included a farm track in the boundary or field margin strip (it can still be present), I have added a green lane and separated the boundary/field margin strip from the crop with a sterile strip. Whilst we identify different components of hedgerows and field margins, it is probably worth remembering that whilst the different components have their own individual attributes, it is their collective value which is most important. Wolton et al. (2013) examined the relationship of 107 species considered as priority and farmland indicator species Introduction to hedgerows and field margins 5 associated with hedgerows with five elements of hedgerows (trees, shrubs, hedge base, field margin and ditches). They found that 65% of species were dependent on more than one hedge component, and 35% were dependent on three or more.

Crop influences The type of crop and its management have a profound impact on the flora and fauna of field boundaries. The major and most obvious division of crops is into grassland and arable. In the latter, hedgerow/field boundary removal to improve efficiency of crop production has led to some areas being largely denuded of semi- natural landscape features and others left with a much reduced stock, and the use of synthetic fertiliser and pesticides has drastically modified field boundary animal and plant communities (Robinson & Sutherland 2002; Petit et al. 2003). In grassland systems, the main division is into grassland that is used for grazing and that used for primarily for grass production (hay, silage, zero-grazing) although late-season ‘after- math’ grazing or early spring grazing may still occur. Field boundaryFrancis vegetation in permanent, extensive pasture is undoubtedly the most valuable for biodiversity, provided stocking densities are reasonable. Whilst traditionaland hedge management (laying) was designed to make hedges stockproof, the expense of maintaining hedges in this way has led to the wholesale use of fences. Sheep, in particular, are very good at denuding basal hedgerow vegetation and eroding hedge banks if not controlled. Unfortunately, in some cases, farmers haveTaylor been known to spray out boundary vegetation around hedges to prevent shorting of poorly sited and poorly maintained electric fences. Protecting the herbaceous field boundary vegetation and pal- atable shrubs in field boundaries from being completely eaten-out for biodiversity conservation purposes requires protective measures (Figure 1.3). Field boundaries around intensive grassland materialcan suffer from both uncontrolled stock grazing and some of the issues prevalent on arable land; for example, chemical sprays and fertilis- ers used to manage monoculture grassland can drift into the boundary vegetation, and close ploughing, when re-establishing the sward, can sever shrub and tree roots. In some areas, stock are now maintained in very large open fields. Here, paddocks are not defined by hedges or other field boundaries but are purely notional and defined Copyrightusing electric fencing (Teixeira et al. 2017).

The field boundary Greaves and Marshall (1987) defined a field boundary as being composed of a barrier such as a ‘hedge, fence or wall, the hedgebank if present with its herbaceous vegetation, and any associated water course such as a ditch or drain’ which some e.g. Hahn et al. (2014) appear to have misinterpreted as excluding grassy margins. This latter is understandable given the written description used by Greaves and Marshall (1987) does indeed seem to omit grass strips/banks as a field boundary on their own (i.e. without a hedge/fence/wall), but scrutiny of the figure in the origi- nal paper shows that ‘grass baulk’ is included in the ‘barrier’ component. Whilst not 6 John W. Dover

Francis and

FIGURE 1.3 In intensive grazing systems it may be necessary to take protective measures to prevent the base of hedgerowsTaylor from being completely denuded. Source: © John W. Dover the most accessible term, ‘baulk’material does mean ‘a ridge left unploughed between fur- rows’ (Sykes 1982), an ‘unploughed ridge’ (Schwartz et al. 1988) or ‘a narrow strip of grass in a common arable field. Used for access, grazing, etc.’ (Hollowell 2000). So the field boundary, whatever it is made up of, is the ultimate structure that delimits a field. Of course, even this is a simplification, as any given field boundary may be made up of a number of these structures in combination, e.g. there may be a length of tall hedge,Copyright followed by a section of short hedge with scattered trees, followed by a section of wood edge. The hedged sections may be on a raised bank with a ditch that runs only partly along its length before petering out. Ditches are associated structures which are usually considered part of the field boundary.

Green lanes Green lanes (see Figure 10.3) are unmetalled trackways with field boundaries either side (Dover & Sparks 2001), but the actual configuration (width, length, depth, vegetation) can vary widely due to their organic development from a range of origins, including ancient drove roads (Belsey 1998). Whilst perhaps the ‘classic’ green lane of lowlands has hedges either side (Dover et al. 2000), some may not have hedges at all but be composed of a sunken track (holloways; Muir 1981) such that the Introduction to hedgerows and field margins 7 earth banks and herbaceous vegetation create the same effect. In upland landscapes, hedges are usually replaced by dry stone walls and, here, green lanes composed of double stone walls can frequently be found. The topography and structure of any given green lane can vary substantially, and it will typically link to many other field boundaries along its length. The most important features of a green lane, from an ecological standpoint, are probably the unsealed track surface, the enhanced micro- climate due to wind shelter between the hedges/walls/earth banks, the distinct plant communities they hold, their structure (including presence of trees) and the less intensive management they seem to get compared to other field boundary types (Dover & Sparks 2001; Walker et al. 2006).

Intersections or nodes The term ‘node’ or ‘intersection’ is used in landscape ecology (Forman & Godron 1986; Noss & Harris 1986) in relation to field boundaries where they meet or intersect or where they have junctions with other semi-naturalFrancis elements such as woods, riparian areas or uncropped patches of land. Such areas often have greater abundance or species richness of flora and fauna than linearand sections of field boundaries (Figure 1.4), but this may depend on the nature of the field boundary and management (Lack 1988; Fry 1991; Dover 1996; Dover et al. 1998). Taylor

material

FIGURE 1.4 A field corner, or ‘node’, in a barley field with abundant wildflowers and arable plants. The crop behind the fenced and ‘gapped-up’ hedge is Jerusalem artichoke, used as a game cover crop. A narrow sterile strip, created by chemical means, clearly delineates the crop headland from the field boundary. Source: © John W. Dover 8 John W. Dover

