Contingent Valuation and Choice Experiments dominate among the methods, but also deliberative or participatory valuation approaches, production function/damage function as well as Contingent Ranking, Hedonic Pricing and Travel Cost have been applied. With a larger base of valuation studies, it would be possible to calculate the intervals and standard values by more advanced methods (e.g. quantitative meta-analysis). Many studies are done of recreational benefits, but these benefits do not present the whole picture.