Assessing the cost-effectiveness of the water purification function of wetlands for environmental planning

Abstract

A reduction of nutrient input into freshwater and marine water bodies is a prerequisite for the restoration of healthy aquatic ecosystems and for the achievement of the ambitious goals of the European Water Framework Directive and the HELCOM and OSPAR convention. In Northern Germany, phosphorus inputs from point sources were reduced by nearly two-thirds compared to the phosphorus load in the period 1980–1985. This success was made possible by the investment of 2.1 billion € since 1985 in the development and enhancement of waste water treatment plants. However, these investments had only little effect on nitrogen inputs, which enter water bodies mainly from non-point sources. In 2002, the federal state Schleswig-Holstein implemented a peatland rehabilitation program aiming to restore the water purification function of this wetland type. The rationale of this plan is based on an economical analysis of the effects of the investments in the waste water action plan. A reduction of the P load by 1 kg has mean costs between 70 and 100 €. Based on model calculation, restoring wetlands for water quality purification will cost between 1 and 50 € per retained kg of nitrogen when considering a 10-year time span. Compared to the waste water action plan, wetland restoration is also a cost-efficient strategy for nutrient load reduction. For 10% of the investments of the waste water action plan, the nitrogen load from Schleswig-Holstein can be reduced by 10%; this will require rewetting of 20,000 ha of wetlands. The implementation of this strategy as well as the application of the concept of ecosystem services in environmental management is currently limited by a lack of political support and funding for such projects from higher political bodies such as the European Union.