You may not be aware, but it’s likely you have come into contact with invasive species at some point, whether it’s at home in your garden, on your travels, playing outdoors or even when you’re out shopping. 

They lurk in our watercourses, dominate our riverbanks and even cause structural problems to our homes. They are just waiting for an opportunity to spread - and that opportunity could be you!

What are invasive non-native species (INNS)?

A non-native species is one that originated elsewhere and has been introduced to an environment. This could be a plant, animal, fungus or bacteria. Not all non-native species are harmful, but those that are are labelled invasive. Invasive species: 

  • grow and reproduce quickly
  • have no natural control mechanisms (e.g. predators)
  • spread aggressively, out-competing native species for resources (light, oxygen and food)

These species are so efficient at reproducing and spreading they completely suppress our native species and change ecosystems.

They impact our environment, economy, infrastructure, leisure and enjoyment and even human health.

Some facts

  • There are 1,402 non-native plants in the UK, but only 108 (8%) are considered invasive.
  • Approximately 60% of invasive plants come from horticulture.
  • Clearing the Olympic site of Japanese knotweed cost an estimated £70 million. 
  • Invasive species are estimated to cost the British economy £2.2 billion per year.
  • It is a criminal offence to plant or cause to grow a non-native invasive species that is listed on Schedule 9 in the wild. This offence carries penalties of up to £5,000 fine and/or 2 years imprisonment.
  • Research indicates that it takes at least ten years to eradicate giant hogweed where it has succeeded in seeding, and four to five years to eradicate Japanese knotweed.

The impact of invasive non-native species

The spread of invasive species is a global problem and they have been dubbed the greatest threat to global biodiversity after habitat loss. 

Our efforts focus on aquatic and riparian invasive species. The impact of invasive species on our native wildlife and waterways has been well documented with millions of pounds being spent clearing congested ponds and rivers. Delicate habitats and species have been pushed to extinction under carpets of New Zealand pigmyweed (Crassula helmsii).

Invasive species affect: 

The way you live: INNS can have direct impacts on our health. For example, giant hogweed contains photosynthetic venom which when touched causes blistering burns to the skin. Species such as Japanese knotweed and Himalayan balsam can also increase the possibility of flooding in highly infested areas.

The environment: Impacts of INNS are so significant, they are considered to be one of the greatest threats to biodiversity worldwide. They threaten the survival of rare native species such as the white clawed crayfish and damage sensitive ecosystems and habitats like freshwaters and wet woodlands.

The economy: INNS cost the British economy approximately £2.2 billion per year. Japanese knotweed can cause huge damage to man-made structures like building foundations and tarmac roads and floating pennywort can choke water causes, preventing recreational uses of freshwaters. 

What can you do? 

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.

The Lake District attracts millions of visitors each year, bringing the threat of new invasive species inadvertently being introduced. The environmental damage caused by invasive non-native plants can be irreversible, and the impact on tourism, and therefore our economy, would be equally significant. Not to mention the resident communities who live and enjoy the water environment.

Here’s how you can help: 

  • Learn about biosecurity, and make sure you Check, Clean, Dry every time you use our waterways
  • Learn to spot invasive species
  • Help remove invasive species at one of our volunteer events
  • Form a community group to pull Himalayan balsam along a stretch of river near you - we’ll help you get started 


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.