Perception of naturalness in landscape and its relationship to vegetation structure

Landscape and Urban Planning, I9 ( 1990) 333-352 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

333

Perception of naturalness in landscape and its relationship to vegetation structure R.J. Lamb and A.T. Purcell Department ofilrchltecture.

Ckiversity q/Sydnev. N.S. W: 2006 (Australia)

(Accepted for publication 3 April 1990)

ABSTRACT Lamb, R.J. and Purcell, A.T., 1990. Perception of naturalness Landscape Urban Plann., 19: 333-352.

in landscape and its relationship

to vegetation structure.

The perceived naturalness of 7 I landscapes depicting a range of structural vegetation forms and various levels and kinds of structural alteration was judged by 8 I subjects of varying age and academic background. The subject’s judgements of naturalness were analysed in relation to the dimensions of Specht’s classification of vegetation structure and the kind and extent of structural change. Judgements of naturalness fell in the upper half of the possible range. but varied continuously between the limits, indicating that absence of human intervention is not the only basis for naturalness judgements. Withinscene variance decreased with perceived naturalness indicating less consensus in low-naturalness scenes among the subjects. This may be caused by the subjects switching the basis on which judgements are made about conflicting elements common in these scenes. The subjects’ judgements of naturalness were related to ecological naturalness but not equivalent. Tall and dense vegetation was judged more natural than low, open vegetation. The subjects could detect structural changes in all vegetation, but were less discriminating as height increased: they were more sensitive to changes in open vegetation than in dense vegetation. Scrub vegetation was seen as less natural than others, and the subjects rated all structural changes in it equally unnatural. This may relate to cognitive dimensions of involvement with the scene and implications of human scale. Agents of structural change were seen as unnatural (e.g. grazing, dereliction and weed invasion) but fire was not. The implications of differences in perceived and ecological naturalness for landscape planning and design are discussed.

INTRODUCTION

There have been a large number of attempts to quantify the value of the visual landscape to the community (e.g. Jacobs, 1975 ). These attempts were initially made in response to the impetus of legislation firstly from America and now in many countries requiring the consideration of landscape quality in producing Environmental Impact Statements and similar planning documents as part of the decisionmaking process of resource use and development. The applied orientation of research in this area has resulted, in part, in a preoccupation with consensus of judgement, and a lack

0169-2046/90/$03.50

0 1990 Elsevier Science Publishers B.V.

of development of theory to explain why landscape quality is important in human experience, and how this experience operates (Brancher, 1969; Appleton, 1975; Kaplan, 1975; Ulrich, 1986; Kaplan and Kaplan, 1983). The validity and efficacy of landscape perception research has thus been under threat from two directions: an inability to demonstrate consensus of judgement and to answer theoretical questions (Purcell and Lamb, 1984; Dearden, 1987 ) . The research to be reported here seeks to make more objective one of the, as yet, under-developed theoretical constructs in the area of landscape experience - the concept of naturalness.

334

Various approaches to assessing landscape quality which can be loosely described as psychophysical methods study individuals’judgements of preference or other aspects of the experience of a range of landscapes (e.g. Shafer, 1969; Kaplan et al., 1972; Shafer and Tooby, 1973; Zube et al., 1974). Such judgements have then been related to the physical attributes of the landscapes by using regression techniques on judgements of preference or scenic quality. Alternatively multivariate methods, such as factor or cluster analysis, or multidimensional scaling may be used to model the underlying structure of the descriptive judgements in order to develop theoretical models of the landscape experience, with subsequent analysis of the sets of landscapes associated with particular dimensions or clusters carried out to identify relevant physical attributes. Both approaches, whether they have been concerned with the physical attributes of the landscapes only (e.g. Shafer et al., 1969; Zube, 1973: Schroeder et al., 1986) or with comparing patterns of response with theoretical models of landscape experience (Dearinger, 1979; Purcell and Lamb, 1984; Purcell. 1987 ), have demonstrated the major importance of perceived “naturalness” in landscape assessment. Further the “naturalness” dimension hs been shown to be highly significant in a variety of types of landscapes ranging from forest-dominated landscapes (e.g. Shafer et al., 1969; Williamson and Chalmers, 1982 ) to those dominated by man-made structures, such as housing and industrial development (Kaplan et al., 1972; Zube, 1973; Lamb and Purcell, 1982). In addition there is a more recently developed area of research concerning the relations between aesthetic, affective and physiological responses to the visual landscape where, in common with other approaches, there is an emphasis on the central significance of naturalness as represented by vegetation (Ulrich,

K.J. LAMB

ANtI

4.7.

l’tIK(‘ELL.

1986; Dearden, 1987; Herzog, 1989; Hull and Harvey, 1989 ) . While naturalness is a theoretically and/or practically important concept in all of these research areas, the specification of what is meant by naturalness has been somewhat fuzzy. In general terms “naturalness” has been equated with vegetation presence and proportion in scenes, or in some instances with other natural elements (e.g. water, rock etc.) or simply the absence of man-made interventions. In a recent review of the research relating vegetation in landscapes to human response (Ulrich, 1986), this author shows that the terms “naare freture”, “ vegetation”, and “naturalness” quently used interchangeably, or in ways which do not make clear to what they refer. The necessity for a closer examination of the influence of certain of the physical qualities of vegetation on judgements of preference is referred to in recent work as diverse as that on street tree plantings (Schroeder, 1986), cross-cultural and sub-cultural comparisons of preferences for natural settings (Kaplan and Herbert, 1987), and differences in perceived environmental challenge and preference for landscapes in groups of children (Bernaldez et al., 1989).

