Invasive Species

Impacts vary; plants like Japanese Knotweed and Himalayan Balsam blanket river banks, preventing growth of native plants, and leaving banks vulnerable to erosion when they die back in the winter. American mink have predated water voles to near extinction in the Chilterns, although careful control helped the last remaining water vole population to recover and has enabled re-introduction on some Chilterns rivers. American Signal Crayfish have acted as a carrier of crayfish plague which has decimated populations of the native white clawed crayfish, leading to its extinction locally.

This summer we, our partners and local groups have a huge amount of work planned to tackle some of these problems.

• Volunteers from Chiltern Society, Misbourne River Action, the River Chess Association and the Ver Valley Society will be running ‘balsam bashes’ to hand pull Himalayan Balsam
• CCSP staff and Chesham Environmental Group volunteers have recently undergone training to treat Japanese Knotweed by stem injecting pesticides (to prevent spread to the nearby chalk stream)
• Groundwork staff and volunteers will continue to clear invasive floating pennywort from the lower Misbourne
• River Chess Association are running their bi-annual water vole survey this year. In conjunction with this, CCSP will be monitoring for mink activity.

What can you do?

There are actions that we can all take to control the spread of invasive non-native plants

• Check, clean, dry – it is easy to transfer seeds, plant material and invertebrates between sites. Make sure that boots, waders, nets and equipment are checked and any plant or animal material removed before you leave the river. Clean kit thoroughly, using hot water if possible, and then dry completely to stop the spread.
• Report – help us monitor invasive non native species by recording sightings using this app – developed by the Colne Valley Fisheries Consultative
• Get involved with some practical volunteering through your local river group or with the Chiltern Society