Continued footpath widening in the Cairngorm Mountains, Scotland

Continued footpath widening in the Cairngorm Mountains, Scotland

Biological Conservation 49 (1989) 201 214 Continued Footpath Widening in the Cairngorm Mountains, Scotland Art N. Lance Royal Society for the Protec...

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Biological Conservation 49 (1989) 201 214

Continued Footpath Widening in the Cairngorm Mountains, Scotland

Art N. Lance Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, SG19 2DL, UK

Ian D. Baugh Nature Conservancy Council, Northminster House, Peterborough, PEI IUA, UK

& John A. Love Nature Conservancy Council, Achantoul, Aviemore, PH22 1QD, UK

(Received 2 July 1988; revised version received 9 January 1989; accepted 13 January 1989)

ABSTRACT Mountain footpaths near Cairn Gorm, Scotland, grew wider after an access road and chairlift were built in the 1960s, and have continued to widen during the 1980s. The paths are now eroding in many places, and secondary tracks alongside have proliferated. Attire of six paths measured during 1981-82 to 1986, mean increases in width ranged from 0"2 to 1"3 m, and mean widths in 1986 ranged f r o m 1"7 to 10"2 m. The sixth path did not increase, but was the only one to be used much less than formerly. Widening and erosion at the other five are predicted to worsen unless access is reduced during the non-skiing season.

INTRODUCTION In the Cairngorms, a network of footpaths has developed since 1946 (Watson, 1984), extending from main access points on the lower slopes to 201 Biol. Conserv. 0006-3207/89/$03"50 4"' 1989 ElsevierSciencePublishers Ltd, England. Printed in Great Britain

Art N. Lance, Ian D. Baugh, John A. Love

202

popular vantage points such as the principal summits. The condition of some of these paths has been monitored since 1960-61 when a road and chairlift into the area were built for skiers. The road and chairlift operate at all seasons, and since construction the number of visitors to the Cairngorms has greatly increased. The footpaths have grown wider and more pronounced (Watson, 1967; Gilmore, 1975; Baugh, 1979), and soil erosion and damage to the surrounding vegetation have also increased (Watson, 1985). The Cairngorms are Britain's premier arctic-alpine conservation area (Ratcliffe, 1977), and concern is growing at the amount of damage being done. This paper describes changes in the paths since 1981, and a method for monitoring changes in width more rigorously than hitherto.

PATH LOCATIONS A N D ACCESS We studied six of the most long-established paths, five on the heavily visited northern side of the Cairngorms, and one on the less visited southern side (Fig. 1). Baugh (1979) described the characteristics of these paths, TABLE 1 Characteristics of the Paths

Path Start a Altitude End ~ Altitude Measurement (m) (m) spacing (m) 2

A

520

B

530

10

3b

F

1 130

G

1 000

100

4

A

520

C

730

25

6

D

1 130

E

1 130

100

11

H

1 090

I

1 230

15

12

J

560

K

1 000

100

Soil

Peat over boulders Thin mineral over grit Peat over boulders Thin mineral over grit and gravel Thin mineral, then grit and gravel Peat, then grit and gravel

Adjoining vegetation h Calluna/Trichophorum damp heath

Juncus tr(fidus, Nardus snowbed Calluna/Trichophorum damp heath

Juncus tr(fidus, Nardus snowbed Empetrum, moss, Juncus tr~'dus Calluna/Trichophorum damp heath, then Empetrum, moss, and

Juncus trifidus Location as on Fig. 1. b Plant communities are described in full by McVean & Ratcliffe (1962).

Footpath wideningin the Cairngorms

203

,;.~32., I '-'~ ,;/Access

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',

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/ ~ ~ "

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.',. [ D

. ~ o ~ / / . . -'~-~ j /

e

, Lochan ~," ,) G I (1215) /

~/-

~

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~

F ~Lochan ~_~ Buidhe ~-~"~° ~~"

~'c Ben Macdui "'" (1309) o,

km

/

i~

t,,~

Access Road {; ii

Fig. 1. Map of study area, showing paths and principal locations. Path numbers are those used by Baugh (1979) except for path 12 which was not measured in previous studies. Upper case letters at each path indicate the start and end points of the sections measured. Dashed lines indicate unmeasured sections (see Methods). The dotted line to point I denotes a recent stone-paved alternative to path 11. Thin solid lines denote streams.

204

Art N. Lance, Ian D. Baugh, John A. Love

Nethersole-Thompson & Watson (1981) the ecology of the Cairngorms generally. All six paths are clearly defined for most of their lengths, but differ in altitude, substrate, slope, and the type of vegetation alongside (Table 1). One path (11) ceased to be a main route of travel after 1979-80, when an artificial path was built with stones on a more direct line to Cairn Gorm summit (Fig. 1). The other five paths remained well travelled throughout the period. Paths 3b and 6 are part of a popular circular route at high elevation, easily reached by the road and chairlift, and returning to the road via paths 2 or 4 across lower ground. Path 12 is a principal route to high ground from the south, but is reached via a private road which is closed to public visitors' cars. The northern paths are thus more accessible.

METHODS Typically, each path had two main types of ground: (i) a central, heavily trodden strip devoid of vegetation or mostly so; and (ii), on either side, a zone of trampled or stunted vegetation with more bare ground than at undamaged places further away. Usually the edge of a path was detectable as the boundary between heavily trampled and lightly or untrampled vegetation. At some popular viewpoints, however, trampling over a wide area had removed all but a few vestigial plants, soil erosion was occurring, and a defined linear path no longer existed. Watson (1985) was already studying this type of more expansive damage, and so we ignored these places. We also ignored places where, due to extreme exposure, the vegetation was naturally sparse and stunted and so the precise limits of the path were indistinct. These exclusions shortened the measured parts of the paths considerably, but left us with fewer subjective judgements about where path edges lay. The more heavily worn paths (or stretches of path) often had one or more secondary tracks alongside the main one, separated by less trampled vegetation. ('Track' is defined as one central strip plus its two trampled zones on either side.) Where they ran near to one another, these secondary tracks were not always wholly discrete, but we counted the number identifiable at each measurement point. We also counted the points at which erosion was eating into the path edge; sometimes this was severe enough to have washed away the path edge entirely and destroy the plant cover for some distance beyond. No meaningful measure of path width could be made at such places. Previous studies of these paths have used two basic measurements and a third one derived from the other two: (1) width of bare ground; (2) width of

Footpath widening in the Cairngorms

205

ground with damaged vegetation; and (3) overall width of path (the sum of 1 and 2, minus any undamaged vegetation mixed in with them). Bare ground is a less subjective measure than the others, but 'overall width' defines a path more realistically. Overall width and width of bare ground are the measures we use in this paper. Where secondary tracks occurred, we measured each one separately and then summed them. The previous studies of these paths used arbitrary distances between measurement points. Such points were located by pacing (typically 100 between points) and so the number of measurements was determined by the length of the path, the average stride length of the measurer, and variations in stride-length due to rough or steep ground, rather than by statistical considerations. Likewise, the measurement locations changed from study to study (Baugh, 1979). These methods may have been quick and simple to use, but they confined the data analyses to comparing crude means and (often) heterogeneous variances. For some paths, they also resulted in wasteful over-sampling. In September 1981, for each of the six paths, we defined a standard starting point, a standard section to measure, and a fixed set of measurement points at regular intervals, sited by metric tape. Starting points were prominent landmarks alongside the path, for relocation at later dates and by different people. From pilot data at 100m intervals for each path, we obtained sample means and variances with which to estimate the number of measurements needed for detecting a minimum change in path width with a desired level of statistical assurance. We chose a threshold of >~50 cm change in width, at >/80% assurance of detecting a real change of that size, and ~<5% likelihood of falsely detecting such a change. The number of measurements needed for this, divided by length of path, gave the measurement interval for each path. For paths with more heterogeneous widths, we added three to four extra measurement points as a further safety margin. For paths 2, 4 and 11, these procedures resulted in shorter sections measured but more measurements per section than in the earlier studies (Fig. 1). By using the same fixed measurement points on successive occasions, we were able to compare m e a n changes in width by paired t-test, rather than changes in m e a n width by unpaired test. The advantages of this are discussed later. We measured paths 2, 4 and 11 in late August 1981, and paths 3b, 6 and 12 in late August 1982. From the rates of change recorded at these paths in earlier studies, we expected a change > 50 cm to be statistically detectable in about 4 years, and so we re-measured all six paths in September October 1986. Measurements were made by Lance and Baugh in 1981-82, and by Lance and Love in 1986, assisted by D. Holland.