There have been a number of attempts at assessing “naturalness”. One involved the use of “naturalism” indices (Linton, 1968; Zube et al., 1974; Williamson and Chalmers, 1982) based on a range of land cover types judged for their naturalness. A second approach (Daniel et al., 1977) related forest types to perceived naturalness, and Balling and Falk ( 1982 ) five “biome” types to age group preferences. A wide variety of psychophysical work concentrating narrowly on forests exists, but provides scant theoretical development and surprisingly little detail on the relationship between the physical properties of vegetation and preference (Ulrich, 1986). There is evidence that large trees

PERCEPTION OF NATURALNESS IN L4NDSCAPE

are preferred over small (e.g. Herzog, 1984), and that dense understory reduces preference. The restricted objectives of much of this work and its concentration on forestry practices limit the generality of the findings to a small number of forest types and to trees as the only type of vegetation of concern. By contrast natural vegetation contains a range of types of which forest is only one, and, even in forest vegetation, there may be a range of layers comprising life forms other than trees which contribute to the visual qualities of the scene. However, there are ways of assessing naturalness in vegetation which offer greater objectivity than that exemplified in many of the studies referred to above. Various ecological classifications of naturalness exist, which can be used to make judgements of “ecological naturalness” of the kind familiar to biologists: of these the structural and floristic are the most familiar, and can encompass all known vegetation types. By using an ecological measure of naturalness it is feasible to include most of the commonly seen types of vegetation in a given region. Ecological judgements of naturalness include the degree to which the vegetation exhibits typical structure and floristic composition: such judgements are frequently made in landscape and resource use planning and to support the need for nature conservation, or in assessing the effects of rehabilitation in natural areas. Ecological naturalness is relatively well defined; the relationship between it and perceived naturalness and preference has not been closely considered. Vegetation is the most consistent component of naturalness as described by a variety of authors. The major elements of vegetation structure as ecologically understood (height, projective foliage cover or density, and floristic identity of the uppermost stratum) are likely to be the most visually distinctive. As a consequence, comparisons of judgements of naturalness with ecologically defined naturalness based closely on these aspects of vegetation structure might make clearer the basis on

335

which judgements of scenic quality are made. In addition to the criteria of vegetation structure above, various agencies of change to this structure (e.g. fire, weed invasion, grazing use, mechanical damage and various kinds of management practices) are occasionally cited as resulting in judgements of lowered perceived quality or are inherent in many assessments of scenic quality. These can be examined more closely within the context of an ecological definition of naturalness. No systematic attempt to do this for a naturally occurring range of vegetation types has previously been made and this is the aim of the experiment to be reported. Subsequent research will have to examine the relationship between perceived naturalness, preference and ecological naturalness. METHOD Selection qf landscapes The structural vegetation classilication of Specht ( 1970), describes all the vegetation types it is possible to find in Australia in terms of height and life-form of the dominant stratum, and projective foliage cover of that stratum. In all, 44 structural vegetation forms are identified. Not all vegetation forms exist in every geographic region; it was decided initially to use landscapes which exist in the general geographic zone of the central coast and near mountains of New South Wales, Australia. In this region, 19 of the possible 44 structural vegetation forms were considered likely to be common and extensive enough to form major components of the landscape (Table 1). While vegetation height and density are perhaps the most important visual qualities of vegetation, the question of floristic identity can also give distinctiveness to certain vegetation types which would be classified under the same structural form. A dominant species could for example be of distinctive shape or colour or be texturally different from others of similar form

K..I. L4MH AND A.T I’UK(‘ELL

336 T-\BLE

I

Structural vegetation forms considered to be common or extensive enough central coast and nearby mountains of New South Wales, Australia (derived Lift-form/projective Life form

follage

height

Height

(m

) of tallest stratum Dense

Cover

( 70- 100% )

( ni ) Trees

Shrubs Herbs: Grasses Scdgcs

> 30 10-30 S-IO 2-j O-2

Tall closed forest Closed forest Low closed forest Closed scrub Closed heath Closed Closed

grassland sedgeland

and perhaps judged differently. Most Australian vegetation with tree dominants have evergreen eucalypts as the most conspicuous species, but some such as those for example with C’ullitris spp. (cypress) and Allocasuarina spp. (she-oak) with their needle-like foliage are distinctive among other similar structural forms. In view of this it was decided to include floristically distinctive vegetation forms as well as more typical examples of each structural type where these were common in the region. Vegetation maps and survey material were used to locate areas where the various vegetation forms existed, these were visited, and colour slides were taken on Ektachrome film with a Nikon FM camera and 35-mm wide-angle lens. Light conditions were standardized as far as possible by taking photographs only between 1O:OOand 14:OO h on predominantly cloudless days in autumn. Compositional variation was minimized where possible by ensuring that photographs contained only one vegetation type and similar topography. A variation which cannot be controlled is the extent of view, since this varies to some degree with both the density and height of the vegetation. The process above resulted in a large number of slides of natural vegetation (ecological sense). However, there are other causes of variation in vegetation structure unaccompan-

to form major components from Specht. 1970)

( fen )

of the landscape

in the

( %I) of tallest stratum

Mid-dense ( RO-70%

Sparse

)

( I O-30%)

Tall open forest Open forest Low open forest Open scrub Open heath

Tall woodland Woodland Low woodland Tall shrubland Low shrubland

Open grassland Open sedgeland

_

ied by obvious signs of human intervention in the landscape which would have been included in the “naturalness” dimension by previous workers (e.g. Williamson and Chalmers, 1982; Zube, 1973). These include the influence of fires (a very important part of both the natural and man-influenced environment of Australia ), grazing by domestic stock (which may not be accompanied by vegetation overstorey clearing), invasion by weeds (a common occurrence in coastal Australia often causing profound floristic and structural change to natural areas) and dereliction of previously agricultural or residential land. Where possible, examples of structural vegetation forms exhibiting each of these factors, rated on an arbitrary scale of the severity of disruption of natural vegetation structure (viz. minor, major, extreme disruption) were photographed and added to the slide set.

