I am doing my research under finding economic value for the conservation of a rain forest. my main objectives are to find the wtp value that visitors going to pay for the conservation activity and to find the factors that effect for the wtp value.
From what i know, contigency evaluation method (CVM) is often used by researchers to determine WTP value for ecosystem services value of forests.
However, it requires you to create a situation that reflects your objective and can convince your respondents to believe that hypothetical situation will actually happen to the site in future.
You can read more on CVM method for WTP value to determine if this method suits to your need.