206

Art N. Lance, Ian D. Baugh, John A. Love

Tests of assumptions in the statistical analysis A footpath is effectively a transect, and transect measurements have some inherent problems for data analysis. Transects are seldom homogeneous throughout, and measurements which are evenly spaced may show nonrandom patterns. Also, the traffic on a path may not be the same throughout: deterred by distance, bad weather, or the condition of the path, some walkers may turn back before they complete the route. All measurements at each date as well as for changes between dates were therefore tested for trends and other departures from randomness and normality: (i)

from measurement to measurement, by runs test and by counts of runs above and below the median; (ii) over the path as a whole by Spearman rank correlation coefficient, width versus distance from origin; (iii) by Chi 2 for goodness-of-fit to the Normal distribution; and (iv) by F-test for homogeneity of variances. The runs tests also served as tests of independence among the measurements (Sokal & Rohlf, 1981). Further; the four tests together gave useful information on changes within different parts of a path, as distinct from the path as a whole.

RESULTS

Measurement to measurement within paths Trends in the measurements showed no consistent pattern from path to path. Runs in the data were mostly well inside expected limits, indicating that neighbouring measurements varied randomly and independently of each other. The main exception was path 2, which tended to be wider at the near end than at the far end (Spearman rS = -0"44,p < 0"01), a trend which had strengthened by 1986 (rS = -0"54). This path also had fewer runs than expected, indicating that similar measurements tended to occur in groups. Conversely, path 11 was wider at the far end (rS = 0"33, p < 0"05), but by 1986 this had been nullified by a tendency for bigger changes also at the far end (Spearman rS = 0"06). Variances for most paths did not differ significantly between years, but large measurements were more frequent than expected from the Normal distribution. These large widths came mostly from places where erosion was starting. For tests of mean change, all measurements were therefore

Footpath widening in the Cairngorms

207

TABLE 2 Mean Path Widths (m) and 95% Confidence Intervals Path 2

3b

4

6

I1

12

1981 1 9 8 6 1981 1986 1981 1986 1982 1986 1982 1986 1982 1986 Mean OW a +95% CI - 9 5 % CI

8.9 9.7 8.3

Mean WBG" +95% CI - 9 5 % CI

4-9 5.2 4-6

10-2"* 1.5 11.1 1.9 9.5 1.1 6.3** 6.7 6-0

1.3 1.7 1'0

1.7 2.0 1.5

3.0 3.3 2.7

3'6** 3.9 3.3

1.5 2.0** 1.8 2.4 1.3 1.7

7-0 7.6 6.5

6,9 7.5 6.3

5.2 6.4 4.2

4,8 6,0 3.9

1.4 1.7 1.2

2-0 2.2 1.7

2"5** 1.4 1.9"* 2'8 1.7 2.2 2.3 11.2 2.6

6"8 7.3 6"3

6.6 7.1 6.1

2.8 3,5 2.2

3.3 4-2 2,5

All values are back-transformed from their equivalents in loge(l + X), except for: Path 11 (WBG), transformed as (X -°'4 - 1)/-0.4 Path 4 (WBG), transformed as X °5 Path 2 (OW), transformed as (X 0.5 _ 1)/-0.5 The power coefficients were found by iterating the Box-Cox procedure (Sokal & Rohlf, 1981). a OW, Overall width; WBG, Width bare ground. ** = p < 0.01, 1981 or 1982 versus 1986, by paired Student-t (two-tailed) on differences in the transformed values, point by point.

transformed to log e (1 + J0 (with three exceptions, as noted below Table 2). The means and 95% confidence limits in Table 2 are shown as backtransformed values.