When all slides had been collected two main features of the set were apparent. Firstly, there was a great deal of redundancy in vegetation forms which are widely distributed in coastal New South Wales (e.g. woodland and open forest ). and secondly that others were poorly represented (in particular grassland, sedge-

PERCEPTION OF NATURALNESS IN LANDSCAPE

337

TABLE 2 Vegetation forms represented and number of slides in each cell of the experimental slide set

varying age and academic discipline, and 44 were staff of a large department store. Instructions and procedure

Life-form/projective foliage height (m ) of tallest stratum

Cover (%) of tallest stratum

Life form

Height (m)

Dense (70-100%)

Mid-dense (30-70%)

Sparse (IO-30%)

Trees

>30 IO-30 5-10 2-5 o-2

3 6 0’ 8 7

6 8 3 4 5

4 9 8 0 0

0 0

0 0

Shrubs Herbs: Grasses Sedges

‘0 value indicates that the vegetation type was poorly represented in the area or that an insufficient range of structural changes in it could be found.

land and shrubland forms) because of rarity or restricted occurrence in the region. In addition the distribution of representative slides was uneven within the vegetation forms present because of various logical relationships between factors influencing vegetation structure (e.g. it is not possible to find derelict rainforest or grazed heath in the region because normal agricultural practice does not put either vegetation form to grazing use). Redundancy was reduced in the slide set by selecting good examples of the common structural vegetation forms and types of disruption, along with distinctive floristic types where appropriate. The number of slides in each cell of the matrix describing the final slide set in shown in Table 2. A total of 7 1 slides representing 12 structural vegetation forms was retained. Subjects

One of the purposes of the work was to obtain estimates of naturalness from people of diverse backgrounds, since educational experience in particular might influence judgement of naturalness made by people with botanical/ biological knowledge. A total of 81 subjects participated: 37 were university students of

The subjects were tested in groups of about 12, slides being shown on a carousel projector with zoom lens. Prior to the test, the subjects were briefed by one of the authors as follows. A brief statement of the objectives of the study was made; to examine what is meant by naturalness in landscape by ordinary people. The reasons for the use of slides as ways of representing landscapes rather than in situ judgement were discussed and a description of the slide collection and selection procedures given. The importance of people’s perceptions of scenic quality in planning was discussed, and the idea of variations in perceived naturalness introduced by showing a representative selection of slides from the experimental slide set. The examples were shown while the procedure for rating the degree of naturalness was outlined. The subjects were thus familiarized with the range of visual material to be used. Ideally the whole slide set would be shown to the subjects but the number of slides involved made this impractical. Judgement of naturalness of each slide was made on a separate page on which was drawn a horizontal line 130 mm long with the words “not at all natural” on the left and “completely natural” on the right hand side. It was explained that a mark made at the left end of the line meant a slide with the subjects’ idea of a view that was not at all natural, and that one marked at the right end would be one appearing completely natural. A mark at an intermediate point would indicate how close the scene was to either completely natural or not at all natural in appearance. It was decided not to subdivide the scale into units because of possible dimensional biases introduced and problems with the subjects not using the ends of the scale. It was made clear that the ends of the scale represented the subjects’ ideas of ideal and anti-ideal naturalness: this approach was

33x

K J

taken so as to put the landscapes into a broader overall context. It is possible that the slides did not contain landscapes seen as either a completely natural or not at all natural type and avoids interpreting the highest (lowest ) scoring scenes in the particular set used as being representative of the ideal (anti-ideal) type. It was stressed that ratings should be made independently by subjects and that there were no “correct” answers since individual points of view could differ and this was an important possible discovery. Each slide was shown for 10 s, and two different orders of the set were used, the slides having been arranged in the carousel in random order: l-7 1 and 7 1- 1.

TABLE Mean

RESULTS

AND DISCUSSION

naturalness

scores standard

deviations

and variances

in rank order

Slide

Position

Mean

Standard

access

in experimental

naturalness

dcvlation

No.

order

score’

(SD)

12/1x 6/X 7/1x

II 1x IY

53.5

40.5

1647.8

53.7

36.4

1331.6

53.0

41.X

IX3l.Y

6

5X.0

38.7

I4YY.X

2113

43

5X.4

40.7

1621.7

ofslidc

Variance

-

?/II 7/x

I4

5Y.Y

40.6

1654.X

11/37

I6

6 I .1

40. I

1613.3

417 I?/11

I5

6I h

3Y.6

1515. I

20

67.7

41.x

174x.4

13/1-I

13

72.1)

3Y..3

1546.3

17/15

39

77.7

3Y. I

1530. I

l/l’)

47

73.X

31 .o

168X.9 I5YY.7

35

75.0

39.4,

3125

4-I

76.5

35.3

1156.3

4/l4

50

76.X

36.6

l34l.S

l3/lS

77

7X.2

41.1

1702.1

X/l6

57

7X.6

36.7

1316.7

l/71

6X

7Y.Y

36.4

1377.0

4/Y 4/ 6

34

x0.5

35.5

I764.?