Boundary strips Because of the crisis in farmland biodiversity and the increasing recognition of the ecosystem services (especially pollination) delivered by hedgerows and field margins (see below), agri-environment schemes have been developed in an attempt to mitigate some of the impacts of modern intensive farming. One of the most popu- lar approaches is to take out of production a narrow strip (typically between 2 m to 12 m, but in some cases up to 24 m, wide; Haaland et al. 2011) around the field boundary and modify it in some way (see Figure 7.5 and Figure 13.5) or to change the management of the crop margin. In the case of the latter, Conservation Head- lands have been developed for arable (primarily cereals; see below and Chapter 4), and whilst the term has also been adopted by some for modifying grass margins (Haysom et al. 1999, 2000, 2004; Cole et al. 2007), the approach is fundamentally different and is described, briefly, below. There has been much less research aimed at softening the impact of crop management on field margin flora and fauna in grassland systems Francisthan in arable (Fritch et al. 2017). However, some studies have been carried out using methods such as simply excluding grazing from the margins of an existing sown sward (sometimes coupled with reduced agrochemical inputs). Other approachesand include rotovation or spraying a marginal strip of an existing sward followed by natural regeneration from the seedbed or rotovation followed by sowing wildflowers (sometimes with a grass mix) or other species (Haysom et al. 1999, 2000, 2004; Cole et al. 2007; Sheri- dan et al. 2008; Potts et al. 2009; Fritch et al.Taylor 2011; Anderson et al. 2013; hUallacháin et al. 2014; Woodcock et al. 2014; Wiggers et al. 2016; Fritch et al. 2017). Stock control, through fencing, and an annual hay (removal) cut or autumn/winter grazing was still used in these studies. In general, all these approaches tended to have some benefit in diversifying the sward structure/composition and increasing invertebrate abundance/richness even bymaterial simply relaxing the grazing management. However, natural regeneration tended to allow the development of a sward with aggressive weeds and is probably not acceptable in most circumstances, so sowing wildflower/ grass mixes is likely to have the most benefit even though it is a more costly option. In arable systems, the exact approaches vary from country to country and with crop type.Copyright Haaland et al. (2011) reviewed the literature on the impact of sown wildflower strips (Figure 7.5) in central and northern Europe on farmland insect abundance and diversity. They found that sowing wildflowers around field boundaries, after cultivation, was generally superior to sowing a mixture of grasses or allowing natural regeneration of the seedbed. However, seed mixtures targeted specifically at pollinators or aimed at producing nectar-rich swards could be superior to general wildflower mixes. Species groups responded differentially to strip characteristics (geographical location, seed mixture, sward structure and management, age and flower density), and most species identified as benefitting from margin management in the studies were relatively common. Studies published since the review of Haaland et al. (2011; Appendix 1.1) suggest that the effects of margin strips on biodiversity may be context dependent, i.e. their value appears to be greatest in Introduction to hedgerows and field margins 9 homogeneous rather than heterogeneous landscapes (the latter having a higher proportion of semi-natural vegetation than the former) and that, with suitably tailored seed mixtures, they may be a source of natural enemies whose action can potentially reduce the need for pesticide application on the adjacent crop by preventing pest outbreaks reaching the economic threshold for spraying (Tschumi et al. 2015; Appendix 1.1).

Sterile strips Sterile strips (Figure 1.4) are used in arable systems to reduce ingress of weeds into the crop from the field boundary (Vickery et al. 2002). If there is no boundary strip, then the sterile strip will be immediately adjacent to the field boundary, whereas if some kind of boundary strip has been planted it will be located between the boundary strip and the crop edge. Sterile strips can be created in one of two ways, by maintaining a weed-free soil surface by rotovation (i.e. mechanical means) or by spraying a persistent wide-spectrum herbicide. Mechanically managedFrancis sterile strips are usually much wider than those created by spraying (due to the need to get a tractor round the crop edge). In the past, the chemical Atrazine was used to create sterile strips (Boatman & Wilson 1988), but this chemicaland has now been banned in the EU (Sass & Colangelo 2006), and other chemicals, such as Glyphosate, are used instead (Anonymous 2008b). Taylor Conservation Headlands The headland, in agricultural parlance, is the area of a field that is used for turn- ing by agricultural machinery (Muir 1981). The term ‘Conservation Headland’ was adopted by the Cereals and Gamebirds Research Project run by the Game Conservancy Trust (now thematerial Game and Wildlife Conservation Trust) to describe the practice of modifying the management at the edge of cereal crops (Sotherton et al. 1989). Essentially, broad-spectrum herbicides (which kill broadleaved plants and grasses), fungicides with known insecticidal activity and insecticides were not sprayed on the outer 6 m of cereal fields, whilst grass weed herbicides and fungicides shownCopyright to have little or no insecticidal activity were. There were modifications to this general rule, e.g. spot spraying of the herbicide fluroxypyr was allowed to control infestations of cleavers Galium aparine (Boatman et al. 1988). Hence, ‘Con- servation Headlands’, described in detail in Chapter 6, contain a wide range of broadleaved plants, including rare arable ‘weeds’ (Wilson & King 2003) if present in the seed-bank (see Chapter 2), whilst minimising losses to crop yield. A subsequent modification of the technique uses reduced fertiliser inputs (Kleijn & vanderVoort 1997; Walker et al. 2007), which, by reducing crop vigour, allows more light to penetrate the canopy and reduces competition with broadleaved plants. The system was developed initially as a way of improving the availability of invertebrate food for grey partridge Perdix perdix chicks during a critical stage of their development but was soon shown to have a wider biodiversity value. 10 John W. Dover

Historical development of hedgerows Baudry et al. (2000) give a good roundup of historical studies and cite Rack- ham (1986), who indicated that archaeological evidence confirms the presence of hedges in Roman times and who also suggested some remaining examples of hedged field boundaries in the Land’s End Peninsula of Cornwall (UK) were of prehistoric origin. Pollard et al. (1974) considered the first reference to a British hedge to be 547 AD in the Anglo-Saxon Chronicles; nevertheless, they considered some field boundaries, if not the hedges on them, to be Roman. More recently, Müller (2013) gives a chronology of field boundaries, suggesting by inference the early Palaeolithic to be the earliest use of dead hedges (i.e. linear barriers composed of cut branches), though probably used as defence against predators, and around 11,000 BC the use of woody/shrubby hedges. The origin of hedgerows is a subject that continues to fascinate people inter- ested in landscape development and ecology, whether from an amateur or professional perspective. Possibly the most influential work in this respectFrancis in the UK was that of Max Hooper, who developed a rule-of-thumb method whereby hedges could be dated by counting the number of shrubs in 30-yard lengths. His work suggested that a hedge’s age could be approximately assessedand by assuming that one species was added for each 100 years of its existence (Hooper 1970). This method is surprisingly robust provided precautionary measures are taken – including pilot studies correlated with documentary records (Pollard et al. 1974). This caution is necessary, because the number of species inTaylor a hedge at any given time is the sum of the number of species when the hedge was first created and the accumulated number of additional species gained over time, as well as the impact of past management, local environmental factors, geology and geography (Wilmot 1980). One of the critical points, then, is the number of species that were in the hedge initially – and this will be strongly related tomaterial how and why the hedge was created in the first place. Forman and Baudry (1984) recognised three main origins of hedgerows:

• Planted – deliberately created, typically using a single species (although mul- tispecies plantings may have arisen from whips derived from nearby woodland (PollardCopyright et al. 1974)). Plantings may be on a bank and associated with a ditch. • Spontaneous – trees and shrubs develop along pre-existing structures such as unhedged field boundaries, fences, walls or ditches from seeds dispersed by wind or animals such as birds. • Remnant – typically a result of tree clearance where a strip of trees/shrubs is left along the ownership boundary.

