Biodiversity and Conservation 3, 555-565 (1994)

Valuing biodiversity and nature conservation at a local level

G . D . G A R R O D * a n d K . G . W I L L I S Centre for Rural Economy, Department of Agricultural Economics and Food Marketing, University of Newcastle upon Tyne, Newcastle upon Tyne NE1 7RU, UK

Received 5 January 1994; revised and accepted 11 March 1994

At a time where much of the discussion about major issues in nature conservation is necessarily undertaken at a global level, it is still important to consider the needs of the smaller organizations who do much of the grass roots work in the protection of wildlife and biodiversity. This study focuses on one such group, and examines how the contingent valuation method can be used to help to inform its decisions relating to the management of its portfolio of reserves in order to maximize benefits to its members. This paper argues that at a local level, where actions will not have significant global effects, contingent valuation methodology can inform decisions by asses- sing the value of additional reserves or particular conservation programmes to members in terms of their willingness to pay to acquire or implement them.

Keywords: conservation, contingent valuation, wildlife trusts.

Introduction

While much of the current debate about nature conservation is taking place at a national or international level, discussing such far-reaching and potentially controversial topics as sustainability, irreversibility, and safe minimum standards, a substantial pro- portion of practical conservation work is being performed by small organizations at a local level.

Local environmental groups, such as the wildlife trusts which flourish across the UK, are unlikely to own unique ecosystems, and for them such global issues, while of great importance, are less imperative. The preservation of any unique natural resource systems is more likely to be in the hands of a national agency, such as English Nature, and local groups are left to care for those smaller and less glamorous areas which are nevertheless of great importance to the biodiversity of local ecosystems. This work is often carried out by volunteers, and is funded in the most part by subscription and do- nations rather than by central government.

At this local level it is often necessary to make trade-offs between the limited re- sources available to groups, and the sites which they are able to manage. This is possible because at this level the loss of a site, or the failure to acquire one, would not usually lead to irreversible ecosystem losses, although it could reduce the supply of the natural resource. Economic considerations of the benefits of local wildlife sites are, therefore, unlikely to be clouded by issues of irreversibility or safe minimum standards,

*To whom correspondence should be addressed.

0960-3115 © 1994 Chapman & Hall

556 Garrod and Willis

and hence are amenable to conventional techniques of economic appraisal and the use of the efficiency criterion to prioritize decisions by capturing the trade-off between benefits and the resource costs necessary to achieve them. This is not to say that the standard tools of economic analysis are not useful in cases where irreversibility is an issue, only that their application is more difficult both methodologically and ethically.

Valuing wildlife in monetary terms is appropriate in a number of situations relevant to wildlife trusts. First, under the current legal framework in the UK, rights to wildlife have to be purchased. Conservation organizations large and small, all purchase or rent land for nature reserves. Through these means, or by entering into management agree- ments under the Wildlife and Countryside Act 1981, compensation is paid to land- owners or tenants in respect of the net profits foregone in conserving wildlife. Thus, nature conservation is already perceived as incurring a cost, and quantifying its benefits in monetary terms makes a comparison with these costs considerably easier. Second, wildlife trusts have restricted budgets, and must ensure that through their portfolio of nature reserves they are providing value for money in terms of their members' pre- ferences. Such value-for-money arguments may be demonstrated by members' will- ingness-to-pay (WTP) to support the trusts through their subscription fees. In addition fund-raising activities for particular wildlife projects show an implicit recognition that the benefits of conservation can be perceived by people, and be valued by their WTP to acquire them.

Contingent valuation has been employed to value a wide range of wildlife preserva- tion benefits to users and non-users both in Europe and the United States (see, for example, Brookshire et al., 1983; Samples et al., 1986; Bowker and Stoll, 1988). This study applies contingent valuation methods (CVMs) to value changes in the supply, as well as the management, of local nature reserves. It is at the level of local nature reserves and Sites of Special Scientific Interest (SSSIs) that most additions to, and sub- tractions from, wildlife protection occur in the UK. These smaller areas represent an extremely important aspect of nature conservation, and as a whole deserve as much at- tention as those few sites which generate national media coverage and interest.

The objectives of this study were to focus on one local wildlife trust, and to attempt to elicit from a sample of its members their preferences and monetary valuations for a number of habitats and conservation initiatives. The success or otherwise of this objec- tive should provide some valuable evidence regarding the feasibility of using similar methodologies to assist the forward planning and policy appraisal of such organiza- tions.

