Differential effects of valuation method and ecosystem type on the monetary valuation of dryland ecosystem services: A quantitative analysis

The method of monetary valuation of ecosystem services has been argued to depend on the type of ecosystem under consideration and the choice of valuation method. Still, the impact of these factors has been hardly studied in a quantitative manner. This study aims to analyze the differential effects of ecosystem type and valuation method on the values estimated for ecosystem services, as well as the potential impact of these effects on aggregated values for ecosystem services. Drylands pose a highly relevant case to investigate these impacts, because they are particularly diverse in ecosystem types, the provided ecosystem services and, hence, are also expected to be estimated with various methods. Our analysis is based on a quantitative analysis of monetary estimates for ecosystem services (expressed in Int$/ha/yr) that were compiled in a comprehensive database containing 512 observations from 57 studies located in drylands worldwide. Our results reveal that the estimated values for dryland ecosystem services depended on the type of ecosystem and method under consideration. Several of these differential effects had a significant impact on the aggregated mean values for dryland ecosystem services. Cultivated lands had high mean values for provisioning services, in particular for food provision, but low values for regulating services. In dry forests, biodiversity-related services were estimated high, in contrast to semi-deserts and arid wetlands. Compared with other methods, market pricing estimated low values for climate regulation and high values for biological regulation. When values were aggregated for ecosystem services, market pricing was found to impact the mean value for climate and biological regulation significantly. Our results highlight the importance of explicit consideration of methods and ecosystem types in monetary valuation, which could lead to more accurate approximation of ecosystem service values.