The earliest field boundaries were probably simple structures made with whatever material was at hand, developing in sophistication over time. Whilst spontaneous hedges require an influx of seeds to initially develop, both planted and spontaneous hedges require seed dispersal to increase in species richness over time (as per Hooper’s rule). Forman and Baudry (1984) examined the origin of shrubs and trees Introduction to hedgerows and field margins 11 in two European and two North American sites and concluded that, in the major- ity of cases, hedge shrubs were bird dispersed, whilst trees were primarily wind dispersed. They concluded that spontaneously developed hedges were primarily composed of bird-dispersed seeds (from a study in New Jersey, USA), whilst the shelterbelt hedges in the Great Plains (USA) were primarily composed of wind- dispersed material, which were probably derived from planted stock. In Europe, the UK hedgerow shrubs were primarily bird-dispersed, but the trees originated from wind-dispersed propagules; in Brittany, the trees were primarily bird or mammal dispersed whilst the shrubs were a mix of wind and bird dispersed. In the UK, older field boundaries tend to be curvilinear or irregularly shaped, probably as a result of assarting (forest clearance) or following natural boundaries, contours or established tracks (such as drove roads). From the mid-1700s onwards, new field boundaries were often more rectilinear in form resulting from the Private or General Parliamentary Enclosure Acts, which enabled the division of commonly held land into discrete fields. During the major period of the ‘Great Enclosures’ (1750–1850) hedges were typically established using a single Francisspecies (hawthorn, Crataegus monogyna) and ran to some 321,869 km, at least doubling the entire length planted over the previous five centuries (Rackham 1986).and However, ‘enclosure’, as a legal term, is not just the establishment of field boundaries; it also means that land can be farmed ‘in severalty’, i.e. independently of others, and requires the quashing of the rights of others over the land. That informal and formal legal and physical process had, of course, been going on forTaylor centuries prior to the Parliamentary Enclosure Acts and continued alongside them and into the 19th century (Hollowell 2000). As to present times, it is usual to plant multi-species hedges to maximise biodiversity benefits (Anonymous 2008a).

Change in extent, statusmaterial and condition of hedgerows and other field boundaries Since the end of World War II, the intensification of farming, land consolidation programmes, urban expansion, opencast mining and commercial and infrastructure development (Baudry & Burel 1984; Dowdeswell 1987; Fry 1991) has led to a substantialCopyright loss of hedgerows and other field boundaries. Land consolidation is the process whereby disparate landholdings, spread across a landscape, are col- lectively reorganised into contiguous ownership blocks; intensification, including hedgerow and other field boundary removal, typically follows. For example, a land consolidation programme in Brittany in 1982 subsequently led to a 50% reduction in hedgerows (with negative consequences for linnets Acanthis cannabina living in nearby heathland; Eybert et al. 1995). Perhaps the most well-documented loss of managed hedgerows comes from the UK. Pollard et al. (1974) and Hooper (1981), citing (Locke 1962) suggested the stock of hedges in England, Scotland and Wales (Great Britain, GB) to be about 804,672 km ‘at the end of the 1950s’. Dowdeswell (1987) indicated 230,000 km of hedge had been lost between 1946 and 1974, presumably using the estimated 12 John W. Dover average annual loss of 8,047 km given in Pollard et al. (1974) and Hooper (1981). However, these early estimates cannot compare in accuracy with those from the UK Countryside Survey, which was initially based on a random stratified land-use survey of GB. Over time, the survey increased its scope to cover the whole of the UK by including Northern Ireland, and the number of sample squares was also increased due to this and changing policy requirements. So whilst 256 squares were surveyed in GB in 1978, 384 squares were examined in 1984, 508 in 1990, 569 in 1998 and 591 in 2007. Hence estimates have been based on increasing sample sizes over time (Table 1.1). The results indicated that between 1978 and 1984 some 28,200 km of managed hedge was lost from GB compared with a gain of just 3,600 km (e.g. from new plantings), but over the period 1984–1990 the net loss was considered to be 121,000 km (174,300 losses vs. 53,300 gains; Barr et al. 1991). Not all losses were removals, as a high proportion of ‘lost’ hedges changed from the definition used for managed hedgerows to a different category such as a line of trees (of the 174,300 losses, 111,500 were a result of changing boundary type). The definitions of different boundary types used by the CountrysideFrancis Survey have been modified over time, so data given in the most recent report (Carey et al. 2009b) is not completely compatible with earlier reports (e.g.and Barr and Gillespie (2000) but the trends remain the same. The 1998 survey period suggested that there was a slight gain in the stock of hedges over the period 1990–1998; however, data from the last survey in 2007 showed a further decline in the extent of managed hedges (Table 1.1). If we use the rough estimate ofTaylor the length of hedges from Pollard et al. (1974) and the stock of hedges from the latest Countryside Survey (Carey et al. 2009b) (and accept that the result is going to be easily criticised on the basis of different methodologies), then it appears that since the late 1950s GB has lost about 41% of its net stock of managed hedgerows (i.e. after the balance between losses of existing and the planting ofmaterial new hedges is taken into account). Whilst the emphasis of this book is on hedgerows, it is clear that field boundary stocks are dynamic, with losses and gains recorded for different field boundary types. In GB, between 1984 and 2007, the total length of woody linear features (which includes hedges) has declined relatively modestly from 710,000 to 700,000 km (–1.4%), and walls have declined from 198,000 to 174,000 km (–12%). On the other hand, theCopyright lengths of banks/grass strips have increased from 56,000 to 64,000 km (+14%), and fences increased from 571,000 to 664,000 km (+16%). The length of lines of trees has rocketed from 32,000 to 114,000 km (+256%) – partially reflect- ing the cessation of management of many hedges such that they are now considered to be lines of trees/relict hedges (Carey et al. 2009b). The herbaceous vegetation of hedgerows has also undergone drastic change over time, with significant decreases in species richness between 1978 and 1998 – though no subsequent change was detected by the Countryside Survey in 2007. Species composition also changed, with the proportion of more competitive species and those characteristic of shaded, fertile or less acidic soil conditions increasing between 1978 and 2007 (Carey et al. 2009b). The increase in shade tolerance of the herbaceous community was considered to reflect the increase in unmanaged Introduction to hedgerows and field margins 13

TABLE 1.1 Estimates of hedgerow loss in GB (England, Scotland and Wales) using information from Pollard et al. (1974), Countryside Survey data (Barr et al. (1991), and Carey et al. (2009b).

Survey period Length of managed Number of 1 x 1 km Cumulative Cumulative hedges sample squares compared loss (km) loss (%) Late 1950s @804,672 1978 648,600 256 1978–1984 624,000 256 24,600 3.9 1984–1990 506,000 340 142,600 22 1990–1998 508,000 508 140,600 21.7 1998–2007 477,000 569 171,600 26.6 hedgerows. These general trends were also reflected in a 70-year study based on 357 hedgerow sites in southern England by Staley et al. (2013). At the level of the individual hedgerow, species richness increased (for both woodyFrancis and herbaceous flora), although different sites became more similar (homogeneous) over time. At the regional level, the herbaceous community of hedgerowsand declined over time, whilst the shrubby species composition increased (see further Chapter 3).

