Himalayan balsam (Impatiens glandulifera) promotes soil erosion along watercourses, according to research published in the Journal of Soil Sediments last month (Dec 2013).
Philip Greenwood and Nikolaus Kuhn from the University of Basel show that erosion along riparian zones is statistically greater where Himalayan balsam is present when compared to topographically comparable sites that support natural vegetation.
Their work involved taking over 700 soil surface profiles along a stretch of river in northwest Switzerland. The measurements were taken over an eight month period covering the time before dieback occurred to the germination and seasonal regrowth of new plants.
As people are aware, Himalayan balsam has invaded most of the UK’s river catchments and has been implicated in promoting soil erosion along the riparian zones due to its preference for damp, nutrient-rich soils, and its rapid dieback. Despite the implication, its influence on the sediment dynamics of river systems remains unconfirmed.
Given the wide distribution of this plant throughout inland river systems, the authors suggest that the presence of Himalayan balsam is likely to contribute to nutrient-rich sediment entering aquatic environments and steadily reduce water quality in affected catchments.
Drs Greenwood and Kuhn highlight the need for effective control measures that are capable of halting or even slowing the rate of Himalayan balsam invasion if affected European Union member states are to meet and maintain key water quality standards set by the Water Framework Directive (WFD) when fully implemented in 2015.