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The extent and condition of heather on moorland in the uplands of England and Wales
Biological Conservation 71 (1995) 155-161 Elsevier Science Limited Printed in Great Britain ELSEVIER
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THE EXTENT A N D CONDITION OF HEATHER ON M O O R L A N D IN THE U P L A N D S OF E N G L A N D A N D WALES R. D. Bardgett,* J. H. Marsden English Nature, North-West Regional Office, Blackwell, Bowness-on-Windermere, Cumbria, UK, LA23 3JR
& D. C. Howard Institute of Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands, Cumbria, UK, L A l l 6JU (Received 2 June 1993; revised version received 25 November 1993; accepted 6 December 1993)
INTRODUCTION
Abstract
The extent and condition of heather on moorland in England and Wales, and within different biogeographic regions, were estimated from a survey of 122 1-kin squares. The sample was stratified using the ITE Land Classification, selecting only squares from the upland land classes (i.e. 17-28). Taking England and Wales together, the estimated areas of moorland, and heather on moorland, were 14150 + 810 and 11440 + 790 km:, respectively. The results suggest that a large proportion (47%) of the heather on moorland in England was dominant (> 50% cover) and in good condition, and only a small proportion (24%) showed growth forms associated with overgrazing and management neglect. In Wales, 43% of the heather was suppressed (< 25% cover) and 38% showed signs of over-grazing and management neglect. The estimated areas of heather with greater than 25% ground cover in England and Wales were 4030 + 530 and 2990 + 560 km 2, respectively. In terms of regional distribution, most heather was found to be within the west Midlands (3 410 +_260 km2), south Wales (2 930 + 250 km2), and north-east England (2540 + 320 km 2) biogeographic regions. In north and south Wales, and south-west England, a large proportion of the heather was suppressed or damaged, probably by over-grazing, neglect or inappropriate management. In the more northerly biogeographic regions, where large areas of moorland are managed for red grouse Lagopus scoticus, the heather was in better condition. A large proportion of suppressed and~or damaged heather was found to be within land class 17, which predominates in Wales, the west Midlands and southwest England. The findings are discussed in relation to conservation and policy.
Heather moorland with mosaics of semi-natural grassland, dwarf-shrub heaths and bogs forms a distinctive habitat, and supports an ecosystem of international importance (Ratcliffe & Thompson, 1988), British heather moorlands are particularly important as they represent a substantial proportion of this habitat in Europe and support a diverse invertebrate and vertebrate fauna (Ratcliffe & Thompson, 1988; Usher & Thompson, 1993). In recent years, substantial areas of heather moorland have been lost to afforestation (Nature Conservancy Council, 1984, 1986), agricultural reclamation (Parry et al., 1981), and man-induced change to upland grasses, the last often caused by over-grazing by sheep (Felton & Marsden, 1990). In the Peak District, Anderson and Yalden (1981) estimated losses of 36%, heather moorland over the period 1913-81. Similar losses have also been recorded in Cumbria (Nature Conservancy Council, 1987) and in different regions of Scotland (Sydes, 1988). These losses have been a matter of widespread concern for nature conservation in upland Britain (Felton & Marsden, 1990). The most recent study of the extent of heather in England and Wales involved the use of satellite imagery (Bradbury et al., 1989). The resolution of the Landsat TM images restricted the measurement of heather (Calluna vulgaris only) to areas where it comprised more than 25% of the ground cover. Areas where it forms less than 25% ground cover offer potential for heather to expand and become the dominant species (Marrs & Welch, 1990). The condition of heather, in terms of morphological damage associated with over-grazing, was not assessed. The objective of this study was to determine, by ground survey of a stratified sample of 1-km squares, both the present extent and condition of heather-dominated vegetation in the uplands of England and Wales. In addition, the survey was conducted to provide an estimate of the potential for regeneration of damaged heather in England and Wales, and within different biogeographic regions.
Keywords: over-grazing, land class, heather regeneration, biogeographic-region, Calluna.
*Present address: AFRC-Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwth, Dyfed, UK, SY23 3EB. © Crown copyright (1995). 155
156
R. D. Bardgett, J. H. Marsden, D. C. Howard
For the purposes of this survey, the term 'heather' is used to describe all species of ericaceous dwarf-shrub, including common heather Calluna vulgaris, crossleaved heather Erica tetralix, bell heather Erica cinerea, bilberry Vaccinium myrtillus, and crowberry Empetrum nigrum. Moorland is a vaguer, more widely used term which carries an inherent suggestion of moderate to high elevation. The Land Utilization Survey of Great Britain (see Stamp, 1948) amalgamated moorlands with heathland, rough pasture and common land, while Hart (1955) considered moorland to be synonymous with rough grazing land. A recent comparison of land cover definitions (Wyatt et al., 1993) suggests that moorland is usually unenclosed, with the soils having a peaty top. There is overlap and an indistinct boundary between moorland, heathland and bogs: for this study any unenclosed land in the selected land classes was considered as moorland.
