Determining conservation priodties Ralf C. Buckley Principal Environmental Scientist, Consultant Division, AMDEL, Flemington St., Frewville, SA 5063, Australia.
ABSTRACT One important component in achieving an optimal compromise between mineral development and environmental conservation is to rank different geographical areas according to their priorities for development and conservation respectively. The latter is considered here. There are three main steps in assigning conservation priorities: (i) acquisition and assessment of information on the existing baseline environment and on potential impacts; (ii) assignment of values to the environmental components concerned and integration of these to yield overall values foi"alternative possible conservation targets; and (iii) incorporation of logistic considerations to determine the practical priorities for conservation. One particularly critical aspect of this process is the relative significance of different conservation criteria, specifically including the presence of rare Species, high diversity, pristine condition and representativeness. These criteria all reflect the same underlying conservation values, but their relative significancevaries from case to case. Their integration is based on professional judgement rather than any formal algorithm and explicit guidelines for such judgement are needed to promote consensus in' the determination of conservation priorities.
INTRODUCTION To achieve a balance between mineral exploration and other forms of development on the one hand, and environmental conservation On the other, the relative value of land areas for different purposes must be assessed and compared. Ideally, these values should be assessed in the same units, but no satisfactory unit for measuring both value for development and value for conservation has yet been found. An alternative approach is to rank differentgeographical areas according to their development value on the one hand and their conservation value on the other, and compare the two rankings so that, other factors permitting, areas with high development priority and low conservation priority can be allocated to development, and vice versa. This is m o r e straightforward since numerical comparisons are made only within each set of units rather than between two sets, and the final comparison is non-parametic. Such a comparison is of course only one c o m p o n e n t in the overall process of attempting to optimise resource allocation. Use of land for one purpose, for example, may change its value for another, and hence it is important to assess the sensitivity of the areas concerned to the impacts associated with different potential forms of development. Priorities for development are generally assigned EnvironmentalGeochemistryand Health, 1985,7(3), 116-119.
according to the estimated net economic return to the intending developer or the assessed socioeconomic benefit to the region or community involved, and these can generally be expressed in dollar or dollar-convertible terms with reasonable repeatability. H o w should conservation priorities be assigned? This contribution attempts to analyse the processes involved, and to identify the most critical steps. To those professionally involved in nature conservation, most of the considerations outlined here will be second nature, but this analysis may help to focus attention on the critical issue of explicit weighting and ranking of conservation values as a step in assigning conservation priorities. To those who are not themselves involved, but whose activities may impinge on the processes of nature conservation - for example, those involves in the development of mineral resources, primary industries, and tourism -- this analysis provides a rationale for assessing conservation significance which may be of value in m a n a g e m e n t , particularly at the project planning stage where alternative sites, techniques and m a n a g e m e n t strategies are available. The process of practical conservation can usefully be subdivided as follows: A. Determination of conservation priorities: 9 information acquisition and assessment - baseline - impact 9 value assignment 9 priority assignment B. Implementation of conservation measures: 9 legislation 9 physical protection (and positive m a n a g e m e n t , where appropriate) 9 public education This discussion is concerned only with determination of priorities, but the implementation steps are relevant since the logistic aspects of assigning conservation priorities include the feasibility of implementing them. The difficulties in converting information to policy have recently been examined in general terms by Sebek (1983), Ruckelshaus (1983), and Harris (1984), and a specific example by Shapiro (1984). In principle the first three steps under (A) above, are consecutive: since information acquisition requires time and money, however, they are generally p e r f o r m e d iteratively in practice.