The Northumberland Wildlife Trust

The Northumberland Wildlife Trust (NWT) is part of a network of county wildlife trusts which extends all over Britain, under the umbrella of the Royal Society for Nature Conservation (RSNC). This network has a total membership of around 200 000 people (about 0.36% of the population), and in 1988 had a total operating income of over £6 000 000 (Dwyer, 1991). Between them, the trusts are responsible for over 53 000 ha (approximately 0.25% of the land area of the UK) making them the third largest landholding conservation organisation in the UK after the National Trust and the Royal Society for the Protection of Birds (RSPB).

The wildlife trust network exists to protect and enhance wildlife and wildlife habitats

Valuing biodiversity and nature conservation at a local level 557

as an investment for the future, and aims to create a greater appreciation and under- standing of wildlife, and a greater awareness of the need for their conservation. The movement also encourages active participation in conservation, providing more oppor- tunities for people of all ages to enjoy wildlife and wild places in towns and countryside.

The NWT is in all respects a typical county wildlife trust; like most others it is regis- tered as a charity, and most of its work is undertaken by volunteers, assisted by a small team of professional staff. It controls over 2000 ha making it one of the larger trusts in this respect. The NWT is actively involved in conserving the wildlife of a large area of the north-east of England, managing 61 nature reserves, some of which protect rare and threatened species such as the merlin and the large heath butterfly (Coenonympha tullia). In addition the NWT promotes the conservation of otters, badgers, red squirrels and other endangered species found locally, and also works with local authorities to safe- guard areas important to wildlife. The NWT also has a consultative and educational role, advising local authorities over planning applications, and landowners about caring for wildlife, as well as working with local schools and industry.

In the administrative year 1992/1993 the NWT had 4150 members, with adults paying an annual subscription of £10.50 per year. Total membership subscriptions amount to one-fifth of all income received, the remainder being derived from legacies, donations, charitable trusts, grants, sponsorship and fund-raising activities.

The questionnaire survey

There are several techniques which could be used to estimate the benefits which members of the NWT would derive from an increase in the number of reserves or from the implementation of various conservation initiatives by the Trust. CVM was chosen because it presents respondents with a market-like scenario within which to state their WTP for additional habitats or for proposed conservation schemes. The CVM exercise is akin to the expenditure decisions which respondents face every day, and is realistic in that it equates the provision of additional outputs (i.e. in terms of additional reserves or new initiatives) with t-he payment of additional membership fees. Use of an alternative technique, the travel-cost method, would have required the development of a complex multi-site model which could be used to estimate the use benefits accruing from sites: this was not feasible within the cost constraints of the study. CVM also facilitates the investigation of the theoretical determinants of people's WTP for additional habitats. This is achieved through modelling respondents' WTP as a function of their frequency of visits to habitats, membership of environmental organizations, income and other socio-economic characteristics.

The CVM study was based on a mail questionnaire survey of current members of the NWT. Normally, a postal survey would not be suitable for an application of CVM (e.g. see Arrow et al., 1993). There are several reasons for this. First, mail surveys can result in a high degree of non-response: this can be damaging if the non-responses are not randomly distributed throughout the sample population. Second, problems may arise if respondents feel that the questionnaire is confusing, or find the issues described within it hard to understand. In a one-to-one survey the interviewer may be able to help the re- spondent to overcome these problems, while with the mail surveys no such assistance is at hand.

These problems mean that it is very difficult to apply a CVM mail survey to the

558 Garrod and Willis

general public. However, these problems may not be particularly serious when the po- pulation to be sampled has demonstrated an interest and knowledge in the subject to be addressed. This is the case with members of the NWT. Their membership of the organi- zation implies an interest in, and sympathy with, local nature conservation. In most cases this will be supported by a working knowledge of local wildlife, their habitats and the issues concerning their relationship with the broader ecosystem in which mankind plays a part. Individuals sampled from such a population should, on the whole, have no difficulties answering a well-designed questionnaire relating to wildlife habitats and the activities of the Trust.

The questionnaire was structured to elicit information on a variety of issues including: the threats perceived to different types of habitats by members; their preferences for dif- ferent habitat types; and their frequency of visits to various habitats, and NWT reserves during the preceding year. Open-ended CVM questions were used to elicit WTP bids for an additional reserve in each habitat type, and WTP for specific NWT conservation programmes. Information was also gathered on the socio-economic characteristics of re- spondents.

