Himalayan Balsam (H.B.) occurs in dense stands along the River Otter, as on most waterways throughout Europe. It spreads by explosive seed dispersal directly; or via mud inadvertently transported by cattle, boots and vehicle tyres; or, above all, via water which bathes riverbanks downstream with a steady supply of seed. HB competes with natural vegetation and can dominate it in woods, hedgerows and on riverbanks. Reducing biodiversity can have negative effects. For example, because it dies off completely in winter, riverbanks may be exposed to erosion, and their inhabitants, such as water voles, left without protective cover against predators.
Current control methods for H.B. are labour-intensive and require catchment-wide organization. This happened recently in the Otter until austerity terminated the involvement of the Environment Agency in 2014. Current strategy is smaller scale, focussing on tributary valleys in which volunteer teams annually improve the level of control. The Tale Valley Trust has been doing this since 2005 while the OVA has worked closely with Clinton Devon Estates in the Lower Otter tributaries since 2012. Once all tributaries are clear, the main valley can be tackled. As such, the project is obviously very long-term. It remains to be seen whether current national research on fungi will speed up the process. It is also possible that some sections of the Otter will benefit from the presence of beavers who are partial to HB.
A team of dedicated OVA volunteers clear Himalayan balsam on Thursday and Saturday mornings; if you would like to volunteer to help the team please contact Patrick Hamilton via our contact form.
Click on the links below for the following reports: