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SEPG 1779 - Date Awarded 2000

Evaluation of the status and ecological value of green lanes

J.W. Dover

Abstract

Green lanes are composed of an unmetalled farm track with field boundaries either side; boundaries can be grass banks, hedges, wood edge or stone walls. We describe studies on the basic dimensions and structure of green lanes, and their botanical composition. The importance, status and protection of green lanes are discussed as well as their potential role within agri-environment schemes for promoting biodiversity in the wider countryside.

Introduction

Field boundaries are usually recognised as grass banks, hedges, wood-edges or stone walls. In some cases there may be an associated ditch or farm track between the field boundary and the crop. A green lane is composed of a farm track with field boundaries either side. The size of the track should be enough to permit farm traffic (stock or tractor) and therefore excludes narrow footpaths. This definition would also exclude tracks enclosed for their whole length with woodland on both sides (a woodland ride) or tracks that have been metalled or completely surfaced with stone. Some green lanes are over 2000 years old and cultural monuments in their own right (Belsey, 1998), but some of the physical attributes of green lanes could be created over much shorter timescales.

For the purposes of the UK Countryside Survey methodology (Barr et al., 1993), green lanes are not recorded as discrete landscape elements. Currently no accurate estimates exist for the UK stock of green lanes, loss/gain statistics or any physical or biological parameters. In 1976 unsurfaced roads and green lanes were estimated by Belsey (1998) to have a total extent of 8480km. The highway status of green lanes is variable e.g. bridleway (foot, horse and bicycle access), BOAT (byway open to all traffic), footpath (pedestrian traffic only) RUPP (Road used as public path), PROW (Public right of way), ROW (right of way). There is no unified status for green lanes, which makes policy and conservation difficult (Belsey, 1998).

The ecological value of green lanes is not well understood. For example Belsey (1998) concentrates on the features of green lanes derived from hedgerow literature rather than from green lanes as a landscape unit. In this report new data is presented on the basic structural parameters of green lanes from a study in Cheshire.

Structural Features of Green Lanes

A survey of green lanes in Cheshire was carried out between the 18/7/2000 and 29/8/2000 to produce basic statistics on the structure and dimensions of green lanes and their botanical characteristics. Five Ordnance Survey ‘Pathfinder’ map sheets (Nos: 757, 758, 774, 775 and 790) with an aggregate area of  approximately 1000km² (Figure 1) were visually assessed for  potential green lanes, additional information on potential green lane locations was given by Malcolm Ainsworth (Cheshire County Council Footpaths Officer). Each potential green lane identified was visited, and if fitting a minimum set of criteria, was then surveyed (see Introduction, paragraph 1).  In addition to basic dimensional data (determined by pedometer and tape measure) five randomly selected positions along the length of the green lane were surveyed for botanical composition. At each point the woody element composition of the boundary structure (e.g. hedge, wood edge) was determined by recording the species incidence in a 10m linear section of the boundary on each side of the track (the incidence of the woody climbers bramble (Rubus fruticosus) and dog rose (Rosa canina) were also recorded). In addition, the ground flora were surveyed by recording from a 1m² quadrat placed on each boundary bank in turn, and also in the mid-line of the track (Figure 2) and the condition of the track and any ‘Threatening processes’ identified. This latter category reflected any process which would modify an idealised green lane similar to that depicted in Figure 2, i.e. one with a well vegetated track and largely intact boundary features.

Within the survey area 46 green lanes were surveyed. These green lanes, in some cases, included contiguous lengths which were interrupted by other green lanes branching off them, sharp changes in direction, or where some other feature made subdivision appropriate. The total length of green lanes surveyed was 20.856km, the mean length of a green lane was 453+4m, the shortest being 57m long and the longest 1,245m. The length of the boundary hedges was recorded from a subset of 33 green lanes and gave a total length of 26.7km from a total green lane length of 14.1km (i.e. 189% of the green lane length). Mean hedge length/green lane was 810+8m (min.: 114m, max.:1898m) cf mean green lane length of 427+4m (min.: 57m, max.: 949m). Ditch incidence was recorded, but vegetation overgrowth made length determination impractical: 31 of the 46 green lanes had at least one ditch. The mean species richness of the green lanes (derived from the boundary and track species surveys) was 36.1+1.0. Subdivisions of the species richness data and other metrics are given in Figure 2.

Only 26% of green lanes were considered to have an undamaged grass track, with the majority 45%) having grass + tractor wheel ruts (Table 1). Hedge management was principally by tractor-mounted flail (76%) whilst the remaining green lane hedges appeared to be unmanaged. Twenty-eight percent of green lanes had no threatening processes evident, with farm vehicle erosion (24%) being the most frequent process identified (Table 2).

Figure 1 The Cheshire green lanes study area. Map outline gives the boundaries of Cheshire. Shaded areas not surveyed; rectangles relate to coverage by OS 1:25000 Pathfinder maps. Dots indicate positions of green lanes surveyed.

