Invasive Non-native Species - protecting the biodiversity of our waterways

Monday, June 3, 2019

We are working hard to protect our native species from invasive non-native species including Himalayan balsam and American mink

There has been a lot of publicity around the UN's recent report that highlights the unprecedented and dangerous threat of the planet-wide loss of biodiversity. Over 1 million animal and plant species are facing extinction, and the report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) highlights several human-led reasons for this loss, ranked, for the first time, by importance. There are five on the list, and the fifth is one which is close to my working life: the introduction and spread of non-native invasive species.

Invasive Non-Native Species (INNS) week 2019 was 13-17 May,  and I wanted to use this opportunity to highlight some of the work the Wildlife Trust BCN is doing in the fight against them with our INNS projects.

Himalayan Balsam

Himalayan Balsam is present along a number of our riverbanks in the three counties. Whilst it may seem that the flowers look nice and they provide a nectar source for a variety of pollinators it is worth remembering the true cost against any benefit.

Along riverbanks, Himalayan Balsam thrives and regularly out-competes other native aquatic vegetation, with the exception of nettle and bramble, reducing riverbanks to monocultures rather than rich biodiverse environments.

Himalayan Balsam is also shallow rooted and dies back in the winter meaning that once it has dominated a river bank, it shades out the native vegetation and then dies back, leaving the ground bare and unstabilised by the deeper-rooting native species. This can lead to greater bank erosion in winter floods and increased sediment entering the watercourse, smothering fish spawning gravels.

The Wildlife Trust has Himalayan Balsam projects in Bedfordshire and Cambridgeshire where we map and pull Himalayan Balsam to reduce its dominance on a river. These projects aim to work from the source of the Himalayan Balsam downstream in order to try to eradicate it completely.

American mink

American mink are also a big concern in our river valleys. As a generalist predator, American mink have been responsible for decline in large numbers of ground nesting birds and have played a key role in the decline of our water voles. Their presence in the catchments across the country present a big challenge for the recovery of species that have suffered from their predation.

The Wildlife Trust BCN is working with partners to address American mink across all three counties. The Trust monitors the distribution of the species and how this matches up with our data on water voles. This helps us target our conservation efforts to buffer and improve the resilience of localised water vole populations.

Floating Pennywort

We also support the Environment Agency’s floating pennywort project on the Great Ouse through our River Wardens scheme. Our volunteers spot any plants that require removal and report them, in order to prevent this invasive species from making its way up to the Ouse Washes.

What you can do

Volunteer with us

If you are interested in any upcoming events to help our waterways in the three counties this year, please get in touch at and include your county of interest (Bedfordshire, Cambridgeshire or Northamptonshire) in the subject line.

Stand up for nature

The loss of biodiversity is a complex and pervasive issue that affects all of us and requires urgent action by governments. Alongside our work on the ground, we are campaigning for the government to put legislation into place that supports the building of a nature recovery network. Join our campaign for a Wilder Future and join our demand for a strong Environment Act that will support and bolster the work we do. 

More information

If you would like to know more about any INNS you may have seen in your area the Non-Native Species Secretariat has excellent resources and can be found at:


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