THE POSSIBLE INFLUENCE OF THE INVASIVE PLANT, IMPATIENS GLANDULIFERA (HIMALAYAN BALSAM), ON THE SEDIMENT DYNAMICS OF INLAND RIVER SYSTEMS IN TEMPERATE REGIONS

Impatiens glandulifera (common English name: Himalayan Balsam) was introduced into Europe from the Himalayas ca. 150 years ago, whereupon it was soon noted for its invasive tendencies. It is now found in most temperate European countries, as well as across parts of east and west North America, and in New Zealand. Its preference for damp, shady conditions and fertile soils, but tendency to suffer rapid dieback during cold weather, has for many decades implicated it in promoting soil erosion along riverbanks and the riparian zone, particularly along inland watercourses. Despite the strong implication, its likely influence on sediment dynamics has only recently been proven during a study conducted in northwest Switzerland. We use this communication to re-evaluate the significance of those findings and also take the opportunity to draw on very preliminary results from additional on-going investigations undertaken, both at the same site and from an additional catchment in the UK, to hypothesize whether I. glandulifera may act as an ‘erosion accelerant’. Key findings from both locations are used to discuss whether, under certain geomorphological and hydrological conditions, I. glanduliferamay actually induce repeat cycles of colonization and dieback; often followed by extreme erosion. Given the relentless spread of this plant, its likely influence on the sediment dynamics of river systems is discussed with regard to a possible breakdown in their hydro-geomorphic functioning. We suggest that a failure of key morphological components to fulfil basic ecosystem services could adversely perturb the sediment dynamics of affected river systems; thus making the delivery of effective catchment management strategies very challenging in the future.