Figure 2 Anatomy of Cheshire Green Lanes. Statistics derived from a survey of 46 green lanes

The general picture that has emerged from the above studies is that green lanes are of low incidence, and often occur in clusters (Figure 1). The stock of green lanes detected probably does not represent all the green lanes in the study area, as searching maps for potential lanes is unlikely to reveal all actual green lanes. Within the study area there appears to be a clustering of green lanes in the western half of the study area. Examination of the surveyor returns showed that many potential green lanes in the eastern part of the study area were rejected because of the status of the track (sealed surface). However some potential green lanes were missed during the survey (for example four in sheet 775 and 1 in sheet 758).

There has been some concern concerning the potential for off-road driving activities to cause damage to green lanes (Dover et al., 2000). This does not appear to be a significant factor in green lane condition in the Cheshire lanes surveyed, with farming activities more likely to cause churning of the track. Recreational activities whether caused by vehicles, horse-riding or walking affected only 9% of the green lanes examined (Table 2). Interestingly, some of the green lanes appear to be threatened by neglect, if these remain unmanaged they may well become linear woods rather than green lanes. A preliminary inspection of the botanical data indicated a different, and impoverished, mid-line flora compared with the banks, but also that the mid-line flora contained some species not found in the banks. Moderate disturbance of the track is likely to be beneficial for overall botanical species richness and may provide micro-habitats for invertebrates using bare-earth habitats.

Discussion

The study of green lanes in Cheshire is strongly suggestive of a small and possibly declining stock of green lanes. Several sites visited but rejected for study were of a similar dimension to surveyed green lanes, but differed in that they had sealed surfaces. It is likely that where frequent access is required, green lanes have been surfaced. As Sparks et al. (1999) pointed out, not all green lanes will be of equal value to a particular species or group of species, and that green lanes need management to remain open and retain their benefit as wildlife habitat, agricultural movement corridors and places for countryside recreation.

The data so far available on green lanes strongly suggests that they are valuable as biodiversity reservoirs in actively farmed landscapes. Data, particularly on butterflies, is compelling coming from both upland and lowland sites and from studies with a wide geographical separation within England. Comparative studies (Dover & Sparks, 2001) have clearly shown that for plants and butterflies that green lanes are superior to other field boundary habitats. The likely reasons include: the enhanced shelter and modified microclimate found in green lanes; their  historical continuity – some with known continuity of existence over thousands of years (Belsey, 1998); their lower agricultural inputs, compared with adjacent field boundaries; relatively low management regimes; high structural diversity (almost double the length of hedgerow, high and wide banks, areas of bare ground for colonisation, etc).

As green lanes do appear to be different in terms of botanical and structural composition compared with other farmland habitats, it is likely that other species benefit from the same features. For example farmland birds may well find green lanes a better refuge and foraging ground than grass banks or single hedged boundaries. Many of the features of green lanes are accrued over time (e.g. enhanced plant species complement), but some can be created over a very short time-span: shelter can be enhanced within a few years of  planting a new hedge parallel to an existing one, vegetation structure can similarly change over a short time-span by modifying management intensity. Green lanes may be highly cost-effective in terms of  environmental benefits and would make suitable structures for habitat enhancement and creation within agri-environment schemes. Although there appears to be loose protection for green lanes within the existing Hedgerow Regulations (Sparks et al., 1999), their vulnerability to destruction by resurfacing (compare the concrete green lanes and hedged tracks with their grass counterparts above) requires stronger levels of protection than currently exists and their recognition as important landscape elements by development of a specific planning status. We also need studies based on a wider range of taxa.

Acknowledgements

We acknowledge the field assistance of  W. Fells and P. Howe. We are indebted to M. Taylor of Cheshire County Council for background on green lanes. The Cheshire green lanes survey was supported with a British Ecological Society Small Projects Grant (No: 1779).

References

Barr, C.J.; Bunce, R.G.H.; Clarke, R.T.; Fuller, R.M.; Furse, M.T.; Gillespie, M.K.; Groom, G.B.; Hallam, C.J.; Hornung, M.; Howard, D.C. & Ness, M.J. (1993) Countryside Survey 1990.  Main Report. Department of the Environment, London.

Belsey, V. (1998) The Green Lanes of England, Green Books Ltd, Totness.

Dover, J.W. & Sparks, T.H. (2001). Green lanes: biodiversity reservoirs in farmland? In Hedgerows of the World: their ecological functions in different landscapes (eds C.J. Barr & S. Petit). IALE(UK), Lymm (in press).

Dover, J.W., Sparks, T., Clarke, S., Gobbett, K., & Glossop, S. (2000) Linear features and butterflies: the importance of green lanes. Agriculture, Ecosystems & Environment, 80, 227-242.

Sparks, T.H., Hann, J.P., & Greatorex-Davies, J.N. (1999) The influence of field boundary structure on butterflies. Aspects of Applied Biology 54: 235-240.

Note: This report is a modified component of ‘Dover, J.W. & Sparks, T.H. (2001). Green lanes: biodiversity reservoirs in farmland? In Hedgerows of the World: their ecological functions in different landscapes (eds C.J. Barr & S. Petit). IALE(UK), Lymm.’ to be published on the 5^th September 2001.

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