Dear Tom,
I recommend that you put positive and negative impacts together. For example, if the interviewee gives point 1 for the question Well-preserved water resources, water bodies and natural habitats, it indicates for water resources, ecotourism brings actually negative impacts, but not positive impacts. So whether these factors are positive or negative will be drawn from your data, not be divided by yourself.
That means, you can reorganize your questionnaire. Some items are very similar. You need only to list all possible impacts, regardless its belongs to negative or positive, or belongs to economic or cultural. Just list it. After data collection, you can use factor analysis to test whether there are different aspects of impacts (for example, here, ecological, cultural and economic), whether there are also negative impacts although ecotourism pays attention to conservation. You can have some research hypothesis that those impacts can be divided into different groups. However, the questionnaire cannot hint the interviewees that these items for negative impacts, or those items for economic impacts, and so on.
I don't know whether I have explain my suggestions well.