ارزیابی اقتصادی خدمات اکوسیستم، یک مطالعه موردی برای از بین بردن پوشش گیاهی آبزیان در حوضه Nete (بلژیک)

In the last decades, lowland rivers were forced to drain larger water quantities during ever shorter time periods. This is mainly caused by current and historic land-use changes (e.g. increase of built area) and increased intensification of agriculture practices (e.g. drainage). River flow, however, is hampered by human artefacts such as weirs and dams as well as by naturally occurring aquatic vegetation. To avoid flooding and water related problems, river managers opt to remove aquatic vegetation. According to the European Water Framework Directive (2000/60/EC), all costs of water management should be charged for (full cost recovery requirement). This study aims to assess whether or not this is achieved in case of aquatic vegetation removal. This method is illustrated through a case study of the Nete Catchment, Belgium. Results show that flood control benefits exceed costs by only a small amount in wet years, but costs exceed benefits in dry years. If decision makers account for even a few ecosystem services, the costs of vegetation removal exceed the benefits in both scenarios. Only local stakeholders in flood risk areas can benefit from aquatic vegetation removal during wet summer seasons.