Estimating the Preservation Value of World Heritage Site Using Contingent Valuation Method: The Case of the Li River, China

: World Heritage Sites (WHSs) play an important role in sustaining community identity and enhancing local economic development through tourism. Although the Li River was designated as a WHS in 2014, severe damage to its ecosystem and environmental problems have been reported in recent years. Thus, the purpose of this study is to estimate residents’ willingness to pay (WTP) for the preservation of the Li River using a contingent valuation method. Moreover, a two-stage approach using hypothetical and real setting scenarios was utilized to reduce a hypothetical bias and overvaluation. Logit models were used to estimate the preservation value and compare factors influencing WTP between the hypothetical and real scenarios. The results of this study support the usefulness of a two-stage approach to avoid hypothetical bias and estimate a realistic preservation value. In the real setting scenario, WTP was 144.66–163.90 Yuan (USD 20.83–23.60) per capita per year, and the aggregate value was 721–818 million Yuan (USD 104–118 million) depending on mean WTP and truncated WTP. The study findings provide useful implication to support government’s fund and sustainable efforts to preserve the Li River.


Introduction
To promote the preservation and sustainability of natural and cultural resources, the United Nations Educational, Scientific and Cultural Organization (UNESCO) designates World Heritage Sites (WHSs) that are assessed to have an exceptional value to humanity [1]. Since the establishment of the Convention Concerning the Protection of the World Cultural and Natural Heritage by UNESCO in 1972, the number of WHSs has increased, with 845 cultural sites, 209 natural sites, and 38 mixed sites having been included on the World Heritage List (WHL) [2]. Additionally, a tentative list of many candidate sites that each UN member country plans to apply for WHS status is available. However, research indicates that WHS designation may not guarantee the sustainability of natural or cultural assets [3,4]. Cases of WHS degradation by natural and/or human influences have been reported. For instance, in 2017, the WHS label of the Arabian Oryx Sanctuary in the Sultanate of Oman was revoked due to excessive poaching and the government's decision to cut the park size by 90%. This incident led to a large decline in the population of rare animals [5]. The Dresden Elbe Valley in Germany was also delisted in 2009 after a four-lane bridge was constructed in the middle of its previously designated international tourists, attracting more than 80 million visitors in 2017 [12]. The famous landscapes of the Li River are shown in Figure 1.

Contingent Valuation Method (CVM)
CVM uses utility theory as its theoretical background [13,14]. It has been widely used for the valuation of natural or heritage tourism resources [1,15]. CVM is a method used to directly estimate the economic value of tourism resources by assessing both use and non-use value. Furthermore, CVM can quantitatively measure personal WTP which cannot be measured in reality by setting up a hypothetical situation (i.e., inquiring about respondents' WTP) [16]. The preservation value of the Li River cannot be quantified in reality, and can only be estimated by using a hypothetical situation. Thus, this study used CVM to estimate the preservation value of the Li River for Guilin residents, which is an invaluable asset as a WHS.
CVM uses either open-ended or closed-ended questioning methods. Open-ended questions require respondents to independently provide their WTP using unitary bidding games and/or payment cards [17]. Closed-ended questions mainly use DC or repeated bidding games. In particular, DC-CVM has been most commonly used ever since its first application in the appraisal of economic purchases of goose-hunting licenses [18]. DC-CVM performs the following steps. First, a hypothetical situation is set up. Second, the category of payment amounts are determined based on open-ended questions in pretesting situations. Finally, respondents express their WTP with regard to the amount randomly given by answering either "Yes" or "No." In other words, this method only requires respondents to answer "Yes" or "No" for the given payment amount. Hence, it is relatively easy for respondents to express their personal WTP amount compared with the payment card in open-ended questions [19]. It is extremely similar to the consciousness-determining circumstance of trading in real-life situations [19]. Therefore, DC-CVM can effectively reduce a strategic bias [20]. Given that the questions can easily be answered, a starting-point bias can also be effectively reduced, and thus DV-CVM is favored by many researchers [20][21][22]. Given that DC-CVM is based on a hypothetical situation, a hypothetical bias may occur in such a way that the respondents' WTP is over-estimated,