Changes in width, whole paths By 1986, three of the six paths (2, 4 and 6) had increased significantly in overall width (p<0"01; Table 2). They also had significantly more bare ground (p < 0.01). All of these changes exceeded the detection threshold of 50 cm. Of the other three paths, path 3b had a higher mean overall width and more bare ground than previously, path 12 had more bare ground but a lower mean overall width, and path 11 was lower in both measures. However, none of these latter changes exceeded 50 cm, and they were not statistically significant (p > 0.1). Path 11 was the path that had been replaced by a new and shorter route in the late 1970s. Bayfield (1986) suggested that the old path began to narrow after the new one was built. Together, the evidence from Table 2 and from correlations within the path (previous section) was that the farther sections did become narrower after 1981, but the nearer reaches (and the path as a whole) did not.

208

Art N. Lance, lan D. Baugh, John A. Love

Changes relative to previous width Widening was proportional to the previous width of the path, over the path as a whole and for the individual measurement points within it. Of the three paths which widened significantly between 1981 and 1986, path 2 showed the biggest increase but the smallest as a percentage of previous width. Path 6 (narrowest of the three) showed the reverse. Although not statistically significant, path 3b (narrower still) had the biggest relative increase of the four and so it too was consistent with these trends. Within paths, narrow places tended to widen more than already wider places (r-values, Table 3). This suggested that the paths became more uniform with time. The trend toward uniformity seemed greatest at wider paths, since these showed bigger mean changes in width per unit of previous width (% values, Table 3). However, wider paths also had more places with erosion (see below), and the r-values for these wider paths were relatively weak. Thus, as a path grew wider, it tended to become more uniform in width from place to place, except where erosion caused the opposite effect by eating into the path edge more than at other places.

Number of tracks per path Path 2, the widest, was multiple-tracked for 80% of its length (Table 4). Path 3b, the narrowest, had only one track except at one measurement point. The other four paths had intermediate numbers of tracks, although the TABLE3 Relative Changes, P o i n t b y P o i n t , Within Paths

Path

Overall width Width of bare ground

(i)" r (ii) % (i) r (ii) % n

2

3b

4

6

-0.37** 12.4 -0.46** 29.8 64

-0.80** 12.7 -0.69** 2'6 15

-0.57** 16"8 -0.44** 26"7 50

-0-39 35'5 -0.46 30"2 19

11 -0.43** -25"9 -0.45** - 18"2 60

12 -0"39** 19'6 -0.15 19"5 29

" (i) Correlations (r) between initial width and change in width thereafter; from variables transformed as loge(1 + X), except as noted below Table 2. New power coefficients were obtained for the dependent variable (change in width) for paths 2, 4 and 11. (ii) Mean percentage change in width per unit of initial width; % = mean per cent change in width, calculated as (y/x)* 100%, where y = mean change in width at x = mean initial width, back-transformed from the regression of y on x, point by point within the path. *, p < 0.05; **, p < 0.01.

