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La révélation des substitutions entre biodiversité et paysage dans les projets d’aménagement : l’intérêt de la
méthode des choix contingents
Vanja Westerberg, Robert Lifran
To cite this version:
Vanja Westerberg, Robert Lifran. La révélation des substitutions entre biodiversité et paysage dans les projets d’aménagement : l’intérêt de la méthode des choix contingents. 2008. �hal-02821954�
« Eliciting Biodiversity and Landscape Trade-off in Landscape Projects:
Pilot Study in the Anciens Marais des Baux, Provence, France»
Robert LIFRAN
Vanja WESTERBERG DR n°2008-12
Eliciting Biodiversity and Landscape Trade-off in Landscape Projects:
Pilot Study in the Anciens Marais des Baux, Provence, France R. Lifran
1, V. Westerberg
2Abstract
The purpose of this paper is to elicit preferences of the local population for various organizational and management changes in the landscape of the agricultural area called “Ancien Marais des Baux”, at the foothill of the Alpilles Mountain, in Provence. We present preliminaries results from a pilot survey conducted in the area in the winter of 2008. In our research, the environmental resource is the landscape, defined in terms of its attributes and levels these attributes would take with and without various management options. We use the Choice Experiment to determine what the preferred landscape is, and under wetland restoration, the most desired features that the wetland should provide. The random parameter logit model is employed to take into account variances in unobserved preference heterogeneity.
Consistent with expectations, we observed that respondents who are neither green, have little attachment to wetlands, have poor understanding of wetland services, are WTP less ceteris paribus for all the attributes in question, compared to the respondents that have green behaviour, knows about wetlands or cares about their existence in Marais des Baux. Not surprisingly, the respondents considering the wetland in Marais des Baux, part of their cultural heritage, wants to visit it in the future, and preserve it for future generations, have the greatest WTP for any combination of attributes. We also observed the importance of mosquito control in any support of wetland restoration among respondents. Indeed, restoration on an advanced scale is only accepted in the presence of biological mosquito control. Distinct landscape features, such as tree hedges which still allows for the view of the massif of the Alpilles are valued equally high as the recreational opportunites related to the wetland. Biodiversity is low on the priority list compared to other attributes, but still positively valued.
Key words: Cost-benefits Analysis, Choice experiments, Wetlands restoration, Landscape Résumé
Dans ce papier, nous présentons les résultats d’une enquête pilote réalisée dans une zone humide convertie à l’agriculture intensive dans les années Soixante dix, est confrontée aujourd’hui à des choix difficiles d’orientation. Il s’agit d’identifier et de mesurer la diversité des préférences de la population locale grâce à l’utilisation d’une enquête de choix contingents. La ressource environnementale que nous étudions est le paysage, défini par des attributs pertinents, en termes d’habitats, de biodiversité, de présence de haies, d’usages et d’accès, ainsi que de niveau d’un attribut de paiement pour les modifications proposées. En accord avec les anticipations, nous avons observé que les répondants qui n’avaient pas un comportement à orientation « verte », qui n’ont pas d’attachement particulier pour les zones humides, et qui ont une faible compréhension de leur utilité ont, ceteris paribus, une propension à payer moins forte pour tous les attributs en question que ceux qui ont un comportement plus « vert », qui connaissent les marais des baux, et y portent un intérêt pour le futur. De plus, l’enquête nous a donné une mesure plus précise des interactions entre les attributs de paysage et de biodiversité, la crainte des moustiques et le désir de voir les Alpilles étant des facteurs limitants de la restauration des marais et l’extension des haies d’arbres.
Mots-clefs : Analyse Coûts-Bénèfices, Choix contingents, Restauration des Zones Humides, Paysage
1 INRA, UMR LAMETA, 2 place viala, 34060 Montpellier, FR
2 INRA, UMR LAMETA, 2 place viala, 34060 Montpellier, FR, Corresponding author: Vanja Westerberg: westerbe@supagro.inra.fr
Introduction
The purpose of this paper3 is to elicit preferences of local people for various organizational changes in the landscape of the Former Wetland called “Ancien Marais des Baux”4.
The history of land use in Marais des Baux is one which is marked by continuous attempts to drain the wetland dating back to the Roman era. None of these attempts can nevertheless be compared to that of the polderisation and installation of electrical pumps in the late 1950s. One may appropriately classify agriculture as inherent to the ancestral landscape of the valley, and more so in the last half decade.
The rising costs of the water control and the high amenity values of the place have fostered a critical reflection of the former agricultural orientation, making the case for a new set of management options, - in particular, whether to go ahead with wetland restoration. In the mean time, a series of recent private incentives offset by various triggers has made the Anciens Marais des Baux a focus of attention to various public and private institutions questioning what the future holds for the valley. Why does this matter?
Because wetlands are amongst the earth’s most productive ecosystem that provides many direct and indirect services to society, such as their ability to provide distinct landscape qualities, recycle nutrients, check for flooding and boost biodiversity. Indeed, the surrounding area possess a high heritage value, and has consequently a real tourist attraction, supporting a lot of cultural, recreational and residential services.
To manage this, and protect typical local landscape and biodiversity the local authorities have developed a cooperation in the institutional framework of the Regional Park of the Alpilles Mountains (PNR of Alpilles). Together with the environmental NGO “A Rocha France”, the PNR is engaged in a consultation process regarding the burning issues of the restoration of “Anciens marais des Baux”5.
Amongst a variety of stakeholders ranging from landowners, regional and local planners, consensus over the future landscape configuration of the Vallée des Baux is far from settled. Indeed, the opinions and expectations are diverse regarding the potential expansion of the wetland, which today figures 1/6th of its initial size (300 hectares). On the one hand, a number of public bodies are interested in buying land and reclaiming wetland (Agence de l’eau, Conservatoire du littoral, Caisse des Dépots et Consignations) or compensating landowners for undertaking wetland restoration (Natura 2000). On the other hand, this is coupled with a degree of resistance amongst local authorities, mainly due to the fear of mosquitoes explosions and loss of jobs in the agricultural sector. As it is eventually landowners who have the final say, much research consisted of grasping their preferences in order to establish the fragility and firmity of status quo; that is, the landscape as it looks today, and identify future alternatives. With ten different landowners, whom each have their individual preferences about the future landuse of the Anciens Marais des Baux, any conclusion was far from homogenous. This reflects the high uncertainty related to future commodity prices, agricultural support, the frequency of flooding and differences in underlying motivations (prestige, quietness, eco-tourism, profit). In addition of the cultural values attached to this very iconic Provence’ landscape, one could list also biological and ecological values, demonstrated by the nomination of the area by the Natura 2000 sites directory.