Contingent Valuation Method (CVM)
CVM uses utility theory as its theoretical background [13,14]. It has been widely used for the valuation of natural or heritage tourism resources [1,15]. CVM is a method used to directly estimate the economic value of tourism resources by assessing both use and non-use value. Furthermore, CVM can quantitatively measure personal WTP which cannot be measured in reality by setting up a hypothetical situation (i.e., inquiring about respondents' WTP) [16]. The preservation value of the Li River cannot be quantified in reality, and can only be estimated by using a hypothetical situation. Thus, this study used CVM to estimate the preservation value of the Li River for Guilin residents, which is an invaluable asset as a WHS.
CVM uses either open-ended or closed-ended questioning methods. Open-ended questions require respondents to independently provide their WTP using unitary bidding games and/or payment cards [17]. Closed-ended questions mainly use DC or repeated bidding games. In particular, DC-CVM has been most commonly used ever since its first application in the appraisal of economic purchases of goose-hunting licenses [18]. DC-CVM performs the following steps. First, a hypothetical situation is set up. Second, the category of payment amounts are determined based on open-ended questions in pretesting situations. Finally, respondents express their WTP with regard to the amount randomly given by answering either "Yes" or "No." In other words, this method only requires respondents to answer "Yes" or "No" for the given payment amount. Hence, it is relatively easy for respondents to express their personal WTP amount compared with the payment card in open-ended questions [19]. It is extremely similar to the consciousness-determining circumstance of trading in real-life situations [19]. Therefore, DC-CVM can effectively reduce a strategic bias [20]. Given that the questions can easily be answered, a starting-point bias can also be effectively reduced, and thus DV-CVM is favored by many researchers [20][21][22]. Given that DC-CVM is based on a hypothetical situation, a hypothetical bias may occur in such a way that the respondents' WTP is over-estimated, thus resulting in overvaluation. Therefore, in this research a two-stage method (using hypothetical and real scenarios) was used to minimize hypothetical bias.
CVM has been applied in various settings, including the evaluation of recreation value and non-use value of tourism resources, the evaluation of compensation value of natural resources, and the valuation of intangible cultural heritage [23]. In addition to the valuation of natural/cultural resources, another important use of CVM is to investigate the main factors affecting valuation. Prior studies have shown that the main factors affecting WTP include payment amount, demographic variables (e.g., age, education, marital status, and income), and psychological constructs (e.g., place attachment, perceived value, and revisit intention) [11]. For example, a study on the preservation value of Dokdo Island, South Korea showed that payment amount, age, income, patriotism, and support are the most influential factors affecting the WTP of South Korean residents [16]. Moreover, in a study assessing the economic value of Hallyu (also known as the Korean Wave), payment amount and education were found to be the significant factors affecting the WTP of Chinese pop-culture tourists to Korea [24]. A comparative study of residents' and tourists' WTP for the preservation value of endangered harbor seals found that payment amount, income, education, attitude to environment, human oriented attitude, and attitude to the spotted seal are the most important factors affecting payment amount [25]. In the valuation of mudflats, Choi et al. found that festival experiences influence visitors' WTP by confirming a significant effect of functional value [26]. In the case of the Grand Canal in China, a CVM study found that place, identity, and revisit intention are differently associated with residents' and non-residents' WTP [1]. Hence, given that the lives and social activities of Guilin residents are complexly intertwined with the Li River, capturing the effects of socio-demographic and psychological factors (i.e., involvement, place attachment, and perceived value) in the valuation of the river is important.

