Valuing conservation of Giants Tortoises in the Galapagos Islands Should continental Ecuadorians participate in conservation programs?

Transcription

1 Valuing conservation of Giants Tortoises in the Galapagos Islands Should continental Ecuadorians participate in conservation programs? Abstract Balancing tourism and economic development with biodiversity conservation has been a challenge currently facing many developing countries, especially those counting on large pristine areas such as Ecuador. The Galapagos Islands and their giant tortoises are major contributors to Ecuadorian national income. However, these species are seriously threatened by introduced rodents and the costs of conservation programs cannot currently be covered by the Ecuadorian Government. This study aims to estimate the economic value of the conservation of giant tortoises in the Galapagos Islands and evaluate the possibility of funding conservation programs. Using the contingent valuation method we estimate the willingness-to-pay of continental Ecuadorian households for the implementation of a conservation program to preserve the giant Galapagos tortoises. In addition we analyze how to use this information to design policies to preserve this specie. Results indicate that mainlander households are willingness-to-pay a premium for conserving this specie and support the application of conservation policies in Galapagos. Using this information, different design of environmental premiums are presented and the possibility of implementation of several conservation programs are analyzed showing the feasibility of financing these schemes and that policy makers should consider this potential economic benefit to conserve this National Heritage Site and boosts sustainable development. Keywords: Conservation, contingent valuation, Galapagos Islands, giant tortoise, willingness to pay. JEL classification: D11, Q22, Q26 1

2 1. Introduction The accelerated increase of tourism activities in pristine and natural areas of developing countries has contributed to boost the economic development of many of these nations. However, poorly designed legislations and lack of sustainable tourist programs have caused this development to have a high cost in terms of ecosystem degradation and irreversible biodiversity loss. Therefore, the conservation of diverse ecosystems is needed to ensure provision for future generations (Costanza et al., 1997). Increasing environmental awareness has led to several actions on the part of governments all over the world to mitigate or prevent this accelerated loss of biodiversity. One of these actions is the creation of protected areas and biological reserves (Silva and Desilvestre, 1986). This article presents a case of study based in Ecuador, where protected areas cover 17% of the national territory (approximately 46,000 Km 2 ), with the Galapagos Islands being the most important. The Galapagos are located in the Pacific Ocean, approximately 600 miles west of Ecuador. They are a group of islands that make up one of the largest, complex, diverse and best preserved oceanic archipelago in the world. This archipelago contains a unique combination of marine and terrestrial ecosystems, a fact that explains why it was declared a Natural World Heritage in 2001 by the United Nations Educational, Scientific and Cultural Organization. The natural wealth of the Galapagos Islands is the basis of the local economy and an important contributor to the national economy. Galapagos-related tourism industry reported earnings of $418.8 million USD in 2006, of which an estimated $63M USD enters the local economy (Epler, 2007). However, the conservation of biodiversity is threatened by the introduction and presence 2

3 of invasive species, which represents the major environmental risk in Galapagos. These invasive species compete directly for space and food with native species. The giant Galapagos tortoises, which are the official symbol of Galapagos Islands, are threatened by rodents, specifically rats 1, which were introduced by pirate and buccaneer ships in the late seventeenth century and by current cruises and sporadically by subsequent colonization into the archipelago. These rodents represent nowadays a serious threat to tortoises. They are the most aggressive species among the exogenous vertebrates currently in Galapagos because they have a high reproductive and dispersal capacity, compete for food with native wildlife, are carriers of diseases and prey mainly on birds and reptiles, including giant tortoise eggs and newborns. Thus, for instance, on Pinzon (one of the Galapagos Islands) there is no survival of juvenile turtles due to the presence of these rodents. Giant tortoises, which have a large herbivorous cap, are important in the maintenance of terrestrial biological balance due to they are the unique seed dispersers of different plants on the islands. Therefore, this study focuses on the creation of a conservation program based on the eradication of introduced rodents in uninhabited islands of the Galapagos. 2 Results gathered from several monitoring trips carried out after a treatment in 2007 in the North Seymour Island of Galapagos showed that this eradication program is successful. Once rodents are eradicated, there would be a natural restocking of giant tortoises in the uninhabited islands, which would increase the chance of juvenile giant tortoises surviving to sexual maturity and hence reproduction. 1 For simplification, in this paper we use the terminology rodents and rats as equivalent. 2 This poison is specific to rodents and therefore the risk to other species of suffering direct or secondary poisoning by eating dead rodents is very low. 3