25

no.5

36.3

1370.0

7/30

21

XI.0

41.4

1716.7

13116

24

Xl.7

37.1

l3YO. I

l/l5

67

x3.1

34.4

I I x5.0

X/3

73

X3.6

37.0

1371.‘)

5131

53

x3.5

37.8

1430.7

l7/3S

4x

S4.6

36.3

13lY.7

TIX

52

n4.Y

3X.6

I4Y7.7

13136

63

X4.Y

36.4

1325.5

l2/ZY

56

x5. I

is.4

1757.1

1414

30

x5.4

36.2

1313.1

3

X6.7

3j.Y

13X6.4

64

X6.X

32.4

1053.3

313

4Y

X7.6

33.7

I I3Y.5

13/Y

55

XX.1

33.7

1131.’

13127

54

x0.0

36.6

1344.5

17136

71

Y2.3

30.3

l/34

60

Y1.3

31.6

l3/17

70

Y3.’

7Y.Y

32

Y4.0

32.2

IO405

13/X TIX

51.32

Y I Y.6 1002.7 XY4.3

x

Y-l.7

34.3

I 177.7

3126

2Y

44.0

3h.7

1347.6

h/23

IO

Y5.6

2X.0

413

62

Y5.7

32.6

I063.7

5130

42

Y7.h

35.9

1701.8

3

9X. I

30.x

03Y.7

65

YY. I

26.5

707.5

51

YY.9

2Y.5

872.0

I/h

I/X j/33 I?/3

Table 3 shows naturalness mean scores and standard deviations for all the slides arranged

.A T. I’t:KC’EI.L

3

for the slide set arranged

l3/33

Data were recorded by dividing the scale line on which judgements to each stimulus were recorded into l-mm segments, and counting the segment in which each judgement was made, starting from the left (the “not at all natural” end). Scores could thus be integers between 1 and 130. The data were submitted to analysis of variance using the SPSS package. The experiment was a non-orthogonal randomized blocks design, the factors analyzed in factorial combination. Only interactions up to the second order were called for: it was considered that the difficulty of interpreting higher level interactions made their use of questionable value even if higher degrees of significance could be obtained. Factors used were foliage height of upper stratum (five classes), projective foliage cover (three classes), dominant floristic element (two genera) agent of structural alteration (four types) and extent of alteration (four levels ).

ILAMH AND

788.8

3/lO

6’)

100.0

30.9

056.0

l4/13

36

loo.5

2Y.Y

X98.7

5137

61

100.6

2Y.5

x71.x

5126

37

I0l.0

34.6

I201 .Y

PERCEPTION

OF NATURALNESS

IN LANDSC4PE

TABLE

3 (continued)

Slide access No.

Position of slide in experimental order

Mean naturalness score’

Standard deviation

13125 7126 z/20 l/31 5/34 6124 l4/32 6111 l/14 6115 2124 6/18 l4/2l l/26 14129 13/24 6113 6111 14131 3/l

66 38 33 18 4s 5 31 46 40 26 59 41 58 9 17 7 12 2 22 I

101.1 101.6 102.3 103.0 104.4 105.1 105.4 105.5 107.0 107.8 107.9 108.1 108.3 108.5 109.2 109.6 II I.1 1 I I.2 I1 I.6 I 15.4

28.2 30.8 27.1 26.0 31.1 29.0 26.5 27.6 24.1 27.9 20.2 29.4 24.8 20.4 24.2 23.1 21.9 20.1 21.6 19.2

‘Means

are derived

339

Variance

(SD) 800.0 951.0 739.7 676.9 970.5 842.5 703. I 764. I 611.5 781.6 408.8 868.6 616.6 414.7 589. I 535.6 483.3 403.7 469.6 370.9

from 7 I observations.

in rank order. All slides were rated by subjects as in the mid and upper range of naturalness, scores falling between 53.3 and 115.4 on a possible scale 0- 130. The absence of obvious human intervention such as structures, artefacts or managed land probably led to high naturalness ratings. The range of perceived naturalness varied continuously between the limits above indicating that, despite the absence of man-made influence, a large range of variation in naturalness was perceived among the scenes depicted. The absence of human interventions in scenes or the “greenness” alone are clearly not the only basis for judgements of naturalness. This in itself would indicate that various indices of naturalness dependent simply on absence of clear human influence, i.e. where all vegetation is treated as equal (e.g. Zube, 1973)) do not take sufficient account of discriminations made among vegetation types. A second type of naturalness rating is a naturalism index (e.g. Williamson and Chalmers, 1982) using judgements of expert panels which are based on “landcover” types. These probably contain

implicit discriminations both between vegetation types and land uses which are characterized by particular vegetation types. Neither of these two methods of assessing naturalness is therefore sufficiently sensitive to discriminations based on vegetation type, the first because it treats all vegetation as essentially the same, and the second because any discriminations which do occur are implicit in the overall naturalism index assigned by averaging the judgements of a small number of experts. Within-scene variance in the naturalness mean scores tended to decrease with increasing perceived naturalness. Over the range of scenes standard deviations ranged from 42.8 to 19.2. Variance would normally be expected to increase with increasing mean value, but in this case a decrease is caused by a greater lack of consensus in the low-naturalness scenes between subjects. A similar result was reported by Williamson and Chalmers ( 1982) who concluded that the degree of consensus in photo sort ratings by 19 groups of observers of diverse backgrounds was dependent on the degree of naturalism in the scene. High variance may result from respondents judgements being spread across the scale of naturalness. As pointed out by Purcell and Lamb ( 1984) however, lack of consensus as illustrated only by measures of variance may be misleading. High variance across scenes can result from a small number of groups of observers changing their point of view (switching the basis on which judgements are made), particularly in response to scenes with conflicts between major elements. For example (see Table 3 and Fig. 1 ) Landscape 11 (mean naturalness score (mns) 53.5, standard deviation (sd) 40.5 ) and Landscape 19 (mns 53.9, sd 36.4), among the lowest in perceived naturalness and highest in variance, both exhibit conflicts between natural vegetation and man-made alteration (an abandoned track in 11 and the effects of grazing in 19). The conflict could be more cognitive: Landscape 28 (mns 53.7, sd 36.4) could be seen as

R.J. L4MB

4ND

4.T

PLJR~ELI.

