IW14 Red-listed inland water habitat types

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Development

A red-list assessment for habitat types in Finland was published in 2008. Approximately 40% of inland water habitat types were evaluated as endangered and one third as near threatened. A greater share of inland water habitat types are threatened in southern than in northern Finland.

Streams are more threatened than lakes and ponds. The list of critically endangered habitat types includes streams and rivers in clay-dominated catchment areas. Their distribution is centered in areas in southwest Finland which have been heavily modified by humans already for a long time. All stream habitat types are locally endangered in southern Finland whereas in northern Finland only very large rivers have been evaluated as endangered. In general, the size of the stream increases its vulnerability. The impacts of land use and loading accumulate downstream in a river system, and large rivers are also more often built and regulated than smaller ones.

The share of red-listed lake habitats is smaller than that of running water habitats. Most threatened lakes nationally are chalky lake, lakes with very short retention times and, mainly in southern Finland, naturally eutrophic lakes. The share of these lake types is only a few percentages of the total lake area. Most of the lake habitat types (as much as 90% of the total lake area) are assessed as near threatened. Ponds and small lakes are generally in a weaker state than lakes. The most threatened pond types are naturally eutrophic ponds, chalky ponds and ponds with occasional brackish water influence.

Spring habitats were evaluated vulnerable in the national assessment. There are however regional differences in their conservation status. Spring habitats are endangered in southern Finland but in northern Finland they have been evaluated to be under least concern. The natural state of the spring habitats has nevertheless somewhat weakened also in the North.

Threats

Land use in the catchment area is the most significant threat to inland water habitats. Agriculture, drainage, peat production and forestry (including fellings, soil preparation and fertillization), cause changes in discharge as well as the loads of nutrients, organic matter and solid particles. Inland waters have also been polluted by nutrient loads from industry and municipalities. These loads have decreased (see IW1, IW2), which is reflected by the improved water quality of several large lakes. In additon, the inland water habitat types are threatened by water and shore construction as well as regulation of water courses. Timber floating and clearing of streambed for flood control or drainage have affected small water bodies. Groundwater abstraction is a threat to especially spring habitats and habitats with significant spring influence.