4 In order to estimate the economic value of conservation of giant tortoises in the Galapagos Island we designed a tailor-made study using the contingent valuation method (Mitchell and Carson, 1989, Hanemann, 1994, Bateman, et al., 2002). This methodology represents a viable alternative in the formulation of management and conservation policies related to the loss of biodiversity caused by the presence of introduced rodents. The Galapagos Management Plan, 2006 has mentioned the need for an economic valuation of their environmental services to robustly internalize environmental costs that involve the exploitation of Galapagos wildlife. Therefore, this study aims to contribute to the valuation of part of these environmental services (giant tortoises) in order to provide information to the authorities for the design of conservation and sustainable tourism policies. The literature related to the economic valuation of environmental goods or services cites the seminal study of Constanza et al. (1997), who value ecosystem services and natural capital on a global scale. This study assigns a value for them off $16-54 trillion USD, with an annual average of $33 trillion USD. Richardson and Loomis (2009) use the Contingent Valuation Method and performed a meta-analysis of several studies to value endangered, threatened and rare species. Loomis and White (1996), in their review of 49 contingent valuation studies, found that both the different characteristics of the species under study and different designs of questionnaire employed, significantly influenced the willingness to pay (WTP). In the same vein, Jackobsson and Dragun (1996) valued the conservation of plant and animal species threatened in Victoria, Australia finding that the WTP varies depending on the design of the scenario presented to respondents. 4

5 There are a few recent studies on environmental valuation related to marine species. Rudd (2007) used choice experiments to value the porbeagle shark within a conservation program that consisted of a group of several endangered aquatic species and found a positive willingness to pay to preserve these species off the Atlantic coasts of Canada. Also, Ressurreição et al. (2011) estimated the WTP to avoid the increasing loss of marine species in the Azores archipelago (Spain); they found that there is a greater willingness to pay for conserving marine species like a set than in an individual way. Among the studies directly related to turtle s conservation, Whitehead (1992) used the contingent valuation method to estimate the WTP of Americans to develop a protection program for sea turtles in North Carolina, USA. In a similar study applied in China, Jianjun et al. (2010) concluded that people living in Beijing have positive WTP for marine turtle conservation. Nevertheless, to our knowledge, there are no studies about economic valuation of the giant tortoise. On the other hand, in general typical valuation studies only present the values of the good or goods under study without analyzing how these figures can be used to design economic policies. In this paper we use our results to suggest funding options and policies to support conservation programs in the Galapagos islands. The remainder of this paper is structured as follows: Section 2 describes the methodology framework of this study, Section 3 shows the empirical results and discusses implications for policy and Section 4 summarizes the main conclusions. 5

6 2. Methodology We use the contingent valuation method (CVM) (Bateman and Willis (1999); Bateman et al., (2002); Hanemann, (1984); Mitchell and Carson, (1989)) to elicit the WTP of Ecuadorian for the conservation of giant tortoises in the Galapagos Islands. The CVM has become one of the most popular stated preferences methodologies used to value environmental goods that do not have an established market (Mitchell and Carson (1989), Hanemann (1994) and Bateman, et al. (2002)). This methodology has been used previously to value biodiversity, e.g. Constanza et al. (1997), Nunes et al. (2003), Yao and Kaval (2008) and Ressurreição et al. (2011). The CVM is a survey based method in which individuals are elicited the amount of money they are willing to pay for a change in the good or service under study, and in this way obtaining its value in terms of the subjects preferences. In this study we use the double bounded dichotomous choice elicitation method (DB-DC) (Hanemann et al. 1991), in which individuals are presented two bids sequentially in a closed-ended or referendum format. The referendum format has shown to be easier to answer compared to an open-ended format because of the greater familiarity that respondents have with these choices in real markets (Hanemann, 1994). In this case, the amount offered in the second dichotomous question depends on the respondent s answer to the first question. If the respondent answers Yes to the first elicitation question, he or she is offered a higher amount in the second one and if the answer to the first elicitation question is No, a lower amount is offered in the second bid (Carson et al. 1986, Hanemann et al. 1991, Alberini et al. 1997). It has been shown that the DB-DC format is statistically more efficient than the singlebounded because it reduces the variance in the estimation of willingness to pay (Hanemann, et al. 1991, Kanninen, 1993, Alberini, 1995). 6