3 This research project has been funded by the Program ”Paysages et développement durable” of the French Department of Environment , Sustainable development and Landscape Planning ( MEDDAT)
4 The “Ancien marais des Baux” is an area located in Provence, not far from Arles, between the Alpilles Mountains and the Plain of the Crau. It span over 1700 ha, and three municipalities (Maussane les Alpilles, Le Paradou, Mouriés)
5 http://www.alpilles.org/index.htm
Figure 1 : Location and extent of original wetlands
For these reasons, it is crucial to submit all the future potential landscape changes to a careful appraisal, including general public consultation and scientific audits. The pilot survey we are presenting in this paper is an ingredient to this process. In a complex social and ecological environment, multiple stakeholders and conflicts of interests may easily translate into a maintenance of the status quo.
Nevertheless, we believe that a step stone to conflict resolution is the proposition of future scenarios highlighting how resources can be allocated to achieve the best payoffs to society. It should nevertheless be recognised that the results provided in this paper are only one element of a comprehensive CBA taking into account the various ecosystem services that wetlands may provide to the society.
In the process of appraisal of any prospective’ changes, it is of primary importance to:
- identify and measure the relevant attributes supporting cultural and ecological values and services (Parts 2 and 3),
- to present to local authorities and citizens a map of social preferences enabling and facilitating negotiation among stake holders (Parts 4).
Consequently, in this study, we do not attempt to account for the entire total economic value of any landscape change. Rather, we wish to gain an insight into the nature of trade-offs that are inherent in public preferences over the range of possible future landscape configurations herein comprising some of the use and non-use values. In an attempt to clarify the picture, this study applies choice experiments (CE:
Louviere et al., 2000). A choice experiment is a highly ‘structured method of data generation’ (Hanley et al.,2006), relying on carefully designed tasks or “experiments” to reveal the factors that influence choice.
The CE can estimate economic values for any environmental resource, and can be used to estimate non- use as well as use values. It enables estimation not only of the value of the environmental resource as a whole, but also of the implicit value of its attributes, their implied ranking and the value of changing more than one attribute at once (Birol et al 2006)
The environmental resource is the landscape in our case, defined in terms of its attributes and levels these attributes would take with and without various management options. As such we use the CE to determine what the preferred landscape is, and under wetland restoration, the most desired features that the wetland should provide. To what extend do people derive welfare from passive recreation, and is this considered compatible with hunting? Is the resistance to wetland restoration lessened, if we introduce mosquito control and in that case, what kind of mosquito control? How much are enhanced recreational facilities valued relative to biodiversity enrichment and/or the management of mosquitoes? The inclusion of a monetary attribute in the CE constrains choice behaviour within a private budget constraint and allows us to answer questions such as how much more the public is willing to pay for wetland restoration relative to open agricultural fields and/or a larger degree of tree coverage? The aim is to identify the most fruitful
landuses of the Anciens Marais des Baux from the point of view of local citizens. The trade-offs between attributes being conducted in this study are not easy. But at the level of policy discourse, taxpayers are commonly asked to make such stark trade-offs. Part 2 provides a theoretical insight in to the theory behind the choice experiment method and the statistical models employed. In part 3, the major elements in the desing of the choice experiment implicit to Marais des Baux are presented. Part 4 presents the results of the survey, and the conclusions drawn from here.
2 The Theory behind the Choice Experiment Method
In the application of the choice experiment, the individual is presented by the use of a questionnaire for a hypothetical choice situation, from which only one alternative can be chosen between two or more. Every alternative in a choice set is described by several attributes which can have several levels over the different alternatives.
To fit within a discrete choice framework, three central assumption must be held (Train, 2002). First, the alternatives must be mutually exclusive from the decision makers perspective: choosing one alternative necessarily implies not choosing any of the other alternatives. Second, the choice set must be exhaustive, in that all possible alternatives are included. This can be achieved by ncluding an “opt-out possibility6” whereby the respondent has a possibility of choosing none of the other alternatives . Third, the number of alternatives much be finite. The researcher can count the alternatives and eventually be finished counting (Train, 2002).
2.1 The characteristics theory of value and random utility theory
CEs are based on two fundamental building blocks: Lancaster's characteristics theory of value, and random utility theory (RUT). Lancaster (1966) asserted that the utility derived from a good7 comes from the characteristics (attributes) of that good, not from consumption of the good itself. The value of a good is then given by the sum of the value of its attributes (Hynes and Hanley 2006).
Random utility theory is the second building block and is derived as follows: A decision maker, n faces a choice among J alternatives. The utility that decision maker n obtains from alternative j is Unj, j= 1,…J.
This utility is known to the decision maker but not to the researcher. But the researcher observes some attributes of the decision maker, and can specify the function that relates these observed factors to the decisions makers’ utility, called the representative utility Vnj. The individuals n=1,…,N face a choice among J alternatives, denoted j=1,…,J and chooses the alternative that provides the greatest utility. He chooses alternative i, if and only if Uni > Unj. J ≠ i. Utility is then decomposed as:
Unj = Vnj + εnj, (1)
where Unj is the latent, unobservable utility held by consumer n for choice alternative j, Vnj is the systemic or observable portion of utility that consumer n has for choice alternative j, and εnj is the random or unobservable portion of the utility that consumer n has for choice alternative a (Train 2003). Now, the probability of consumer n choosing alternative i from a choice set Cn is equal to the probability that the
6 An Opt-out option gives the respondent a possibility of choosing the present ”status quo” situation whereby the alternatives associated with a change in tax can be excluded. Forced choices which can lead to an overestimation of demand is thereby excluded.
7 In our application “the good” is the landscape of the Anciens Marais des Baux
systematic and stochastic components of option i for consumer n are greater than the systematic and random components of option j for consumer n in choice set Cn.