Fig. I. Examples of scenes from the naturalness judgment cxperimcnt with above average varlancc compared with their mean naturalness score (mns). I I Open scrub with abandoned tracks: Sydnc) Harbour Natlonal Park. 19 Woodland with the undcrsurrounding derelict farmland: Pipcclaq Point Park. Narrabccn Lakes. 15 store? grazed by sheep: Duffys Forest. 28 Woodland (‘loscd scrub invaded b> exotic weed species foIlowIng partial clearing: Sydney Harbour National Park.

PERCEPTION

OF NATURALNESS

IN LANDSCAPE

341

K.J

FIN. ()pen

I.

(contd.

) 27

Low open fbrcst wth

heath in natural

condition:

tmnal Park. 54 LOM woodland

rnechanlcal

Kuring-gal

invaded

damage caused b> fire control

C‘hasc National

b! exotic wed

spmcs:

Park.

79 (‘Iused

\chlclcs:

LAMB

4ND

4.T.

[>a\ Idson State Kccrcatlon

heath in natural

1’1pccla) Point Park. Narrabcen

condition: Lakes.

Sbdnq

PIIRC’ELL

.Area. 7

Harbour

I

Na-

PERCEPTION

OF NATURALNESS

IN LANDSCAPE

343

K J. LAMB

344

Fig. 1. (contd.) 37 Tall woodland Lakes. 4 I Tall open forest invaded

invaded b>l tropical climbers and other exotic weed species: by exotic weed species: Jamieson Park. Narrabeen Lakes.

Mlddle

Creek

AND

A T. PIIKC‘ELL.

Valley,

Narrabeen

PERCEPTION

OF NATURALNESS

IN LANDSC-\PE

a natural background and derelict foreground for those who recognize it, or as a natural boundary between two vegetation types; Landscape 15 (mns 61.6, sd 39.6) might appear a natural scene, or, to those who know, a weedinvaded and degraded area. Throughout the slide set, scenes with above average variance in relation to their mns (e.g. Landscapes 27, 2 1, 54, 29, 37 and 41) showed either natural vegetation dominated by low shrubs and with little apparent internal variation (2 1,29) or taller vegetation with structural change caused by mechanical damage (27) or invasion by new species of unnatural type (54, 4 1 ) or life-form ( 37 ). In any of these cases the scenes may have been seen as natural, or representing a conflict between natural elements and agents of structural change, mainly human in origin. None of the measures of the subjects’ educational background, age, sex, place of living for extended periods and countries of origin explained the distribution of mean naturalness score or variance within the data, so possible groups of the subjects with differing points of view could not be attributed to these variables. effects qf interactions between structural criteria and agents of change on perceived naturalness The results of the effects of interactions between the various structural criteria and agents of change in vegetation on perceived naturalness are shown on Fig. 2 a-d. The main effects of these are not presented, because it is invalid statistically to deal with main effects separately if a significant interaction between them can be demonstrated. In the present cases significant differences exist for all interaction factors. Because the experimental design is highly asymmetric (cells contain variable numbers of slides for various reasons detailed above) it is difficult to calculate a meaningful measure of significant difference which can be applied over the whole data set. In considering the interactions of factors, where a variable number of

345

means may be involved in creating the interaction tables, it is not appropriate to use a simple measure of significant difference (e.g. LSD). This is because the value of significant difference between any two means must be increased as the distance between them in rank order increases. This helps to account for differences in the numbers of means contributing to each cell of the interaction table. It was decided to use Duncan’s Multiple Range Test within the interaction tables as a measure of significant difference because this test is scaled to account for the distance between means when they are ranked. Interactions between structural criteria Vegetation dominated by trees of above 30 m in height was judged most natural in appearance no matter what the foliage cover (Fig. 2a). As foliage cover increased, the height of trees became more important in making judgements of naturalness (e.g. vegetation with dominant trees of lo-30 m in height was judged more natural with dense foliage cover than with medium cover). This result conflicts with the conclusion of Ulrich ( 1986) that preferred unspectacular natural scenes with trees are generally ordered and park-like, with relatively unrestricted field of depth and a focal point of some type. There appears to be a distinction between naturalness and preference in this case, the ratings of perceived naturalness in this study not following the trends of preference described by Ulrich. Hull and Harvey ( 1989), showed that the density of trees was positively correlated to affective responses of pleasure and arousal, but pointed out the necessity to distinguish between “molar” and “molecular” landscape qualities when assessing the contribution of various factors to the experience of landscapes. In addition it should be pointed out that, in the experiment reported here, it is the interaction of the two factors of height and density which are important, not the contribution of each separately. However, vegetation dominated by shrubs of

K.J. L.AMH 4ND .A T. PIIKC’ELL

346

(a)

Mean Naturalness Score (mns)

