Wetlands in cold ecoregions

– Water type description –

• Wetlands in general

  Wetlands are ecosystems whose formation and characteristics are largely dominated by water. There is a great variation of wetland type throughout Europe, linked to the diversity of climate, landform and human intervention. They have specially adapted flora and fauna.

  Three main wetland ecosystem types can be distinguished. Bogs are low-nutrient, peat-based ecosystems maintained by precipitation and dominated by mosses. Forested bogs are found in sub-tundra and in the pre-Alps, where they are characterised by mountain pine.
  Fens are due to waterlogging by mineral-enriched groundwater and are characteristically peat-based. Sedge and reed vegetation is generally succeeded by scrub and woodland unless management intervenes.
  Marshes are non-peat forming herbaceous wetlands, which may be temporarily, seasonally, or permanently waterlogged or flooded. They are common around lakes and on river floodplains, where they may form mosaics with floodplain woodlands.

  Wetlands form essential linkages and buffers with other ecosystems, and play a key role in carbon dynamics. They are used by migrating birds and fish to complete life cycles, and generally are habitat for many highly specialised and often rare or endangered species.

  Wetlands are particularly sensitive habitats, threatened by a range of indirect as well as direct threats. Alterations in temperature or nutrient levels, or in the quality or quantity of the water supply will change the character of the habitat, affecting species survival and the ability of the wetland to provide benefits to human communities.

The pristine status

Wetlands in high latitudes and mountainous regions are predominantly ‘mires’, characterised by the accumulation of peat. These unique systems support highly adapted plants and animals, notably a wide range of carnivorous plant species. Rain-fed rivers, wholly dependent on atmospheric inputs for their water and solute supplies, also develop in regions having adequate precipitation. Fen peats develop in sites fed by groundwater, which may be on slopes, in basins, or on river floodplains and lake margins. Some peatlands are extensively forested.

Many peatlands in high latitudes are important for breeding and migratory birds, fish, and mammals such as reindeer and rodents, which support predator populations. In Sweden, wet forests and bogs provide habitat for about 200 threatened species of plant and animal.

Human impact

Peat-dominated wetlands have been altered by a wide range of impacts, including natural drying of the peat mass beyond its ability to retain a high water table, effects of acid rain and eutrophication, drainage for forestry and agriculture, and mining by the peat industry for energy and horticultural products.

Climate change impact

Climate change threatens the stability of mires by increasing decomposition rates due to higher temperatures and lowering of water tables. Reduction of the carbon store, increased flux of CO2 and possibly of CH4, contribute to further amplification of greenhouse gas production. Disruption of intact mire surfaces also increases the generation of ‘coloured water’, with potential effects on aquatic ecology, the breeding cycles of important fish species, and flood control.