Involvement
Serif et al. [27] first conceptualized involvement as perceived personal importance and/or consumer interest in buying, consuming, and disposing of goods, services, or ideas [28]. According to the general rules of individual behavior [29], the extent and time of individual participation in a particular environment influence attitude and behavior. Involvement can be divided into psychological acceptance and repeated participation, which may influence individuals' attitudes and psychological status to participate in an event. The concept of involvement has been applied to studies on situational marketing and consumer behavior [30,31]. In recent years, involvement has been applied in the tourism field mostly to study how tourists' involvement influences their perception, satisfaction, or environmental protection behavior. For instance, Wang and Li [32] found that tourists' involvement in birdwatching influences their willingness to adopt environmentally friendly behaviors. In their study on the leisure involvement of cyclists, Yu and Tian [33] found that involvement produces a significant direct influence on happiness and a significant indirect influence through leisure benefits. Zhang and Li [34] also found that leisure involvement has a significant positive influence on the environmentally friendly behavior of tourists and a significant indirect influence through place attachment.
Most previous studies on involvement have also focused on tourists rather than local residents [35]. As an inherent variable of attitude, the formation of involvement takes time to accumulate [36]. Therefore, examining how residents' involvement influences their perception about environment and pro-environmental behaviors at a tourist destination is suitable. In accordance with the findings of previous studies, this study posits that the involvement of residents at a tourist destination has a positive influence on their environmental attitude and behavior. Thus, this study proposes that residents' involvement positively influences their WTP for the preservation of the Li River.

Place Attachment
Place attachment, developed from place and attachment theories, has been applied in the fields of environmental psychology, social psychology, and sociology [37]. Place attachment emphasizes the psychological and behavioral connections that individuals have with a place [38]. Place attachment reflects the emotional psychological status of individuals to a certain place/environment. For instance, individuals' cognition and acceptance of a specific environment and their interaction with the environment make them feel comfortable, safe, and willing to stay in that place [39]. Forming attachment takes time, and visit frequency is one of the expression modes. For residents, forming an attachment relationship with their domiciles is easy. Bao and Yang [40] studied the process of place attachment of the residents of West Street in Yangshuo. The results of their study showed that the appropriate level of commercialization plays an important role in producing the place attachment of local residents. In the field of environmental psychology, previous studies found that place attachment has a positive influence on environmental attitude and environmental protection [41]. In their study on the residents of Xidi and other ancient villages, Tang et al. [42] concluded that place acceptance of ancient village residents has a significant positive influence on their attitudes toward resource protection in the villages. In the case of a resort in Zhejiang, Fan et al. [43] also confirmed a positive relationship between place attachment and the environmental responsibility of tourists. This result indicated that the higher the place attachment, the higher the likelihood of practicing environmentally responsible behavior. Thus, this study proposes that place attachment with the Li River is positively associated with residents' WTP for the preservation of the river.

Perceived Value
Perceived value is defined as a tourist's comprehensive evaluation of the efficiency of a tourism product or service [44]. Recognized as a world natural heritage site, the Li River is considered to have an exceptional value to humanity, which makes preserving the current status of the river's natural environments and ecosystem worthwhile. The Li River is an important tourist resource for Guilin to attract domestic and international tourists. Guilin residents have built a strong and intimate connection with the Li River as a living foundation [45]. Perceived value is the subjective evaluation of Guilin residents on the preservation of Li River. Perceived value is an important construct to understand the environmental protection attitude and behavior of Guilin residents.
In consumer behavior studies, consumers' perceived value has been shown to have a positive influence on their buying behavior [46]. The research results of Yu, Tian, and Shu [47] indicated that tourists' value perception has a significant influence on their subsequent behavior. The stronger the value perception of tourists, the more likely that they will visit a sightseeing place again. In an empirical study of the Sun Island Scenic Area in China, Dou [48] found that tourists' perceived value has a positive influence on their environmental behavior. The higher the tourists perceive the quality of the tourism resource, the more likely they are to practice environmental protection. Chiu et al. [46] argued that tourists' perceived value has a positive direct influence on their environmentally responsible behavior and a significant indirect influence through satisfaction. Therefore, this study proposes that that when viewing the Li River's preservation value, Guilin residents will positively accept protection behavior and will be willing to pay more for the river's preservation.