Ralf C. Buckley INFORMATION ACQUISITION The first step, information acquisition and assessment, is an objective process in the sense that it is amenable to scientific testing. It aims to determine what there is to conserve and how it functions - the baseline assessment - and what changes would be produced by external disturbances- the impact assessment. The first involves inventory, mapping, pattern analysis, experimental process studies (see eg., Buckley 1984, Prodgers 1984). In practice such information is never complete, and a degree of subjectivity is involved in estimating the magnitude and nature of the deficiency. Such deficiencies, however, can always be reduced by collecting further data. Similarly, impact assessment is largely a process of comparison and deduction, but is still classed as objective since the assessment is a prediction that c a n - and often i s - tested by actual application of the external disturbance considered. The detailed processes and problems of environmental impact assessment have been reviewed recently by Baggs (1983), Beanlands and Duinker (1984), and Hirst (1984). Assessment may be compelled to rely on expert opinion when data are lacking, but though the distinction between data and opinion is of course important, opinion on baseline and impacts can always be subjected to test by further observation or experiment. VALUES AND PRIORITIES Values~ in contrast, are by definition untestable, and differ from one person or organisation to another, particularly in the relative weighting of commerce and conservation. The two do not always conflict, but when they do their relative importance is a continual bone of contention. This aspect will be considered later, but first it is necessary to determine how conservation values can be established. As demonstrated in the recent review by Roome (1984), many different criteria have been proposed. In general, high conservation value is assigned to items, species, assemblages, areas, heritage artefacts - which are irreplaceable or unusual. Things which are common and easily replaceable may also be very valuable, but are generally not in such urgent need of conservation- though there is the danger that items which are initially common will continue to be exploited without control or conservation long after they have been reduced to rarity, since they are sti!l perceived as common. The overall philosophy of nature conservation has been discussed in detail by Ratcliffe (1977) and more recently by Salim (1984). The presence of rare or endangered species or their support systems, or unusual species assemblages and associations, thus provide primary conservation criteria. Support systems comprise food and habitats, particularly those required for critical life stages such as breeding and migration. High diversity, either of species, communities, habitats or terrain types, is another major criterion, as is pristine condition: freedom from weeds, feral animals, clearance, overgrazing, overburning, pollution, and engineering structures or activity. High diversity and pristine condition are often exceptional in their own right, largely as a result of past and present human activity. They also embody the endangered-species criterion indirectly, as follows. On
117
a global scale, existing data on species taxonomy, distribution and populations are very incomplete. Hence many species may become endangered before we have even become aware of their existence. Such species are more likely to be present in diverse than depauperate communities. Hence conserving diverse though incompletely described ecosystems may be more effective, overall, in conserving as many individual species as possible, than conserving small remnant populations of species known to be endangered. This argument is often supported by the suggestion that such remnant populations may become extinct in any event despite our best efforts to conserve them and it is therefore wasteful to squander limited resources on their behalf. This, however, is surely an unduly pessimistic view, since there are numerous examples of species which have been successfully rescued from the threshold of extinction and bred back to self-sustaining populations. Such measures certainly are expensive, however, and conservation resources certainly are limited, so the practical feasibility of conserving remnant populations will depend on the life history characteristics of the species concerned, together with a range of logistic aspects. The criterion of "representativeness" has also been used in assigning conservation values, particularly in recent years, and the creation of representative reserve networks to conserve an example of each ecosystem within a given area is often a major aim of conservation organisations. This criterion still embodies the same primary values, but more indirectly. If an effective way to conserve as many species as possible is to preserve diverse ecosystems, then the most effective way to preserve the greatest diversity on a global scale is to conserve a representative section of as many different ecosystems as possible. Representative reserve networks are hence a means to the conservation of maximum diversity overall. They have an additional advantage in providing reference areas against which to assess future change in unprotected portions of the ecosystems concerned. There are hence a number of different conservation criteria- rare species or assemblages, high diversity, pristine condition, representativeness- which are all valid and which are all related in principle. Effective conservation of individual species, communities or heritage items generally requires protection of defined geographical areas where they occur, however, in addition to any legislation giving them formal protected status. Hence in practice conservation values are rarely assessed independently: they must be combined or integrated to assign overall values to alternative areas. The four major criteria listed above do not always coincide for any given set of areas, so to assign overall conservation values the criteria must be ranked or weighted in some way. There is no fixed ranking, because the significance of each criterion is variable, depending on the degree of rarity, diversity, modification, and so on. In addition the value attached to a rare species depends on the actual species concerned, and its significance in determining overall conservation values depends on its overall conservation status; specifically on its representation in existing conservation reserves elsewhere. Similarly, there are many different possible measures of diversity and of condition.
