fens

Fens are a type of wetland characterized by persistent waterlogging and peat formation. They are minerotrophic wetlands fed by mineral-rich groundwater or springs, which distinguishes them from bogs that accumulate peat primarily from precipitation.

Geographically, fens occur in temperate and boreal regions of Europe, North America, and parts of Asia, often in river valleys, low-lying plains, or along lake margins. Groundwater input maintains higher nutrient levels and pH, typically neutral to alkaline, supporting ongoing peat accumulation as plant matter decomposes in water-saturated soils.

Vegetation in fens is diverse, with communities of sedges, grasses, reeds, rushes, and mosses. Sphagnum moss is common in some fens but less dominant than in bogs. Calcareous or nutrient-rich fens host a distinct flora, including lime-tolerant species, and they can support specialized invertebrates and a variety of birds and damselflies.

Human activities such as drainage for agriculture, peat extraction, and urban development have reduced fen extent and altered hydrology in many regions. Nutrient pollution from agriculture can shift plant communities, often reducing biodiversity. Restoration efforts focus on rewetting drained areas, restoring groundwater inputs, and protecting fen cores from nutrient influx.

Fens remain important for biodiversity, water purification, and landscape value. Several fen sites are protected under national or international designations, and ongoing conservation and restoration programs aim to preserve their hydrology and native plant and animal communities.