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METHODS Survey squares The survey covered a random sample of 122 1-km squares, stratified into eight groups using the ITE Land Classification (Bunce et al., 1991). Only squares in the upland land classes were selected, since upland heather moorland is not present in the lowland classes. Since the survey only covered England and Wales, the land classes used were 17, 18, 19, 20, 22, 23, 24 and 25 (sample squares are shown in Fig. 1). The frequency distribution of the 122 sample squares in relation to the ITE Land Classification is shown in Table I. Sites were visited between November 1990 and March 1991. A brief description of the individual ITE land classes (Bunce et al., 1991) is given in Table 2. Heather condition Percentage ground cover and height of the five ericaceous 'heather' species within each visually distinguishable stand were used as the key indicators of vegetation condition. Homogeneous stands of 'heather' larger than 1 ha were mapped at the 1 : 10 000 scale and assigned to one of three percentage ground cover categories: 1, present but < 25%; 2, 25-50%; 3, > 50%. These categories were comparable with those used by Bradbury et al. (1989) to classify heather as suppressed, sub-dominant, or dominant, respectively. The height of heather plants was recorded in three categories: <15 cm; 15-30 cm; > 30 cm. Where Calluna vulgar& was present, and its growth form suggested over-grazing, neglect or other inappropriate management, individual stands were assigned to an additional category of 'damaged heather'. This category included stands of tall, over-mature and dead heather as defined by MacDonald and Armstrong (1989) as well as 'heather' showing morphological distortion associated with over-grazing. The area (ha) of open moorland, 'heather' on moorland, and 'heather' within each of the categories of cover, height and condition was recorded for each
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i Fig. l. Geographical distribution of 1-km survey squares and location of upland biogeographic regions (MacDonald et al., 1989) within England and Wales. Biogeographic regions are numbered as: 1, north-east England (Cheviot, Kielderhead, Moor House and Cross Fell, Upper Teesdale and Durham Moors, Yorkshire Dales, Howgill Fells and Howarth Moor); 2, north-west England (Lake District and Bowland Fells); 3, North York Moors; 4, west Midlands (Peak District, Long Mynd, Clun Forest, Beacon Hill, Radnor Forest and Black Mountains); 5, north Wales (Snowdonia, Rhinogs and Berwyn Mountains); 6, south Wales (Southern Cambrian Mountains and Brecon Beacons); 7, south-west England (Dartmoor and Exmoor). square. These sample data were used to estimate total areas for both England and Wales, and for the different biogeographic regions (MacDonald et al., 1989) (Fig. 1), using the frequency distribution of land classes within each country and region given in Table 1 (mean coverage per square for each land class and the area of that land class within the region). Biogeographic regions represent the major geographic variation in moorland vegetation in England and Wales, and therefore may extend over the boundaries of both countries (e.g. west Midlands). Each region combines the broad ecological differences shaped by climate, topography
Extent and condition of heather on moorland
157
Table 1. Frequency distribution of Land Classes 17-28 and surveyed squares within England, Wales and biogeographic regions
Land class
No. of squares surveyed
England
Wales
North-east England
North-west England
17 18 19 20 21 22 23 24 25 26 27 28
53 15 12 5 0 20 8 1 8 0 0 0
3698 1952 2107 912 9 2648 688 195 1978 899 1401 894
9001 928 42 245 0 3 41 0 0 0 0 0
1516 93 181 438 7 2455 431 27 1549 87 832 395
91 606 566 135 2 74 176 166 304 627 297 371
North Yorks West Moors Midlands" 1 3 51 ll 0 0 0 0 98 159 246 48
3387 1233 1320 418 0 252 81 2 27 154 26 80
North Wales
South Wales
South-west England
1563 504 23 38 0 3 31 0 0 0 0 0
5141 421 8 113 0 0 10 0 0 0 0 0
1000 20 0 4 0 0 0 0 0 0 0 0
aThe West Midlands region extends over upland areas in both England (Peak District, Long Mynd) and Wales (Clun Forest, Beacon Hill, Radnor Forest and Black Mountain).
Table 2. Land use, types of semi-natural vegetation and soil types found in the ITE Land Classes in which sites were sampled
ITE Land Class Number
Land use
Semi-natural vegetation
17
Mainly pastures with some good grassland
Mainly rough grassland types, but some moorland
Brown earths and brown podzolics but with a range of other soils
18
Predominantly rough grazing with some limited pasture
Mainly moorland with extensive peatland and montane grassland
Brown podzolics, brown rankers, peats
19
Mainly rough grazing or forest
Mainly moorland but also mountain grass and peat types
Varied upland types but brown earths, podzols and peats the most common
20
Much pasture, but some good grassland and occasional crops
Mainly rough grassland types but some peatland
Gleys and brown earths with some other upland soil types
22
Mainly rough grazing, but some woodland and occasional crops
Mainly moorland, otherwise varied
Peaty gleys, peaty podzols, but other upland soils also
23
Limited open range grazing
Mainly moorland types, but also mountain grassland and peatland
Peats, peaty podzols and brown rankers
24
Limited open range grazing
Mainly peatland types, but also montane grassland
Brown rankers, peats or peaty podzols, some peaty gleys
25
Mainly barley
Restricted to a few grassland types
Brown earth, gleys and gleyed brown earths
and geology. Detailed descriptions of the different biogeographic regions shown in Fig. 1 are given by MacDonald and Armstrong (1989). RESULTS The total estimated area of moorland, and 'heather' on moorland, in England and Wales, was 14,150 + 810 and 11,440 + 790 km 2, respectively (Table 3). Approximately 55% of the total area of moorland, and 'heather' on moorland, was within England. Over a large proportion (47%) of moorland area in England, 'heather' was dominant (> 50% ground cover), and 24% showed growth forms associated with over-grazing, neglect and other inappropriate management ('damaged heather') (Fig. 2). In contrast, a large proportion (43%) of the total area of 'heather' in Wales was found to be
Typical soil type
suppressed (< 25% cover) and/or showing growth forms associated with over-grazing, neglect and other inappropriate management (38%) (Fig.2). Figure 3 shows that the mean coverage of suppressed 'heather' (<25% cover) per km square was greatest in land classes 23 and 17 (26 and 24%, respectively), while 'damaged heather' was most abundant in land class 17 (mean coverage of 20% per km square). Thus, both suppressed and 'damaged heather' are prevalent in Wales and other regions where land class 17 predominates(Table 1). The estimated areas of 'heather' with over 25% ground cover in England and Wales were 4,030 and 2,990 km 2, respectively (Table 3). The biogeographic regions with the greatest estimated areas of moorland were the west Midlands (4,080 km2), south Wales (3,550 kin2), and north-east England (3,340 km2), while
158
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25-50%
>50%
<15cm lS-30cm
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'lleather' categories Fig. 2. The percentage (%) abundance of 'heather' within the categories of ground cover (< 25%; 25 50%; > 50%) a n d height (< 15 cm; 15 30 cm; > 30 cm), a n d ' d a m a g e d heather', in E n g l a n d a n d Wales.
