Opinion divided on the merits of cord-grass
Published 26/11/2013 | 05:42
Common Cord-grass presents a conservation conflict. It is a creeping grass that grows on tidal mud and sand in estuaries. Once it gets established it grows very vigorously and is so extremely aggressive that it takes over large areas of ground forming extensive swards.
It is not native to Ireland; the hybrid was introduced here for its amazing ability to hold mud in estuaries. It has an extensive root system that binds and stabilises mud. Once the grass gets established not only does its root system prevent erosion of the mud but its stems and leaves trap suspended mud particles in the water thereby causing the mudflat to grow.
Over time the deep-rooted mud-binder fixes large areas of soft sediments making them suitable for reclamation for port and other developments. The potential of the wonder grass was realised by port authorities, developers and local authorities and in the 1940s it spread rapidly from its original introductions to counties Cork, Clare and Down with subsequent introductions to Dublin, Donegal and Mayo.
It can grow from small fragments and can be transported by waterbirds, waders and wildfowl so it spread rapidly and is now a common and widespread plant around our coastline.
While developers saw merit in encouraging its spread, conservationists took, and still take, a different view. They see Common Cord-grass as a threat because it out-competes the native plants that grow on mudflats and its monoculture swards take over large areas of mud forming depriving waterbirds of their feeding grounds.
Colonisation by the mud-binder can also alter the physical shape and structure of mudflats resulting in changes in drainage, increased flooding, blockage of navigational channels and reduced recreational amenity value of an area.
Consequently, Common Cord-grass, also known as Spartina, features on the 'Most Unwanted' list of invasive aliens and proposals were made to try to eradicate it or at least control its spread.
However, the EU Habitats Directive lists Spartina swards as features that Member States should conserve. While it makes sense for Member States elsewhere in the Union to conserve cord-grasses in countries that they are native to, it raises the question whether we should be cherishing a most unwanted, invasive, hybrid alien.
At present, ambivalence persists: Common Cord-grass features on both the 'Most Unwanted' list of invasive aliens with examples of spraying with herbicide to kill it and on the list of protected habitat types with examples of active conservation.