P(i|Cn) = Prob [(Vni +εni) > (Vnj + εnj)] j ≠ i = Prob [(εnj − εni) < (Vni − Vnj)] j ≠ i (2)
The probability that each random term εnj − εni is below the observed quantity Vni − Vnj is bounded between zero and one, according to the logistic cumulative distribution function. To empirically estimate (3), it is assumed that the stochastic components are independently and identically distributed (IID) with an extreme value distribution. This implies that the unobserved factors are uncorrelated over alternatives, as well as having the same variance for all alternatives. These assumptions lead to the use of multinomial (sometimes called conditional) logit (MNL) models to determine the probabilities of choosing i over j options (Bennett et al 2001;Hesher et al 2005):
j e i
U e U
j
Vnj Vni nj
ni
exp( )) ) exp(
(
Pr /
/
(3)
The scale parameter scales the coefficients to reflect the variance of the unobserved portion of utility8. The indirect utility function estimated is
k m b
a n n
ni Z Z Z S S S
V 1 12 2 .... 1 2 ... (4)
Where β is the alternative specific constant (ASC) which accounts for variations in choices that are not explained by the attributes or socio-economic variables. The number of wetland management scenario attributes considered is n and the number of social and economic characteristics of the respondent employed to explain the choice of the wetland management scenario is k. The vectors of coefficients β1 to βn and βa to βm are attached to the vector of attributes (Z) and to a vector of individual characteristics (S) that influence utility, respectively. When parameter estimates are obtained, the compensating surplus welfare measure, can be estimated from the MNL using the following formula:
)) (
( )
( V
0 Y V
1 Y Z
n)
V1 - (Vo 1/
-
CS
n (5)where βM is the marginal utility of income9 (assumed to be equal to the coefficient of the cost attribute);
V0 represents the utility of the status quo and V1 represents the utility of the change scenario.
Limitations of the MNL
8 But the scale parameter does not affect the ratio of any two coefficients. Since it drops out of the ratio, marginal rates of substitution are not affected by the scale parameter.
9The division by αn translates utility into euros, since 1/αn = dYn/dUn.
The hurdle when using the MNL model is that choices must satisfy the independence of irrelevant alternatives propperty. Misprediction arises with the MNL when the addition or subtraction of any alternative from the choice set affect the relative probability of individual n choosing any other alternative (Hensher et al 2005). Furthermore, while the MNL can represent tastes that vary systematically in the population in relation to observed variables it cannot represent differences in tastes that cannot be linked to observed characteristics. When taste variation is partly random, the logit is a mispecification. This is because the IID assumption implies that the unobserved portion of utility for one alternative is unrelated to the unobserved portion of utility for another alternative. With this in mind, the theory of choice merits a mention.
The heart of the rational model of economics is the idea that consumers seek to maximize innate, stable preferences over the quantities and attributes of the goods they consume. The original formulation of RUM as a behavioural hypothesis started from the standard model (such as the MNL), with choice probabilities conditioned on observed attributes of alternatives and characteristics of the decision maker and randomness attributed to unobserved heterogeneity in tastes, experience, and information on the attributes of alternatives (McFadden 2001).
In psychological theories of the choice process, the individual is less organized - Affect and motivation are key determinants of attitudes and feed into the choice process. Unobserved sources of heterogeneity may come from past experiences or hidden attitudes10. In these theories, the economists' calculus of utility assessment and maximization is reduced to one of many factors in the decision-making environment.
Evidence suggests that individuals are poor natural statisticians, placing too much weight on readily available information and exemplars, and too little on background information that is more difficult to retrieve. Subject consequently employ numerical prompts or use heuristic cues as responses instead of substantive knowledge (McFadden 2001).
Thus, under random taste variation, preferences are heterogeneous and accounting for this heterogeneity enables estimation of unbiased estimates of individual preferences (Train 2003). (Adamowicz and Boxall, 2001). Preference heterogeneity can be accounted for by using respondent’s social, economic and attitudinal characteristics directly as interaction terms with choice specific attributes. But these methods do not detect for unobserved heterogeneity. In the words of McFadden 2001: “Until the day comes when brain science understands how the cognitive mechanisms operate for a broad spectrum of economic decisions, I suspect that the standard model [RUM – MNL], enhanced to account for the most systematic perceptual illusions, will prove to be the best platform for evaluating most economic policies”. This is the workings of the mixed logit model, in which unobserved preference heterogeneity, can be accomodated for. Under this general heading falls the random parameter logit model (RPL) and the latent class model (LCM).
2.2 The mixed logit model
The mixed logit probability can be derived in a number of different ways (see e.g. Train 2003), but the most popular, and also most straightforward, is the random parameters approach (Greene and Hensher 2007). This approach involves mapping taste variations to specific individuals through re- parameterisation of the mean and the standard deviation of the distribution of each random parameter.
This way, each β-parameter associated with an attribute is treated as a random parameter, having both a mean and a standard deviation, instead of being treated as a fixed parameter, where all behavioural
10 The perception of hunting may for example vary across respondents, and those particular perceptions may be related to other attitudes that the respondents hold regarding the other attributes. In one of the focus groups it came forth that one of the respondents considered hunters as “care takers and stewards of the environment”. Consequently, a respondent that may express a pro-environmental attitude toward wetland restoration may for the same reason have a pro-hunting attitude. Whereas for another respondent the exact opposite could be true, for whom a pro- environmental attitude is associated with an anti-hunting attitude
information is captured by the mean, and the standard deviation in effect is zero (Hensher and Greene 2003).
In the random parameters approach, individuals n=1,…,N face a choice among J alternatives, denoted j=1,…,J in T choice sets, t=1,…,T. The individual’s utility from alternative j in choice set t is specified as
ntj ntj n
ntj x
U (1)
The K1 vector xntj defines the full set of observed explanatory variables in terms of the attributes of the alternatives and the decision maker (Greene, 2002). βn is a K1 vector of coefficients of these variables for person n representing that persons tastes and the εntj is a random term assumed IID type 1 extreme value distributed independent of βn and xnjt. The βn varies over individuals in the population with density
f , where matrix θ is a vector of the true parameters of the taste variation, e.g. representing the mean and standard deviation of the β’s in the population.The individuals evaluate each alternative within each choice set based on their own preferences. That is, tastes vary only across individuals but not across choice sets and alternatives for each individual. In other words, utility is correlated over choice sets for each individual and over alternatives for each choice set. Hence, β is only subscripted with n.