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o-tll 17
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20 21 22 Land Class
23
24
25
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the smallest area of moorland was in the North York Moors (60 km 2) (Table 3). Although the proportions of moorland with 'heather' present varied little between the different biogeographic regions, the proportions of 'heather' within the different categories of height, cover and condition varied considerably. In both north and south Wales, the proportion of 'heather' suppressed and/or showing growth forms associated with over-grazing, neglect or other inappropriate management was greater than 40% (Fig. 4). Similarly, in south-west England, a large proportion (38%) of the 'heather' was damaged by over-grazing or management neglect (Fig. 4). In the North York Moors, north-east and north-west England, however, approximately 50% of the area of 'heather' was dominant
Table 3. Estimates of total moorland, and 'heather' moorland, and different categories of height, cover and condition for England and Wales, and the biogeographic regions (all figures of area and standard errors (_+) are expressed as '000 of km z) Country
Biogeographic region
South West South Wales North Wales North-west England West Midlands North Yorks Moors North-east England England Wales England a n d Wales
Area of moorland
0.65 _+0.05 3.55 +0,26 1.28 __+0.10 1.18 0.09 4.08 -+0.26 0.06 -+0.01 3.34 0-34 7.79 _+0.47 6.36 _+0.46 14-15 _+0-81
Area of heather
0.54 -+0.05 2.93 __+0.25 1.08 __+0.09 0.90 0"09 3.41 __+0.26 0"05 __+0.01 2-54 0.32 6.19 _+0.46 5.25 _+0.45 11-44 _+0.79
Height
Cover
< 15 cm
15 30 cm
< 30 cm
< 25%
25-50°/,,
> 50%
Area of damaged heather
0.20 -+0.03 1.07 -+0.16 0-39 +0.06 0.36 -+0.06 1-24 -+0.16 0-02 __+0.00 0-95 0.16 2.31 _+0.26 1.92 +0.29 4.27 _+0.48
0.17 -+0.03 0.92 +0.16 0.35 -+0.06 0.29 -+0.05 1.06 -+0.15 0.02 __+0.00 0.86 0.17 2.01 _+0.25 1.65 _+0.29 3.66 +0-48
0.17 _+0.04 0.94 __+0.18 0.34 __+0-06 0.25 __+0.06 1.12 __+0-18 0.02 __+0.00 0.72 0.18 1.87 _+0.29 1-68 _+0.32 3.56 _+0.54
0.24 +0.04 1.27 __+0.19 0.44 -+0.06 0.29 __+0.05 1.26 __+0.16 0-01 __+0.00 0.91 0.14 2-16 +0.24 2.27 _+0-33 4.42 _+0-51
0.11 _+0.02 0.58 -+0.13 0-21 __+0.04 0.16 -+0.04 0.61 +__0.11 0-01 __+0.00 0.51 0-09 1.15 _+0.17 1.05 _+0.22 2.20 _+0.35
0.19 -+0.04 1.07 __+0.19 0.42 +0.07 0-45 -+0.07 1.54 __+0.21 0.03 -+0.01 1.12 0.24 2-88 _+0.36 1.94 _+0.34 4.82 _+0.61
0.21 +-0-03 1.11 __+0-16 0.39 __+0-06 0.17 -+0.04 1.01 __+0.14 0.01 _+0.00 0-56 0.10 1.48 _+0'29 1-98 _+0-29 3-46 _+0.45
Extent and condition of heather on moorland
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R. D. Bardgett, J. H. Marsden, D. C. Howard
(>50% ground cover), while only 15-20% showed growth forms associated with over-grazing or management neglect (Fig. 4). Little difference was found in the proportions of 'heather' in the different height categories, within the countries or biogeographic regions (Fig. 4). DISCUSSION The estimated area of moorland in England and Wales in this survey is comparable with that given by Felton and Marsden (1990). However, the results of this survey suggest that the area of 'heather' with less than 25% ground cover is approximately 20% greater than was estimated by Bradbury et al. (1989), using Landsat TM satellite imagery, despite the fact that they included areas of lowland heath. This discrepancy was probably due to the inability of the Landsat TM satellite imagery to identify areas of moorland that were dominated by bilberry V. myrtillus, particularly when less than 15 cm tall. Moorland vegetation dominated by bilberry often occurs as an intermediate stage in the grazing-induced succession from heathland to grassland (Ratcliffe, 1959), and was widely recorded in the present survey. The major difference between this survey and that of Bradbury et al. (1989) was in the relative extent of 'heather' in both England and Wales. Data from this survey suggest that 55% of the total 'heather' was within England, whereas the Landsat survey (Bradbury et al., 1989) and the 1984 ITE Countryside Survey (Barr et al., 1986), estimated 79% and 83%, respectively. The inclusion of moorland dominated by bilberry in this survey is the most likely reason for the higher estimated area of 'heather' in Wales. This study suggests that there are approximately 440,000 ha of suppressed, and therefore potentially recoverable, 'heather' (Marrs & Welch, 1990) in England and Wales. It is generally accepted that both the cover and condition of 'heather' on moorland will decline when grazing pressures exceed 1.5-2 ewes ha ~ (Lance, 1987; Bardgett & Marsden, 1992). Therefore, in order to regenerate suppressed 'heather', grazing pressures need to be reduced below this level, or removed completely for periods of the year (Felton & Marsden, 1990; Marrs & Welch, 1990). In this study, most of the suppressed 'heather' was shown to occur in the biogeographic regions of south Wales and the west Midlands, where a large proportion of the heather was also damaged by over-grazing or management neglect. Although less in total extent, a large proportion of the 'heather' in north Wales and south-west England was also suppressed and/or damaged by over-grazing and management neglect. In contrast, 'heather' on moorland in the North York Moors, north-east and north-west England was generally in good condition, with large areas where it was the dominant vegetation type. Despite this, there were considerable areas of suppressed and damaged 'heather', particularly in north-east England. The occurrence of large areas of suppressed and damaged 'heather' in north and south Wales and