80

70

Height of tallest stratum

Vegetation

“Z$ 003

““;‘“6& rUfnG;ow3

33-i

3

3

3

0 3

-4

oh)-” 00 ” GO NV103 333-1

form

Sparse (1 O-30%)

Mid-dense (30.70%) Projective

Dense (70~100%)

FoIlage Cover

FIN. I!. (a) Effect of mean naturalness score of the interaction between height of the dominant vegetation stratum and projective follage cober. Bars surmounted by the same letter are not significantly dtfferent (Duncan’s Multiple Range Test; P ~0.01 ). (b ) Effect on mean naturalness score of the interaction between projective foliage cover of the dominant stratum and the extent of Impact of various agents of structural change. Bars surmounted by the same letter are not significantly different (Duncan’s Multiple Range Test: I’< 0.0 I ). (c) Effect on mean naturalness score of the interaction between height of the dominant vegetatlon stratum and the extent of impact of various agents of structural change. Bars surmounted by the same letter arc not significantlq chffercnt (Duncan’s Multiple Range Test: I’< 0.01 ). (d) Effect on mean naturalness score on the interaction between the hclght of the dominant vegetation stratum and the type of agent of structural change. Bars surmounted by the same letter are not slgnilicantly different (Duncan’s Multiple Range Test: Pt0.01 ).

2-5 m height was judged to be of lowest naturalness, and this judgement was unaffected by density. This unusual result might be explained in terms of cognitive dimensions of the subject’s experience of the scenes. Judgements of naturalness are closely related to preference or liking for the scene, since what has been labelled a naturalness dimension usually accounts for a large proportion of the variance in

preference judgements about landscapes (e.g. Wohlwill, 1976; Ward and Russell, 1981; Herzog, 1989). Preference in most experiments can be shown to relate to “content” and both dimen“making sense” and “involvement” sions (Kaplan and Kaplan, 1983). In the scenes shown to the subjects, shrubs of 2-5 m in height, because of their relationship to the height of a human viewer, restrict extent of

PERCEPTION OF NATURALNESS

347

IN LANDSCAPE

t (W 110-

Mean Naturalness Score (mns)

Sparse (1 O-30%)

Mid-dense (30-70%)

Projective

Dense (70.10!2%)

Foliage Cover

Fig. 2 (continued).

view and therefore offer little “prospect” (Appleton, 1975 ), “legibility” and “mystery” (Kaplan, 1975 ) or “affordance” (Gibson, 1979): all these can be thought of as cognitive “making sense” or “involvement” dimensions positively related to scenic preference. Recent work supports the notion that the restriction of mid-ground view causes reduced preference (e.g. Kaplan and Herbert, 1987; Bernaldez et al., 1989). Further, the restricted extent ofview may cause the viewer to consider more closely the proportions of the human body as the scaleobject projected into the scene; the involvement dimensions of “mystery” (Kaplan and Kaplan, 1983 ) may become more closely related to the scale of the viewer than is the case in panoramic views. The dimension of “scale” then might not only be a global dimension, but become more cognitive as elements within the

scene restrict the extent of view, and as information on depth and distance becomes more detailed and attributable to discrete and recognizable elements of the scene. For this vegetation type then the various issues above related to preference may also be related to the experience of naturalness. Interactions between structural criteria and extent of structural change

Fig. 2b shows the interaction of foliage cover and extent of the impact of various agencies of structural change on judgements of naturalness. Subjects were capable of detecting changes in structure, and rated all vegetation types as less natural when structurally altered. The ability to discriminate level of interference altered with the foliage cover. All levels of interference were judged as equally unnatural

K.J. LAMB AND 4.7. PCIR(‘F1.L

348

Mean Naturalness Score (mns)

Shrubs O-2m

Shrubs 2-5m

Trees 5-10m

Life-form

/ height

Trees 10.30m

Trees >30 m

of tallest stratum

Fig. 2 (continued).

with sparse foliage cover. As foliage became more dense the ability to discriminate between levels of interference became finer. In dense vegetation, extreme structural alteration caused mainly by grazing or weed invasion was judged as showing lowest naturalness. Clearly indices of naturalness in landscape scenes should include estimates both of floristic (i.e. based on species composition) and structural naturalness, since viewers are capable of discriminating both aspects to some extent. In particular those naturalness indices including either explicit or implicit weightings on the basis of landcover types (e.g. Zube et al., 1974; Williamson and Chalmers, 1982) would require closer examination in terms of the kind of vegetation structure and prominent species they contain. In Fig. 2c it can be seen that ability to dis-

criminate levels of structural interference is also related to vegetation height. As the vegetation becomes taller, the ability to discriminate between natural and altered vegetation decreases: in the tallest forest, extensively altered structure was judged more natural than that with minor alteration. In lower-growing vegetation however, all levels of intervention were seen as decreasing naturalness except for minor interventions in low shrub-dominated communities (heaths). Viewers may have been confused in this case by the similarity between naturally open heaths and those made open by foot and vehicular traffic, clearing, etc. However the foregrounds of many of these scenes were “concealed” by low-growing vegetation in the terms used by Herzog, and yet were rated in the lower part of the naturalness scale, in contrast to the positive effect on preference re-

PERCEPTION OF NATURALNESS IN LANDSCAPE

349

100

90

Mean Naturalness Score (mns)