Model Specification
As discussed earlier, this study used DC-CVM. First, Guilin residents were asked if they were willing to pay a preservation fund of a randomly given bid amount (A Yuan). Then, the WTP for the given amount was converted into a probabilistic model. Lastly, logit models were used to estimate the preservation value of the Li River WHS. The preservation value was mainly determined by the compensating variation proposed by Hicks [49].
To protect the Li River, Guilin residents could choose to pay or not to pay a given preservation fund (A). In paying the preservation fund, Guilin residents could enjoy the benefits from the Li River such as clean air and water, free entrance to scenic spots, and a good ecosystem. On the contrary, Guilin residents would no longer enjoy any utility from the Li River if they did not pay the preservation fund, which can be expressed with the following function [17]: where U = utility function; v = indirect utility function; Y = income; j = 1 (pay a given bid); j = 0 (not pay a given bid); s = individual social and economic variable (e.g., gender, age, and education); and j = random variable with average value of 0. On the basis of utility theory, Guilin residents would be oriented with individual maximum utility to make a choice from the foregoing two solutions [16]. The indirect utility function for Guilin residents to choose to pay the randomly given bid amount of A Yuan and enjoy the utility from the Li River can be expressed as {v (1, Y-A; s)}. On the contrary, the indirect utility function for Guilin residents to choose not to pay the randomly given bid amount and give up enjoying the utility of the Li River is {v (0, Y; s)} [50]. Individuals would accept the offer in the condition as v (1, Y-A; s) As the bid amount (A Yuan) changed, the change in utility can be expressed as ∆v. The difference of utility for Guilin residents under the two circumstances is shown in Formula 2 [17]:

Logit Model and Willingness to Pay (WTP)
The utility difference (∆v) in this study model is the continuous data of the independent variable: paying A Yuan and enjoying the utility of the Li River or not paying A Yuan and giving up the utility of the Li River. The dependent variable is the discrete data of 0 and 1, and the logit model is used with maximum likelihood estimation. As for the preservation value of the Li River in terms of the circumstance of the maximum WTP of Guilin residents for preservation, the method of measuring WTP includes two ways. The first method is the mean WTP, which assesses the value by numerical integration from 0 to infinity as follows [51]: where α = constant and β = coefficient of bid amount. The second method is the truncated mean WTP, which estimates the value by numerical integration from 0 to Max A (maximum bid amount) as follows: Of the two methods, the truncated mean WTP is considered more appropriate due to statistical efficiency, consistency with theoretical constraints, and aggregation ability [52].

Contingent Valuation Method (CVM) Setup
A hypothetical scenario was used to determine the situational value of the Li River [53]. In this study, basic information about the Li River was provided to the respondents. Furthermore, the following hypothetical scenario was given to elicit the respondents' WTP for the preservation value of the Li River.
The Li River is a pearl among the beautiful rivers and mountains of China. It is the essence of Guangxi's landscape, the quintessence of Guilin's mountains and rivers, and a place with one of the most developed karst peak forests in the world. It was included by the State Council "First Batch of National Key Scenery Resorts" in 1982 and designated as an AAAAA scenery resort in 2007. The Guilin karst landforms were included on the WHL in 2014. The development and utilization of the Li River not only has natural, beautiful scenery for tourists, but also provides employment and economic development for Guilin residents on the Li River. However, in recent years the natural environment in the scenic area of the Li River has been seriously damaged, especially the water quality. Protection of the Li River can not only provide tourists with a quality sightseeing destination, but also furnish the local residents with an opportunity for development and a good living environment. Perhaps most importantly, preserving the river can protect this treasured heritage for the next generations. Since the Li River has sight-seeing, cultural bequest, economic development, and other values, it is extremely necessary for local residents to protect it.
It is not possible to assess the monetary value of the river, but in the interest of scientific analysis, this study is using monetary value for discussion. Hereinafter, you will be questioned about a "preservation fund" regarding your perceived value of the Li River. The "preservation fund" does not exist in actuality, but is instead used as the basis for hypothetical questions to evaluate preservation of the Li River for academic purposes.
DC-CVM has various merits, however a hypothetical bias may still be observed [54]. Respondents are likely to over-value their WTP due to the hypothetical bias, thus over-assessing the preservation value of the river. Therefore, this study adopted a two-stage approach to reduce such bias. The first stage was the hypothetical scenario and the second stage was the real setting scenario.
In the first stage (a hypothetical scenario), the first DC question was presented as follows: In the case of protecting the Li River, are you willing to donate A Yuan to the "preservation fund" annually?
The bid amount range (total of nine amounts) of "preservation fund" for the Li River was determined from open-ended questions in a pre-test with 30 Guilin residents. The amounts were 10 Yuan (1 Yuan = US$0.144), 50 Yuan, 100 Yuan, 150 Yuan, 200 Yuan, 300 Yuan, 500 Yuan, 800 Yuan, and 1000 Yuan. The bid amount was randomly assigned and the respondents were only required to answer "Yes" or "No." In the second stage (a real setting scenario), an additional DC question was presented as follows: Would you be willing to provide your contact information (mobile number/WeChat/mailing address, and name)?