south-west England is probably related to over-grazing by sheep. This suggestion is supported by the finding of Bardgett and Marsden (1992) that more than 70% of open moorland in these regions was grazed above the threshold of 1.5 ewes ha ~. In north-east and north-west England and the North York Moors, however, most of the open moorland was grazed below this level (Bardgett & Marsden, 1992). The more southerly regions are also dominated by moorland within Land Class 17, which was found to have a very high mean coverage of both suppressed and 'damaged heather', as compared with other land classes. Land Class 17 is dominated by marginal land with moderately productive brown earth and podzolic soils under pasture and improved grassland. 'Heather' moorland within this land class is often subject to periodic heavy grazing pressures by virtue of the large numbers of sheep on adjacent, more productive, grassland. The occurrence of large areas of moorland dominated by 'heather' in the more northerly regions, however, is likely to be related not only to lower grazing pressures, but also to the widespread management of moorland (e.g. burning) for red grouse. The high proportion of suppressed 'heather' found within land class 23, which predominates in northern England, is likely to be in part related to biotic limitations for growth rather than over-grazing, since this land class is dominated by rocky and precipitous slopes at high altitudes. Within these more northerly biogeographic regions where most of the 'heather' on moorland is dominant (> 50% cover) and in good condition, regional management policies are required to maintain their condition and regenerate localised areas of damaged 'heather' (e.g. moorland fringes). This survey highlights the tremendous potential to regenerate and hence increase the extent of heatherdominated moorland throughout England and Wales, and particularly in the upland areas of the west Midlands, south-west England, and north and south Wales. The case for targeting government policy to regenerate 'heather' moorland in these areas is strengthened further because they are outliers from the main upland block centred on the northern Pennines (principally the north-east and north-west of England) which are dominated by the 'classic' C. vulgaris-V, myrtillus and C. vulgaris-Eriophorurn vaginatum communities (Usher & Thompson, 1993). Moorland areas within the outlying regions are of considerable conservation importance since they represent geographical limits of heathland plant communities (e.g. Calluna-Eriophorum mire in south-west England) and provide different combinations of 'heather' species, such as the well developed Vaccinium vitis-idaea and E. nigrum heaths of the Peak District, and north and south Wales (Ratcliffe & Thompson, 1988). They also support important breeding populations of moorland birds (e.g. red grouse L. scoticus, hen harrier Circus cyaneus and merlin Falco columbarius) which are often close to the southern edge of their ranges in Britain. The abundance and diversity of moorland vertebrates and invertebrates are dependent not only on the overall extent of 'heather' moorland,
Extent and condition o f heather on moorland
but on vegetational, topographical, climatic and landuse variation within and between different biogeographic regions (Usher & Thompson, 1993). A review of conservation issues for heather moorland in Great Britain generally is given by T h o m p s o n et al. (1995).
ACKNOWLEDGEMENTS We would like to thank the many farmers, landowners, agents and gamekeepers who freely granted access to their land. Particular thanks should go to Paul Evans and Leigh Lock, who conducted much of the survey work; Bob Bunce of the Institute of Terrestrial Ecology, Merlewood Research Station, for his advice and assistance with data analysis; M a r k Felton of English Nature, for his support and guidance throughout the project; and the anonymous referees for their valuable comments on the manuscript.
REFERENCES Anderson, P. & Yalden, D. W. (1981). Increased sheep numbers and the loss of heather moorland in the Peak District, England. Biol. Conserv., 20, 195-213. Bardgett, R. D. & Marsden, J. H. (1992). Heather condition and management in the uplands of England and Wales. English Nature, Peterborough. Barr, C. J., Benefield, C. B., Bunce, R. G. H., Ridsdale, H. A. & Whittaker, M. (1986). Landscape changes in Britain. Institute of Terrestrial Ecology, Abbots Ripton, Huntingdon. Bradbury, P., Howard, D. C., Bunce, R. G. H. & Deane, G. C. (1989). Production of maps and estimates of area. In Heather in England and Wales, ed. R. G. H. Bunce. HMSO, London, pp. 5-17. Bunce, R. G. H., Howard, D. C., Clarke, R. T. & Lane, M. (1991). ITE Land Classification: classification of all 1-km squares in Great Britain. ITE, Merlewood, Grange-overSands (unpublished report). Felton, M. & Marsden, J. H. (1990). Heather regeneration in England and Wales. Nature Conservancy Council, Peterborough. Hart, J. F. (1955). The British moorlands - - a problem in land utilization Univ. Georgia Monogr., No. 2.
161
Lance, A. N. (1987). Estimating acceptable stocking levels for heather moorland. In Agriculture and conservation in the hills and uplands, ed. M. Ball & R. G. H. Bunce. ITE Syrup., No. 23, 109-15. MacDonald, A. & Armstrong, H. (1989). Methods for monitoring heather cover. Nature Conservancy Council, Peterborough. MacDonald, A., Brown, A. & Thompson, D. B. A. (1989). Heather moorland: nature conservation value and biogeographic variation. In Heather regeneration in England and Wales, Annex 3, J. H. Marsden & M. Felton. Nature Conservancy Council, Peterborough (unpublished report). Marrs, R. H. & Welch, D. (1990). Moorland wilderness: the potential effects of reduced grazing pressure. Institute of Terrestrial Ecology, Huntingdon (unpublished report). Nature Conservancy Council (1984). Nature conservation in Great Britain. Nature Conservancy Council, Peterborough. Nature Conservancy Council (1986). Nature conservation and afforestation in Britain. Nature Conservancy Council, Peterborough. Nature Conservancy Council (1987). Changes in the Cumbrian countryside. Nature Conservancy Council, Peterborough. Parry, M., Bruce, A. & Harkness, C. (1981), The plight of British moorlands. New Scient., 28, 550-1. Ratcliffe, D. A. (1959). The vegetation of the Carneddau, North Wales, I. Grasslands, heaths and bogs. J. of Ecol., 47, 371-413. Ratcliffe, D. A. & Thompson, D. B. A. (1988). The British uplands: their ecological character and international significance. In Ecological change in the uplands, ed. M. B. Usher & D. B. A. Thompson. Blackwell Scientific Publications, Oxford, pp. 3-36. Stamp, L. D. (1948). The land of Britain: its use and misuse Longmans, London. Sydes, C. (1988). Recent assessments of moorland losses in Scotland. Nature Conservancy Council, Peterborough. Thompson, D. B. A., MacDonald, A. J., Marsden, J. H. & Galbraith, C. A. (1995). Upland heather moorland in Great Britain: a review of international importance, vegetation change and some objectives for nature conservation. Biol. Conserv., 71, 163-78. Usher, M. B. & Thompson, D. B. A. (1993). Variation in the upland heathlands of Great Britain: conservation importance. Biol. Conserv., 66, 69-81. Wyatt, B. K., Greatorex Davies, N., Bunce, R. G. H., Fuller, R. M. & Hill, M. O. (1993). Comparisons of land cover definitions. Dictionary of surveys and classifications of land cover and land use. ITE Merlewood, Grange-over-Sands (unpublished report).