Landscape issues Taylor How long is a hedgerow? This somewhat prosaic question is actually quite important, especially when trying to count hedgerows and measure changes in extent. Is a hedgerow, for example: material • the total uninterrupted length of a hedge irrespective of the number of adjoining hedges or other field boundaries, • the distance between two abutting hedges on any particular side, • or the extent of a particular land use along its length on any particular side?

Each of theseCopyright will give different answers, and each will be equally valid depending on the context and questions being asked of the dataset (Baudry et al. 2000). For connectivity, the density of hedges in an area, the frequency and extent of gaps and the number of connections between hedges (and with other landscape elements) may be the most important parameters.

Fragmentation and associated landscape ecology terms When the concept of island biogeography theory (MacArthur & Wilson 1967) was first applied to terrestrial landscapes, the latter were conceptualised as binary systems only containing habitat (patches) and non-habitat (matrix). In such a system the matrix was considered devoid of resources and unable to support dispersers 14 John W. Dover from habitat patches. Further elaboration of the concept recognised the existence of a wider suite of landscape elements (rather than just habitat), introduced corridors and stepping-stones that promote movement, barriers that retard it and later a realisation that the matrix itself contained resources and could be better visualised as being variably permeable (spatially and temporally; see Dover and Settele (2009) for an overview and source references). The intensification of agriculture since the 1940s caused extensive habitat loss and ‘fragmentation’ of semi-natural habitat, lead- ing to the need to understand how fragmentation affected species at the local and landscape scale and how to mitigate its effects. What we loosely term ‘fragmentation’ has distinct stages; starting from a notional homogenous habitat we can recognise four distinct states:

• ‘Intact’ habitat can be considered as a relatively homogeneous block containing 10 % or less non-habitat; • ‘Variegated’ habitat would have 11–40% non-habitat; • ‘Fragmented’ habitat would have 41–90% non-habitat; Francis • ‘Relictual’ habitat would have 91% or greater non-habitat (Hobbs & Wilson 1998). and Nor is fragmentation a single, one-off, process of habitat destruction as, in addition, it includes: Taylor • ‘Shrinkage’ the subsequent reduction in size of remaining fragments; • ‘Attrition’ where fragments are subsequently lost.

The initial process of habitat destruction that leads to fragmentation, coupled with subsequent shrinkage and attritionmaterial all combine to increase the ‘isolation’ of habitat patches (i.e. the gap between remaining habitat increases). This has potentially dev- astating impacts on populations (Hobbs & Wilson 1998). If fragments get too small they may be unable to support a viable population (Brito & Grelle 2006) and be too far away to be reinforced from other patches or to be recolonised (Forman & Godron 1986; Fahrig & Merriam 1994). The concept of the ‘metapopulation’ (Levins 1970;Copyright Hanski 1999) thus becomes relevant. Metapopulations are landscape- scale structures which are composed of a number of separate habitat patches which interact such that even a small number of movements of reproductively viable individuals dispersing between them can maintain genetic integrity, restock vacant habitat that had gone extinct through catastrophic stochastic events such as fire and buttress flagging populations. The interaction between populations of the different patches thus increases viability (persistence) of the species in the landscape in the long-term (compared with the fate of a single habitat patch). Not all habitat patches within a given metapopulation may be equally viable, for example, because they are too small to maintain a population long term or because the habitat quality is low. Such variability is recognised in terms of source-sink dynamics, whereby some patches are net exporters of individuals (dispersers) whilst others are net importers Introduction to hedgerows and field margins 15 of individuals (i.e. sinks). Whilst the presence of a sink habitat may seem fairly use- less, its presence may ultimately contribute to metapopulation stability even if it only maintains a population for a few generations or acts as a stepping-stone to other more viable patches. If habitat patches in a population are destroyed, this may lead to increased isolation of the remaining patches and threaten metapopulation stability or viability. Maintaining the ability of species to move throughout the landscape (and hence cross the ‘matrix’) is thus paramount. Hedgerows can potentially act as wildlife corridors, helping to reduce the impact of habitat fragmentation by joining remnant patches together (Diamond 1975). In the context of climate change adaptation, Lawton et al. (2010) considered that hedgerow networks (Forman & Baudry 1984) may help species to track newly available climate space and leave former habitat that had become unsuitable. Unfor- tunately, it is clear that hedgerow networks have also become fragmented due to field amalgamation, resulting in large gaps and a reduction in connections between hedgerows (Barr & Gillespie 2000). Corridors can have negative as well as positive benefits, potentially exposing dispersers to predation and promotingFrancis disease trans- mission etc. (Simberloff et al. 1992; Laine 2004). Whether hedgerows are essential or just useful for dispersers will depend on the individualand species/species group and its degree of specialisation (Dover & Settele 2009). Individual species’ responses to a hedgerow as corridor will also depend on how features such as gaps are perceived, i.e. the difference between ‘functional connectivity’ and ‘physical connectivity’. In the former, gaps may exist, but if the speciesTaylor is happy to move across the gaps then it is functionally connected even though the hedgerow is not continuous (With 1997). This also implies that if something is physically connected, it may not be functionally connected if some attribute important to the target species is missing. Contrariwise, stepping-stones (Forman 1995), small patches of habitat, which could include small discontinuousmaterial runs of hedgerow or even individual hedgerow trees (see Chapter 10), may also aid dispersal even though they are physically discontinu- ous. It is also worth remembering that a corridor for one species may be a barrier for another (Dover & Settele 2009). There has been a kind of implicit assumption that a physical area termed ‘habitat’ contains all the resources needed for a given organism, but this is patently absurd, as anyone whoCopyright considers the process of migration must acknowledge. Birds, for example, may migrate huge distances because of temporal changes in food resources or the need to move to somewhere that contains some other vital resource such as nest sites (Mönkkönen et al. 1992). Thus, it is clear that species move between areas of resources, and it is more useful to think in terms of a resource patch than a strictly delimited area that contains all the resources needed by a species. Resources may indeed overlap in distribution (i.e. all present in much the same physical space), but they may also be spatially separated. This resource-based approach is one that has been pioneered by Roger Dennis and co-workers (Dennis et al. 2003; Dennis et al. 2006; Van Dyck 2010; Dennis 2015). So at a more local level, individuals of a species may move between food, overwintering and reproductive sites either in discrete time periods, e.g. between summer versus winter, or during the same period, 16 John W. Dover e.g. moving between areas high in food and areas high in reproductive sites (i.e. for non-substitutable, ‘complimentary’ resources; Dunning et al. 1992). Individuals may also move between areas containing the same resource if its presence in one area is insufficient (supplementary resources; Dunning et al. 1992). The two terms are typically used as ‘complementation’ and ‘supplementation’ respectively (see, for example, Ouin et al. 2004). Essentially, corridors and stepping-stones can be considered as gateways to patch-based resources.