209

Footpath widening in the Cairngorms

TABLE 4 Numbers of Measurement Points with One or More Tracks a and Erosion Washouts b Number o f tracks

Number o f measurement points Path

1 2 3 4 >4 Washouts



12 10 15 10 16 7

3b c

4~

6

11 c

1982

1986

12 1981

1986

14 1

18 25 7

12 8

17 2

54 6

13 6

7 I0

0

0

0

1

3

0

2

a Number of separate strips of bare or heavily trampled ground bordered by undamaged vegetation. h Measurement points where erosion had washed away the path edge, and measurement of path width was not meaningful. c At paths 2, 3b, 4, and 11, the frequencies were virtually unchanged between 1981 82 and 1986.

percentage of places with more than one track was not strictly related to path width. Secondary tracks were commonest where paths ran through wet hollows, and sometimes a parallel series occurred, with the outer (presumably newer) tracks being narrower and firmer underfoot than the inner ones. At two of these paths the numbers of tracks changed substantially during the four years, increasing at path 12 and declining at path 6. Nonetheless, the outcome was a higher ratio of bare ground to overall width in both cases (Table 2). Erosion Parts of a path with more than one track were commonly also focal points for erosion. At some of these places, the main and secondary tracks had merged into a single large surface of bare peat or gravel. In the gravel soils of paths 11 and 12 at higher elevations, sheet erosion had in places deepened into rutted channels. Tongues of loose material were cutting through the path edge, washing onto the ground on the downslope side and burying the vegetation there, in the manner described by Watson (1985). The number of such places increased during 1981-86 (Table 4), and erosion of this kind also appeared imminent at several other parts of paths 2, 6 and 12. The role of erosion in the process of path development is considered in the Discussion.

210

Art N. Lance, Ian D. Baugh, John A. Love

Comparison with earlier measurements Bayfield & Lloyd (1973) invented an 'index of extent' (I) for expressing footpath width, in which I=overall width + width of bare g r o u n d - w i d t h of any intervening undamaged vegetation The advantage is that these three factors are reduced to one combined variable, but this is an arbitrary expression and difficult to equate conceptually with 'a path', particularly since width of bare ground is (a) 20

18 16 14. 1210-

~

86-

2~

4-

3b

2-

r

0

(

I

1975

I

6 "---~"

I 1979

l

r

I

I

1981

f

]

I 1986

Year

(b) 120 100 80,.c

60-

40c 0) o

20-

o~

0 -20

11

I -

-40 -

I

I

1975 Year

~

~

1986

1981

Fig. 2. (a) Changes in the Index of Extent (I), 1975-86; (b) variations in extent expressed as a percentage of the Index (I) at the preceding date. Path numbers as in Fig. 1. Path 6 comprises two sections with substantially different widths. Gilmore (1975) and Baugh (1979) measured the full path, but the wider section (from Cairn Gorm to point D) eroded badly after 1979; data for 1981-86 are from the narrower section only.

Footpath widening in the Cairngorms

211

included twice. Undamaged vegetation is usually a subjective judgement as well. However, Baugh (1979) used this index for comparison with Gilmore's (1975) study, and Fig. 2 shows our data expressed this way together with Baugh's and Gilmore's. Being obtained by different sampling methods, the index values for different years are not wholly equivalent, but for three of the paths they enable the trends to be followed for 11 years. Using the slopes of the lines to compare rates of change, Fig. 2(a) indicates that path 11 (with much reduced traffic) began to narrow sharply after 1979, but then showed little change. Path 3b (the narrowest path) increased at a slow steady rate. Path 6 increased quickly between 1975 and 1979 but more slowly during 1981-86. Path 2 appeared to increase more slowly after 1979 than before, but path 4 increased faster with time. Path 4 runs alongside path 2, and, to some extent, substitutes for it. When path 2 began to become badly eroded, more walkers may have preferred to use path 4. As a proportion of the index of extent, these variations in change were more distinct. Figure 2b shows rate of change as a percentage of the index value at the preceding date. As in Fig. 2(a), the rate of increase at path 3b was essentially constant, and the narrowing of path 11 had all but ceased by 1981. However, the other paths showed substantial changes in rate. Path 6 doubled its rate of increase after 1979, and path 4 increased its rate five-fold. The increase at path 2 slowed markedly during 1979 81, but quickened again during 1981-86 (indicating that any relief gained from a preference for path 4 (previous paragraph) was only temporary and partial). These proportionate variations---some of them over quite short periods--suggest that the rate of widening was quite sensitive to the factors influencing it.

