Evaluating the impact of Impatiens glandulifera on riparian erosion.

Impatiens glandulifera is an invasive non-native species (INNS) commonly associated with erosion due to its perceived negative impact on native species diversity, which is thought to lead to a reduction in soil cover during winter months. As an INNS, it is widely managed for its supposed environmental harm, with common control methods including cutting and hand-pulling. However, hand-pulling may exacerbate erosion by disturbing soil structure. As I. glandulifera is particularly prolific in riparian zones, any erosion may contribute to sedimentation in nearby watercourses, potentially degrading water quality.
Despite frequent claims linking I. glandulifera to increased erosion, little empirical evidence exists to substantiate this association. There is also no clear consensus on whether the species significantly reduces native plant abundance or diversity. Furthermore, no prior studies have evaluated the impact of managing I. glandulifera on sediment loss.
This research quantifies sediment loss, native species abundance and diversity, and soil physical properties in areas invaded by I. glandulifera across seven sites in the Yorkshire-Derwent catchment, UK. Additionally, sediment loss from riverbanks was assessed before and after management interventions using a Before-After-Control-Impact (BACI) experimental design.
This study’s key finding is that I. glandulifera presence does not cause elevated sediment loss and that it does not reduce native species abundance or diversity. Species composition was found to differ significantly in invaded areas, suggesting that I. glandulifera segregates into microhabitats due to competitive interactions with perennial herbs and grasses. Moreover, hand-pulling was shown to moderately increase sediment loss compared to cutting.
This is the first study to simultaneously examine the effect of I. glandulifera on both riparian sediment loss and vegetation composition. This approach was crucial in providing a robust defence of results that challenge a widely accepted viewpoint in the scientific community and these findings will help land managers make informed decisions regarding the risks associated with the invasion and management of I. glandulifera.