Salt-Marshes on Peat Substrate: Where Blanket Bogs Encounter the Marine Environment

COTT, G.M.; JANSEN, M.A.K., and CHAPMAN, D.V., 2012. Salt-marshes on peat substrate: where blanket bogs encounter the marine environment. Salt marshes typically develop on low-energy coasts under the influence of the tide. However, there are peat salt-marshes along the west coast of Ireland that formed in an inherently different way. This paper examines the ontogeny of these salt-marshes and highlights their uniqueness both in an Irish and global context. The peat of these marshes formed in postglacial times when climatic conditions were such that ombrogenic blanket bogs formed along the western Atlantic coast of Ireland. A subsequent marine transgression caused a shift from freshwater to saline conditions, and these bogs now support salt-marsh vegetation. These systems have been termed “Fringe” marshes in the Irish salt-marsh inventory. Unlike other organogenic salt-marshes in Europe, they formed under predominantly freshwater conditions, thus making them unique in geological foundation. This paper examines the complexity of natural controls on salt-marsh systems and relates this to the ecological character of fringe marshes. It emphasises that their position on the western Atlantic seaboard, coupled with peat substrate and its inherent properties, could drive a unique ecological character. Ongoing and future threats to these habitats are discussed. The term “Fringe” is used internationally in many other contexts and therefore does not specifically describe these peat substrate marshes. In order to distinguish the peat salt-marshes of the west coast of Ireland from those formed under different conditions, the term “Ombrogenic Atlantic Salt-Marsh” is proposed.