118
Determining conservation priorities
The relative significance of different conservation criteria currently appears to be an ar~a of divergent opinion, and deserves further attention. My own personal opinion is that there is no universal ranking of conservation criteria, and priorities must be assessed on a case-by-case basis, for the reasons summarised below. The only general constraint on possible rankings is that no single criterion is universally pre-eminent. This can be illustrated as follows. The herculean efforts of the W.H.O. and others to eradicate the smallpox virus (Harris 1984), for example, show that in this case at least the preservation of a species is greatly outweighed by other considerations. At the other extreme, the preservation of species, such as, for example, the giant panda, is generally acknowledged to outweigh any potential economic return from exploitation of its habitat (Gengtao 1985). Between these extremes there is no sudden threshold, but rather a gradual scale of perceived values, which varies with individual perception. My impression of public opinion in the Western w o r l d - a general overview subject to variation at local, regional and national scales - is that m o s t mammals and birds would be seen as of equal value by some and lesser by others. Invertebrates are generally seen as of lesser significance than vertebrates. Within the invertebrates, the larger and more conspicuous crustaceans, molluscs, actinozoans and arthropods, such as crayfish, giant tritons, reef corals and birdwing butterflies, are generally seen as of greater value than their smaller and less conspicuous relatives or than the less well known groups such as worms, amphipods and isopods. These in turn are seen as more significant than the protozoans. This is not to imply that these smaller and less conspicuous organisms are not valuable but merely to observe that they are perceived by the majority of people as less valuable than the larger and more conspicuous species (cf. Ratcliffe 1977, p.10). Since rarity is a relative measure, and since different species are assigned different conservation values, and some are assigned no value at all, the presence of endangered species is therefore not a binary all-ornothing parameter, but one which can take a wide range of values including zero. Hence it cannot always take priority over other conservation criteria. Diversity, condition and representativeness are by definition real-number or at least ordinal parameters, no matter what precise measures are used to define them. A diverse assemblage of common and widespread and weedy plants and their associated insect pests would be assigned low conservation value no matter how many species it contained, as would, say, a complete pristine area of completely bare rock, or a very representative area of very overgrazed rangeland. Hence none of the four conservation criteria can be given general pre-eminence. This leads to a universal and well-known problem in practical conservation: given a set of alternative potential conservation areas, all differing in all four parameters, how can the areas be ranked in terms of overall conservation value? Is a diverse and pristine area of vegetation supporting a diverse community of birds and mammals, for example, of greater or lesser conservation value than an otherwise barren area supporting, say, an endangered worm, snail or lichen? Is it more important to conserve the
areas supporting the only remaining breeding populations of bilbies or orange-bellied parrots*, or a representative area of jarrah-~ forest? In principle such questions are unanswerable, since values are by definition subjective and untestable, but in practice they must be answered during every conservation operation. What guidelines are available? In practical conservation, the aim is to define conservation priorities- the definition of conservation values is merely a means to this end. As long as the priorities can be assigned unequivocally, the values need not be defined with absolute precision. Logistic constraints on the final assignment of conservation are numerous. The first aspect is the current conservation status of the Species or assemblages concerned. The second is existing and potential future land tenure and applicable environmental legislation, often strongly influenced by special interest pressure groups and by the political attitude of incumbent governments. A third aspect is the feasibility and relative ease of physical protection in the face of formal or de facto pressures for alternative land uses, lack of physical resources, and direct action by persons inimical or indifferent to conservation, including military forces in some parts of the world. A fourth logistic aspect is geographic context, including accessibility, availability of adjacent areas for future expansion, proximity to potential sources of adverse impact, and so on. Finally, priorities for conservation may be influenced by priorities for development. On a regional rather than site-specific scale, land use planning must allow for both development and conservation. Its principal aim should be to optimise allocation of land to different uses, but its immediate problem is that economic and environmental values are not measured in comparable or interconvertible units. There have been some attempts to express conservation values in dollar terms (see Bernstein 1981, Bennett 1982), but these have not been very satisfactory. One alternative would be to use a non-parametric comparison, as follows. The region would first be divided into land-use units, each subject to only one potential use at a time (see e.g. Cocks 1984). These units would then be ranked both according to their priority for conservation, determined as outlined above, and also according to their priority for development, determined according to economic criteria. Each unit could then be allocated either to development or conservation according to the ratio of their priority ranks for development and conservation respectively. Though some practical difficulties can easily be envisaged, the approach is conceptually simple and feasible, and avoids the difficulties involved in attempting to express conservation values in dollar terms. A necessary basis, however, is the unambigious determination of relative conservation priorities. CONCLUSIONS The most significant conclusions from this analysis are as follows: Firstly, there are three major steps involved in the determination of conservation priorities: acquisition and assessment of information on the existing *Two Australian endangered species "tAn endangered Australian biological community
Ralf C. Buckley
baseline environment and on potential impacts; assignment of values to the environmental components concerrted, and integration of these to yield overall values for alternative possible conservation targets; and incorporation of logistic considerations to determine the practical priorities for conservation. Since information acquisition and assessment is expensive, these steps are generally repeated in an iterative way, but even though they may, in consequence, appear to be simultaneous, it is important to maintain the distinction between them. Secondly, a critical step in the overall process is the weighting and ranking of different conservation criteria. There are four main conservation criteria, namely the presence of rare or endangered species or assemblages, high diversity, pristine condition, and representativeness. These are all based on the same Primary values but do not always coincide for any given set of possible conservation areas. The quantitative comparison and integration of these criteria to assign overall conservation values relies on professional judgement rather than a formal algorithm, and currently requires explicit attention to achieve maximal consensus. ACKNOWLEDGEMENTS Many of the arguments advanced in this paper have previously been presented and discussed in various forms at the Fifteenth Pacific Science Congress, Dunedin, in February 1983, and at the Workshop in Survey Methods in Nature Conservation, Adelaide, in August 1983. REFERENCES Baggs, S.A. 1983. A simplified method for quantifying environmental impacts in the landscape planning/design process. Landscape Planning, 9, 227-247.
