| In recent years,some stated preference methods,such as contingent valuation method(CVM)and choice experiment(CE),have been widely used by domestic and foreign scholars to evaluate the ecological protection value of wetland.This methods use questionnaire as a tool to construct a hypothetical market to obtain the willingness to pay(WTP)of the respondents and then to obtain the ecological protection value of wetland to be evaluated.However,due to the limitation of time,cost and other factors,it is difficult for researchers to carry out empirical research on every wetland to be evaluated,and also not every wetland is necessary to do empirical research.The benefit transfer method can effectively solve this problem.By collecting a large number of existing empirical research results(Study Site)and using statistics and econometrics methods,this method can transfer the existing evaluation results to the place to be studied(Policy Site),thus,the resource value of the place to be studied is obtained.The evidence shows that the benefit transfer method can be used as an effective method to evaluate the ecological protection value of wetland.Meta-analysis is the most promising method of benefit transfer.This method can obtain information from a large number of original empirical studies,making the process of benefit transfer more scientific and effective.The differences of wetland service type,wetland type,wetland area,number of beneficiary population,GDP per capita and research time between different empirical studies can be used as variables in Meta-analysis.Therefore,the requirement of high similarity between the study site and the policy site is relaxed.However,the same as other benefit transfer methods,this method is also influenced by publication selection bias.The main reason for the appearance of this bias is the exclusion of the literatures with not significant results in Meta-analysis.Studies have shown that the existence of publication selection bias will affect the accuracy of Metaanalysis and benefit transfer.It is very important to solve the problem of publication selection bias.In this paper,we first add factors to the Meta-regression model to characterize the publication selection bias,and construct a Meta-regression model that can eliminate the influence of publication selection bias.Secondly,we collect the research results of using CVM to evaluate the value of wetlands in China,and establish a value transfer database.Then,appropriate meta-regression model is chosen by examining the existence of the publication selection bias in the database or not.Finally,the benefit transfer model is established,and the ecological protection value of the wetland in Sanjiang Plain was evaluated by the model.The results show that:(1)there is no publication selection bias in the database,so the general form of Meta-regression model is chosen in Metaanalysis.(2)The difference of wetland service type,wetland type,wetland area,the number of beneficiaries and the guiding way of questionnaire will lead to the difference of wetland value valuation,and the wetland location,the way of questionnaire survey,per capita GDP,research time and journal quality had no significant effect on wetland valuation.(3)The benefit transfer model is used to evaluate the ecological protection value of wetland in Sanjiang Plain.It is known from the result that when using open questionnaire,the ecological protection value of wetland in Sanjiang Plain was 136 million yuan in 2015 and 603 million yuan in 2015 when non-open questionnaire was adopted.(4)The results of error test,paired t test and relative coefficient test show that the predicted value of Meta-regression is consistent with the observed value of empirical study.It is feasible to use this benefit transfer model to evaluate the value of wetland in Sanjiang Plain,and the estimated value obtained by the method of benefit transfer can be used as an effective reference for ecological protection value of wetland in Sanjiang Plain. |
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