0006-3207(94)00042-5
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THE EXTENT A N D CONDITION OF HEATHER ON M O O R L A N D IN THE U P L A N D S OF E N G L A N D A N D WALES R. D. Bardgett,* J. H. Marsden English Nature, North-West Regional Office, Blackwell, Bowness-on-Windermere, Cumbria, UK, LA23 3JR
& D. C. Howard Institute of Terrestrial Ecology, Merlewood Research Station, Grange-over-Sands, Cumbria, UK, L A l l 6JU (Received 2 June 1993; revised version received 25 November 1993; accepted 6 December 1993)
INTRODUCTION
Abstract
The extent and condition of heather on moorland in England and Wales, and within different biogeographic regions, were estimated from a survey of 122 1-kin squares. The sample was stratified using the ITE Land Classification, selecting only squares from the upland land classes (i.e. 17-28). Taking England and Wales together, the estimated areas of moorland, and heather on moorland, were 14150 + 810 and 11440 + 790 km:, respectively. The results suggest that a large proportion (47%) of the heather on moorland in England was dominant (> 50% cover) and in good condition, and only a small proportion (24%) showed growth forms associated with overgrazing and management neglect. In Wales, 43% of the heather was suppressed (< 25% cover) and 38% showed signs of over-grazing and management neglect. The estimated areas of heather with greater than 25% ground cover in England and Wales were 4030 + 530 and 2990 + 560 km 2, respectively. In terms of regional distribution, most heather was found to be within the west Midlands (3 410 +_260 km2), south Wales (2 930 + 250 km2), and north-east England (2540 + 320 km 2) biogeographic regions. In north and south Wales, and south-west England, a large proportion of the heather was suppressed or damaged, probably by over-grazing, neglect or inappropriate management. In the more northerly biogeographic regions, where large areas of moorland are managed for red grouse Lagopus scoticus, the heather was in better condition. A large proportion of suppressed and~or damaged heather was found to be within land class 17, which predominates in Wales, the west Midlands and southwest England. The findings are discussed in relation to conservation and policy.
Heather moorland with mosaics of semi-natural grassland, dwarf-shrub heaths and bogs forms a distinctive habitat, and supports an ecosystem of international importance (Ratcliffe & Thompson, 1988), British heather moorlands are particularly important as they represent a substantial proportion of this habitat in Europe and support a diverse invertebrate and vertebrate fauna (Ratcliffe & Thompson, 1988; Usher & Thompson, 1993). In recent years, substantial areas of heather moorland have been lost to afforestation (Nature Conservancy Council, 1984, 1986), agricultural reclamation (Parry et al., 1981), and man-induced change to upland grasses, the last often caused by over-grazing by sheep (Felton & Marsden, 1990). In the Peak District, Anderson and Yalden (1981) estimated losses of 36%, heather moorland over the period 1913-81. Similar losses have also been recorded in Cumbria (Nature Conservancy Council, 1987) and in different regions of Scotland (Sydes, 1988). These losses have been a matter of widespread concern for nature conservation in upland Britain (Felton & Marsden, 1990). The most recent study of the extent of heather in England and Wales involved the use of satellite imagery (Bradbury et al., 1989). The resolution of the Landsat TM images restricted the measurement of heather (Calluna vulgaris only) to areas where it comprised more than 25% of the ground cover. Areas where it forms less than 25% ground cover offer potential for heather to expand and become the dominant species (Marrs & Welch, 1990). The condition of heather, in terms of morphological damage associated with over-grazing, was not assessed. The objective of this study was to determine, by ground survey of a stratified sample of 1-km squares, both the present extent and condition of heather-dominated vegetation in the uplands of England and Wales. In addition, the survey was conducted to provide an estimate of the potential for regeneration of damaged heather in England and Wales, and within different biogeographic regions.
Keywords: over-grazing, land class, heather regeneration, biogeographic-region, Calluna.
*Present address: AFRC-Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwth, Dyfed, UK, SY23 3EB. © Crown copyright (1995). 155
156
R. D. Bardgett, J. H. Marsden, D. C. Howard
For the purposes of this survey, the term 'heather' is used to describe all species of ericaceous dwarf-shrub, including common heather Calluna vulgaris, crossleaved heather Erica tetralix, bell heather Erica cinerea, bilberry Vaccinium myrtillus, and crowberry Empetrum nigrum. Moorland is a vaguer, more widely used term which carries an inherent suggestion of moderate to high elevation. The Land Utilization Survey of Great Britain (see Stamp, 1948) amalgamated moorlands with heathland, rough pasture and common land, while Hart (1955) considered moorland to be synonymous with rough grazing land. A recent comparison of land cover definitions (Wyatt et al., 1993) suggests that moorland is usually unenclosed, with the soils having a peaty top. There is overlap and an indistinct boundary between moorland, heathland and bogs: for this study any unenclosed land in the selected land classes was considered as moorland.