DISCUSSION

The sampling method Previous studies of these paths have compared successive unpaired sets of measurements. Except in the unlikely event that they come from identical places, unpaired measurements will differ from each other in sampling variation. This difference increases the variance in the two sets together. At paths with highly heterogeneous widths the difference is likely to be large in relation to change in width, weakening the test of change at a given sampling effort. A single set of fixed sample points eliminates this extra variation. A heterogeneous path then becomes an advantage; the wider the range of widths, the more strenuous is the test of change in width, for the same

212

Art N. Lance, lan D. Baugh, John A. Love

sampling effort (Steel & Torrie, 1960). The highly varied paths 2, 4 and 12 especially lend themselves to this. Fixed-point sampling is not without drawbacks, nonetheless. Erosion as in Table 4 reduces the number of points available for long-term monitoring, which may then need to add new sample points and revert to unpaired comparison. To forestall but also anticipate this eventuality, we adjusted sample size to sample variance for each path, at the outset. The method thus provided for both options.

Changes in the paths Five of the six paths were expected to become wider, if previous trends continued. Three of them did so (2, 4 and 6), in width of bare ground as well as overall width. A fourth path (3b) also increased in both of these respects, although not statistically significantly. Changes in the fifth path (12) were mainly internal, as discussed in the next section. The sixth path (11) was previously thought to be narrowing after the traffic on it declined (Bayfield, 1986), but it showed no significant mean change in width after 1981. Path 2 is wider at one end than the other, and became more so during 1981-86. Path 2 runs from the main carpark on Cairn Gorm, has the lowest elevation of the six, and no uphill gradients. It is the most convenient path for short walks or for nearness to shelter when the weather is poor. Its near end may thus be receiving more traffic than its far end, but the path as a whole also widened more than the other five paths we measured. It is also much the poorest in condition underfoot.

Proliferation of tracks and erosion Paths 2, 4, 6, 11 and 12 had more than one track for much of their lengths, and parts of paths 2, 11 and 12 were eroding badly. As well as leading from the main carpark at Cairn Gorm, paths 2 and 4 run over peaty soil. Once denuded of plant cover, the surface of peat soils soon breaks up if exposed to frequent trampling, especially when the soil is wet. As well as causing the path to widen faster than elsewhere, eroding places are more difficult to traverse, causing walkers to detour round them and create other tracks alongside. One particularly badly eroding section of path 2 had as many as seven separate tracks. At path 12, eroding places and extra tracks became more frequent between 1981 and 1986; the surface of this path deteriorated even though it did not widen significantly. Path 6 did widen significantly, but the number of places with more than one track declined; apparently the tracks had widened enough to merge with one another.

Footpath widening in the Cairngorms

213

Taken as a whole, these changes suggested a general trend of development, beginning with the simple widening of a single track (e.g. path 3b), proceeding to erosion and the occurrence of secondary tracks (path 12 in 1981), thence to the widening and merging of these (path 6) and the further creation of others (path 12 in 1986). Eventually, the path becomes a braided, eroding web (path 2).

Potential for continued widening Terrain and other site features affect path widening (Bayfield, 1973), but the biggest factor is doubtless the amount of traffic. Aitken (1985) has described the general increase in walkers on Scottish mountains. Data from 1973 and 1980 showed that the tendency of walkers to venture beyond Cairn Gorm and onto the National Nature Reserve (NNR) increased significantly between those two years (Lance, 1981). Paths 2, 3b, 4, 6 and 11 on Cairn Gorm and the N N R all grew wider during that period. Only path 11 has since ceased widening, even though the number of walkers on the N N R has also since declined (if less so than on path 11; A. Watson, pers. comm.). The history of path 11 suggests that, if the amount of traffic can be substantially reduced, path widening may stop and perhaps even reverse, provided that erosion has not set in. Otherwise, as paths 2, 6 and 12 suggest, once a path has lost its vegetative cover, widening may be maintained as much by soil erosion as by trampling, regardless of whether the amount of traffic increases or not.

