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Monitoring the Impact of Himalayan Balsam

MulkearLIFE, through Catherine Daly, a 3rd Year student (B.SC in Wildlife Biology) in the Institute of Technology Tralee and a Mulkear Conservation Volunteer, has been monitoring the impact of Himalayan Balsam within the Catchment.

Catherine Daly monitoring work, Bilboa River, June 2011 (Image – Ruairí Ó Conchúir)

Himalayan balsam (Impatiens glandulifera) is a native of the western Himalayas. It was brought to Ireland as an exotic garden plant and escaped from gardens, naturalising in the wild especially along river banks (riparian zones). It forms seed pods which explode scattering the seeds up to 7m from the parent plant. The plant has a high level of nectar production which attracts pollinators competing with native plants. It grows in very dense stands with significant foliage. These factors contribute to it suppressing native plants and their ability to grow especially along river banks.

Close-up Himalayan balsam and explosive seed pods (Image – Ruairí Ó Conchúir)

Plants die back in autumn, exposing bare river banks to winter and spring erosion. Banks devoid of vegetation are prone to erosion, increased risk of bank slippage and consequently the potential for sedimentation. This can cause damage to fish spawning beds and habitat e.g. lamprey and salmon. Within the Mulkear catchment Himalayan balsam has become a significant problem. It is now a well established invasive species, out-competing native vegetation along river banks. This in turn reduces the food sources and nesting habitat for insect, bird and mammal species. In certain stretches of the river it is the dominant flora species for hundreds of metres of river bank.

Himalayan balsam infestation on the Mulkear (Image – Ruairí Ó Conchúir)

Given the extent of the spread of Himalayan balsam in the catchment, it is of critical importance for MulkearLIFE to understand what impact this is having on riparian biodiversity. The riparian zone is of key importance for both land and aquatic life. It is the zone of interaction between where the water and land merge with important feeding and nesting habitat in grasslands,scrub or riparian woodlands. A variety of mammals, like the European Otter, use the river to fish for food and construct holts in the scrub in or adjacent to the riparian zone. Trees and exposed river banks in this zone provide nesting habitat for birds e.g. kingfisher, dipper and sand martins. Many insects species have a life cycle that is part aquatic and part terrestrial and will only be found in riparian zones e.g. may fly. Insects in turn are food for other species, both those found in and out of the water, as well as performing as eco-system services, acting as pollinators for plants. The number and the variety of different species within these riparian habitats gives an overall indication of the richness of the biodiversity which is supported. In the most simplle terms: the greater the variety the healthier the habitat.

Species rich riparian zone, Blackboy Br., Bilboa River, June 2011 (Image – Ruairí Ó Conchúir)

The purpose of the monitoring work, being undertaken by Catherine Daly and MulkearLIFE, is to see what effect Himalayan balsam is having on species richness in the riparian zone and to assess the effectiveness of manual clearance. Ms. Daly is reviewing the density of plant growth and the effect it is having on native species on 50m2 plots at different sites in the catchment. These sites are being monitored and recorded for the duration of the growing season. Several plots have been cleared of Himalayan balsam by manually removing them (pulling then up). This occurred during the early stages of initial growth. Re-growth of seed still present in the plot is now being monitored. Other sites are bring kept clear to study regeneration of native vegetation. Additional plots, one with no Himalayan balsam infestation and another with considerable infestation, are being used for comparison purposes. Initial results are expected in September 2011. The survey work will continue for the next number of years.

Catherine Daly at monitoring site, June 2011 (Image – Ruairí Ó Conchúir)

Monitoring Site with Himalayan Balsam removed, March 2011 (Image – Catherine Daly)

Catherine Daly monitoring on site (Image – Glen Wightman)

Monitoring Site, March 2011 (Image – Catherine Daly)

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