Ecosystem services Ecosystem services, the benefits that biodiversity delivers directly or indirectly to humans, are typically divided into four different categories:

• Supporting services – those that are fundamental to life and global function- ing such as photosynthesis, soil formation, water and nutrient cycles • Regulating services – processes involved in providing anFrancis environment that supports human life, e.g. climate regulation, pollution control, pollination • Provisioning services – products derived from ecosystemsand • Cultural services – economic and cultural/aesthetic/spiritual values of biodiversity (EASAC 2009) Taylor The importance of specific ecosystem services, in relation to hedgerows and field margins, depends very much on personal viewpoint/context, with different ‘stakeholders’ viewing the values of hedgerows in different ways and depending on their personal capacity. Oreszczyn and Lane (1999) illustrated this nicely by describing, from interviews,material how an agricultural adviser might value the ecological aspects greatest in his/her professional capacity but, as an individual, value the landscape aesthetics equally. The ecosystem services delivered may also be location specific, for example, with cultural value higher where a hedge marks a Saxon parish boundary or for water quality delivery where hedgerows are located near streams or ditches (Cole et al. 2009). From Copyrighta very one-sided production viewpoint, hedgerows take up growing space, may harbour crop pests, shade crops, ‘steal’ water from adjacent crops, remove nutrients and cause compaction on ground along headlands due to vehicle movements during farming operations, all of which conspire to reduce yield; they also cost money to maintain (Teather 1970; McCollin 2000). To balance these perceived disbenefits, we know that field boundaries also reduce soil erosion, are a source for pest predators and parasites, provide pollination services and provide a host of other values relevant to crop production, landowners and society as a whole (Table 1.2). Indeed, in some places hedgerows have had to be re-introduced and other structures such as beetle banks developed (Chapter 7) to reintroduce values lost through field amalgamation. I recall visiting a farm in Cambridgeshire which had been purchased by a landowner with an aim of increasing farming efficiency. He also TABLE 1.2 Ecosystem services delivered by hedgerows. Service names from the Millennium Ecosystem Assessment (Reid et al. 2005) identified by Cole et al. (2009) in normal type plus additional services they omitted/aggregated in italics. Sources in addition to Cole et al. (2009) used in the table compilation: Forman & Baudry 1984; Baudry et al. 2000; Oreszczyn & Lane 2000; Wong & Dickinson 2003; Ouin et al. 2004; Wolton 2012; Dover 2015.

Type of service Specific service Function/examples of service Supporting Soil formation Soil formation services Photosynthesis Production of oxygen Primary Production of chemical energy in the form of production organic matter Nutrient cycling Recycling of materials such as carbon, phosphorous, nitrogen Water cycling Recycling of water

Regulating Air quality Air pollution control, e.g. Francisremoval of services regulation particulates and nitrogen dioxide; prevention of agrochemical drift Climate regulation Sequestration of andcarbon dioxide, source of renewable energy, temperature and humidity control, wind shelter for stock and crops; energy efficiency (shading, wind shelter); moderationTaylor of urban heat island effect as part of green infrastructure Water regulation Run-off and flood control (ditches, banks, infiltration pathways, rainfall capture reducing peak flows, transpiration, and material promoting evaporation); irrigation channelling Erosion regulation Soil retention (soil stabilisation by roots), windbreaks to reduce erosion (capture of blown/suspended soil particles) Water quality/ Removal of sediments and pollutants, purification prevention of agrochemical drift into Copyright watercourses Pest control Source of predators and parasites of crop and livestock pests Pollination Nectar, pollen and nesting resources for pollinators Natural hazard Prevention of landslides and costal erosion; reduction snow breaks for railways Boundaries and Delimitation of ownership boundaries barriers and containment of stock; prevention of agrochemical drift; defence in warfare Sense of well-being Impact of natural environment on human well-being, mental and physical health (Continued) 18 John W. Dover

TABLE 1.2 (Continued)

Type of service Specific service Function/examples of service Provisioning Food Human: fruit, nuts, foraged salad and vegetable services items, ‘wildflower’ and berry wine materials, flavourings for speciality liquors (e.g. sloe gin). Stock: fodder (e.g. ash and elm) Fibre Timber, fenceposts, wood for small turnery products/tools Fuel Wood (from trees, coppicing/cutting hedge shrubs) Biochemicals and Dyes, natural herbal remedies (medicinal pharmaceuticals plants) Ornamental resources Flowers and shrub branches Genetic resources Seeds for production of plants of local provenance Cultural services Recreation and Field sports (habitat for quarry species and ecotourism shooting stands), cross-countryFrancis walking along footpaths Cultural heritage Cultural and historicaland artefact (ancient hedge), values regional management styles, historical socio-political landscape influences (e.g. Saxon parish boundaries; UK Enclosure Act plantings) Education OutdoorTaylor classroom: natural history education + basis for a wide range of educational topics from mathematics to history Aesthetics/ Source of inspiration for visual and written inspiration art, appreciation of landscape character; material screening of development/ugly structures Sense of place Delimitation of personal space/privacy; regional identity Biodiversity services Corridors and Facilitation of movement through the stepping-stones landscape Refuges Shelter from predators, hibernation/aestivation sites CopyrightHabitat Living space for plants and animals Complementary and Provision of additional and other essential supplementary resources for mobile species resources had an interest in field sports. Field boundaries were removed, farm staff sacked and tied houses sold off; ploughing, planting, fertilising, spraying, and harvesting were all contracted in by the estate agents left in charge, and the only directly employed member of staff left on the farm was the gamekeeper (who had a radio to call the police with when illegal hare coursers intruded from London). The owner was confounded when he discovered there were few gamebirds left to shoot; hedges then had to be replanted. Introduction to hedgerows and field margins 19

Cole et al. (2009) screened the ecosystem services identified by the Millennium Ecosystem Assessment (Reid et al. 2005) and considered that 22 were relevant to English farmland conditions. Of these, they considered that 19 ecosystem services were delivered by hedgerows as part of an evaluation of UK agri-environment schemes, though in their analysis they excluded/aggregated some due to the context of their work. Some of these latter have been restored in Table 1.2, some added they did not consider relevant, as well as additional services not specifically identified. Analyses of ecosystem services often do not include biodiversity, which, of course, is a value in its own right (Cole et al. 2009). Many of the ‘regulating’ ecosystem services are mentioned in the following chapters, especially in relation to the suppression of agrochemical drift (e.g. Chapters 5 and 6), pest control (Chapter 7) and pollination (Chapter 9).