7 2.1 Questionnaire design and survey implementation The design of the survey followed the recommendations issued by the panel of experts from National Oceanic and Atmospheric Administration (NOAA) (Arrow, et al., 1993) and also those cited by Mitchell and Carson, (1989), Bateman, et al., (2002) and Mitchell, (2002). Several meetings and focus groups were held with Galapagos National Park managers, public and private organizations, experts involved in conservation and general public. Based on the collected information, two pilot studies were conducted to verify the performance and readability of the questionnaire as well as to allow researchers to observe the respondents reaction regarding the scenario and willingness to pay questions. The first pilot study was conducted using an open-ended elicitation format, in order to collect information that led to the design of the payment vector. The second pilot study consisted of 40 surveys with a double-bounded elicitation format. Results from pilot studies showed that the preferred payment method was a fixed monthly fee in the electricity bill, which was applicable for a period of three years in our study. The final design of the questionnaire contained four sections. The first section consisted of a set of attitudinal questions, aimed at gauging respondents appreciation of conservation in the Galapagos. Section 2 presented the scenario, which described the current conservation condition of the Galapagos Islands, and presented the valuation exercise. In this section, the management plan of conservation of the giant tortoises based on the eradication of introduced rodents in 7

8 uninhabited islands was presented. The aim of this activity was to encourage tortoise natural regeneration by 90% and therefore their conservation in treated islands (64 thousand ha approx.). A cheap-talk script was included in this part of the survey (as recommended by Cummings and Taylor, 1999 and Aadland and Caplan, 2003), in order to reduce the hypothetical bias typically criticized in this type of study. The last section of the questionnaire consisted of sociodemographic questions used to characterize the respondents and to study the representativeness of the sample, by categories such as age, gender, income, education level, among others. Based on the two previous pilot studies and following Cooper s optimal design methodology (1993) and adjustment of the survival functions of WTP, the payoff vector consisted of five bids: 0.50, 1, 1.50, 2.50, and 4 USD. The presentation of these bids was randomly assigned to meet the portion of the payoff vector design. Following the guidelines recommended by Arrow et al. (1993), a total of 673 interviews (face to face) were undertaken by four trained interviewers between June and August 2010 in three cities in Ecuador: Guayaquil, Quito and Baños. The survey was conducted as personal interviews with the householders or family members over 18 years old involved in common household expenditures. A stratified random sampling was selected according to the income level of residence area. 8

9 2.2 The economic model In this study, we used a random utility model. This model allows obtaining Hicksian welfare measures through the indirect utility function (Hanemann, 1984). When incorporating the demand for environmental services, the utility consumer function (u) is given by: u j p y q ε v, ;, [1] j j where j takes the value of zero at baseline of the proposed environmental change and 1 in the final state, p is a vector of prices, y represents the family income, q is a vector of quality of the good and ε is the random term with zero mean and identically distributed. The difference between the two stages in indirect utility estimation is given by: p, y A ; q v p, y q v v1 t 1 0 ; 0, [2] Where Ai is the amount to pay for an environmental improvement proposal. Assuming a linear functional form for the indirect utility function, the difference in indirect utility functions is given by the following expression: v A t [3] Because this study uses a DB-DC format, the probability of responding Yes or No to the dichotomous questions can be expressed as follows (Hanemann and Kanninen, 1999): 9

10 u yy yes, yes 1 G A t P Pr i, [4] l nn no, no G A t P Pr i, [5] u yn yes, no G A G A P Pr t t i, [6] l ny no, yes G A G A P Pr t t i, [7] In this case, kl Pi is the probability that the event kl occurs with k and l representing responses Yes (y) and No (n). A t is the first value given, u At is the highest value offered after an initial positive response, and l A t is the lowest value offered to an initial negative response. GA ( ) represents the cumulative distribution function of the maximum willingness to pay on the part of individuals (Hanemann, 1991). The estimation problem is solved by the method of maximum likelihood with the joint density function given as: n L P i 1 yy nn yn yy d i i nn d i yn d i ny d P P P ny i i i i [8] The superscripts kl di are binary indicators taking the value 1 if the event kl holds for individual i; otherwise it is set to 0. Finally the mean willingness to pay is calculated as: WTP [9] where represents the parameter of all variables except for price, and represents the parameter of the price variable. 10