Future consequences for these paths Damage to soils and vegetation is now widespread on the high plateau of the Cairngorms National Nature Reserve and the Northern Corries Site of Special Scientific Interest which adjoins it (Watson, 1985). The damage is most severe at parts which are reached by the chairlift and the footpaths studied here. In 1985, the nature reserve was bought from a private landowner by the Royal Society for the Protection of Birds, a nongovernmental conservation body. However, a private company owns the chairlift, and government bodies own the adjoining land and access road. Much of path 2 leading from this road is now a peaty quagmire studded with emergent boulders. If the traffic on it is not greatly reduced, path 2 may soon become a continuous eroding scar for most of its length.+ Unless the present easy access by road and chairlift is reduced during the non-skiing season, a similar fate may await paths 3b, 4 and 6. + Since 1986. this path has been attificially surfaced

214

Art N. Lance, lan D. Baugh, John A. Love

A C K N O W L E D G E M ENTS We thank Dave Holland for help with fieldwork in 1986, and A d a m Watson and Colin Bibby for comments on the manuscript. M. J. Everett kindly drew the figures. For use in future monitoring, details of each path and copies o f the raw data are lodged with the authors and with Dr Watson at the Institute of Terrestrial Ecology, Banchory, Scotland.

REFERENCES Aitken, R. (1985). Scottish Hill Paths. A Reconnaissance Survey of their Condition. Countryside Commission for Scotland, Perth. Baugh, I. (1979). The Condition of Some Footpaths in the Northern Cairngorms. Nature Conservancy Council, Edinburgh. Bayfield, N. G. (1973). Use and deterioration of some Scottish hill paths. J. appl. Ecol., 10, 635-44. Bayfieid, N. G. (1986). Penetration of the Cairngorm mountains. Scotland, by vehicle tracks and footpaths: Impacts and recovery. Proc. Int. Wilderness Research Conf.: Current Research. Gen. Tech. Rep., INT-212. Ogden, Utah, US Department of Agriculture, Intermountain Research Station. Bayfield, N. G. & Lloyd, R. J. (1973). An approach to assessing the impact of use on a long distance footpath--the Pennine Way. Recreation News, Suppl. 8. Gilmore, D. N. (1975). Recreation--its impact and management in the northern Cairngorms. MSc thesis. University College, London. Lance, A. N. (1981). Evidence to a Public Local Inquiry into proposed further skiing facilities at Cairn Gorm, Scotland. Nature Conservancy Council, Edinburgh. McVean, D. N. & Ratcliffe, D. A. (1962). Plant Communities of the Scottish Highlands. Monographs of the Nature Conservancy, No. 1. London, HMSO. Nethersole-Thompson, D. & Watson, A. (1981). The Cairngorms. Melven Press, Perth. Ratcliffe, D. A. (ed.)(1977). A Nature Conservation Review. Cambridge University Press, Cambridge. Sokal, R. R. & Rohlf, F. J. (1981). Biometry. W. H. Freeman, New York. Steel, R. G. D. & Torrie, J. H. (1960). Principles and Procedures of Statistics. McGraw Hill, New York. Watson, A. (1967). Public pressures on soils, plants and animals near ski lifts in the Cairngorms. In The Biotic Effects of Public Pressures on the Environment, ed. E. Duffey. Natural Environment Research Council, London. pp. 38-45. Watson, A. (1984). Paths and people in the Cairngorms. Scottish Geogr. Mag., 100, 151-60.

Watson, A. (1985). Soil erosion and vegetation damage near ski lifts at Cairn Gorm, Scotland. Biol. Conserv., 33, 363-81.