Measures
Measurement items for psychological variables that were included were: involvement ("There is a connection between me and the Li River"), adopted from Wang and Li [32]; place attachment ("The Li River and I are one"), adopted from Tang et al. [42]; and perceived value ("The Li River has a very high protection value"), adopted from Yu, Tian, and Shu [47]. These psychological variables were measured with a five-point Likert scale (1 = strongly disagree, 2 = disagree, 3 = neutral, 4 = agree, 5 = strongly agree). Additionally, socio-demographic information of the respondents was collected.

Data Collection
For the purpose of collecting a representative sample from the population of Guilin, this study used the Sixth National Census Data of Guilin in 2010 [55]. To reflect the quota of age and gender, a total of 306 samples were gathered in the scenic and residential areas of the Li River (see Table 1). The respondents were invited to participate in the survey by tourism instructors and undergraduate students who had been trained for the purpose of the survey and the survey procedures to ensure collection of appropriate samples.

Demographics
As shown in Table 2, 51.3% of the respondents were males and 48.7% were females. The respondents aged from younger than 20 years to older than 60 years was evenly distributed, meeting the quota sampling proportion used in this study. Education level ranged widely, from middle school to below postgraduate levels. The samples with an educational level of high school and below made up 66% of the total sample, showing a relatively low educational level. Respondents with an average monthly income of below 10,000 Yuan comprised 88.0% of the total sample. Married respondents represented 61.4%, single respondents represented 38.6%, and respondents with children accounted for 58.5%.

Probability Distribution of WTP for the Li River
The probability distributions of WTP for the hypothetical and real setting scenarios are presented in Figure 2. The probability distributions of WTP for both scenarios gradually declined as higher bid amounts were given. A total of 44.12% (n = 135) of the respondents were willing to pay in the hypothetical scenario, compared with 22.22% (n = 68) in the real setting scenario. The results confirmed that a hypothetical bias existed. For instance, for a bid amount of 10 Yuan, 38.24% of the residents were willing to pay in the real setting situation, compared to 82.35% in the hypothetical situation. For a bid amount of 300 Yuan, 14.71% of the residents were willing to pay in the real setting scenario, compared to 35.29% for the hypothetical scenario. That is, a large hypothetical bias among the residents' WTP became larger when lower amounts were given.

Socio-demographic and Psychological Variables
Four socio-demographic variables were included in the logit model: age, education level, marital status, and monthly income. Three psychological variables, namely, involvement, place attachment, and perceived value, were also included.

