City of Mariehamn for Nabben wetland - Åland

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Nabbens multifunctional wetland
A wetland close to the city benefits water quality, biodiversity, and residents.

Nabben wetland is nominated for the 2022 Nordic Council Environment Prize.

In the area of Nabben, the city of Mariehamn has created a multi-functional urban wetland adjacent to coastal waters with moderate water quality. Here, it has been possible to create an area that both purifies the coastal waters and increases biodiversity, while also becoming a space for learning and recreation for the city’s residents.

The wetland consists of several steps, the first of which separates particles and microplastics. This is followed by a sedimentation basin which purifies run-off water from the residential and industrial area north of the wetland and which also serves as an attenuation basin when it rains. Finally, there is a smaller fishing wetland, intended for pike fry, to promote biodiversity in the coastal zone.

The wetland has many positive effects on plant and animal life, as well as the aquatic environment. Seabirds thrive here and near the wetland, frog pits have been constructed to promote the presence of amphibians in the park-like environment surrounding the wetland. Schoolchildren have built bird and bat boxes, and along the area’s hiking trails there are shelters that inform visitors about the purpose and function of the wetland, and about the plants and animals that inhabit it.

The City of Mariehamn is planning to follow up on the Nabben wetland by building a similar wetland on the other side of the city at Svibyån where nutrients from agricultural land are leaching into the sea.