Across all our catchments West Cumbria Rivers Trust works to remove and control invasive non-native species (INNS) to promote biodiversity, reduce flood risk and protect our river ways. Luckily for us, we only have a small number of aliens present in our area (Himalayan balsam, American skunk cabbage, Japanese knotweed and American signal crayfish), which we run control programmes for with the help of our volunteers.

The Issue

Invasive non-native species are animals or plants which have not colonised naturally, but have been introduced (accidently or deliberately) by people and now have the ability to pose a threat to the environment, economy or people. Currently, there are over 2000 non-native plants established in the UK but not all of these are invasive. Around 15% of these plants pose a threat to the way we live and once established, their damage is irreversible.

INNS impact us through:

  • Costing the UK economy around £1.8 billion a year through causing damage to structures and roadways, dominating rivers and causing erosion. Japanese knotweed can cause huge damage to man-made structures like building foundations and tarmac roads.
  • Being one of the top five drivers of biodiversity loss, leading to the dramatic decline of native wildlife such as white-clawed crayfish and the tansy beetle. The tansy beetle was originally widespread across Britain yet with the introduction of Himalayan balsam, which outcompetes tansy, the beetle’s supply of food and shelter, the tansy beetle has been restricted to two populations in the UK.
  • Threatening the survival of rare native species and outcompeting plant life in fragile ecosystems such as wet woodlands and freshwaters. American skunk cabbage outcompetes mosses and lichens in wet woodlands, reducing biodiversity in these rare environments.

What we’re doing

In Cumbria we are fortunate to only have a relatively small number of invasive species, but we also have many freshwater resources - lakes, tarns, rivers and becks - that are of great ecological and economic significance. Invasive species have the potential to cause substantial damage to these fragile ecosystems, so it is vital that we all take responsibility for protecting them.

How you can help:

  • Learn about biosecurity, and make sure you Check, Clean, Dry your clothes, equipment and footwear every time you leave the water
  • Learn to spot invasive species and Be Plant Wise - 60% of invasive plants come from horticulture
  • Help remove invasive species at one of our volunteer events, held regularly throughout the summer months to pull Himalayan Balsam 
  • Form a community group to pull Himalayan balsam along a stretch of river


Our work on invasive non-native species is part of a county-wide collaborative effort to stem the introduction and spread of freshwater and riparian invasive non-native species (INNS) within Cumbria.

We work with many organisations to tackle INNS, including the Environment Agency, Natural England, the Lake District National Park, National Trust, Derwent Owners Association, the Borough and County Council and, perhaps most importantly, a significant number of volunteers who are passionate about their environment and work tirelessly to keep Himalayan balsam in check.

As with all our project work, INNS management is dependent on funding and we endeavour to incorporate INNS management into all our applications for funding. Where funding for this work is not available, we continue to keep a record of INNS identified while providing support and advice to our partners and the public.