The researcher observes xntj’s, but not βn or the εntj , (if he did then the choice probability would be standard logit ). The standard logit probability of individual n choosing alternative i in choice set t conditional on βn can then be written as:
J
j x x n
nti
ntj n nti n
e L e
1
(3)
As the individual evaluates a series of choice sets, the conditional probability of observing a sequence of choices i(n, t) from the choice sets is the product of the t conditional probabilities of the standard logits, as put forward in equation (3):
) ( )
( ( ,) n
t
t n nti n
n L
S
(4)However, as βn is unobservable to the analyst, it is not possible to condition on β. Instead, the unconditional choice probability is determined as the integral of equation (4) over all possible values of βn weighted by the density of β. Assuming linear-in-parameters utility, the mixed logit probability for observing a sequence of choices i(n, t) for individual n is then
S f d
Pn( )
n n (5)The analyst's final goal is to estimate , the population parameter that reveals the distribution of the individual parameters, that is the mean and variance of
.
Thus, the mixed logit probabilities does not depend on values of , theses probabilities are a function of and ’s and are integrated out. The mixing distribution, f() can be discrete wth taking a finite set of distinct values. In this case the mixed logit becomes the latent class model. This specification is usefull when there are M segments in the population, each of which has its own choice behaviour or preferences. The choice probability is:Pni = Mm=1Sm(eb’mxni/j eb’mxnj)
Alternatively, in the random parameter model, f() is specified to be continous with a normal, lognormal, triangular or uniform distribution, allowing explicitly for a range of attitudes towards attributes within the population. These models can be used to generate probabilities for choice and hence estimates of marginal values for each attribute and compensating surpluses (CS) for changes between different choice profiles.
The random parameter logit approach has an intuitive appeal in so far as it allows explicitly for a range of attitudes towards attributes within the population, identifies which attributes have significant levels of heterogeneity in preferences, and quantifies the degree of the spread of values around the mean. The latent class model however, provides further insight into the data by endogenously identifying groups of respondents who have similar preferences for particular attributes, but where preferences vary considerably between groups. The LCM analysis evaluates choice behaviour as a function of observable attributes of the choices11 and latent heterogeneity in the respondents, sorted into M classes based on statistical information criteria (Hynes and Hanley (2007)). Due to its powerful combination of being able to specify a model that simultaneously estimates the marginal benefits associated with different attributes for different groups and assigning group membership the LC model is likely to become an important tool for resource managers in the future. Indeed, people may have a wide range of motivations for visiting wetlands. Some will be attracted by the wetland itself and the wildlife it provides a home to, while more local users may simply find it a convenient place to walk their dog. To examine what types of investment in recreation facilities that generate the greatest welfare gains, one needs to explore the heterogeneity of consumers’ surplus values for wetland recreation between alternative uses and users (Christie et al 2007, Hynes and Hanley 2007). In this study we would have liked to employ the latent class model, but since it is a pilot study, our sample size does not permit for using this approach. We therefore limited ourselves to the random parameter logit.
3. The design of the Survey Questionnaire
A questionnaire is a data-collection instrument that sets out in an formal way the questions designed to elicit the desired information. This is not a trivial task, even very simple questions require proper wording, formal, content, placement and organisation if they want to elicit accurate information. Since the questionnaire require respondents to consider how a changes in a non traded good or service, the policy, whether real or hypothetical should be perceived as realistic and feasible (Bateman et al 2001).
The determination of the relevant attributes and their levels was a long iterative process spanning over several months the summer / Autumn 2007. Firstly, the actual valuation problem was formulated, and
11 In the introductory and follow up questions from the questionnaire, statements will be used to develop an index of environmental consciousness and wetland awareness. As such, psychometric measures on latent attitudes about the environment can be developed (by factor analysing principal component analysis). See chapter 4.
attributes of interest were identified. The information gathering process was a combination of field visits with landowners and policy makers, and personal interviews of different stakeholders and experts (regional nature parc, mosquito experts hydrologists and ecologists). Subsequently, the identified attributes and their levels were pre-tested in focus groups, which brought additional insigth into appropriate survey questions on attitudes and opinions, knowledge, familiarity and use of the good and demographics. The attributes were chosen to meet the following requirements (Bergman et al 2006):
• Relevant to the problem being analysed,
• Credible and realistic,
• Capable of being understood by the sample population, and
• Of applicability to policy analysis.
3.1 Attributes’ identifcation
Amongst a variety of stakeholders ranging from landowners, regional and local planners, consensus over the future landscape configuration of the Vallée des Baux is far from settled. Identifying policy relevant attributes alone results ins a long list. In particular we identified: The size of the wetland, tree hedges, farm employment, Research and Education (related to wetland ecosystem services), Hunting, Access and Recreation, Biodvidersity, Mosquitoes, The invasive water flower species Jussie, and various wetland ecosystem services, such as waste similation, risk of flooding, and aquifer replenishment. This list is too comprehensive to be included in the choice expeirment, as it is usually adviced to incluce maximum 5-6 attributes (Nielsen et al 2006, Bennett et al 2001).
In choosing an optimal subset, the guiding principle was that the attributes were of the greatest relevance to the public as a whole and capable of being understood by the sample population. As for ecosystem services, forexample, stated preferences will be not simulate true preferences when members of the public possess a poor understanding of ecosystem services (Christie et al 2007). The identified subset of most pertinent attributes are : Size of the wetland, Tree hedges, Access and recreational activities, Biodiversity, Mosquito control, and we explain our motivation for including these in the following paragraphs.
3.3 Interactions between Landscape qualities and wetland restoration
Land use denotes the human employment of land, such as settlement, recreation, pasture, rangeland and fields. Any change in land use will affect the landscape configuration in the Vallée des Baux. Departing from the milestone of the European landscape convention in which “All forms of landscape are crucial to the quality of the citizens’ environment reflecting the diversity of their common cultural and natural heritage and as the foundation of their identity” (Dury, ) - The landscape can not be studied without being interested in the preferences of individuals for this good. From the point of view of the road that cuts directly through the Anciens Marais des Baux or the free unlimited access to the dyke, the landscape in the Marais des Baux is non-excludable and non-rival. Nevertheless, different social groups confronted with this landscape do not attribute the same value to it. We consequently chose to distinguish them according to their attitudes, socio-demographic characters and time that they spend in the affected area.
