Does it make economic sense to restore rivers for their ecosystem services?

Abstract

Temperate forests managed to maximize sustainable yield of wood products can reduce the availability of dead wood on the forest floor and in adjacent streams, which in turn can impair ecological processes such as retention and transformation of organic matter. Lack of tools to link ecological processes with their effects on human well-being leads forest managers to ignore the cost on other services from terrestrial and aquatic ecosystems. We examine how adding dead wood to restore stream channel complexity affects the provision and value of selected ecosystem services, mainly related to the retention and transformation of matter and cycling of nutrients, as well as to the effects on aquatic biota. Specifically, we evaluated the cost-effectiveness of stream restoration through a comparative analysis of four reach-scale projects in streams flowing through temperate forest and into a drinking water reservoir and two scenarios of active and passive restoration at the basin scale. Results indicate that the lack of dead wood in streams has an important economic cost because of the effects on fish provisioning, opportunities for recreation and tourism, water purification and erosion control. Active reach-scale restoration resulted in a 10- to 100-fold increase in the monetary benefits provided by streams, accounting as much as 1·8 € per metre of restored river length each year. Results of the reach-scale cost-benefit analyses estimated that the time required to recover the active restoration investment ranged from 15 to 20 years in low- to middle-order streams. Synthesis and applications. Our study showed that restoration of natural wood loading in streams greatly increases the ecosystem services they provide. The benefits in terms of the analysed services surpass the costs of active restoration over realistic timeframes, whereas this was not the case for passive restoration. Inclusion of other ecosystem services such as conservation of biodiversity might make restoration more economically profitable. Overall, our study provides a decision framework for managing temperate riparian forests in the context of ecological services. Our study showed that restoration of natural wood loading in streams greatly increases the ecosystem services they provide. The benefits in terms of the analysed services surpass the costs of active restoration over realistic timeframes, whereas this was not the case for passive restoration. Inclusion of other ecosystem services such as conservation of biodiversity might make restoration more economically profitable. Overall, our study provides a decision framework for managing temperate riparian forests in the context of ecological services