119
Beanlands, G.E. and Duinker, D.N. 1984. An ecological framework for environmental impact assessment. Journal of Environmental Management, 18. 267-277. Bennett, J.W. 1982. Valuing the existence of a natural ecosystem. Search, 13, 232-235. Bernstein, B.B. 1981. Ecology and economics: complex systems in changing environments. Annual Review of Ecology and Systematics, 12, 309--330. Buckley, R.C. I982. Environmental sensitivity mapping: what, why and how. Minerals and the Environment, 4, 151-155. Buckley, R.C. 1984. The significance of biological inventories in determining conservation priorities. In: Myers, K., Margules, C.R., and Musto, I. (eds.), Survey Methods for Nature Conservation, 2, 382-386. CSIRO, Canberra. Cocks, K.D. 1984. A systematic method of public use zoning of the Great Barrier Reef Marine Park, Australia. Coastal Zone Management Journal, 12, 359-383. Gengtao, C. 1985. China establishes more nature resources. Biological Conservation, 31, 1-5. Harris, S. 1984. What is scientific knowledge and for whom? Address to the Australian and New Zealand Association for the Advancement of Science (ANZAAS), Canberra, 17 May 1984. flirst, S.M. 1984. Applied ecology and the real world. II. Resource management and impact assessment. Journal of Environmental Management, 18, 203-213. Miller, W.L. and Byers, D.M. 1973. Development and display of multiple objective project impacts. Water Resources Research, 9, 11-20.
Prodgers, R.A. 1984. Collection and analysis of baseline vegetation data. Minerals and the Environment: 6, 101-104. Ratcliffe, D.A. (Ed.) 1977. A Nature Conservation Review. Cambridge University Press, Cambridge. Roome, N.J. 1984. Evaluation in nature conservation decision-making. Environmental Conservation, 11,247-252. Ruckelshaus, W.D. 1983. Science, risk, and public policy. Science, 221, 1026--1028. Salim, E. 1984. Why conservation? The Environmentalist,4, 97-108. Sebek, V. 1983. Bridging the gap between environmentalscience and policy-making. Ambio, 12, 118-120. Shapiro, H.A. 1984. Coastal area management in Japan: an overview. Coastal Zone Management Journal, 12, 19-56. (Received March 12, 1985; accepted after revision June 12, 1985.)
ABSTRACT One important component in achieving an optimal compromise between mineral development and environmental conservation is to rank different geographical areas according to their priorities for development and conservation respectively. The latter is considered here. There are three main steps in assigning conservation priorities: (i) acquisition and assessment of information on the existing baseline environment and on potential impacts; (ii) assignment of values to the environmental components concerned and integration of these to yield overall values foi"alternative possible conservation targets; and (iii) incorporation of logistic considerations to determine the practical priorities for conservation. One particularly critical aspect of this process is the relative significance of different conservation criteria, specifically including the presence of rare Species, high diversity, pristine condition and representativeness. These criteria all reflect the same underlying conservation values, but their relative significancevaries from case to case. Their integration is based on professional judgement rather than any formal algorithm and explicit guidelines for such judgement are needed to promote consensus in' the determination of conservation priorities.