11 3. Results 3.2 Descriptive results Out of 673 responses obtained in the final survey, only 607 observations were considered in the estimation. The excluded responses corresponded to protest answers, e.g. people who disagreed with the hypothetical market because they believe the government or tourists visiting the Galapagos are those who should cover the conservation costs of giant tortoises. Another argument offered by these respondents was that the proposed management activity was not going to work well. Table 1 shows the descriptive statistics of the respondents and Ecuadorian households according to the National Institute of Statistics and Census (INEC). A Chi-squared test showed that there were no statistically significant differences in all the variables under study except for years of education and age. 11

12 Table 1. Demographic characteristics on the sample surveyed and population of Ecuador according to INEC 3 Respondents Ecuadorian population Male 46% 49% Female 54% 51% Age (in years) (Householder) Family Members 4 4 Years of Education Electricity Bill $19,4 $ 20,75 USD Monthly Family Income $475 $448 (1,6 members) The average age of the sample was found to be 37, whereas the average age of householders in Ecuador is 45 years old. This difference is due to the national survey only contemplates householders, while the survey conducted in this study took also into account family members who contribute to household expenses. This reason also explains the difference in the level of education. In general terms, the sample is fairly representative of the Ecuadorian population and we can claim that the estimated WTP is representative of the population that will be affected by the implementation of the policy. Table 2 shows the results for some attitudinal questions related to Galapagos, presented in the first section of the questionnaire. Most of the respondents (94%) have heard and know about the 3 Database of the Employment, Unemployment and Underemployment National Survey (December 2009). 12

13 Galapagos Islands. Both the percentage of people who have visited the Galapagos, as well as those with a concrete plan to travel to the islands are low, with 9% and 8% respectively; the explanation for these numbers is the high cost associated with visiting these islands. Out of these respondents, 77% are very concerned about nature conservation, which indicates that there is interest in preserving the environment, though only 22% of respondents know about management activities developed in Galapagos. 90% of respondents consider them very important and 87% considers the eradication of rodents in uninhabited islands a very effective program in the Galapagos. Table 2. Results of attitudinal questions related to Galapagos Attitudinal questions % of those interviewed Have heard of the Galapagos 94 Have visited the Galapagos 9 Have plans to travel to the Galapagos 8 Concerned about nature conservation 77 Have heard management activities in the Galapagos 22 Think rodent eradication in the Galapagos is important 90 Think the rodent eradication program is effective Econometric Results Using the 607 effective responses available for the analysis, we estimated several probit models assuming a linear functional form for the indirect utility function, which included attitudinal and socio-economic variables. We report in this paper the model that presented the combination of the variables that were relevant for this specific study and that also showed the best statistical fit 13

14 according to the analysis of the likelihood function. The independent variables considered in our estimations were the level of monthly household income, years of education of the respondent, the number of adults working in the households, knowledge of management programs in the Galapagos, and belief in the efficacy of rodent eradication. Table 3 shows the estimation results of the DB-DC probit model with the covariates mentioned above. All the estimated coefficients presented the expected signs. The price coefficient is negative, indicating that the higher the price offered, the lower the probability that people are willing to pay for conservation of giant tortoises. The estimated coefficient for the variables income, years of education and the number of working adults in the household had a positive sign, showing that older people with higher education level or households with larger number of people contributing to family expenses are willing to pay more to conserve the giant Galapagos tortoises. The coefficients of the dichotomy variables Know Galapagos management programs and Efficacy in the activity of rodent eradication were positive and significant, indicating that households that know the management programs carried out in the Galapagos or those that consider the activity of rodent eradication as effective on uninhabited islands, are more likely to be willing to pay for the conservation program. Using the estimated coefficients in the previous model, we calculated for mainlander households the willingness to pay on a monthly basis in order to preserve the giant tortoises in the Galapagos uninhabited islands. Results indicate that, in average, these households are willing to pay an extra $1.95 USD monthly on top of the current cost of the electricity bill for the proposed conservation 14