Results of Logit Model for the Hypothetical and Real Situations
Binary logistic regression analysis was separately conducted for the hypothetical and real setting situations by using SPSS 23.0 (IBM Corporation, Armonk, New York, USA) (see Table 3). In the hypothetical situation, payment (bid) amount, involvement, place attachment, perceived value, and income had a significant influence on residents' WTP for the preservation of the Li River. While the hypothetical bias was easily observed in the CVM, more attention should be paid to the real setting situation [26]. In the real setting situation, payment (bid) amount, perceived value, and income also had a significant effect on respondents' WTP. Additionally, some extra variables existed, such as age and marital status, which had a significant effect on respondents' WTP in the real setting. On the contrary, education level had no influence on WTP in either setting. As predicted, bid amount showed a negative relationship with residents' WTP. This indicates that the higher the bid amount, the lower the residents' WTP. Only the effect of perceived value was significant; involvement and place attachment were insignificant in the real setting scenario.

Socio-demographic and Psychological Variables
Four socio-demographic variables were included in the logit model: age, education level, marital status, and monthly income. Three psychological variables, namely, involvement, place attachment, and perceived value, were also included.

Results of Logit Model for the Hypothetical and Real Situations
Binary logistic regression analysis was separately conducted for the hypothetical and real setting situations by using SPSS 23.0 (IBM Corporation, Armonk, New York, USA) (see Table 3). In the hypothetical situation, payment (bid) amount, involvement, place attachment, perceived value, and income had a significant influence on residents' WTP for the preservation of the Li River. While the hypothetical bias was easily observed in the CVM, more attention should be paid to the real setting situation [26]. In the real setting situation, payment (bid) amount, perceived value, and income also had a significant effect on respondents' WTP. Additionally, some extra variables existed, such as age and marital status, which had a significant effect on respondents' WTP in the real setting. On the contrary, education level had no influence on WTP in either setting. As predicted, bid amount showed a negative relationship with residents' WTP. This indicates that the higher the bid amount, the lower the residents' WTP. Only the effect of perceived value was significant; involvement and place attachment were insignificant in the real setting scenario.

Results of Preservation Value
The estimation of the residents' preservation value of the Li River is shown in Table 4 and Figure 3. In the hypothetical scenario, WTP mean was 314.24 Yuan per person as the annual donation to the preservation funding of the Li River, whereas WTP truncated mean was 303.18 Yuan. The preservation value of the Li River with WTP mean was much higher than that with WTP truncated mean . According to the sixth population census, the population of Guilin is approximately 4.99 million. Therefore, the estimation of the total preservation value of the Li River results in an annual amount of 1568 million Yuan based on WTP mean and 1512 million Yuan based on WTP truncated mean . In the real setting scenario, one person is willing to pay 163.90 Yuan annually in terms of WTP mean , as compared to 144.66 Yuan with WTP truncated mean . The estimation of the total preservation value of the Li River annually was approximately 818 million Yuan with WTP mean and 722 million Yuan with WTP truncated mean . Note: ***p < 0.001, **p < 0.01, *p < 0.05.

Results of Preservation Value
The estimation of the residents' preservation value of the Li River is shown in Table 4 and Figure  3. In the hypothetical scenario, WTPmean was 314.24 Yuan per person as the annual donation to the preservation funding of the Li River, whereas WTPtruncated mean was 303.18 Yuan. The preservation value of the Li River with WTPmean was much higher than that with WTPtruncated mean. According to the sixth population census, the population of Guilin is approximately 4.99 million. Therefore, the estimation of the total preservation value of the Li River results in an annual amount of 1568 million Yuan based on WTPmean and 1512 million Yuan based on WTPtruncated mean. In the real setting scenario, one person is willing to pay 163.90 Yuan annually in terms of WTPmean, as compared to 144.66 Yuan with WTPtruncated mean. The estimation of the total preservation value of the Li River annually was approximately 818 million Yuan with WTPmean and 722 million Yuan with WTPtruncated mean.