60

Grazing

Fire

Dereliction

Weed

invasion

Type of agent of structural

Natural

change

Fig. 2 (continued)

ported for this factor (Herzog, 1989). In vegetation dominated by shrubs of 2-5 m in height, naturalness in scenes with structural changes was again judged as lowest of all, and although severely degraded scenes received the lowest mean naturalness score in the experiment, viewers could not appropriately separate minor and major interventions. They were however more sensitive to any factor causing structural change in this vegetation type than in any other and the lack of discrimination of the levels of intensity of intervention could be

seen as an indication that the subjects saw all interventions as equally unnatural. The reasons for this result may be related to meaning attributed to scenes by the subjects based on experience and cultural conditioning (Fenton, 1985 ). Familiarity with vegetation of this scale, which is typical of gardens and other designed human environments with their richness of experience and with which respondents will have had individual close experience (Hull and Harvey, 1989)) may lead to more complex relationships between cognitive dimensions being made within stimuli and hence more so-

phisticated discriminations within scenes. Purcell ( 1987) suggests that judgements related to naturalness are influenced by the position of various recognized alterations to the expected appearance of the landscape, and these are more significant when occurring in the foreground. Included in the data set were a number of scenes of vegetation which had been made park-like in structure by grazing of sheep or horses: these were judged of lower naturalness than similar vegetation which had not been so treated. Again these results conflict with generalizations about preference for manicured foregrounds and smooth ground-planes (e.g. Ulrich, 1986; Kaplan and Herbert, 1987 ). A possible distinction between naturalness and preference is again implicated for this type of vegetation structure. Interactions hetl-tven structural c!f’ugmt.s c~f‘structural chary+>

criteria

and t!pcs

Fig. 2d shows the effect on perceived naturalness of the interaction between type of structural intervention and vegetation height. The data set is particularly uneven in this case for reasons explained earlier. Nevertheless, it can be seen that the effects of grazing and dereliction (usually following failed agricultural use) were recognized and caused among the lowest judgements of naturalness in the experiment. The landscapes so produced are relatively open, park-like, and ordered: yet the perceived naturalness is low. This adds further weight to the contention that in certain interactions of structural criteria, naturalness and preference are not equivalent. The effects of fire on the other hand were seen to have little influence on naturalness. This result could be strongly culturally influenced since it would be expected that subjects from countries where fire is unusual in natural systems would see it as unnatural in the first instance or fail to recognize its effects. The Australian subjects saw fire and its effects as natural, both in recently burned and regenerating scenes. In these cases the effect of fire in making great changes to the

extent of view and smoothness of the groundplane, did not alter the ratings of naturalness. As pointed out by Kaplan and Herbert ( 1987 ), familiarity with the landscape’s physical features is also important in preference. Weed invasion of natural areas was seen as unnatural, but recognition of it decreased as vegetation height increased. Once again the effect of the rating of scrub vegetation invaded by weeds as having the most unnatural appearance is striking. However, it is also significant to note that the presence of exotic plant species in scenes caused decreased naturalness judgements even where their presence did not result in changes to the overall vegetation structure of height, life form or foliage cover. This result indicates that the specific identity of the plants involved in scenes may be important to the experience of naturalness. The necessity for more work concerning the identity of plant species has been cited by workers in the preference area also (e.g. Ulrich, 1986; Kaplan and Herbert, 1987; Schroeder. 1986 ). In much of this work the inadequate distinction between naturalness and preference may have led to a confusion between the contribution of the simple physical attributes of scenes and more complex psychological dimensions contributing to the experience of landscape. This illustrates further the necessity for an adequately defined naturalness dimension. In this experiment subjects made quite fine discriminations on the basis of species identity: clearly measures of naturalness which do not assess the contribution of this factor are not sufficiently sensitive, and some (e.g. estimates of landcover type) too gross to be of general use. Implications and planning

qf‘rcwlts,fVr

landscape

managtwtwt

The implications of these results in practical terms are many. Ecological naturalness and perceived naturalness are related but not equivalent. As a consequence, decisions made about design and management of landscapes

PERCEPTION

OF NATLJRrZLNESS

351

IN LANDSC4PE

must acknowledge that separate objectives may be necessary for ecological and scenic management programmes. For example, heaths are seen as less natural than forests, but from ecological perspectives they may be valuable to preserve. On the other hand, severely weed-invaded forests are seen as natural, despite the fact that their ecological values are diminished. Decisions on management of landscapes based solely on scenic criteria would need to be specially aware of the dynamic changes caused by such influences as weed invasion. Increasing change in structure leading to the degeneration of the vegetation is likely (for example open forest may become closed scrub with little internal variation), and the scenic quality of the landscape will be consequently reduced over time. It is important that land managers be aware of the different values implied by ecological and scenic assessments: each may require different planning and management procedures. It is also necessary to remember that dynamic ecological processes continue within all vegetation whether or not it has suffered structural change and that its scenic qualities may not be stable over time. In relationship to landscape design, rehabilitation and regeneration two results are especially relevant. The first is that expected vegetation structure is the main criterion of naturalness, and that viewers may discriminate quite finely in terms of unexpected species, life-forms, etc. particularly in low-growing vegetation. The second is that, at least for the subjects of this experiment conducted in Australia, the effects of fire were seen as natural even for scenes of recently burned vegetation. The use of fire as a management tool in fire and weed control, and species conservation programmes would appear unlikely to conflict with scenic objectives, although this is often given as a reason against Iire use in these circumstances.