15 program. This WTP resulted to be statistically significant and represents a 9% increase in the average monthly electricity bill. Table 3. Constant Price Income Results of the DB-DC probit model with covariates Variables Coefficient 0.56 ** (0,21) -0,85 ** (0,03) 0,23 ** (0,09) Years of Education Know management programs Efficacy of the management activity Working adults in households Willingness to Pay 0,03 * (0,01) 0,36 ** (0,11) 0,40 ** (0,13) 0,12 * (0,05) 1,95 (0,06) Likelihood function -881,97 Standard error values in brackets n = 607 observations Note: * Statistically significant at 5% level, ** 1% level. 15

16 3.4 Analysis of Conservation Policy Introduced rodents are present in eight of the nineteen of the largest Galapagos Islands, covering an approximate area of 694,000 hectares (88% of the total land area of all islands). The cost to eradicate these rodents in three uninhabited islands (North Seymour, Rabida and Pinzon), which together constitute an area of 2,500 ha, is $1.7 million USD 4. Therefore, the eradication of introduced rodents in the uninhabited islands (64,000 ha) would cost about $25 million USD over a period of three years, when the program is projected to last. Respondents are willing to pay in average $1.95 USD per month for a period of three consecutive years through a fixed fee (premium) in the electricity bill for the conservation of giant tortoises in uninhabited islands of Galapagos. Given that continental Ecuador has 3,385,955 residential customers of electric energy (Electric Coverage Census INEC 2010), about $79 million USD would be collected in the first year of the implementation of the program. It is important to mention that given the current social policies of the country, there are constraints in applying this premium to all households in Ecuador. The Ecuadorian government currently funds more than 50% of the cost of electricity to the lower class (subscribers who consume up to 130 kwh per month, representing 61% of residential subscribers). For this reason, the collection of the additional fee in the electricity bill would be applied only to those subscribers who consume above 130 kwh, resulting in an annual value of $31 million USD. By projecting the annual value for a period of three years (which was established in the payment 4 The amount of $1.7 million USD was obtained after talking with the principal environmental manager of the Galapagos National Park, based on the Project Pinzon: Ecosystem restoration of the Galapagos Islands through introduced rodent removal, April,

17 vehicle) and applying a social discount rate of 12%, the present value of the total funding collected would be approximately $83 million USD. If an analysis that considers only the need to cover the $25 million USD for rodents eradication on uninhabited islands is performed, the additional payment on the monthly energy bill for 39% of Ecuador's total subscribers that consume over 130 kwh will correspond to $0.52 USD in the first year, $0.47 in the second and $0.42 in the third one, applying a discount rate of 12%. However, if the full amount of $1.95 USD per household is collected, resulting in a potential economic benefit of $ 83 million USD, the program to eradicate rodents could be fully covered in all the inhabited islands of Galapagos (with a cost of $25 million USD) and depending on conservation priorities outlined by the operators of the PNG, it would partially cover the program to eradicate rodents in the four inhabited islands (630,000 ha). The cost of this project is about $275 million USD over a period of approximately 16 years. Moreover, the money assigned by the Galapagos National Park to fund the three centers of breeding and rearing of giant tortoises in captivity ($400,000 USD per year) could be set aside as another priority program for conservation, because of the recovery and natural restocking of giant tortoises in the treated islands. Additionally, other flora and fauna that are also affected by the presence of rodents, such as petrels, boobies, cactus, among other would recover their population levels. Overall, the benefit from the eradication of rodents on the islands is shown to be positive, not only for conservation of the giant tortoises but also for other wildlife that is also threatened by the presence of these rodents. From the social point of view, this policy is similarly beneficial due to 17

18 the inhabitants economic dependency on the conservation of the Galapagos Islands natural wealth. 5 In order to present a more detailed analysis of the way the results of our contingent valuation study could be used in the design of policy instruments to support conservation in the Galapagos islands, Table 4 shows a summary of some conservation options for rodent eradication in uninhabited and inhabited islands. The WTP estimated for tortoise conservation ($ 83 million USD) could totally finance the eradication of rodents in uninhabited islands and partially in the inhabited ones. The best way to allocate these funds is a topic of political decisions and is out of the scope of this paper. Table 4.- Political conservation options for rat eradication in Galapagos Islands. Political conservation options (Islands for rat eradication treatment) Current situation.- Rabida, Pinzon and North Seymour (uninhabited islands)* Islands surface (ha) % of the total Galapagos Islands surface (788,000 ha) Cost estimated for treatment (million USD) WTP estimated for tortoise conservation (million USD) % of rodent eradicatio n in islands treated Time estimated for treatment (years) 2, % % 1 Option 1. All uninhabited islands 64,000 8% % 3 Option 2. All uninhabited and inhabited islands ** 694, % % 16 *Rodent eradication treatment has already been carried out with success in these uninhabited islands. ** The treatment application in inhabited islands is complemented with other rat eradication strategies due to the interaction with the local residents. 5 The tourism industry in Galapagos generated $418 million USD in 2006 (Epler, 2007). 18