Late in 1992, after the questionnaire had been piloted, an updated version was mailed to 500 members of the NWT. These were drawn by selecting every eighth name on the list of members. Replies were anonymous and a pre-paid envelope was provided for this purpose. A follow-up letter was sent to everyone in the sample 10 days later, requesting those who had not done so to respond. A total of 227 fully completed questionnaires were obtained, representing a 45.4% response rate. This was comparable with the response rates achieved in a number of mailed CVM surveys of similar size documented by Mitchell and Carson (1989). Of the 16 mail surveys listed by those authors, nine failed to obtain a response rate as high as the one achieved by this study, though two much smaller surveys had response rates of over 70%. There was no evidence to suggest that the non-responses in this survey were not randomly distributed throughout the sample population.

Results

Habitat preferences The preamble to the questionnaire was designed to encourage respondents to consider their preferences and their use of habitats, as a prelude to the use of CVM questions to determine their WTP for additional habitats. Perceptions and preferences for dif- ferent habitats by NWT members were ascertained by asking respondents in respect of:

(i) threatened habitats, to imagine that they had 100 points which could be used to take action to increase the number of these protected habitats, and to allocate their points between habitats to reflect how they thought habitats, which were threatened, ought to be augmented in the UK.

(ii) personal preferences for habitats, respondents were asked to put aside their feelings about which habitats require greater protection, and to again allocate 100 points between habitats, but this time in a way which expressed their personal interest and preferences for them.

Valuing biodiversity and nature conservation at a local level 559

Respondents' interest in habitats was also investigated by examining their behaviour, in particular the number of visits they made to each of the different habitats over the previous 12 months. Both revealed and expressed preferences for different habitats are shown in Table 1.

On average respondents perceived the most threatened habitats to be broad-leaved woodland; hay meadows; coastal sand dunes and salt marshes; river beds and streams; and marsh and fen. Habitats associated with conifer forests and with large man-made lakes were perceived to be least under threat. Mean personal preferences for habitats corresponded quite closely with average perceived threats, with the correlation coeffi- cient between the two strongly statistically significant at 0.8514. Personal preferences were low for conifer forests, peat bogs, large man-made lakes, and marsh and fen; but high for broad-leaved woodland, heather moorland, river beds and streams, and coastal dunes and salt marshes.

There was less correlation between threatened habitats and the number of visits made to them in the preceding 12 months (r = 0.3975), though as would be expected there was a strong correlation between number of visits to habitats and personal preferences for habitats (r = 0.7386). It is interesting to note that, in spite of the fact that conifer forests and large man-made lakes were neither preferred nor considered threatened, those habitats attracted an above average proportion of visits from respondents.

Frequency of visits to habitats

On average, respondents made 68 visits to wildlife habitats over a year, only 22 of which were to NWT reserves. Table 2 shows the ten most, and the ten least, popular

Table 1. Expressed preferences and revealed preferences for wildlife habitats

Perception of Personal Number of which habitats preferences visits made are threatened for habitats by respondents (denoted by (denoted by to habitats a score out a score out in previous of 100) of 100) 12 months

Mean s.d. Mean s.d. Mean s.d.

Conifer forest Broadleaved woodland Heather moorland Peat bog Traditional hay meadows Marsh and fen Ponds Large man-made lakes River beds and streams Coastal sand dunes and

salt marshes Total

2.370 4.290 3.088 5.718 4.449 9.019 19.497 13.778 22.220 16.167 11.519 27.458 8.281 8.889 12.277 12.961 6.193 11.093 9.731 12.058 3.982 6.820 0.964 2.778

13.718 10.448 10.211 10.555 2.629 8.262 10.136 8.273 5.977 7.684 1.911 6.523 8.779 7.624 9.264 9.484 9.409 22.944 2.215 4.342 2.594 5.441 5.515 18.645

11.334 10.502 12.916 10.551 11.973 30.708 13.013 9.905 15.806 12.402 13.753 33.501

68.321 96.799

560 Garrod and Willis

Table 2. Mean annual visits by respondents to the ten most and ten least visited NWT reserves in the survey

Ten most visited reserves Mean visits Ten least visited reserves Mean visits

1. Cresswell Pond 3.8370 2. Druridge Pools 3.6960 3. Hauxley 2.4977 4. Colywell Bay 1.5682 5. Holywell Pond 1.4713 6. Wallsend Swallow Pond 1.4229 7. Big Waters 1.3568 8. Close House Riverside 1.0528 9. Cocklawburn Dunes 0.5770 10. Grinden Lough 0.4581