Conclusion Hedgerow networks have become fragmented over time due Francisto the pressure on agriculture to deliver increased levels of efficiency. Nevertheless, hedgerows are, in some places, the only semi-natural habitat left in some intensive farming landscapes both providing habitat for wildlife and delivering essentialand ecosystem services. The loss of farmland biodiversity has led to attempts to counter this by the development and incentivisation of agri-environmental measures and also through statute to reduce further loss. Nevertheless, hedgerows and field margins and the biodiversity they harbour face considerable challengesTaylor now and, with issues such as climate change, in the future, as will be evident from a perusal of the following chapters.

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material

Copyright APPENDIX 1.1 Studies aimed at improvingCopyright the biodiversity value of arable field margins (earlier studies reviewed by Haaland et al. 2011)

Main crop Country No. Duration Margin managementmaterial imposed Organisms studied Outcomes Source treatments

Field bean Sweden 2 2011: Field 1. Control: Crop only Plants: Pollination Landscape factors interacted Herbertsson and bean 2013: (strawberry or field bean) success of strawberry with pollination success. et al. (2018) Strawberry Strawberry 2. Sown Wildflower strip + Fragaria vesica and Adjacent to the wildflower crop (strawberry or fieldTaylor field bean Vicia faba. strips, pollination success was bean) Strawberry and field Pollinators of strawberry; depressed in heterogeneous bean studies were separate. flies, solitary bees + landscapes but enhanced Monitoring adjacent to sown other Hymenoptera in the distant crop edges. wildflower strip, and at the (not bumblebeesand or In more homogeneous edge of the crop > 160 m honeybees) and field landscapes pollination was distant; control sites monitoring bean: bumblebees + enhanced near the wildflower at one field edge. Seed honeybees monitoredFrancis strips and depressed at the mixtures in wildflower strips by direct observation distant crop edges. varied. (experimental plants were in pots) but not analysed.

Arable (no Germany 2 2012–2013 1. Hedgerow + single Hymenoptera: Species-specific and landscape Hoffmann et al. specifics wildflower strip in a predatory solitary composition differences (2018) given) 500-m-diameter area. wasps were detected. Ancistrocerus 2. Hedgerow with several Foraging/provisioning nigricornis (a hunter of crop wildflower strips within of nests of two species pests: caterpillars) built more 500-m diameter studied in relation to brood cells the closer the trap proximity to wildflower nests were to wildflower strips; strips using trap nests. but the number of brood cells also increased with a greater proportion of grassland in the study area. Fewer prey items were used to provision a cell in heterogeneous landscapes. Trypoxylon figulus (a hunter of pest predators: spiders) built fewer nests in proximity to wildflower strips. In sites with single wildflower strips, more cells were built in areas with higher levels of grassland; in sites where several wildflower strips were present, the lack of grassland was compensated for. For T. figulus wildflower strips were considered an adult rather than larval resource. Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments

Field bean Sweden 2 2011: Field 1. Control: Crop only Plants: Pollination Landscape factors interacted Herbertsson and bean 2013: (strawberry or field bean) success of strawberry with pollination success. et al. (2018) Strawberry Strawberry 2. Sown Wildflower strip + Fragaria vesica and Adjacent to the wildflower crop (strawberry or field field bean Vicia faba. strips, pollination success was bean) Strawberry and field Pollinators of strawberry; depressed in heterogeneous bean studies were separate. flies, solitary bees + landscapes but enhanced Monitoring adjacent to sown other Hymenoptera in the distant crop edges. wildflower strip, and at the (not bumblebees or In more homogeneous edge of the crop > 160 m honeybees) and field landscapes pollination was distant; control sites monitoring bean: bumblebees + enhanced near the wildflower at one field edge. Seed honeybees monitored strips and depressed at the mixtures in wildflower strips by direct observation distant crop edges. varied. (experimental plants were in pots) but not analysed.

Arable (no Germany 2 2012–2013 1. Hedgerow + single Hymenoptera: Species-specific and landscape Hoffmann et al. specifics wildflower strip in a predatory solitary composition differences (2018) given) Copyright500-m-diameter area. wasps were detected. Ancistrocerus 2. Hedgerow with several Foraging/provisioning nigricornis (a hunter of crop wildflower strips within of nests of two species pests: caterpillars) built more 500-m diameter studied in relation to brood cells the closer the trap proximity to wildflower nests were to wildflower strips; strips using trap nests. but the number of brood cells also increased with a greater material proportion of grassland in the study area. Fewer prey items were used to provision a cell in heterogeneous landscapes. Trypoxylon figulus (a hunter of pest predators: spiders) built Taylor fewer nests in proximity to wildflower strips. In sites with single wildflower strips, more cells were built in areas with and higher levels of grassland; in sites where several wildflower strips were present, the lack of Francisgrassland was compensated for. For T. figulus wildflower strips were considered an adult rather than larval resource.

(Continued) (Continued)

Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Copyright Rape and Belgium 5 2013–2015 1. Control: Grass (G) only Invertebrates: Pollinator richness was lowest Uyttenbroeck winter 2013/14: Rape sown. pollinating species in the control. Pollinator et al. (2017) wheat 2014/2015: 2. G+ Very low Functional Insects searching for floral species richness and evenness Winter Diversity (FD) Wildflowers rewards monitored via were not positively affected wheat (WF) sown. transects; pollinator by increasing levels of 3. G + Lowmaterial FD WF. networks monitored in plant functional diversity 4. G + High FD WF. permanent quadrats. in wildflower sowings and 5. G + Very high FD WF resulted in less flower visiting Functional diversity treatments rather than more. created from a mixture of 7 plant species/treatment assessedTaylor on flower colour, flower type, UV reflection, presence of a UV pattern, flowering period, plant height from a pool of 20 species. A mix of 3 grasses also and sown with the wildflowers Rape and Belgium 5 2013–2015 As for Uyttenbroeck et al. Invertebrates: High functional diversity (FD) Hatt et al. (2017) winter 2013/14: Rape (2017) aphid predatorsFrancis of wildflower sowings did wheat 2014/2015: (Chrysopidae, not correlate with increased Winter Coccinellidae; Syrphidae) abundance or richness of aphid wheat Invertebrates sampled predators. Coccinellidae were using pan traps. more strongly associated with low or intermediate levels of FD. Suggested that individual species, not present in all treatments, caused the response.

