Coastal & Floodplain Grazing Marsh is periodically inundated pasture or meadow with ditches which maintain the water levels & contain standing brackish or fresh water (UK HAP, 1995).
- Site: Periodically flooded, water-containing ditches
- Soil: Low-lying alluvial/peat soils
- Main species: Rushes & grasses
- UK: 300,000 ha
- Coastal & floodplain grazing marsh is found on low-lying alluvial (soil deposition by flowing water) & occasionally peat soils, around estuaries & along river floodplains.
- In Northern Ireland this habitat has developed due to the conversion of marine & coastal wetland habitats to grassland as a result of coastal defence & flood protection works.
- There are two main types of grazing marsh: Coastal grazing marsh occurs in flat coastal areas, typically behind coastal defences or natural barriers such as sand dunes. They are drained by a network of ditches containing standing water throughout the year. Floodplain grazing marsh is usually associated with larger slow-flowing rivers & lakes, where it can be drained by a network of ditches. Whereas coastal grazing marsh is often derived from reclaimed saltmarsh of mudflats, much of floodplain grazing marsh was swampy woodland, fen or reedbed (NIEA, 2005).
- Coastal grazing marsh supports brackish species found alongside typical freshwater wetland plants e.g sea club-rush Scirpus maritimus & sea rush Juncus maritimus.
- Inland floodpain grazing marshes support rush-dominated pasture & semi-improved/improved grassland.
- Many of the plant communities are similar to those described in the NVC of Great Britain. These include MG10 Holcus lanatus – Juncetum effusus rush-pasture, MG9 Holcus lanatus – Deschampsia cespitosa grassland, MG11 Festuca rubra – Agrostis stolonifera – Potentilla anserina grassland & MG13 Agrostis stolonifera – Alopecurus geniculatus grassland, which occur around larger lakes in the lowlands such as Lough Beg. Others include MG6 Lolium perenne – Cynosorus cristatus grassland, MG7 Lolium perrene leys & related grassland.
Current Status in UK & Northern Ireland
- There are an estimated 300,000 ha of coastal & floodplain grazing marsh in the UK.
- England holds the largest proportion with an estimated 200,000 ha in 1994. However a small proportion is semi-natural grassland, supporting a high diversity of native plant species (5,000 ha in England, approx. 10,000 ha in the UK).
- NI contains an important proportion of the UK resource, but the extent of this is not well-understood. The Northern Ireland Breeding Wader Survey (Partridge, 1988) surveyed lowland damp grasslands for breeding waders, which roughly equates with this habitat. It identified 615 lowland damp grassland sites, with important concentrations around Lough Neagh (3284 ha) & Upper Lough Erne (2922 ha). Only 13 were coastal sites (covering >344 ha), although these did not include four sites in the Downpatrick marshes & the Quoile Pondage. Follow up surveys have revealed significant losses since this survey.
- Coastal grazing marsh is found at three main sites in NI: Strand Lough, the Quoile Pondage (Co. Down) & the shores of Lough Foyle. Due to reclamation of large areas of saltmarsh & mudflats in the Foyle estuary during the 19th century, a large area of coastal grazing marsh was created. This area has been drained, with limited areas of wet grassland remaining & significant areas under improved grassland & cereals.
- Inland floodplain grazing marshes are more widespread in NI. This habitat occurs on flat low-lying areas, frequently as a mosaic with other wetland habitats (e.g. lakes & fens). Extensive areas of floodplain grazing marsh include Lough Neagh & Lough Beg and Upper Lough Erne (Finn Floods ASSI).
- The NICS (2000) recorded a rapid decline (28%) in species-rich wet grassland in the lowlands between 1991 & 1998, which included losses from coastal & floodplain grazing marsh.
- Factors that threaten the habitat include drainage which has resulted in declines in the area of grazing marsh, scarce species & breeding wader populations, sea defence works, habitat fragmentation, residential development, airborne pollution & climate change. Further threats include agricultural improvement (e.g. cultivation, fertiliser & pesticide use, ploughing & re-seeding), overstocking & overgrazing, groundwater abstraction & inappropriate management, which may result in vegetation changes.
- Grangemore[Bann Estuary ]
- Lough Foyle
- Lough Neagh & Lough Beg