52 = Wedges Rigg 0.0044 52 = Chirdon Head 0.0044 52 = Muckle Samuels Crag 0.0044 52 = Paddaburn Moss 0.0044 52 = Silver Nut Well 0.0044 52 = Hummel Knowe Moss 0.0044 58 = Chirdon Head No visits 58 = Haining Head No visits 58 = Pundershaw No visits 58 = South Close Field No visits

hab i ta t s in terms o f the average number o f visits m a d e to them by indiv iduals in the sample. Clear ly, hab i ta t s re la ted to water features were highly popular . Hab i t a t s with

general ly low visit rates included quarr ies , crags, mosses and bogs. Aggrega t ing the visit rates f rom the sample across the whole N W T membersh ip suggested tha t over a year,

the 61 N W T reserves receive an es t imated 90 150 visits f rom N W T members .

Willingness to pay for wildlife habitats

Responden t s were asked wha t was the mos t they would be will ing to pay each year in add i t iona l member sh ip fees in o rde r for the N W T to establ ish one extra reserve in each

Table 3. Respondents' willingness to pay for an additional reserve in each habitat type

Habitats Additional annual sum (£)

Mean Standard WTP deviation

Maximum bid by any respondent

1. Conifer forest 2. Broadleaved woodland 3. Heather moorland 4. Peat bog 5. Traditional hay meadows 6. Marsh and Fen 7. Ponds 8. Large man-made lakes 9. River banks and streams 10. Coastal sand dunes and salt marshes

Total WTP

0.286 1.165 50 2.323 4.877 50 0.673 2.085 20 0.789 2.648 30 1.441 2.981 20 0.684 1.750 10 0.853 2.317 20 0.284 1.200 10 1.047 2.437 15 1.662 4.561 50

10.045 16.082

n = 226.

Valuing biodiversity and nature conservation at a local level 561

of the habitats specified in the questionnaire. The mean WTP values for the different habitats shown in Table 3 should reflect the preferences of respondents, their percep- tions of the need for additional habitats in the light of the current NWT reserve portfo- lio, and the availability of these habitats outside NWT ownership in northern England.

As suggested by the expressed preference questions, conifer forest and large man- made lake habitats had the lowest mean WTP for an additional reserve. Respondents were willing to pay considerably more for an additional broadleaved woodland habitat, a coastal dune habitat, or a traditional hay meadow habitat. Combined WTP for one extra reserve in each habitat amounted to £10.05 per person. It may be noted that this value is of the same order of magnitude as the current annual subscription for the NWT, suggesting that some members derive considerable consumer surplus from the Trust's existing activities and its current reserves. This conclusion is of course pre- mature. For example, if respondents believed that any additional sites would possess at- tributes not present in the current set of reserves, then they might place a large value on the acquisition of these sites, while not being inclined to support activities on existing sites. Also, it is possible that the design of the questionnaire and the sequencing of the bids have biased WTP estimates upwards (see Majid et al., 1983) implying that consumer surplus is somewhat smaller than indicated here.

The survey also investigated three projects which the NWT were currently consider- ing: conserving the Border mires; protecting the red squirrel in Kielder Forest; and es- tablishing a new headquarters to replace their existing cramped accommodation in temporary wooden buildings. The valuation of these projects was again made on the basis that support for them would require an additional annual payment on top of existing membership fees. Support for these different projects is documented in Table 4. The CVM responses suggested that members would be willing to pay an aggregate of £2404 per year towards the conservation of Border mires; £9444 per year for the con- servation of the red squirrel in Kielder Forest; but only £1492 per year towards the pro- vision of a new headquarters for the Trust.

Clearly a programme to protect the red squirrel in Kielder Forest received by far the most popular support, whilst spending money in administrative headquarters com- manded least. However, in terms of WTP for these projects, differences were not so clear cut. Whilst a new headquarters received less than half the support obtained by the Border mires, WTP by those responding positively was greater for the headquarters than for the mires, so that the average individual contribution was greater.

Table 4. Percentage of respondents willing to pay for the three proposed NWT pro- grammes with their mean WTP values

Programme Percentage of Mean respondents annual WTP (£)* with non-zero WTP

Border mires 39.4 1.47 Red squirrels 77.4 2.94 Headquarters 17.2 2.09

*Includes zero bids.