19 4. Conclusion This study values the conservation of giant tortoises in the Galapagos Islands through the estimation of the willingness to pay of continental Ecuadorian householders for conservation programs. A difference from most of other studies in the literature, which only find the value respondents attach to a certain species, this study show how this value can be used in the design of conservation policies and redistribution of funding obtained from premiums to different conservation programs of what is the symbol of the Galapagos Island. This has been identified as an important issue due to the high participation tourism has in the total national income of the country. Results indicate that households in Ecuador are willing to pay an average premium of $1.95 USD monthly in their electricity bill the payment vehicle used in this study to introduce programs to eradicate rodents and consequently to allow for the conservation of this emblematic specie. The aggregate WTP was be approximately $83 million USD, which would fully cover the cost of the rodent eradication program on the uninhabited infected islands in Galapagos. There are two main ways to use this result. One is the design of a monthly payment of a premium from households, which would not exceed 0.52 cents USD per month the first year and would decrease the following two years. The second option is the introduction of a higher premium (with a maximum of 1.95 USD per month), which would generate a surplus that could be used to cover the cost of programs of rodents eradication in the four inhabited islands of the Galapagos. This surplus would cover up to 20% of the cost of this latter program. These results show the high relevance conservation policies of giant tortoises has for Ecuadorians, who recognize its importance for the development of a sustainable tourism industry that would ensure a continued 19

20 monetary income to the country and an economic sustainable development. To the best of our knowledge, this is the first application of this methodology to giants tortoises. Results show that households with higher monthly income, greater number of adults contributing to household expenses, higher level of education, knowledge about the conservation programs in the Galapagos and the conviction that the management activity is effective are willing to pay a higher premium for conservation programs of the giant tortoises. Therefore, information and education campaigns could be an alternative policy that could also help the support of conservation programs of this specie. Overall, the benefit of rodent eradication on the uninhabited islands of the Galapagos is favorable for both giant tortoise conservation efforts as well as for those focused on other wildlife also threatened by the presence of these introduced rodents. This study shows that it is possible to design policy instruments supported by Ecuadorians as a complement of other policies applied to international tourists and the tourist industry itself. It also quantifies the maximum premium households will be willing to pay for conservation of the giant tortoise and future development of sustainable tourism. Other policy instruments could be analyzed by policy makers, using the figures obtained in this paper; this issue is a matter for future research. Acknowledgments The authors are grateful to the Latin American Environmental Economics Program (LACEEP) for financial support. The authors are also grateful to Professors Fredrik Carlsson, Dale Whittington, Washington Tapia and the participants to the LACEEP workshops for providing helpful comments. 20

