Tackling invasive non-native species (INNS) to help protect our wildlife

Non-native species are plants and animals that have been moved from their place of origin into Britain by humans (intentionally or accidentally). There's thought to be around 2000 non-native species in Britain.

Invasive non-native species (INNS) are non-native specives which have a negative impact on the environment, economy or health of the place they've been moved to. In Britain, it's estimated that 10% of the non-native species are invasive - that's around 200 species, and the number is increasing.

Amongst habitat loss, fragmentation, pollution and climate change, INNS are one of the topmost serious threats to biodiversity in the UK. That's because they have no natural predators, competition or disease, so they thrive uncontrollably, to the detriment of our native species.

Recordings show that around 40% of Britain’s 200+ registered INNS are known to be aquatic. For us, that causes serious concern.

Crassula helmsii otherwise known as New Zealand pigmyweed
Examples of INNS we manage

New Zealand pigmyweed

This succulent is mainly water-based and reduces oxygen levels, chokes abstraction points and filter systems, and forms free-floating mats that present health and safety issues for maintenance staff and recreational visitors at reservoirs.

We're working with CABI to trial biocontrol measures to help develop effective control methods.

Giant hogweed
Examples of INNS we manage

Giant hogweed

This plant was originally brought over to Britain as an ornamental plant in the 19th century. However, it's broad leaves and bushiness means that it blocks the light getting to shorter or slower-growing native species below. It's also dangerous to human health - its sap contains potent phototoxins that cause serious skin blistering.

We're working alongside Tamar Valley Invasives Project and Dartmoor National Park Authority to implement appropriate safety measures.

American signal crayfish
Examples of INNS we manage

American signal crayfish

Brought to European waters to boost the food farming industry, some escaped and were soon outcompeting, and introducing a lethal disease to, the native white-clawed crayfish. Signal crayfish also burrow into reservoir banks, weakening them, and generating sedimentation which reduces water quality.

We're supporting joint research projects with South West Crayfish Partnership and PhD students, and trialling new control methods like deep-water Artificial Refuge Traps, to develop effective control strategies.

Image of a zebra mussel
Examples of INNS we manage

Zebra mussels

These mussels can live in freshwater or slightly salty water. They outcompete local, native species by smothering them or filtering the water of all its nutrients. They also attach to hard surfaces like pipes and boats, causing damage.

We are working with a range of local people, organisations and experts to manage this species to prevent its spread to our reservoirs, protecting our wildlife, our hobbies and our water supply.

South West Lakes Trust logo Environment Agency logo Angling trust logo CABI logo
Dartmoor National Park logo Exmoor National Park logo Tamar Area of Outstanding Natural Beauty logo Devon Invasive Species Initiative logo

Keeping waterways safe for wildlife in other ways

If it wasn’t for our interventions, some of the engineering needed to keep our pipework, treatment works, rivers and reservoirs working correctly can put aquatic life in harms way. We’ve always worked hard to create nature pathways for wildlife to help them overcome the risks and obstacles presented by this infrastructure.

For example, we’ve installed screens at all our water treatment works to stop fish and eels being brought into the works when we abstract water from the rivers.

Another area of concern has been human-made structures in rivers which stop the natural migratory journey of fish species like salmon, eels, shad and trout. That’s why we’ve worked hard with South West Rivers Trust to build fish passes at weirs so that these fish have a risk-free pathway to navigate upstream to their preferred breeding grounds.