562 Garrod and Willis

Mean WTP for a programme to conserve the Border mires (Table 4) exceeded that of mean WTP for an additional peat bog habitat (Table 3). Indeed, WTP for conservation of the Border mires and protection of the red squirrel amounted to 44% of mean WTP for ten additional habitats, one of each type. At first sight these results might suggest that the CVM results were biased and that embedding was a serious problem in this study.

Embedding occurs when a good is assigned a lower WTP value when WTP for it is inferred from the respondent's WTP for a more general good, rather than if the parti- cular good is evaluated on its own (see for example Loomis et al., 1993). However, what this result illustrated was not an embedding effect, but instead the fact that the context in which a good is presented to individuals in a CVM study matters. In this study the change of context was equivalent to a variation in the amount of information provided to respondents about the ecological goods, marsh and fen, and conifer forest. The addition of a further marsh or fen habitat to the Trust's portfolio of reserves has an effect which is in no way equivalent to that of a project to conserve the Border mires. The Border mires are widely known throughout the UK, and are recognized as an ex- tremely important ecological habitat. Moreover, a conservation project on the Border mires could potentially lead to the preservation of a much larger quantity of mire than that which would be added by an additional 'average' reserve. A similar argument holds with respect to red squirrels: an additional conifer habitat, and a conifer habitat with red squirrels, are not the same good.

An important factor in assessing the validity of the results from the NWT survey involves investigating the extent to which the empirical findings of the study were con- sistent with theoretical expectations. Here, interest focuses on the WTP amount, and on regressing it against a set of independent variables believed to be theoretical determi- nants of people's willingness to pay for additional habitats. The sign and size of the es- timated coefficients can be used to judge the consistency or inconsistency of the model with economic theory. Mitchell and Carson (1989) argued that whenever contingent va- luation studies are designed with the intent of gathering data to be used for policy purposes, they should take into account the need to produce theoretically based regres- sion equations, or evidence of their theoretical validity, and this should be presented as a standard part of every CVM study report.

A priori, WTP in order to conserve and protect wildlife might be expected to be a positive function of income, frequency of visits to wildlife habitats, and membership of environmental organizations; and negatively related to unemployment and age of re- spondent. To test these 'expectations' regression analysis was used to predict re- spondents' total WTP for one additional habitat of each type.

Various functional forms were fitted to the data to predict WTP, and the preferred model, based on the double-log form, was chosen on the basis of statistical goodness of fit and because it reflected the effects of the widest profile of explanatory variables (see Table 5). All variables which were statistically significant at the 0.15 level are reported in order to identify a broader than usual set of variables having a significant effect on respondents' WTP. The results of the analysis generally confirmed the a priori hy- potheses about the effect of the respondents' characteristics on WTP. In terms of income, only membership of the highest income group had a statistically significant effect on WTP, though being in three out of the four oldest age categories had a sig- nificant negative effect on WTP. Total WTP for additional habitats was also positively

Valuing biodiversity and nature conservation at a local level 563

related to demand, as evinced by the annual number of visits to listed wildlife habitats by NW T members and to membership of the RSPB, though not to any other environ- mental organization. As expected, household size and unemployment both had a detri- mental effect on WTP.

The R 2 value indicated that the model accounted for nearly 24% of the variation in the dependent variable, which was quite high for a CVM application, though lower than that obtained by Willis et al. (1993) in their CVM study of the WTP of visitors to the Somerset Levels and Moors ESA. However, the N W T value was somewhat higher than those derived in several other recent UK studies, e.g. Cobbing and Slee (1993) and Bateman et al. (1994). High R 2 values are not necessarily evidence of theoretical validity, there may be stochastic variation in the data which overshadows the systematic influence of variables. Nevertheless, high R 2 values do provide some evidence of relia- bility.

Conclusions

A major concern of the NWT is how it should manage its reserves in order to maximize benefits to its members. Should it increase the number of its reserves, and if so, what particular types of habitats would members prefer to see increased, and be willing to pay for if the need arose? Is there a desire on the part of the membership that the Trust should undertake particular conservation projects, for example, a programme to protect the red squirrel, or another to protect the Border mires, and how much would members be willing to contribute to such schemes? CVM can inform decisions on these questions, by assessing the value of additional reserves or particular conservation programmes to members in terms of their WTP to acquire or implement them.

