Wetlands in temperate 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 temperate regions include a large proportion that are the result directly or indirectly of human intervention. Their diversity and often close association with human activities makes it difficult to define any truly pristine condition. Hydrological and nutrient conditions are fundamental factors determining characteristics. Species supported range from those adapted to highly acidic, low nutrient conditions to those that require circum-neutral to slightly alkaline conditions. Marked seasonal variations are typical due to variations in temperature and waterlogging, but these tend to be less extreme than in the cold ecoregions or in the Mediterranean.

Human impact

It is probable that no wetland has escaped some human impact, and throughout Europe’s temperate ecoregions, the loss of wetland habitat has been a long and progressive feature of landscape development at least since early mediaeval times. Drainage for agriculture or forestry intensification has been the single most important direct impact, followed by peat mining. Eutrophication, acidification, and regulation of water flow are the most important indirect impacts.

Climate change impact

Climate change will have a significant effect on the maintenance of all peat-dominated wetlands, and on the ability of impacted ecosystems to recover. Desiccation of wetland peats will increase oxidative losses, contributing further to greenhouse warming and the release of coloured water downstream. It is not clear what will be the implications for aquatic biota, but drier wetland surfaces will be invaded by non-wetland species, including woodland species. Changes in flooding regime will impair floodplain wetlands and affect the ways in which they can function in nutrient dynamics,or food chain or habitat support.