Winter wheat Switzerland 2 2014 1. Control: winter wheat Invertebrates: cereal Eggs and larvae of cereal leaf Tschumi et al. crop. leaf beetles beetle and crop damage (2016a) 2. Existing perennial (Oulema sp.) were reduced on wheat wildflower (sown) strip Beetle egg and larval plants adjacent to wildflower abundance (and crop sowings at 5-m but not 10-m damage) assessed at distance. Wheat yields were 5 m and 10 m from higher at both 5- and 10-m wildflower strips or distance where wildflower equivalent width strips present. control (crop) margins by direct observation; adults sampled by sweep netting. Potato Switzerland 2 2013 1. Control: Potato crop Invertebrates: potato Abundance of Syrphidae, Tschumi et al. (nominal 3 m margin). aphids, Syrphidae, Chrysopidae and Coccinellidae (2016b) 2. Annual wildflower sowing Chrysopidae and was greater in wildflower (3 m margin) Coccinellidae strips than in potato crop Aphids and eggs/larvae of controls as was syrphid species their natural enemies richness (coccid and chrysopid and parasitised aphids richness not assessed). More directly counted on chrysopid and syrphid eggs potato leaves 1 m and were laid on potatoes adjacent 10 m from wildflower to wildflower sowings and, strip or potato control. aphid abundance on adjacent Flying natural enemies potatoes was reduced by 75%. monitored using cornet traps inside wildflower and potato margin strips and at 10-m distance into the crop. Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Rape and Belgium 5 2013–2015 1. Control: Grass (G) only Invertebrates: Pollinator richness was lowest Uyttenbroeck winter 2013/14: Rape sown. pollinating species in the control. Pollinator et al. (2017) wheat 2014/2015: 2. G+ Very low Functional Insects searching for floral species richness and evenness Winter Diversity (FD) Wildflowers rewards monitored via were not positively affected wheat (WF) sown. transects; pollinator by increasing levels of 3. G + Low FD WF. networks monitored in plant functional diversity 4. G + High FD WF. permanent quadrats. in wildflower sowings and 5. G + Very high FD WF resulted in less flower visiting Functional diversity treatments rather than more. created from a mixture of 7 plant species/treatment assessed on flower colour, flower type, UV reflection, presence of a UV pattern, flowering period, plant height from a pool of 20 species. A mix of 3 grasses also sown with the wildflowers Rape and Belgium 5 2013–2015 As for Uyttenbroeck et al. Invertebrates: High functional diversity (FD) Hatt et al. (2017) winter 2013/14: Rape (2017) aphid predators of wildflower sowings did wheat 2014/2015: (Chrysopidae, not correlate with increased Winter Coccinellidae; Syrphidae) abundance or richness of aphid wheat Invertebrates sampled predators. Coccinellidae were using pan traps. more strongly associated with low or intermediate levels of FD. Suggested that individual species, not present in all treatments, caused the response.

Winter wheat Switzerland 2 2014 1. Control: winter wheat Invertebrates: cereal Eggs and larvae of cereal leaf Tschumi et al. crop. leaf beetles beetle and crop damage (2016a) Copyright2. Existing perennial (Oulema sp.) were reduced on wheat wildflower (sown) strip Beetle egg and larval plants adjacent to wildflower abundance (and crop sowings at 5-m but not 10-m damage) assessed at distance. Wheat yields were 5 m and 10 m from higher at both 5- and 10-m wildflower strips or distance where wildflower equivalent width strips present. material control (crop) margins by direct observation; adults sampled by sweep netting. Potato Switzerland 2 2013 1. Control: Potato crop Invertebrates: potato Abundance of Syrphidae, Tschumi et al. (nominal 3 m margin). aphids, Syrphidae, Chrysopidae and Coccinellidae (2016b) 2. Annual wildflower sowingTaylor Chrysopidae and was greater in wildflower (3 m margin) Coccinellidae strips than in potato crop Aphids and eggs/larvae of controls as was syrphid species their natural enemies richness (coccid and chrysopid and parasitisedand aphids richness not assessed). More directly counted on chrysopid and syrphid eggs potato leaves 1 m and were laid on potatoes adjacent 10 m from wildflowFranciser to wildflower sowings and, strip or potato control. aphid abundance on adjacent Flying natural enemies potatoes was reduced by 75%. monitored using cornet traps inside wildflower and potato margin strips and at 10-m distance into the crop.

(Continued) (Continued)

Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Copyright Winter wheat Switzerland 2 2005 1. Winter wheat with a sown Invertebrates: Abundance of carabids (activity Anjum-Zubair grass margin. Coleoptera: Carabidae density) was higher in the crops et al. (2015) 2. Winter wheat with a sown Beetles sampled using than in the grass or wildflower wildflower margin pitfall traps set in the margins. Following rarefaction strips and 30 m into the analysis, sown wildflower strips material interior of the crop in had higher species richness spring. than in wheat fields and sown grass strips. Sown wildflower strips and grass margins had different carabid communities Taylor to wheat crops. Winter wheat Switzerland 2 2012 1. Control: Winter wheat Invertebrates: cereal Larvae of cereal leaf beetle, Tschumi et al. crop (nominal leaf beetles emerging adults, and crop (2015) 3 m margin). (Oulema sp.) + damage were reduced on 2. Annual wildflower sowing natural enemies: wheat plants adjacent to (3-m margin) predatoryand Hemiptera , wildflower sowings. The Coccinellidae, reduction in crop damage was Neuroptera, Syrphidae, greatest in the zone furthest Carabidae. Francisfrom the wildflower sowing. Beetle egg and larval Adults of natural enemies abundance (and crop were higher in wildflower damage) assessed in two strips than in the equivalent zones (0.5–10.4 m and control wheat margins. 10.5–20.4 m) from the Predatory Hemiptera were wildflower strips more abundant in the crop

or equivalent width adjacent to wildflower control (crop) margins sowings, as were carabids by direct observation; (latter only in the nearest adults sampled by sweep sampling zone to the strips). netting. All natural enemies except carabid beetles were sampled using sweep netting; beetles via pitfall traps. Reed canary Finland 2 2007–2010 1. Control: Reed canary grass Invertebrates: Bumblebee abundance Korpela et al. grass crop/ permanent field bumblebee abundance and species richness of (2013) (bioenergy boundaries /adjacent cereal + species richness invertebrates was enhanced crop) crop. of bumblebees, in wildflower strips for the 2. Wildflower sowings. butterflies and day- first 3 years then declined At each replicate, flying moths in year 4. Specialist butterfly wildflower sowings were Abundance and species abundance increased more established in 6 different richness assessed on slowly than the other orientations/plot sizes. transects. Evaluations indicators and was influenced Five sowings used the same made separately of three by the proportion of forest seed mixture, one was a aspects: bumblebee cover in the landscape. Flower monoculture of Centaurea abundance (pollination), abundance was particularly jacea. Control plots had the combined species important for maintaining similar orientations as the richness of the 3 bumblebee abundance; and wildflower plots invertebrate groups re-sowing was probably (diversity) and the required to maintain local richness of habitat flower quality over time. specialist butterflies (biodiversity). Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Winter wheat Switzerland 2 2005 1. Winter wheat with a sown Invertebrates: Abundance of carabids (activity Anjum-Zubair grass margin. Coleoptera: Carabidae density) was higher in the crops et al. (2015) 2. Winter wheat with a sown Beetles sampled using than in the grass or wildflower wildflower margin pitfall traps set in the margins. Following rarefaction strips and 30 m into the analysis, sown wildflower strips interior of the crop in had higher species richness spring. than in wheat fields and sown grass strips. Sown wildflower strips and grass margins had different carabid communities to wheat crops. Winter wheat Switzerland 2 2012 1. Control: Winter wheat Invertebrates: cereal Larvae of cereal leaf beetle, Tschumi et al. crop (nominal leaf beetles emerging adults, and crop (2015) 3 m margin). (Oulema sp.) + damage were reduced on 2. Annual wildflower sowing natural enemies: wheat plants adjacent to (3-m margin) predatory Hemiptera, wildflower sowings. The Coccinellidae, reduction in crop damage was Neuroptera, Syrphidae, greatest in the zone furthest Carabidae. from the wildflower sowing. Beetle egg and larval Adults of natural enemies abundance (and crop were higher in wildflower damage) assessed in two strips than in the equivalent zones (0.5–10.4 m and control wheat margins. 10.5–20.4 m) from the Predatory Hemiptera were wildflower strips more abundant in the crop