Implicationsjbrfirther

research

This experiment indicates that generalizations equating the dimension of naturalness with preference for scenes containing vegetation are not fully warranted. The interaction of a number of structural criteria related to vegetation in the scene is frequently more important in describing the reason for differences in naturalness judgements than any of them separately; this applied particularly in vegetation not dominated by trees. It is further indicated that experiments examining the relationship between preference and naturalness for the same set of landscapes chosen on the basis of ecological criteria is necessary. REFERENCES Appleton. J.. 1975. The Experience of Landscape. Wiley. New York, NY. Balling, J. and Falk, J., 1982. Development of visual prefcrencc for natural environments. Environ. Behav.. 14: S28. Bernaldez, F.G.. Abcllo. R.P. and Gallardo, D.. 1989. Environmental challenge and environmental preference: age and sex effects. J. Environ. Manage., 28: 53-70. Brancher, D.M., 1969. Crttique of K.D. Fines: Landscape evaluation: A research project in cast Sussex. Reg. Stud., 3: 91-92. Daniel. T.C.. Anderson, L.M.. Schroeder, H.W. and Wheeler. L., 1977. Mapping the scenic beauty of forest landscapes. Leisure Sci.. 1: 35-52. Dearden, P., 1987. Consensus and a theoretical framework for landscape evaluatton. J. Environ. Manage.. 34: 267278. Dearinger, J.A., 1979. Measuring preferences for natural landscapes, Procecdmgs of the American Society of Civtl Engineers. J. Urban Planning Dev. Div.. 105: 63-80. Fenton. D.M.. 1985. Dimensions of meaning in the perception of natural settings and their relationship to aesthetic response. Aust. J. Psychol., 37: 325-339. Gibson, J.J., 1979. The Ecological Approach to Visual Perception. Houghton Mifflin. Boston, M.A. Herzog, T.R., 1984. A cognitive analysis ofpreference for ticldand-forest environments. Landscape Res.. 9: IO- 16. Herzog, T.R., 1989. A cognitive analysis of preference for urban nature. J. Environ. Psychol.. 9: 27-43. Hull, R.B. and Harvey, A.. 1989. Explaining the emotion people experience in suburban parks. Envtron. Behav.. 2 I : 323-345. Jacobs, P., 1975. The landscape image: current approaches to the visual analysis of the landscape. Town Planning Revue. 46: I27- I 50.

352 Kaplan. S.. 1975. .An informal model for the prediction of preference. In: E.H. Zube. R.O. Brush and G.D. Fabos (Editors 1. Landscape Assessment: Values. Perceptions. Resources. Dowden. Hutchinson and Ross Inc.. Stroudsburg, PA. Kaplan, R. and Herbert, E.J., 1987. Cultural and sub-cultural comparisons in preference for natural settings. Landscape IJrban Planning, 14: 281-293. Kaplan, S. and Kaplan, R.. 1983. Cognition and Environment: Functioning in an Uncertain World. Praeger Publishers. New York. NY. Kaplan. S.. Kaplan R. and Wendt. J.S.. 1972. Rated preference and complexity for natural and urban visual material. Percept. Psychophys.. 12: 354-356. Lamb. R.J. and Purcell. .A.T., 1982. .A landscape perception study of the Peninsula area of Warringah Shire: implications for planning controls. building regulations and other arcas of council activities. University of Sydney Occasional Paper. Department of Architecture. 40 pp. Linton. D., 1968. The assessment of scenery as a natural resource. Scott. Geogr. Msg.. 84: 2 I Y-138. Purcell. A.T.. 1987. Landscape perception. prefcrencc and schema discrepancy. Environ. Planning B: Planning Design. 13, 67-91. Purcell. A.T. and Lamb. R.J., 1984. Landscape perception: an examination and empirical investigation of two central issues in the area. J. Environ. Manage.. 19: 31-63. Schroeder, H.W.. 1986. Estimating park tree densities to maximisc landscape esthetics. J. Environ. Manage., 73: 325-333. Schroeder. H.W.. Buhyoff. G.J. and Cannon, W.N.. 1986.

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Cross-validation of prcdtctive models for esthetic quality of residential streets. J. Environ. Manage.. 23: 309-326. Shafer, E.L.. 1969. Perception of natural environments. Environ. Behav., 8: 7 l-82. Shafer. E.L. and Tooby. M.. 1973. Landscape preferences: an international replication. J. Leisure Res.. 5: 60-65. Shafer. E.L.. Hamilton Jr. J.F. and Schmidt. EA., 1969. Natural landscape preference: a predictive model. J. Leisure Res.. I: I-19. Specht. R.L., 1970. Vegetation. In: G.W. Leepcr (Editor). The Australian Environment. CSIRO Publication, Melbourne University Press, Melbourne. Ulrich, R.S.. 1986. Human response to vegetation and landscapes. Landscape Urban Plannmg. 13: 29-44. Ward. L.M. and Russell, J.A.. 1981. The psychological rcpresentation of the molar physical environment. J. Exp. Psychol.: Cieneral. I IO: 111-I 52. Williamson, D. and Chalmers, J.A.. 1982. Perceptions of forest scenic quality in northeast Victoria: a technical report of Phases I and II. Landscape Management Series, Forests Commission of Victoria, Melbourne, Victoria. Wohlwill, J.F., 1976. Environmental aesthetics: the environment as a source of affect. In: I. Altman and J.D. Wohlvvill (Editors), Human Behaviour and Environment: .Advances in Theory and Research (Vol. I ). Plenum Press. New York. NY. Zube. E.H.. 1973. Rating everyday rural landscapes in the northeastern U.S. Landscape Archit., 63: 370-375. Zube, E.H.. Pitt, D.G. and .Anderson. T.W.. 1074. Perception and management of scenic resources in the southern Connecticut River Valley. Institute for Man and Environment. University of Massachusetts. Amherst. MA.