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METHODS Survey squares The survey covered a random sample of 122 1-km squares, stratified into eight groups using the ITE Land Classification (Bunce et al., 1991). Only squares in the upland land classes were selected, since upland heather moorland is not present in the lowland classes. Since the survey only covered England and Wales, the land classes used were 17, 18, 19, 20, 22, 23, 24 and 25 (sample squares are shown in Fig. 1). The frequency distribution of the 122 sample squares in relation to the ITE Land Classification is shown in Table I. Sites were visited between November 1990 and March 1991. A brief description of the individual ITE land classes (Bunce et al., 1991) is given in Table 2. Heather condition Percentage ground cover and height of the five ericaceous 'heather' species within each visually distinguishable stand were used as the key indicators of vegetation condition. Homogeneous stands of 'heather' larger than 1 ha were mapped at the 1 : 10 000 scale and assigned to one of three percentage ground cover categories: 1, present but < 25%; 2, 25-50%; 3, > 50%. These categories were comparable with those used by Bradbury et al. (1989) to classify heather as suppressed, sub-dominant, or dominant, respectively. The height of heather plants was recorded in three categories: <15 cm; 15-30 cm; > 30 cm. Where Calluna vulgar& was present, and its growth form suggested over-grazing, neglect or other inappropriate management, individual stands were assigned to an additional category of 'damaged heather'. This category included stands of tall, over-mature and dead heather as defined by MacDonald and Armstrong (1989) as well as 'heather' showing morphological distortion associated with over-grazing. The area (ha) of open moorland, 'heather' on moorland, and 'heather' within each of the categories of cover, height and condition was recorded for each
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i Fig. l. Geographical distribution of 1-km survey squares and location of upland biogeographic regions (MacDonald et al., 1989) within England and Wales. Biogeographic regions are numbered as: 1, north-east England (Cheviot, Kielderhead, Moor House and Cross Fell, Upper Teesdale and Durham Moors, Yorkshire Dales, Howgill Fells and Howarth Moor); 2, north-west England (Lake District and Bowland Fells); 3, North York Moors; 4, west Midlands (Peak District, Long Mynd, Clun Forest, Beacon Hill, Radnor Forest and Black Mountains); 5, north Wales (Snowdonia, Rhinogs and Berwyn Mountains); 6, south Wales (Southern Cambrian Mountains and Brecon Beacons); 7, south-west England (Dartmoor and Exmoor). square. These sample data were used to estimate total areas for both England and Wales, and for the different biogeographic regions (MacDonald et al., 1989) (Fig. 1), using the frequency distribution of land classes within each country and region given in Table 1 (mean coverage per square for each land class and the area of that land class within the region). Biogeographic regions represent the major geographic variation in moorland vegetation in England and Wales, and therefore may extend over the boundaries of both countries (e.g. west Midlands). Each region combines the broad ecological differences shaped by climate, topography
Extent and condition of heather on moorland
157
Table 1. Frequency distribution of Land Classes 17-28 and surveyed squares within England, Wales and biogeographic regions
Land class
No. of squares surveyed
England
Wales
North-east England
North-west England
17 18 19 20 21 22 23 24 25 26 27 28
53 15 12 5 0 20 8 1 8 0 0 0
3698 1952 2107 912 9 2648 688 195 1978 899 1401 894
9001 928 42 245 0 3 41 0 0 0 0 0
1516 93 181 438 7 2455 431 27 1549 87 832 395
91 606 566 135 2 74 176 166 304 627 297 371
North Yorks West Moors Midlands" 1 3 51 ll 0 0 0 0 98 159 246 48
3387 1233 1320 418 0 252 81 2 27 154 26 80
North Wales
South Wales
South-west England
1563 504 23 38 0 3 31 0 0 0 0 0
5141 421 8 113 0 0 10 0 0 0 0 0
1000 20 0 4 0 0 0 0 0 0 0 0
aThe West Midlands region extends over upland areas in both England (Peak District, Long Mynd) and Wales (Clun Forest, Beacon Hill, Radnor Forest and Black Mountain).
Table 2. Land use, types of semi-natural vegetation and soil types found in the ITE Land Classes in which sites were sampled
ITE Land Class Number
Land use
Semi-natural vegetation
17
Mainly pastures with some good grassland
Mainly rough grassland types, but some moorland
Brown earths and brown podzolics but with a range of other soils
18
Predominantly rough grazing with some limited pasture
Mainly moorland with extensive peatland and montane grassland
Brown podzolics, brown rankers, peats
19
Mainly rough grazing or forest
Mainly moorland but also mountain grass and peat types
Varied upland types but brown earths, podzols and peats the most common
20
Much pasture, but some good grassland and occasional crops
Mainly rough grassland types but some peatland
Gleys and brown earths with some other upland soil types
22
Mainly rough grazing, but some woodland and occasional crops
Mainly moorland, otherwise varied
Peaty gleys, peaty podzols, but other upland soils also
23
Limited open range grazing
Mainly moorland types, but also mountain grassland and peatland
Peats, peaty podzols and brown rankers
24
Limited open range grazing
Mainly peatland types, but also montane grassland
Brown rankers, peats or peaty podzols, some peaty gleys
25
Mainly barley
Restricted to a few grassland types
Brown earth, gleys and gleyed brown earths
and geology. Detailed descriptions of the different biogeographic regions shown in Fig. 1 are given by MacDonald and Armstrong (1989). RESULTS The total estimated area of moorland, and 'heather' on moorland, in England and Wales, was 14,150 + 810 and 11,440 + 790 km 2, respectively (Table 3). Approximately 55% of the total area of moorland, and 'heather' on moorland, was within England. Over a large proportion (47%) of moorland area in England, 'heather' was dominant (> 50% ground cover), and 24% showed growth forms associated with over-grazing, neglect and other inappropriate management ('damaged heather') (Fig. 2). In contrast, a large proportion (43%) of the total area of 'heather' in Wales was found to be
Typical soil type
suppressed (< 25% cover) and/or showing growth forms associated with over-grazing, neglect and other inappropriate management (38%) (Fig.2). Figure 3 shows that the mean coverage of suppressed 'heather' (<25% cover) per km square was greatest in land classes 23 and 17 (26 and 24%, respectively), while 'damaged heather' was most abundant in land class 17 (mean coverage of 20% per km square). Thus, both suppressed and 'damaged heather' are prevalent in Wales and other regions where land class 17 predominates(Table 1). The estimated areas of 'heather' with over 25% ground cover in England and Wales were 4,030 and 2,990 km 2, respectively (Table 3). The biogeographic regions with the greatest estimated areas of moorland were the west Midlands (4,080 km2), south Wales (3,550 kin2), and north-east England (3,340 km2), while
158
R. D. Bardgett, J. H. Marsden, D. C. Howard 50
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25-50%
>50%
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'lleather' categories Fig. 2. The percentage (%) abundance of 'heather' within the categories of ground cover (< 25%; 25 50%; > 50%) a n d height (< 15 cm; 15 30 cm; > 30 cm), a n d ' d a m a g e d heather', in E n g l a n d a n d Wales.
