Wetlands in warm 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

Freshwater wetlands are comparatively rare in the Mediterannean, generally associated with lakes and reservoirs, river deltas and the region’s remaining floodplains. Areas of inland drainage often support seasonal wetlands in landscape depressions but they are often largely saline or alkaline in character. Frequently, the wetlands of the region are part of coupled mosaics of wet and dryland habitat, including lagoons, freshwater and brackish marshes, lakes and dunes. Forested wetlands are now particularly rare.

Human impact

A rich wetland landscape existed until the early nineteenth century, but since then the majority of wetlands have been drained either for agriculture or to eradicate malaria. Such conversions have been particularly intensive in the last 50 years, and have coincided with a high level of pollution of surface drainage waters, and overexploitation of aquifers for irrigation supplies. Many small wetlands have been filled in with urban and domestic waste.

Climate change impact

Evaporation rates will increase and regional water tables will continue to lower as a result of climate change. The combination of these factors will threaten much of the remaining wetland resource of the region, with the exception, in the medium term, of the mountain zones. Some wetlands may be regenerated periodically by extreme flood events, but the continued survival of many species is precarious.