Most of the natural wetlands in agricultural landscapes have been drained to gain more arable land. As a result, a significant loss in biodiversity in these landscapes has occurred. The reduction of wetlands has also severely lowered the nutrient retention capacity of agricultural watersheds. Measures are now taken to improve nutrient retention and biodiversity by creating new wetlands in the agricultural areas. This project is designed to produce knowledge that is critical for achieving the expected environmental goals from the large-scale wetland construction plans proposed by e.g. the Swedish government in the Swedish agricultural landscape. The project approaches the impacts of species composition and diversity on magnitude and stability of ecosystem functioning. This approach will deliver an understanding of important ecosystem processes. This will enable us to deliver concrete guidelines regarding wetland design and management to obtain a considerable increase in nutrient retention in constructed wetlands while, at the same time, supporting biodiversity goals.