The socio demographic and attitudinal attitudes can be treated under model estimation of a given population frame. Tourists and permanent residents however require two separate samples, admitting that their landscape / landuse motives may be distinctly different and require different payment vehicles.
The primary tourist destinations in Vallée des Baux, are cultural artefacts such as the city of Baux itself, the roman aqueduct and the tour de Castillon. Though the activities are not directly linked to recreational
nature experiences, we cannot neglect the importance of landscape in the appreciation of these destinations. Natural setting is often the primary attraction to any tourist resort. Key tourist attractions are typically, specific scenic areas, nature parks and historic sites (Englund 2000). Focus groupss highlighted that the natural patrimony and historical patrimony are each a component part of the overall experience (as focus groups highlighted). At present the demand for natural patrimony is mostly linked to recreational non-use landscape values. Nevertheless, wetland restoration may alter the “demand category”
and enhance potential use values. In the full scale study, we aim to sample both tourists and non tourists.
In the following the definition of attributes and their levels are discussed.
3.3.1 The size of the Wetland
This attribute describes the size of the wetland as comprising ponds, reed beds, and marchland at the place of cereal production and dry grassland at varying extents according to the season. On the one hand it captures people’s easthetical landscape preferences, promoted by the photographic illustration included in the questionnaire. One the other hand this variable captures underlying unobserved opinions that the individual hold about wetlands and/or agriculture. Consequently, some respondents may chose to opt for an advanced level of restoration due to its landscape beauty, while others may chose this option due to its associated ecosystem services or a combination of the two12.
A simple google search confirms that wetlands have distinct and appreciated landscape features, “Many visitors to wetlands immediately appreciate their natural beauty, experience the sense of tranquility they offer and recognize their role in the local landscape”, “They also provide great places for people to explore and reconnect with nature” (google wetland visit). Indeed, open water surface area and the natural vistas associated with them are expected to create non-use values through feelings of serenity and tranquillity (Birol et al 2005). Traditional economics supports the concept that the less there is of some commodity “a wetland”, the more valuable it is. At the level of policy, in areas where almost all natural wetlands have been drained (e.g. Europe, Midwestern USA, etc.), the desire to conserve what few wetlands are left is often very strong (Mitsch and Gosselink (2000)). That this opinion holds between locals in Marais des Baux, is a strong a-priori hypothesis. Since the conversion to agricultural land has been so extensive, and remaining wetlands are placed out of sight for the general public, there may exist a sort of status quo bias for the agricultural landscape as it is today (which a few prior individual level interviews have indicated)
3.3.2 Tree hedges
Maintaing the poplar tree hedges is a Natura 2000 objective applicable to the Marais des Baux. Today they are present in a very fragmented manner, and they have number of conservation priorities (PRN 2006). Likewise, ecologists (from the research centre Tour du Valat) advise that wetland restoration would take place by simultaneously planting of hedgerowsi. Even though technological constraints have impacted in favor of the destruction of hedges, newer ecological constraints play in favour of their planting. Does a particular landscape demand do likewise? In a region of a frequent aggressive wind le Mistral, where the sun shines 6 days out of 7, and in which the Alpilles are closed during the summer months to prevent fire hazards, there may exist a social demand for more shadow or demand for a distinctly structured landscape.
3.3.3 Recreation and access
12 In the questionnaire, follow up questions are used to shed light on the respondents motivation behind his choice.
Natural ecosystems such as wetlands have an important value as a place where people can come for rest, relaxation, refreshment and recreation. Features of beauty, rare or spectacular biodiversity or elements of a site that offer themselves to specific activities –Canoeing, sport fishing, hunting and bird watching are all good examples. Furthermore, with enlarging populations, locally and internationally, affluence and leisure-time, the demand for recreation in natural areas (‘eco-tourism’) will most likely continue to increase in the future. (de Groot et al 2002).
However, it is likely that activities that will disturb and fragment wildlife habitat, such as hunting, fishing, and excessive visits are incompatible with exploiting the full potential for biological diversity. Instead, carefully managed passive recreational uses may ensure the least impact on the wetland ecosystem.
Passive recreation refers to non-consumptive uses such as wildlife observation, walking, biking, in well organised circuits. This is in line with objective 28 of the PNR des Alpilles (PNR 2006). Inspired by the different management strategies in the nearby wetlands of the camargue, two future attribute levels were identified, one with emphasis on “observation and protection” (passive recreation) and the other with
“observation and exploration” (active recreation). Independent of landlord decisions, the dyke being publicly owned, could be equipped to facilitate passive recreation with the establishment of public facilities, such as information boards and observation towers.
3.3.4 Mosquitoes
Focus groups suggested that in the absence of “controlling for the mosquito population”, wetland restoration is not a desired feature between locals. The control of mosquito populations, previsouly taking place through the drainage of wetlands, consist of using biological or chemical treatments to reduce the irritation they cause humans. In the littoral zones of France, the great densities of mosquitoes have long been considered incompatible with tourist development. Consequently, the motivation behind control lies in tourist promoted economic growth and the preventing the spread of illnesses. The locals in the Camargue, continually experience a significant nuisance from mosquitoes ii, although they have lived longer with wetlands than their neighbours in Vallée de Baux. Consequently, the Camargue (Salin-de Giraud/Port-Saint-Louis-du-Rhône) is since 2006 for the first time in history, subject to a preliminary experiment of mosquito control using the biological insecticide the bacteria Bacillus thuriengiensis israelis (Bti) iii. This suggests that a strict mosquito control in the Marais des Baux may be necessary in case of wetland restoration. Besides the use of the chemical toxin, Bti another strategy, more compatible with the conservation and restoration of wetlands is a modification of the schedules of water table variations and the frequencies of variationiv. In conjunction, biological control via fish farming or small fish natural predators of mostique larvae (Gambusies) could contribute to reduce the nuisance while offering alimentary resources for the fauna as a whole.
