Invasive weed species (Giant Hogweed, Japanese Knotweed & Himalayan Balsam) are problematic along the entire course of the River Mulkear and indeed throughout the entire Mulkear catchement. Considerable progress has been made in recent months by Limerick County Council and by the OPW in addressing the extent of the problem with targeted programmes of control and removal. These invasives are a major concern to MulkearLIFE as they outcompete native vegetation, leading to a loss of biodiversity, they also reduce light available for primary producers (dense knotweed canopy) and destabilise riverbanks. Two of these alien species (Giant Hogweed, Himalayan Balsam) die back in the autumn period exposing soil to winter floods which causes erosion problems. This leads to subsequent siltation of fish spawning grounds.
Project Officer Glen Wightman inspects a recently treated Giant Hogweed site
On the Mulkear River the riparian vegetation is being overwhelmed and the invasive weeds continue to expand. These plants are known to outcompete native riparian native species (sedges and grasses) which would normally provide food and cover for fish and other aquatic species. Limerick County Council (LCC) began their treatment of invasive plants in the third Qtr of 2009. A new survey of the catchment was conducted in March 2010 to determine the extent of invasives. Following a planning session with LCC giant hogweed sites were selected for inclusion and significant progress was achieved from April 2010 onwards.
Vegetation surveys were completed prior to this treatment work. Work was also initiated on the Newport River section involving chemical spraying of three invasive weeds by OPW staff. Detailed maps were provided to OPW to outline infected areas. OPW started work on these infected areas in April 2010. Spot checks in May, June and July 2010 in all areas targeted have indicated excellent kill-out rates testament to the high quality work by LCC and OPW crews.