INTRODUCTION To achieve a balance between mineral exploration and other forms of development on the one hand, and environmental conservation On the other, the relative value of land areas for different purposes must be assessed and compared. Ideally, these values should be assessed in the same units, but no satisfactory unit for measuring both value for development and value for conservation has yet been found. An alternative approach is to rank differentgeographical areas according to their development value on the one hand and their conservation value on the other, and compare the two rankings so that, other factors permitting, areas with high development priority and low conservation priority can be allocated to development, and vice versa. This is m o r e straightforward since numerical comparisons are made only within each set of units rather than between two sets, and the final comparison is non-parametic. Such a comparison is of course only one c o m p o n e n t in the overall process of attempting to optimise resource allocation. Use of land for one purpose, for example, may change its value for another, and hence it is important to assess the sensitivity of the areas concerned to the impacts associated with different potential forms of development. Priorities for development are generally assigned EnvironmentalGeochemistryand Health, 1985,7(3), 116-119.
according to the estimated net economic return to the intending developer or the assessed socioeconomic benefit to the region or community involved, and these can generally be expressed in dollar or dollar-convertible terms with reasonable repeatability. H o w should conservation priorities be assigned? This contribution attempts to analyse the processes involved, and to identify the most critical steps. To those professionally involved in nature conservation, most of the considerations outlined here will be second nature, but this analysis may help to focus attention on the critical issue of explicit weighting and ranking of conservation values as a step in assigning conservation priorities. To those who are not themselves involved, but whose activities may impinge on the processes of nature conservation - for example, those involves in the development of mineral resources, primary industries, and tourism -- this analysis provides a rationale for assessing conservation significance which may be of value in m a n a g e m e n t , particularly at the project planning stage where alternative sites, techniques and m a n a g e m e n t strategies are available. The process of practical conservation can usefully be subdivided as follows: A. Determination of conservation priorities: 9 information acquisition and assessment - baseline - impact 9 value assignment 9 priority assignment B. Implementation of conservation measures: 9 legislation 9 physical protection (and positive m a n a g e m e n t , where appropriate) 9 public education This discussion is concerned only with determination of priorities, but the implementation steps are relevant since the logistic aspects of assigning conservation priorities include the feasibility of implementing them. The difficulties in converting information to policy have recently been examined in general terms by Sebek (1983), Ruckelshaus (1983), and Harris (1984), and a specific example by Shapiro (1984). In principle the first three steps under (A) above, are consecutive: since information acquisition requires time and money, however, they are generally p e r f o r m e d iteratively in practice.
Ralf C. Buckley INFORMATION ACQUISITION The first step, information acquisition and assessment, is an objective process in the sense that it is amenable to scientific testing. It aims to determine what there is to conserve and how it functions - the baseline assessment - and what changes would be produced by external disturbances- the impact assessment. The first involves inventory, mapping, pattern analysis, experimental process studies (see eg., Buckley 1984, Prodgers 1984). In practice such information is never complete, and a degree of subjectivity is involved in estimating the magnitude and nature of the deficiency. Such deficiencies, however, can always be reduced by collecting further data. Similarly, impact assessment is largely a process of comparison and deduction, but is still classed as objective since the assessment is a prediction that c a n - and often i s - tested by actual application of the external disturbance considered. The detailed processes and problems of environmental impact assessment have been reviewed recently by Baggs (1983), Beanlands and Duinker (1984), and Hirst (1984). Assessment may be compelled to rely on expert opinion when data are lacking, but though the distinction between data and opinion is of course important, opinion on baseline and impacts can always be subjected to test by further observation or experiment. VALUES AND PRIORITIES Values~ in contrast, are by definition untestable, and differ from one person or organisation to another, particularly in the relative weighting of commerce and conservation. The two do not always conflict, but when they do their relative importance is a continual bone of contention. This aspect will be considered later, but first it is necessary to determine how conservation values can be established. As demonstrated in the recent review by Roome (1984), many different criteria have been proposed. In general, high conservation value is assigned to items, species, assemblages, areas, heritage artefacts - which are irreplaceable or unusual. Things which are common and easily replaceable may also be very valuable, but are generally not in such urgent need of conservation- though there is the danger that items which are initially common will continue to be exploited without control or conservation long after they have been reduced to rarity, since they are sti!l perceived as common. The overall philosophy of nature conservation has been discussed in detail by Ratcliffe (1977) and more recently by Salim (1984). The presence of rare or endangered species or their support systems, or unusual species assemblages and associations, thus provide primary conservation criteria. Support systems comprise food and habitats, particularly those required for critical life stages such as breeding and migration. High diversity, either of species, communities, habitats or terrain types, is another major criterion, as is pristine condition: freedom from weeds, feral animals, clearance, overgrazing, overburning, pollution, and engineering structures or activity. High diversity and pristine condition are often exceptional in their own right, largely as a result of past and present human activity. They also embody the endangered-species criterion indirectly, as follows. On