3.3.5 Biodiversity
The Marais des Baux is uniquely rich in biodiversity. It provides a habitat for a total 208 different bird species (such as the Roller, the purple Heron and Bonelli’s eagle) of which 27 of them are protected by international treaties. Marais de Ilon, a remaining part of the original wetland is an autumn stop off migration point (roosting point) for 600000 swallows. The valley also supports a wide array of fauna diversity, including mammals, amphibians, reptiles and fish. In particular; 46 species of dragonfly, making it one of the highest density zones in Europe, a remarkable population of an aquatic turtle, the European pond terrapin, an endangered species and 9 species of amphibians, amongst the rare and endangered is Pélobate cultripède. Of the rare plant species in the wetland, 6 are listed under the Convention on International trade in Endangered Species of Wild Fauna and Flora (CITES). Due to its
natural patrimony, the area has been remarked in several national and European undertakings, in particular as a Natura 2000 habitat (A Rocha France (2006), Lempers et al 2007).
Through interviews with various science experts engaged in the area13 and supplementing literature, some rough lines can be drawn about the impact of wetland restoration on biodiversity ceteris paribus. A moderate restoration of wetlands would lead to a significant increase in the number of birds such as warders (migratory birds that profit from shallow water and mudflats such as the black wing stilt), herons, ducks and Reed warblers (react quickly in time and figure). Nevertheless, it is considered that the fauna as a whole display threshold effects so that an advanced level of wetland restoration may lead to a more than proportional increase in the number of bird species, with an up to 300% rise14. Furthermore, under advanced level wetland restoration it is also believed that many rare species either previously present in Marais des Baux will return, amongst these are the great bittern (the Butor étoilé) and the white stork.
3.3.6 The monetary attribute
The questionnaire is incentive compatible when true preference revelation is induced. This depends on respondents expectations about provision of the goods, and whether they believe or not that provision of the good is conditional on their WTP amount. The situation we want to evoke is when respondents believe that provision is contingent on their stated values and that they will have to pay the amount they state - it is then in a respondent’s best interest to reveal their true WTP (Bateman et al 2002).
An institutionally feasible option for the financing is the establishment of a new inter-municipal association of management of the Anciens Marais des Baux (syndicat intercommunial d’amenagement et de gestion des Anciens marais des Baux). This would be financed through local taxes from the five bordering municipalities that are considered to be most affected by the change of land use in the Anciens Marais des Baux. From a constitutional viewpoint, an inter-municipal is considered a well controlled body (PRN 2006:p40 and Morvan E, Council of Arles). The payment vehicle consequently refer to an increase in municipal taxes. The levels of the monetary attribute were determined through focus groups, literature reviews of similar studies in and outside France,
Refinement of these attributes took place through literature review, stakeholder interviews and focus groups. Indeed, individuals raise significant issues that are often overlooked or understood differently by researchers.
3.3.7 The number of attribute levels
The number of levels that one uses for a particular attribute is a function of: Number of levels needed to simulate market of interest, the size of the hypothetical design that one can afford and the need to specify non-linear attribute effects. In including three levels for each policy relevant attribute we have achieved to fulfill all of these three criteria and create a 100% efficient design (see section 3.4). The monetary attribute included 6 levels, allowing us to trace out any non-linear utility curve as well as approaching the respondents true willingness to pay (under the condition that our range is reasonable). Table 2 shows the final list of attributes and their levels
Table 2
13 Amongst a naturalist from LPO (bird conservation organisation), an environmental engineer at Parc regional Naturel des Alpilles, and biologists at A Rocha
14 In particular raptors need larger areas and water bodies and who react less quickly to a restored wetland, and will consequently react more than proportionally to greater areas.
Attribute Levels Description Size of Wetland -Status quo
-Moderate restoration -Advanced restoration
In the ‘status quo’ the wetland area would remain as it is at present, covering 1/6th of its natural size i.e. 3 km2 in total
Under moderate restoration The wetland area would be restored to 1/3rd of its natural size i.e. 6 km2 in total.
Under advanced restoration The wetland area would be restored to 2/3rds of its natural size i.e. 9 km2 in total Mosquito
population control
-No public control -Natural control -Chemical control
No public control: This is the status quo
Use of natural control methods such as strict water level management and biological control such as fish.
Use of chemical control from the Bt toxin, a natural occurring bacteria.
Access and
recreation -No access and no facilities
-Visual access -Physical access
Status Quo: The general public have access to the dyke, from which bird watching, fishing and hunting is allowed. There are no facilities
Protection and observation: The visual experience of the restored wetland is enhanced with information signs and observation towers on a surrounding circuit . Hunting is not allowed.
Exploration and observation: There is access to the wetland, with broadway walks and bicycling facilities. Hunting is restricted to certain areas
Hedges -Few
-More -Most
Status quo – few
More allowing a view of the Alpilles Biodiversity -Low Most
-Medium -High
Status Quo - Low: There is little change in the level of biodiversity in the valley.
Medium: The population of common and rare species of ducks, birds, insects, dragon flies, turtles and fish will increase.
High: The population of common and rare species of birds, insects, dragon flies, turtles and fish will increase a lot.
Several rare bird species will return to the valley (without guarantee)
Monetary
attribute Municipal taxes 3,5,10,20,30,50
Any change implies an increase in your municipal tax, used to finance the inter-municipal association of management of the Anciens Marais des Baux.
3.4 The experiment design
Having identified the attributes and their levels, the experimental design permitted the creation of sets of alternatives with individual attribute levels combined to an efficient design. A full factorial design is 100 pct. efficient as all main effects, all two-way interactions and all higher-order interactions between attribute levels are estimable and uncorrelated. A main effect implies that the effect of any one attribute, on the response variable is the same no matter which levels the other attributes takes, while two way interactions or higher order interactions allows us to estimate the joint effect of two or more attributes on the choice of any alternative (Hensher et al 2005). With 5 attributes of three levels and a 6th monetary attribute of 6 levels, our full factorial design yiels: 35 x 61 = 1458 alternative management combinations.
Obviously, making subjects consider all combinations, is too cost-prohibitive and tedious.