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the smallest area of moorland was in the North York Moors (60 km 2) (Table 3). Although the proportions of moorland with 'heather' present varied little between the different biogeographic regions, the proportions of 'heather' within the different categories of height, cover and condition varied considerably. In both north and south Wales, the proportion of 'heather' suppressed and/or showing growth forms associated with over-grazing, neglect or other inappropriate management was greater than 40% (Fig. 4). Similarly, in south-west England, a large proportion (38%) of the 'heather' was damaged by over-grazing or management neglect (Fig. 4). In the North York Moors, north-east and north-west England, however, approximately 50% of the area of 'heather' was dominant
Table 3. Estimates of total moorland, and 'heather' moorland, and different categories of height, cover and condition for England and Wales, and the biogeographic regions (all figures of area and standard errors (_+) are expressed as '000 of km z) Country
Biogeographic region
South West South Wales North Wales North-west England West Midlands North Yorks Moors North-east England England Wales England a n d Wales
Area of moorland
0.65 _+0.05 3.55 +0,26 1.28 __+0.10 1.18 0.09 4.08 -+0.26 0.06 -+0.01 3.34 0-34 7.79 _+0.47 6.36 _+0.46 14-15 _+0-81
Area of heather
0.54 -+0.05 2.93 __+0.25 1.08 __+0.09 0.90 0"09 3.41 __+0.26 0"05 __+0.01 2-54 0.32 6.19 _+0.46 5.25 _+0.45 11-44 _+0.79
Height
Cover
< 15 cm
15 30 cm
< 30 cm
< 25%
25-50°/,,
> 50%
Area of damaged heather
0.20 -+0.03 1.07 -+0.16 0-39 +0.06 0.36 -+0.06 1-24 -+0.16 0-02 __+0.00 0-95 0.16 2.31 _+0.26 1.92 +0.29 4.27 _+0.48
0.17 -+0.03 0.92 +0.16 0.35 -+0.06 0.29 -+0.05 1.06 -+0.15 0.02 __+0.00 0.86 0.17 2.01 _+0.25 1.65 _+0.29 3.66 +0-48
0.17 _+0.04 0.94 __+0.18 0.34 __+0-06 0.25 __+0.06 1.12 __+0-18 0.02 __+0.00 0.72 0.18 1.87 _+0.29 1-68 _+0.32 3.56 _+0.54
0.24 +0.04 1.27 __+0.19 0.44 -+0.06 0.29 __+0.05 1.26 __+0.16 0-01 __+0.00 0.91 0.14 2-16 +0.24 2.27 _+0-33 4.42 _+0-51
0.11 _+0.02 0.58 -+0.13 0-21 __+0.04 0.16 -+0.04 0.61 +__0.11 0-01 __+0.00 0.51 0-09 1.15 _+0.17 1.05 _+0.22 2.20 _+0.35
0.19 -+0.04 1.07 __+0.19 0.42 +0.07 0-45 -+0.07 1.54 __+0.21 0.03 -+0.01 1.12 0.24 2-88 _+0.36 1.94 _+0.34 4.82 _+0.61
0.21 +-0-03 1.11 __+0-16 0.39 __+0-06 0.17 -+0.04 1.01 __+0.14 0.01 _+0.00 0-56 0.10 1.48 _+0'29 1-98 _+0-29 3-46 _+0.45
Extent and condition of heather on moorland
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R. D. Bardgett, J. H. Marsden, D. C. Howard
(>50% ground cover), while only 15-20% showed growth forms associated with over-grazing or management neglect (Fig. 4). Little difference was found in the proportions of 'heather' in the different height categories, within the countries or biogeographic regions (Fig. 4). DISCUSSION The estimated area of moorland in England and Wales in this survey is comparable with that given by Felton and Marsden (1990). However, the results of this survey suggest that the area of 'heather' with less than 25% ground cover is approximately 20% greater than was estimated by Bradbury et al. (1989), using Landsat TM satellite imagery, despite the fact that they included areas of lowland heath. This discrepancy was probably due to the inability of the Landsat TM satellite imagery to identify areas of moorland that were dominated by bilberry V. myrtillus, particularly when less than 15 cm tall. Moorland vegetation dominated by bilberry often occurs as an intermediate stage in the grazing-induced succession from heathland to grassland (Ratcliffe, 1959), and was widely recorded in the present survey. The major difference between this survey and that of Bradbury et al. (1989) was in the relative extent of 'heather' in both England and Wales. Data from this survey suggest that 55% of the total 'heather' was within England, whereas the Landsat survey (Bradbury et al., 1989) and the 1984 ITE Countryside Survey (Barr et al., 1986), estimated 79% and 83%, respectively. The inclusion of moorland dominated by bilberry in this survey is the most likely reason for the higher estimated area of 'heather' in Wales. This study suggests that there are approximately 440,000 ha of suppressed, and therefore potentially recoverable, 'heather' (Marrs & Welch, 1990) in England and Wales. It is generally accepted that both the cover and condition of 'heather' on moorland will decline when grazing pressures exceed 1.5-2 ewes ha ~ (Lance, 1987; Bardgett & Marsden, 1992). Therefore, in order to regenerate suppressed 'heather', grazing pressures need to be reduced below this level, or removed completely for periods of the year (Felton & Marsden, 1990; Marrs & Welch, 1990). In this study, most of the suppressed 'heather' was shown to occur in the biogeographic regions of south Wales and the west Midlands, where a large proportion of the heather was also damaged by over-grazing or management neglect. Although less in total extent, a large proportion of the 'heather' in north Wales and south-west England was also suppressed and/or damaged by over-grazing and management neglect. In contrast, 'heather' on moorland in the North York Moors, north-east and north-west England was generally in good condition, with large areas where it was the dominant vegetation type. Despite this, there were considerable areas of suppressed and damaged 'heather', particularly in north-east England. The occurrence of large areas of suppressed and damaged 'heather' in north and south Wales and