117
a global scale, existing data on species taxonomy, distribution and populations are very incomplete. Hence many species may become endangered before we have even become aware of their existence. Such species are more likely to be present in diverse than depauperate communities. Hence conserving diverse though incompletely described ecosystems may be more effective, overall, in conserving as many individual species as possible, than conserving small remnant populations of species known to be endangered. This argument is often supported by the suggestion that such remnant populations may become extinct in any event despite our best efforts to conserve them and it is therefore wasteful to squander limited resources on their behalf. This, however, is surely an unduly pessimistic view, since there are numerous examples of species which have been successfully rescued from the threshold of extinction and bred back to self-sustaining populations. Such measures certainly are expensive, however, and conservation resources certainly are limited, so the practical feasibility of conserving remnant populations will depend on the life history characteristics of the species concerned, together with a range of logistic aspects. The criterion of "representativeness" has also been used in assigning conservation values, particularly in recent years, and the creation of representative reserve networks to conserve an example of each ecosystem within a given area is often a major aim of conservation organisations. This criterion still embodies the same primary values, but more indirectly. If an effective way to conserve as many species as possible is to preserve diverse ecosystems, then the most effective way to preserve the greatest diversity on a global scale is to conserve a representative section of as many different ecosystems as possible. Representative reserve networks are hence a means to the conservation of maximum diversity overall. They have an additional advantage in providing reference areas against which to assess future change in unprotected portions of the ecosystems concerned. There are hence a number of different conservation criteria- rare species or assemblages, high diversity, pristine condition, representativeness- which are all valid and which are all related in principle. Effective conservation of individual species, communities or heritage items generally requires protection of defined geographical areas where they occur, however, in addition to any legislation giving them formal protected status. Hence in practice conservation values are rarely assessed independently: they must be combined or integrated to assign overall values to alternative areas. The four major criteria listed above do not always coincide for any given set of areas, so to assign overall conservation values the criteria must be ranked or weighted in some way. There is no fixed ranking, because the significance of each criterion is variable, depending on the degree of rarity, diversity, modification, and so on. In addition the value attached to a rare species depends on the actual species concerned, and its significance in determining overall conservation values depends on its overall conservation status; specifically on its representation in existing conservation reserves elsewhere. Similarly, there are many different possible measures of diversity and of condition.
118
Determining conservation priorities
The relative significance of different conservation criteria currently appears to be an ar~a of divergent opinion, and deserves further attention. My own personal opinion is that there is no universal ranking of conservation criteria, and priorities must be assessed on a case-by-case basis, for the reasons summarised below. The only general constraint on possible rankings is that no single criterion is universally pre-eminent. This can be illustrated as follows. The herculean efforts of the W.H.O. and others to eradicate the smallpox virus (Harris 1984), for example, show that in this case at least the preservation of a species is greatly outweighed by other considerations. At the other extreme, the preservation of species, such as, for example, the giant panda, is generally acknowledged to outweigh any potential economic return from exploitation of its habitat (Gengtao 1985). Between these extremes there is no sudden threshold, but rather a gradual scale of perceived values, which varies with individual perception. My impression of public opinion in the Western w o r l d - a general overview subject to variation at local, regional and national scales - is that m o s t mammals and birds would be seen as of equal value by some and lesser by others. Invertebrates are generally seen as of lesser significance than vertebrates. Within the invertebrates, the larger and more conspicuous crustaceans, molluscs, actinozoans and arthropods, such as crayfish, giant tritons, reef corals and birdwing butterflies, are generally seen as of greater value than their smaller and less conspicuous relatives or than the less well known groups such as worms, amphipods and isopods. These in turn are seen as more significant than the protozoans. This is not to imply that these smaller and less conspicuous organisms are not valuable but merely to observe that they are perceived by the majority of people as less valuable than the larger and more conspicuous species (cf. Ratcliffe 1977, p.10). Since rarity is a relative measure, and since different species are assigned different conservation values, and some are assigned no value at all, the