į Agricultural landscape divided by linear features, Northumberland • © Natural England • Graeme Peacock 5. Boundary and Linear Features Broad Habitat Summary Length and change • The total length of woody linear features was • The total length of woody linear features decreased by 547,000km in England in 2007, and was distributed 1.4% (8,000km) in England between 1998 and 2007 mainly between the Easterly and Westerly Lowlands following an increase between 1990 and 1998 and a Environmental Zones. decrease between 1984 and 1990. • The total length of managed hedgerows1 was • The length of managed hedgerows1 decreased by 402,000km in England in 2007, and was distributed 6.1% (26,000km) in England between 1998 and 2007 mainly between the Easterly and Westerly Lowlands with a large proportion of these managed hedges Environmental Zones. turning into lines of trees and relict hedges (which increased signifi cantly), refl ecting a reduction in • The total length of walls was 82,000km in England and management intensity. was distributed mainly in the Uplands and Westerly Lowlands Environmental Zone. • The length of walls decreased by 1.1% (approximately 900km) overall in England between 1998 and 2007, • The total length of banks and grass strips was with the largest losses occurring in the Uplands 42,000km, with much of this in the Westerly Lowlands Environmental Zone. Environmental Zone. 1 The term ‘managed hedgerows’ does not include relict hedges and lines of trees. Countryside Survey: England Results from 2007 CHAPTER 5 • Boundary and Linear Features Broad Habitat 70 Condition • Although there was no change in species richness, there was a shift in community structure and roadside • Species richness in vegetation alongside linear vegetation became more shaded and characteristic and boundary features in England increased by of less acidic conditions in England, between 1978 approximately 3% (from 16.5 to 16.9 species per plot) and 2007. between 1998 and 2007, which was not signifi cant, but there was a signifi cant decrease of approximately 7% • Approximately 25% of walls were in either ‘sound’ or (from 16.1 to 14.9 species per plot over the long-term, ‘excellent’ condition in both 1998 and 2007. The majority between 1978 and 2007, which was less than the 15% of walls across England were in ‘deteriorating’ condition decrease across Great Britain. in both 1998 and 2007. • Following signifi cant decreases in plant species richness along the base of hedges between 1978, 1990 and 1998, no change was detected in England between 1998 and 2007. Stress tolerating plant species increased whilst those of open ground decreased. Plant species characteristic of shaded, fertile and less acidic conditions increased between 1978 and 2007. • There was on average 3.7 woody species per 30m section of hedge in England in 2007, with no detectable change between 1998 and 2007. • 50% of managed hedges were in good structural condition in England in 2007 including criteria for the height of the base of the hedge canopy, cross- sectional area, hedge ‘gappiness’ and the absence of non-native species. į Dry stone walls, North Yorkshire • © Natural England • Dave Key • 32% of managed hedges were in good structural condition and had margins >2m in England in 2007. 2 Only 12% of managed hedges on arable land were in 5.1 Introduction both good structural condition and had appropriately managed margins in England in 2007. A higher proportion The Boundary and Linear Features Broad Habitat includes many of English hedges were in good condition compared to landscape features which characterise the British landscape and Great Britain. refl ect the history of its management. Features such as stone walls and species-rich hedgerows help to distinguish diff erent parts of • No change in plant species richness was detected in the countryside and provide them with landscape character and a Roadside Plots in England between 1998 and 2007, regional identity. and unlike the results for Great Britain there was no signifi cant decline between 1978 and 2007. Whilst the historic role of linear features has been largely to mark boundaries and manage stock, ecologically they constitute a very • Stress-tolerating species increased signifi cantly in signifi cant Broad Habitat within farmland. Hedgerows in England Roadside Plots across Great Britain between 1998 and provide signifi cant habitat for 125 priority BAP species: 70% of 2007, at the expense of ruderal species which showed these are species are relatively numerous and widespread but are a signifi cant decrease. The signifi cant increase in Stress known to be declining rapidly. As well as providing a refuge for Tolerators, and the signifi cant decrease in Ruderal and woodland and farmland species unable to persist in fi elds, Light Scores in Roadside Plots across England was also the Boundary and Linear Features Broad Habitat can provide detected in the Easterly Lowlands Environmental