south-west England is probably related to over-grazing by sheep. This suggestion is supported by the finding of Bardgett and Marsden (1992) that more than 70% of open moorland in these regions was grazed above the threshold of 1.5 ewes ha ~. In north-east and north-west England and the North York Moors, however, most of the open moorland was grazed below this level (Bardgett & Marsden, 1992). The more southerly regions are also dominated by moorland within Land Class 17, which was found to have a very high mean coverage of both suppressed and 'damaged heather', as compared with other land classes. Land Class 17 is dominated by marginal land with moderately productive brown earth and podzolic soils under pasture and improved grassland. 'Heather' moorland within this land class is often subject to periodic heavy grazing pressures by virtue of the large numbers of sheep on adjacent, more productive, grassland. The occurrence of large areas of moorland dominated by 'heather' in the more northerly regions, however, is likely to be related not only to lower grazing pressures, but also to the widespread management of moorland (e.g. burning) for red grouse. The high proportion of suppressed 'heather' found within land class 23, which predominates in northern England, is likely to be in part related to biotic limitations for growth rather than over-grazing, since this land class is dominated by rocky and precipitous slopes at high altitudes. Within these more northerly biogeographic regions where most of the 'heather' on moorland is dominant (> 50% cover) and in good condition, regional management policies are required to maintain their condition and regenerate localised areas of damaged 'heather' (e.g. moorland fringes). This survey highlights the tremendous potential to regenerate and hence increase the extent of heatherdominated moorland throughout England and Wales, and particularly in the upland areas of the west Midlands, south-west England, and north and south Wales. The case for targeting government policy to regenerate 'heather' moorland in these areas is strengthened further because they are outliers from the main upland block centred on the northern Pennines (principally the north-east and north-west of England) which are dominated by the 'classic' C. vulgaris-V, myrtillus and C. vulgaris-Eriophorurn vaginatum communities (Usher & Thompson, 1993). Moorland areas within the outlying regions are of considerable conservation importance since they represent geographical limits of heathland plant communities (e.g. Calluna-Eriophorum mire in south-west England) and provide different combinations of 'heather' species, such as the well developed Vaccinium vitis-idaea and E. nigrum heaths of the Peak District, and north and south Wales (Ratcliffe & Thompson, 1988). They also support important breeding populations of moorland birds (e.g. red grouse L. scoticus, hen harrier Circus cyaneus and merlin Falco columbarius) which are often close to the southern edge of their ranges in Britain. The abundance and diversity of moorland vertebrates and invertebrates are dependent not only on the overall extent of 'heather' moorland,
Extent and condition o f heather on moorland
but on vegetational, topographical, climatic and landuse variation within and between different biogeographic regions (Usher & Thompson, 1993). A review of conservation issues for heather moorland in Great Britain generally is given by T h o m p s o n et al. (1995).
ACKNOWLEDGEMENTS We would like to thank the many farmers, landowners, agents and gamekeepers who freely granted access to their land. Particular thanks should go to Paul Evans and Leigh Lock, who conducted much of the survey work; Bob Bunce of the Institute of Terrestrial Ecology, Merlewood Research Station, for his advice and assistance with data analysis; M a r k Felton of English Nature, for his support and guidance throughout the project; and the anonymous referees for their valuable comments on the manuscript.
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161
Lance, A. N. (1987). Estimating acceptable stocking levels for heather moorland. In Agriculture and conservation in the hills and uplands, ed. M. Ball & R. G. H. Bunce. ITE Syrup., No. 23, 109-15. MacDonald, A. & Armstrong, H. (1989). Methods for monitoring heather cover. Nature Conservancy Council, Peterborough. MacDonald, A., Brown, A. & Thompson, D. B. A. (1989). Heather moorland: nature conservation value and biogeographic variation. In Heather regeneration in England and Wales, Annex 3, J. H. Marsden & M. Felton. Nature Conservancy Council, Peterborough (unpublished report). Marrs, R. H. & Welch, D. (1990). Moorland wilderness: the potential effects of reduced grazing pressure. Institute of Terrestrial Ecology, Huntingdon (unpublished report). Nature Conservancy Council (1984). Nature conservation in Great Britain. Nature Conservancy Council, Peterborough. Nature Conservancy Council (1986). Nature conservation and afforestation in Britain. Nature Conservancy Council, Peterborough. Nature Conservancy Council (1987). Changes in the Cumbrian countryside. Nature Conservancy Council, Peterborough. Parry, M., Bruce, A. & Harkness, C. (1981), The plight of British moorlands. New Scient., 28, 550-1. Ratcliffe, D. A. (1959). The vegetation of the Carneddau, North Wales, I. Grasslands, heaths and bogs. J. of Ecol., 47, 371-413. Ratcliffe, D. A. & Thompson, D. B. A. (1988). The British uplands: their ecological character and international significance. In Ecological change in the uplands, ed. M. B. Usher & D. B. A. Thompson. Blackwell Scientific Publications, Oxford, pp. 3-36. Stamp, L. D. (1948). The land of Britain: its use and misuse Longmans, London. Sydes, C. (1988). Recent assessments of moorland losses in Scotland. Nature Conservancy Council, Peterborough. Thompson, D. B. A., MacDonald, A. J., Marsden, J. H. & Galbraith, C. A. (1995). Upland heather moorland in Great Britain: a review of international importance, vegetation change and some objectives for nature conservation. Biol. Conserv., 71, 163-78. Usher, M. B. & Thompson, D. B. A. (1993). Variation in the upland heathlands of Great Britain: conservation importance. Biol. Conserv., 66, 69-81. Wyatt, B. K., Greatorex Davies, N., Bunce, R. G. H., Fuller, R. M. & Hill, M. O. (1993). Comparisons of land cover definitions. Dictionary of surveys and classifications of land cover and land use. ITE Merlewood, Grange-over-Sands (unpublished report).