or equivalent width adjacent to wildflower control (crop) margins sowings, as were carabids Copyright by direct observation; (latter only in the nearest adults sampled by sweep sampling zone to the strips). netting. All natural enemies except carabid beetles were sampled using sweep netting; beetles via pitfall traps. Reed canary Finland 2 2007–2010 1. Control:material Reed canary grass Invertebrates: Bumblebee abundance Korpela et al. grass crop/ permanent field bumblebee abundance and species richness of (2013) (bioenergy boundaries /adjacent cereal + species richness invertebrates was enhanced crop) crop. of bumblebees, in wildflower strips for the 2. Wildflower sowings. butterflies and day- first 3 years then declined At each replicate, flying moths in year 4. Specialist butterfly wildflower sowings wereTaylor Abundance and species abundance increased more established in 6 different richness assessed on slowly than the other orientations/plot sizes. transects. Evaluations indicators and was influenced Five sowings used the same made separately of three by the proportion of forest seed mixture, one was a aspects:and bumblebee cover in the landscape. Flower monoculture of Centaurea abundance (pollination), abundance was particularly jacea. Control plots had the combined species important for maintaining similar orientations as the richness of the Francis3 bumblebee abundance; and wildflower plots invertebrate groups re-sowing was probably (diversity) and the required to maintain local richness of habitat flower quality over time. specialist butterflies (biodiversity).

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Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Arable UK 10 2008–2009 1. Control: grass strip. Invertebrates: spiders Wildflowers established well in Blake et al. rotation Copyright2. Scarified+wildflower Spider abundance and the sown plots and did best (2013) sowing. richness sampled using where both herbicide and 3. Scarified+wildflower suction. scarification were applied. sowing + full-rate Trends in spider abundance graminicide (once annually). were linked to scarification, 4. Scarified+wildflower sowing herbicide, and sown + full-ratematerial graminicide wildflowers. (once, in year 1 only). 5. Scarified+wildflower sowing + full-rate graminicide (twice, in Year 2 only). 6. Scarified+wildflower sowing + half-rate Taylor graminicide (once annually). 7. Scarified+wildflower sowing + half-rate graminicide (once, in year 1 only). and 8. Scarified+wildflower sowing + half-rate graminicide (twice, in Year 2 only). Francis 9. Full-rate graminicide (once, in year 1 only). 10. Full-rate graminicide (once annually). Treatments carried out on the outer 4 m of existing (planted 2004/5 depending on site) grass buffer strips

Arable UK 4 2008–2009 1. Control: grass strip. Invertebrates: Wildflowers established well in Blake et al. rotation 2. Full-rate selective butterflies the sown plots and did best (2011) graminicide applied to Abundance and species where both herbicide and grass strip. richness assessed on scarification were applied. 3. Soil scarification applied transects. Butterfly abundance, diversity to grass strip + wildflower and richness were best sowing. where both scarification and 4. Selective half-rate herbicide graminicide were used with + scarification + wildflower wildflower sowings and were sowing. Treatments carried also influenced by the species out on the outer 4 m of richness of the wildflower existing (planted 2004) grass community that established. buffer strips Arable Switzerland 2 2008 1. Control: extensive Invertebrates: The abundance of butterflies Haaland and rotation grassland. butterflies was greater in wildflower strips Bersier (2011) 2. Sown wildflower strips Abundance and species than in extensive grasslands. (1–7 years old) richness assessed on Species composition is distinct transects in wildflower between the two types of strips and extensive site, with commoner species grasslands. dominating the wildflower strips. However, one habitat specialist was found only in the wildflower strips – its hostplant was uncommon in the meadows but present in the strips. Several species bred in the strips. Wildflower strips, flower abundance and the presence of forest nearby positively influenced species richness. Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Arable UK 10 2008–2009 1. Control: grass strip. Invertebrates: spiders Wildflowers established well in Blake et al. rotation 2. Scarified+wildflower Spider abundance and the sown plots and did best (2013) sowing. richness sampled using where both herbicide and 3. Scarified+wildflower suction. scarification were applied. sowing + full-rate Trends in spider abundance graminicide (once annually). were linked to scarification, 4. Scarified+wildflower sowing herbicide, and sown + full-rate graminicide wildflowers. (once, in year 1 only). 5. Scarified+wildflower sowing + full-rate graminicide (twice, in Year 2 only). 6. Scarified+wildflower sowing + half-rate graminicide (once annually). 7. Scarified+wildflower sowing + half-rate graminicide (once, in year 1 only). 8. Scarified+wildflower sowing + half-rate graminicide (twice, in Year 2 only). 9. Full-rate graminicide (once, in year 1 only). 10. Full-rate graminicide (once annually). Treatments carried out on the outer 4 m of existing (planted 2004/5 depending on site) grass buffer strips

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Main crop Country No. Duration Margin management imposed Organisms studied Outcomes Source treatments Copyright Arable UK 5 1999–2002 1. Control: arable crop. Invertebrates: Natural regeneration resulted in Pywell et al. rotation 2. Cultivation + natural butterflies, a species-poor, agronomically (2011) regeneration. bumblebees, Araneae, unacceptable sward with a 3. Basic (5 sp.) tall grass seed Opiliones, Coleoptera, high species turnover, unlike mix sown. Heteroptera, Formicidae, tall grass sowings, which were 4. 3-m-widematerial wildflower Chilopoda, Diplopoda stable but species poor and sowing adjacent to and Isopoda. dense. Wildflower sowings, boundary + 3-m-wide Butterflies and bumblebees which included legumes and basic tall grass sowing were monitored using grass-regulating hemi-parasites adjacent to crop (split transects; surface-active (Rhinanthus sp.), produced margin). Taylorspecies were sampled the richest plant community, 5. Wildflower + grass seed using pitfall traps and excluded pernicious weeds mixture (8 sp.). All plots canopy invertebrates and supported a rich and 6 m wide and adjacent to with sweep nets. Soil abundant pollinator and hedges cores were used to herbivore community and identifyand overwintering had a greater abundance of invertebrates. predatory species. Francis