Instead we used three properties of orthogonality, balance and minimum overlap that characterise efficient choice designs to obtain a fraction of all possible combinationsv . The fractional factorial consisted of 36 alternative management combinations, that were split in two blocks each with 9 choice sets. This was derived from guidelines on efficient statistical design and undertaken in the SAS®
software programme following guidelines by Hüber og Zwerina (1996) and Kuhfeld (2004).
The fractional factorial was designed so as to be able to estimate main effects, and interaction effects between attributes where these were considered possible. The fractional factorial did however create some cognitively unrealistic attribute combinations and dominating alternatives. In order to hinder that the respondent could not take certain level combinations and maximise the trade-off made between alternatives, swapping and relabelling (Hüber og Zwerina (1996)) was made in the final stage.
3.5 Minimal survey error
To achieve a high response rate of the questionaire and minimal survey error the tailored design method developed by Dillman (1978, 2000) was applied. It is guided by the principle that people will only answer if their expected reward is greater than their anticipated costs. This is achieved by making the questionnaire short and easy, reducing cognitive demands in relation to more complex questions, while minimising requests to obtain personal information due to the perceived risk associated with this.
Rewards come about by showing positive regard by making the questionnaire interesting. Finally, trust is established by “making the task appear important” by e.g. revealing sponsorship by legitimate authority (L’INRA and CNRS) Finally, the draft questionaire was pre-tested in another focus group, for, question wording, structure and layout.
3.6 The right amount of information ?
An economic valuation of wetland restoration should not serve to “make people in favor” or bias, such an undertaking. In this case, welfare estimates extrapolated to the population as a whole will be biased.
Indeed, increasing the level of information on both the characteristics of an attribute (names and pictures of flora and fauna) and its relative scarcity (such as the extent of reduction over time) have been found to significantly increase mean bids (Garrod and Willis 2000, Jacobsen et al 2007). The initial focus groups held in Marais des Baux revealed the same tendency. On the other hand, CE responses cannot and should not be context free. Market prices are conditional: they depend on institutions, information, supply and demand conditions, and expectations about these (Garrod and Willis 2000). In this survey, we aim to balance the strictly conservative approach and that of engaging respondents in the valuation scenario by providing them a minimal amount of information of the good.
3.7 The use of visual material
In the quest for true preference revelation and realistic monetary estimates, the accuracy of information provided to survey respondents is only one facet. Arguably, unless individuals connect with and understand a piece of information on an emotional ‘affective’ level, then that information will lack meaning. Respondents can distinguish an increase from a decrease and classify changes as either utility improving or diminishing, but if they do not comprehend the magnitude of that change then their response fails to tap into any underlying true preference (and lacks evaluability). In such cases the continuous nature of an attribute level may be reinterpreted as say a category variable or at worse a simple discrete good/bad change, respondents taking a ‘satisfying’ approach rather than a maximising one.In the worst case, an attribute may effectively be ignored, resulting in lack of scope sensitivity (Bateman et al 2007, McFadden 2001). Visual representations of attributes have been found to enhance evaluability, reducing dependency upon heuristics. We therefore used visual information though GIS maps and photos to reduce unfamiliarity with the good concerned. Simplicity and clarity through eg visual designs, is particularly important because respondents are expected to make complex trade-offs between different attributes.
(Dixon, Bateman et al 2007).
4. Data collection and results
Questionaire responses15 were gathered in the course of January and February 2007. This was done by approaching respondents on the street and in their homes. Maximum effort was made to achieve a quota sample of respondents reflecting the population in socio demographic characteristics. Responses were gathered in cities within an equal 10 km radius of the Marais des Baux. The sample size is 89 after deleting one protest bid. The socio demographic characteristics of the respondents and their awareness about the Marais des Baux are illustrated in table 3.
Table 3: Socio demographic characteristics of sampled respondents
Attribute description Mean
Number of years respondent has lived in the city of residence 17.36 Number of yrs the respondent has lived in the region 18.79
Age 42.93
Number of children 0.44
Income 125000
Higher Education 44%
Male 45
Female 55
Did you know there was a wetland at the foothills of the Alpilles
Yes No
43%
57%
Have you visited the Anciens Marais des Baux? Yes
No 22%
78%
Have you visited a wetland elsewhere, e.g. the Camargue ? Yes
No 93%
7%
4.1 Estimation
Policy priorities can be defined from the choices that the respondents have made in the choice sets. The CE permit a revelation of (1) which attributes are significant determinants of the values people place on non-market goods (2) The implied ranking of these attributes amongst the relevant populations (3) The
15 A copy of the questionnaire could be sent on request to the corresponding author.
value of changing more than one of the attributes at once (for example, if a management plan results in a given increase in wildlife protection but reduction in recreation access) (4) and finally, as an extension of the above, the total economic value of a resource or good
(Bennett et al 2001).
All parameter estimations are done using biogeme v15 software (Bierlabe M.). Socioeconomic and attitudianal variables are included by crossing them with the price variable. In the survey, different variables were a priori considered likely to influence the WTP. In particular, age, gender, the amount of years the respondent had lived in the region, respondents who have outdoor nature experiences at least once a week, income and education level. None of these were significant at the 90 pct level of confidence. This is most likely an outcome of too few observations since parameter estimates had the expected sign and rather close to being significant.
Green behaviour was considered likely to positively influence the willingness to pay for some of the attributes.
Likewise, we expect the level of knowledge or attitude that individuals hold about wetlands to influence the willingness to pay. Respondent who all agreed that they were interested in visiting the wetland in Marais des Baux in the future, that they considered wetlands part of their cultural patrimony and wished that they should be conserved for future generations are also expected to have a higher WTP for the wetland attribute. These were all highly significant.
Table 4 Attitudinal variables
Variabel Levels Description Wetland
knowledge 1 (0,52)
0 1 if the espondents who have stated at least 4 times for 5 different wetland ecosystem services, that the particular ecosystem service is significant (biodiversity, flood control etc).
MdBcare
1 (0,53) 0
1 if respondents that have all answered that they would like to visit Marais des Baux in the future, that they consider wetlands part of the natural patrimony and that they consider it important that it is maintained for future generations.
Green 1 (0,39)
0
1 if respondents score high on environmentally conscious behaviour (recycle, donate, etc) or score relatively high on behaviour while having strong green attitudes.