presence of endangered species is therefore not a binary all-ornothing parameter, but one which can take a wide range of values including zero. Hence it cannot always take priority over other conservation criteria. Diversity, condition and representativeness are by definition real-number or at least ordinal parameters, no matter what precise measures are used to define them. A diverse assemblage of common and widespread and weedy plants and their associated insect pests would be assigned low conservation value no matter how many species it contained, as would, say, a complete pristine area of completely bare rock, or a very representative area of very overgrazed rangeland. Hence none of the four conservation criteria can be given general pre-eminence. This leads to a universal and well-known problem in practical conservation: given a set of alternative potential conservation areas, all differing in all four parameters, how can the areas be ranked in terms of overall conservation value? Is a diverse and pristine area of vegetation supporting a diverse community of birds and mammals, for example, of greater or lesser conservation value than an otherwise barren area supporting, say, an endangered worm, snail or lichen? Is it more important to conserve the
areas supporting the only remaining breeding populations of bilbies or orange-bellied parrots*, or a representative area of jarrah-~ forest? In principle such questions are unanswerable, since values are by definition subjective and untestable, but in practice they must be answered during every conservation operation. What guidelines are available? In practical conservation, the aim is to define conservation priorities- the definition of conservation values is merely a means to this end. As long as the priorities can be assigned unequivocally, the values need not be defined with absolute precision. Logistic constraints on the final assignment of conservation are numerous. The first aspect is the current conservation status of the Species or assemblages concerned. The second is existing and potential future land tenure and applicable environmental legislation, often strongly influenced by special interest pressure groups and by the political attitude of incumbent governments. A third aspect is the feasibility and relative ease of physical protection in the face of formal or de facto pressures for alternative land uses, lack of physical resources, and direct action by persons inimical or indifferent to conservation, including military forces in some parts of the world. A fourth logistic aspect is geographic context, including accessibility, availability of adjacent areas for future expansion, proximity to potential sources of adverse impact, and so on. Finally, priorities for conservation may be influenced by priorities for development. On a regional rather than site-specific scale, land use planning must allow for both development and conservation. Its principal aim should be to optimise allocation of land to different uses, but its immediate problem is that economic and environmental values are not measured in comparable or interconvertible units. There have been some attempts to express conservation values in dollar terms (see Bernstein 1981, Bennett 1982), but these have not been very satisfactory. One alternative would be to use a non-parametric comparison, as follows. The region would first be divided into land-use units, each subject to only one potential use at a time (see e.g. Cocks 1984). These units would then be ranked both according to their priority for conservation, determined as outlined above, and also according to their priority for development, determined according to economic criteria. Each unit could then be allocated either to development or conservation according to the ratio of their priority ranks for development and conservation respectively. Though some practical difficulties can easily be envisaged, the approach is conceptually simple and feasible, and avoids the difficulties involved in attempting to express conservation values in dollar terms. A necessary basis, however, is the unambigious determination of relative conservation priorities. CONCLUSIONS The most significant conclusions from this analysis are as follows: Firstly, there are three major steps involved in the determination of conservation priorities: acquisition and assessment of information on the existing *Two Australian endangered species "tAn endangered Australian biological community
Ralf C. Buckley
baseline environment and on potential impacts; assignment of values to the environmental components concerrted, and integration of these to yield overall values for alternative possible conservation targets; and incorporation of logistic considerations to determine the practical priorities for conservation. Since information acquisition and assessment is expensive, these steps are generally repeated in an iterative way, but even though they may, in consequence, appear to be simultaneous, it is important to maintain the distinction between them. Secondly, a critical step in the overall process is the weighting and ranking of different conservation criteria. There are four main conservation criteria, namely the presence of rare or endangered species or assemblages, high diversity, pristine condition, and representativeness. These are all based on the same Primary values but do not always coincide for any given set of possible conservation areas. The quantitative comparison and integration of these criteria to assign overall conservation values relies on professional judgement rather than a formal algorithm, and currently requires explicit attention to achieve maximal consensus. ACKNOWLEDGEMENTS Many of the arguments advanced in this paper have previously been presented and discussed in various forms at the Fifteenth Pacific Science Congress, Dunedin, in February 1983, and at the Workshop in Survey Methods in Nature Conservation, Adelaide, in August 1983. REFERENCES Baggs, S.A. 1983. A simplified method for quantifying environmental impacts in the landscape planning/design process. Landscape Planning, 9, 227-247.
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