Economic valuation of regulating services provided by wetlands in agricultural landscapes: A meta-analysis

This paper presents a meta-analysis of the economic valuation literature on ecosystem services provided by wetlands in agricultural landscapes. We focus on the value of three regulating services, namely flood control, water supply and nutrient recycling. We construct a database containing 66 value estimates, mainly for wetlands in the US and Europe but also a substantial number in developing countries. Values are standardised to USD per hectare per year. The mean (median) values are found to be 6923 (427) USD/ha/yr for flood control; 3389 (57) USD/ha/yr for water supply; and 5788 (243) USD/ha/yr for nutrient recycling. The values of these services are highly variable across individual wetland sites due to, amongst other factors, differences in wetland type, size, the scarcity or abundance of other wetlands in the surrounding landscape, and the socio-economic characteristics of the beneficiaries of these services. We include explanatory variables in the meta-analysis to account for these influences on estimated wetland values. GIS is used to quantify potentially important spatial variables. The meta-regression is used to produce a value function for wetland regulating services, which can be used to transfer values to other wetland sites while controlling for site and context specific characteristics. An illustrative value transfer exercise is conducted to estimate global values for wetland regulating services in agricultural landscapes.