21 References Aadland, D., & Caplan, A. J. (2003). Willingness to pay for curbside recycling with detection and mitigation of hypothetical bias. American Journal of Agricultural Economics, 85(2), Alberini, A Efficiency vs. bias of willingness-to-pay estimates: bivariate and interval-data models. Journal of Environmental Economics and Management. Vol. 29: Alberini, A; Kanninen, B and Carson, R.T Modelling response incentive effects in dichotomous choice contingent valuation data. Land Economics Vol. 73, No. 3: Arrow, K; Solow, R; Portney, E; Leamer, R; Radner, H and Shuman, H Report of the NOAA Panel Contingent Valuation. Federal Register. Vol 58, No. 10: Washington D.C., USA. Bateman, R; Carson, T.Day B; Hanemann, W.M; Hanley N; Hett, T;. Jones-Lee M; Loomes G; Mourato, S; Ozdemiroglu, E; Pearce, D.W; Sugden, R and Swanson J Economic valuation with stated preference techniques: A Manual. Edward Elgar, Cheltenham: UK. Bateman, I.J., Willis, K.G., Valuing Environmental Preferences: Theory and Practice of the Contingent Valuation Method in theus, EU, anddeveloping Countries. Oxford University Press, USA. Bishop, R. and Heberlein, T Measuring values of extra market goods: are indirect measures biased?. American Journal of Agricultural Economic. Vol. 61, No. 5: Carson, R.T; Hanemann, W.M; Mitchell, R.C Determining the demand for public goods by simulating referendums at different tax prices. Working Paper. Department of Economics. University of California, San Diego, USA. Cooper, J Optimal bid selection for dichotomous choice Contingent Valuation surveys. Journal of Environmental and Management. Vol. 24: Constanza, R; d Arge, R; de Groot, R; Farber, S; Grasso, M; Hannon, B; Limburg, K; Naeem, S; O Neill, R; Paruelo, J; Raskin, R; Sutton, P. and Van den Belt, M The value of the world s ecosystem services and natural capital, Nature. Vol. 387: Cummings R. and Taylor, L Unbiased value estimates for environmental goods: a cheap talk design for the contingent valuation method. American Economic Review. Vol. 89, No. 3:

22 Epler, B Tourism, the Economy and Population Growth and Conservation in Galapagos. Puerto Ayora. Report presented in Fundación Charles Darwin: Galápagos, Ecuador. Hanemann, M Discrete/continuous models of consumer demand. Econometrica. Vol. 52 No.3: Hanemann, M Welfare evaluations in contingent valuation experiments with discrete responses. American Journal of Agricultural Economics. Vol. 66: Hanemann, W. Michael, John B. Loomis and Barbara J. Kanninen (1991) "Statistical Efficiency of Double-Bounded Dichotomous Choice Contingent Valuation." American Journal of Agricultural Economics 73:4, Hanemann, M Valuing the environment through contingent valuation. Journal of Economic Perspectives. Vol. 8, No. 4: Hanemann, M; Loomis, J and B. Kanninen Statistical efficiency of double-bounded dichotomous choice contingent valuation. American Journal of Agricultural Economics. Vol. 73: Hanemann, M. and B. Kanninen The statistical analysis of discrete-response CV data. in: I.J. Bateman, K.G. Willis (Eds.), Valuing Environmental Preferences: Theory and Practice of the Contingent Valuation Method in the US, EU, and Developing Countries, Oxford University Press, Oxford: Jackobsson, K. and A. Dragun Contingent valuation and endangered species: Methodological issues and applications. Eward Elgar, Cheltenham: 269. Jianjun, J; Indab, A; Nabangchang, O; Thuy, T; Harder, D and Subade, R Valuing marine turtle conservation: A cross-country study in Asian cities. Ecological Economics Vol. 69: Kanninen, B Optimal experimental design for double-bounded dichotomous choice contingent valuation. Land Economics. Vol.69: Loomis, J. and D.S. White Economic benefits and endangered species: summary and meta-analysis. Ecological Economics. Vol. 18: Mitchell, R. and R. Carson Using Surveys to Value Public Goods: The Contingent Valuation Method. Resources for the Future. Washington, DC: 484. Mitchell, R On designing constructed markets in valuation surveys. Environmental and Resource Economics. Vol. 22:

23 Ressurreição, A; Gibbons, J; Ponce, T; Kaiser, M; Santos, R; and Edwards-Jones, G Economic valuation of species loss in the open sea. Ecological Economics. Vol. 70: Richardson, L. and J. Loomis The total economic value of threatened, endangered and rare species: An updated meta-analysis. Ecological Economics Vol. 68: Rudd, M. A Public preferences and willingness to pay for aquaticspecies at risk conservation programs in Canada. SWGC EnvironmentalValuation and Policy Laboratory. EVPL Working Paper : Memorial University of Newfoundland, Canada. Silva, Maynard, and Ingrid Desilvestre, "Marine and coastal protected areas in Latin America: A preliminary assessment." Coastal Management 14 (4), Whitehead, J Ex ante willingness to pay with supply and demand uncertainty: implications for valuing a sea turtle protection programme. Applied Economics. Vol. 24: Yao, R. and P. Kaval Valuing biodiversity enhancement in New Zealand. Department of Economics Working Paper Series, Number 7/08. Hamilton, New Zealand, University of Waikato. 23