In principle, a wetland can be established almost anywhere. The best waterfowl wetlands, however, are often created by damming in points of the terrain that lie lower than their surroundings.
Damming is often a more cost-effective alternative than a massive dig. For all that, the restoration method that best suits the site and creates the best results must always be chosen case-specifically, because sites that have grown dense with vegetation along the surface, for example, can very rarely be restored by damming.
There are many different criteria for choosing a site for wetlands.
For example, agricultural financial support for non-productive investments encourages the creation of wetlands in naturally field-intensive drainage areas where the expected benefit from wetland water protection is the greatest.
On the other hand, other factors, such as the size of the drainage area, the contours of the terrain, the features of the soil, whether the project is subject to licence, the site’s accessibility and landscape and ecological location may also have a significant effect on the choice of site.
In practice, however, wetlands are established wherever possible, taking into account the surrounding area’s land use and ownership.
Plants as Indicators of Nutrient Content
In our restoration category, the site’s nutrient content is estimated on the basis of its vegetation. Nutrient content plays an important role in terms of waterfowl. Eutrophic or nutrient-rich wetlands have a sufficient amount of food in the form of invertebrates, as well as shelter provided by vegetation for both waterfowl nestlings and mature birds. Rich vegetation and particularly helophytes demonstrate the high nutrient content of the site.
In our wetland questionnaire, the plant genera that symbolised a nutrient-rich wetland area included sedge, horsetail, cattail, reed, pondweed and water lily. Rich canopies of sedge and horsetail, as well as flood meadows are excellent habitats for waterfowl broods, because they offer plenty of shelter and invertebrates for nourishment.
Correspondingly, the genus of sphagnum moss was an indicator of a nutrient-poor wetland site. Wetland areas filled with sphagnum moss offer very little in terms of habitat for waterfowl and waders. The nutrient-poor environment lacks the aquatic invertebrates that they require for food and the level floor of sphagnum moss offers no shelter for nestlings against predators and the elements.
The vegetation of a nutrient-rich wetland is important for waterfowl and the area’s management. The guidebook Kosteikko-opas (slideshare) provide in Finnish more information on wetland plants.