This study has demonstrated clearly that CVM can be a useful tool in informing such local-level management decisions, providing information on the use and non-use values accruing to members, the value of new additional reserves of different habitat types, and

Table 5. Model of NWT members' WTP for wildlife conservation

Dependent variable: In (WTP)

R 2 = 0.2390 Adj R 2 = 0.2094

DF: model 8 DF: error 206

F value: 8.085 Prob > F: 0.0001

Variable Coefficient Prob > ITI Label

INTERCEPT 1.5346 0.0001 LNHABVISIT 0.0888 0.1242 AGEGRP5 - 0.5315 0.0259 AGEGRP7 -0.7883 0.0005 AGEGRP8 -- 1.7419 0.0001 RSPB 0.3251 0.0421 HIGHINC 0.7210 0.0002 LNHOUSESIZE - 0.4334 0.0171 UNEM - 0.7282 0.0559

intercept term In (number of habitat visits) respondent aged 45-54 respondent aged 65-74 respondent aged over 75 RSPB member household income > £30 000 In (household size) respondent unemployed

564 Garrod and Willi,s

the income generation potential for new conservation programmes. Specifically, the study demonstrated that members' preferences were low for a number

of habitats including conifer forests, peat bogs, large man-made lakes, and marsh and fen; and high for broad-leaved woodland, heather moorland, river beds and streams, and coastal dunes and salt marshes. These results were reflected in mean WTP for addi- tional reserves, which was lowest for conifer forest and large man-made lake habitats, and highest for broadleaved woodland habitat, and coastal dune habitats. Overall, the results of the CVM study suggested that members derived considerable consumer surplus from the Trust's existing activities and its current portfolio of 61 reserves. While further, more detailed, work is required to confirm these findings, they may, over the long term, prove valuable to the NWT in their continued efforts to fund local conserva- tion activities.

It was also clear that members would be willing to pay additional membership fees for specific conservation projects proposed by the Trust. The CVM responses suggested that members would be willing to pay an aggregate of £2404 per year towards the con- servation of Border mires; £9444 per year for the conservation of the red squirrel in Kidder Forest; but only £1492 per year towards the provision of a new headquarters for the Trust.

Acknowledgements

The authors would like to thank David Stewart of the Northumberland Wildlife Trust for his help with this study, and also Eliot Baker, Caroline Maher and Alison Murphy for their assistance with the survey. We would also like to thank an anonymous referee for his/her comments. Any errors and omissions remain the responsibility of the authors alone.

References

Arrow, K., Solow, R., Leamer, E., Portnay, P., Randner, R. and Schuman, H. (1993) Report of the NOAA Panel on Contingent Valuation. Federal Register 58, 4601-14.

Baternan, I., Willis, K.G. and Garrod, G.D. (1994) Consistency between contingent valuation es- timates: a comparison of two studies of UK National Parks. Reg. Stud. 28 (in press).

Bowker, J.M. and Stoll, J.R, (1988) Use of dichotomous choice nonmarket methods to value the Whooping Crane resource. Amer. J. Ag. Econ. 70, 372-81.

Brookshire, D.S., Eubanks, L.S. and Gilman, R. (1983) Estimating option price and existence values for wildlife resources. Land Econ. 59, 1-15.

Cobbing, P. and Slee, W. (1993) A contingent valuation of the Mar Lodge Estate, Cairngorm Mountains, Scotland. J. Environ. Plan. Manag. 36, 65-72.

Dwyer, J. (1991) The county wildlife trusts: primary conservation CARTs. Land Economy Discus- sion Paper No. 30. Cambridge: Department of Land Economy, University of Cambridge.

Loomis, J., Lockwood, M. and DeLacy, T. (1993) Some empirical evidence on embedding effects in contingent valuation of forest protection. J. Environ. Econ. Manag. 24, 45-55.

Majid, I., Sinden, J.A. and Randall, A. (1983) Benefit evaluation increments to existing systems of public facilities. Land Econ. 59, 377-92.

Mitchell, R.C. and Carson, R.T. (1989) Using surveys to value public goods: the contingent valua- tion method. Washington DC: Resources for the Future.

Samples, K.C., Dixon, J.A. and Gowan, M.M. (1986) Information disclosure and endangered species valuation. Land Econ. 57, 151-71.

Valuing biodiversity and nature conservation at a local level 565

Willis, K.G., Garrod, G.D. and Saunders, C.M. (1993) Valuation of the South Downs and Somerset Levels and moors environmentally sensitive area landscapes by the general public. Report to the Ministry of Agriculture, Fisheries and Food. Newcastle upon Tyne: Centre for Rural Economy, Department of Agricultural Economics and Food Marketing, University of Newcastle upon Tyne.