Zone. corridors for the movement and dispersal of a range of species. There was also a small but signifi cant increase in the Hedgerows also provide a large number of other ecosystem services number of butterfl y caterpillar food plans in Roadside such as provisioning, cultural and aesthetic landscape quality, and Plots in the Easterly Lowlands Environmental Zone carbon sequestration. Earlier fi ndings from Countryside Survey3 (CS) between 1998 and 2007. showed that there was a signifi cant loss of linear features in the landscape between 1984 and 1990. Recognition of the important 2 Note: For further information on the Broad Habitat classifi cation, sampling plots and other Countryside Survey terminology see Chapter 1 (Introduction and Methodology) 3 See: Countryside Survey 1990 Series: Summary Report (1993). DoE, London. 71 Countryside Survey: England Results from 2007 CHAPTER 5 • Boundary and Linear Features Broad Habitat contribution of these features for biodiversity and concern about The condition of vegetation associated with hedgerows has been their rapid loss led to legislation being introduced in England and recorded since the fi rst CS in 1978 using a 10m x 1m plot (Hedge Wales in 1997 to regulate hedgerow removal. The fi ndings of CS Plot) placed alongside hedgerows to sample vegetation forming in 1998 showed no signifi cant decrease in the lengths of either the hedge an along the hedge base. Numbers and types of plots hedges or walls between 1990 and 1998. were increased in subsequent Countryside Surveys to provide information on boundaries and on specifi c feature types in addition Hedgerows are listed as a Priority Habitat in the UK and have a to the original Hedge Plots. These include plots in which vegetation Biodiversity Action Plan4 (see Box 1.1, UK results from 2007 alongside boundary features was recorded; Roadside Plots which report); conservation targets have been agreed, based on measures were introduced to sample vegetation alongside roads and tracks; of the extent and condition of hedgerows over time. Various criteria and Hedge Diversity Plots, which provide information about the are being used to measure change in condition: some are structural woody species within hedges, but may also be used on other types (e.g. cross-sectional area) and others relate to species composition of woody linear feature. These latter plots span the width of the and to adjacent margin management. In this report, condition criteria hedgerow and are 30m long. Alongside species information, other were only applied to managed hedgerows. data on the condition of hedgerows and other types of woody linear features were collected at Hedgerow Diversity Plots in 2007. 5.2 Reporting on Boundary and Results from the Streamside Plots are included in the Rivers and Linear Features Broad Habitat Streams Broad Habitat, covered in Chapter 8; linear Managed Margin Plots are included in the Arable and Horticulture Broad Habitat in Chapter 3. Results for all other linear plot types are The Countryside Surveys of 1984, 1990, 1998 and 2007 reported here. incorporated mapping of Boundary and Linear Features Broad Habitats as part of the habitat mapping of the whole survey square. Data collected on linear features during the mapping of CS squares Improvements in the methodology and in defi nitions of feature also provide information on the type and condition of the diff erent types over time have enabled more consistent national estimates feature types, some of which are reported here. to be made. For example, defi ning hedges is not a simple process because woody boundary features vary from established species- Ĭ rich hedgerows to a line of newly planted saplings or lines of Table 5.1: Boundary and Linear Feature types remnant scrub, and combinations of these features. The importance Linear Features Description/condition criteria of tight defi nitions became more evident over time and, as with the A line of woody vegetation that has been Broad Habitat data, the most reliable and comparable estimates are subject to management so that trees no longer Hedges for the most recent CS (1998 and 2007). The need to address policy take their natural shape. Hedges may be present with any feature below. questions has required development of more robust defi nitions in the current CS of 2007; the use of surveyor input to help revise the A built structure of natural stone or manufactured blocks, mostly of traditional dry 1998 data has reinforced this (see Chapter 1 of the UK results Wall stone wall construction but including mortared from 2007 report 5). A further complication with linear features is walls. Includes walls with fences or banks/grass that they occur as continuous networks and also as features with strips and/or lines of trees or shrubs. Line of trees or shrubs, in which trees/shrubs several elements adjacent to or often overlapping with one another, Line of trees/ take their natural shape, including those e.g.