Discussion
Many researchers have emphasized the importance of estimating residents' WTP [1,25]. This study is the first attempt to estimate the preservation value of the WHS of the Li River. The results are in line with economic theories which state that WTP is negatively associated with the bid amount. Using a two-stage approach, this study found that WTP for the preservation value was substantially lower in the real setting scenario than in the hypothetical scenario. This finding is consistent with the findings of previous studies [1,24,52]. To enhance the credibility of the WTP values, WTP mean and WTP truncated mean were used [22]. In the hypothetical scenario, Guilin residents' WTP for the protection of the river was 303.18-314.24 Yuan (USD 43.66-45.25) per person per year, and the total or aggregate preservation value of the Li River was 1512-1568 million Yuan (USD 218-226 million) depending on WTP truncated mean and WTP mean . In the real setting scenario, WTP was 144.66-163.90 Yuan (USD 20.83-23.60) per person per year, and the total preservation value was 722-818 million Yuan (USD 104-118 million). The hypothetical scenario exaggerated Guilin residents' WTP by 47.7-52.2% as compared with the real setting scenario, and the total preservation value was over-assessed by 750-791 million Yuan. The findings confirmed the existence of hypothetical bias, supporting the usefulness of a two-stage approach to avoid the hypothetical bias and estimate a realistic preservation value. Additionally, the results showed that the WTP truncated mean was more conservative than the WTP mean . This finding supports the strength of WTP truncated mean in terms of statistical efficiency and aggregation ability. In summary, Guilin residents are willing to pay 144.66 Yuan (USD 20.83) annually for the protection of the Li River based on WTP truncated mean in the real setting scenario, and the total preservation value of the Li River was 722 million Yuan (USD 104 million).
In the two scenarios, the influential factors of Guilin residents' WTP were different to some extent. For instance, bid amount, perceived value, and income were the important variables affecting Guilin residents' WTP for the protection in both scenarios. However, residents' involvement and place attachment had a significant influence on WTP only in the hypothetical situation. Age and marital status had a significant influence only in the real situation. In the hypothetical scenario, residents' psychological variables (involvement, place attachment, and perceived value) had a stronger influence on WTP. However, in the real scenario, demographic variables (age, marital status, and income) seemed to have stronger influences on WTP, indicating a high probability for older, married, and high-income Guilin residents to pay to protect the river. Overall, the findings support that WTP in the hypothetical and real setting scenarios was influenced by individual attributes.
Given that perceived value had a positive influence on WTP in both scenarios, WTP could be increased by enhancing Guilin residents' awareness of the Li River's value. The awareness of the preservation value can be promoted from the angles of option, existence, and bequest values. Promotion activities particularly designed for the residents could be useful for increasing their understanding of the value of the river's natural resources and ecology. For instance, the residents' awareness could be enhanced by taking park tours and other recreational activities in such a way that more residents experience the beauty and nature of the Li River. The perceived value of the Li River could also be enhanced by bolstering the emotional linkage between residents, the integration of residents and the river, and increasing residents' environmental consciousness. Residents must also understand that the protection of the river is not solely the responsibility of the government and that their support is also required.
In the future, the preservation value of the Li River can be assessed from the angle of tourists so that valuation of residents and tourists can be compared. Furthermore, the influences of psychological variables, such as involvement, place attachment, and value perception on WTP can be compared between tourists and residents. Future studies may also explore other key psychological factors affecting the residents' WTP to promote their willingness to protect the river.

Conclusions
The natural heritage and environmental quality of the Li River have a considerable value for Guilin residents. From the perspective of Guilin residents, this study estimated the preservation value of the Li River. Despite the potential risk of degradation of the Li River's ecosystem and the increasing need for governmental financial support, no previous study has attempted to evaluate its valuation using a quantitative approach. Therefore, this study employed CVM, a valuation technique frequently used in environmental studies, to estimate the preservation value of the Li River for residents. This study provides empirical evidence to support governmental sustainable efforts and securing a necessary budget, ultimately contributing to sustainable tourism.
Author Contributions: M.J. contributed to conducting the survey and writing the manuscript. Y.J. contributed to analyzing the survey data and interpreting the results. Y.C. contributed to clarifying concepts and editing the manuscript, and made the manuscript more succinct and readable. C.-K.L. contributed to leading ideas and developing research design. All authors collaborated and agreed to submit this article.
Funding: This research received no external funding.