4.1.1 The multinomial logit model
Variables used in the model, their coding and frequency are specified in table 4. We used the Biogeme package (Bierlaire, 2003) to estimate our models. Three different MNL models were estimated from the data set. The first is the basic model that shows the importance of the chioce set attributs in explaining respondents choices across the three different options “Status Quo – do nothing”, and “do something – alternative A and B” including the ASC. The subsequent models account for interactions.
4.1.2 The most basic MNL
The alternative specific constant (ASC) accounts for variations in choices that are not explained by the attributes or socio-economic variables, thereby capturing the average effect on utility from any attribute
Table 5 without interaction effects
Name Value Std err p-value
ASC (Status Quo) -0.730 0.276 0.01 Moderate Biodiversity 0.379 0.139 0.01 High biodiversity 0.219 0.182 0.23 More hedges 0.369 0.181 0.04 Most hedges -0.0268 0.148 0.86*
Mosquito cntr Natural 0.480 0.139 0.00 Mosquito control BTI -0.791 0.192 0.00 Passive recreation 0.352 0.143 0.01 Active recreation 0.459 0.136 0.00 Moderate wetland size 0.198 0.170 0.24 Advanced wetland size -0.195 0.144 0.17
COST -0.0206 0.00519 0.00
Init log-likelihood: -879,98 Final log-likelihood: -729,23 Adjusted rho-square: 0,158
not included in the model. The ASC of the status quo is significant and negative, supporting the idea that respondets are in favour of landuse changes? Field experience suggest that this could be the assocation that some respondents have between wetlands and other ecosystem services not accounted for in the choice experiement.
The parameter attribute levels of medium biodiversity, intermediate hedges (permitting a view of the Alpilles), passive recreation, active recreation, natural mosquito control, are all significantly different from zero at the 5% level of confidence. This indicates that there is a postive WTP for a landscape that features more hedges, more biodiversity, control of mosquitoes by natural methods, increasing recreational facilities –both of the passive and the active kind. Interestingly however, chemical control of mosquitoes is unfavourable to respondents.
In this basic MNL model, none of the parameters associated with wetland restoration are significant. This is particular, since indeed, increased recreational opportunities and biodiversity are highly associated with wetlands. It nevertheless illustrates the particularity of the CE method, allowing us to capture the value of the individual attributes of a good and not only the value of the good as a whole. The parameter estimate of price is found to be negative and significant, which is in good correspondence with the expectation of that an increasing tax is associated with a negative utility. The existence of a positive interaction effect between wetlandsize and natural mosquito control was hypothesised as possible. This was tested for and showed to be the case (further discussed in part 4)
4.1.3 The MNL with interactions
The attitudinal variables are included in the model by interacting them with the price attribute to thereby investigate to which extent they influence WTP. It is also verified from the covariance-correlation matrix, that none of these three attitude variables are significantly correlated. In accordance with expectations;
knowledge of wetland functions, green behaviour, identification and interest in wetlands are factors which makes respondents have a marginally larger WTP for landscape and activity changes in Marais des Baux. Clearly, the inclusion of interactions, gives us a more fine tuned understanding of how the welfare effects vary between different user groups and levels of awareness.
In the subsequent section, the mixed logit model is explored to avoids major limitations of the standard logit model, allowing explicitly for unobserved taste heterogeneity, i.e. random taste variations across respondents, while not being restricted by the Independence of Irrelevant Alternatives (IIA) property (Hensher and Greene 2003; Revelt and Train 1998; Train 2003).
Table 6
Model with main
effects only Model with interactions Variable Value Std err p-value Estimat
e Std err p-value ASC (Status Quo) -0,56 0.283 0.05 -0.56 0.287 0.05 Moderate Biodiversity 0,3 0.144 0.04 0.29 0.144 0.04 High biodiversity 0,072 0.190 0.70 0.07 0.191 0.72
More hedges 0,50 0.192 0.01 0.52 0.195 0.01
Most hedges 0,08 0.154 0.60* 0.11 0.155 0.50*
Mosquito cntr Natural 0,32 0.151 0.03 0.31 0.152 0.04 Mosquito control BTI -0,77 0.190 0.00 -0.77 0.192 0.00 Passive recreation 0,56 0.167 0.00 0.61 0.170 0.00 Active recreation 0,59 0.145 0.00 0.61 0.147 0.00 Moderate wetland size 0,28 0.174 0.11* 0.28 0.176 0.10*
Advanced wetland size -0,49 0.187 0.01 -0.51 0.189 0.01 Wetland*Natural Mos 0,85 0.331 0.01 0.92 0.335 0.01
COST -0,015 0.0056 0.01 -0.042 0.00840 0.00
COST*Green 0.015 0.00736 0.04
COST*Care 0.021 0.00766 0.01
COST*Wetland 0.015 0.00753 0.04
# of choices 801 801
Adjusted rho-square: 0.160 0.171
Init log-likelihood: -879.988 -879.988 Final log-likelihood: -725.872 -713.933
.
4.2 The random parameter logit model
In the random parameter logit models, an assumption need to be made concerning the distribution of each of the random parameters, i.e. the density functionf
. Since the true distribution is unknown, any distribution could in principle be applied (Carlsson et al. 2003). In most applications, normal and lognormal distribtions are specified (Train, 2003). The normal distribution sets no constraints on the signs of the parameters, while the lognormal distribution is useful when a coefficient is known have the same sign for all respondents. In the present paper, parameters are specified as normally distributed random parameters to allow for both negative and positive preferences for the different attributes. Focus group interviews and a pilot test indicated that this could be expected. The price parameter is held fixed, resulting in a behaviourally plausible negative sign for all respondents. Revelt and Train 1999 suggests fixing at least one coefficient for reasons of identification and stability. In this study, the cost coefficient is fixed while the others are allowed to vary. This makes it convenient to interpret the model, as the WTP for each attribute is thereby distributed in the same way the attributes coefficient.Initially, all the attributes apart from cost were included as random variables, and models with the normal distribution were selected for representation. Estimates which consistently show an insignificant standard deviation over the range of draws were then reestimtated as hanving fixed coefficients. The random parameters identified include the chemical mosquito and active recreation, herein including the acceptance of hunting on the area. The estimates of the chemical mosquito control are well dispersed indicating that there is a diversity of opinion, ranging from deep concern to indifference, and this leads to
