Invasive Non-Native Species

Invasive non-native species (INNS) are plants and animals that occur outside of their natural geographic range which disrupt ecological balance. Many of these species spread rapidly, outcompeting native wildlife and altering habitats, which can lead to declines in biodiversity. Across the Wear catchment, invasive species present an increasing challenge for rivers, streams and surrounding habitats. Below are some of the key invasive species currently affecting our waterways.

Himalayan balsam

Himalayan balsam is an annual flowering plant that readily colonises riverbanks, forming dense stands that outcompete native vegetation and reduce riparian habitat diversity. As the plant dies back during winter, it leaves riverbanks exposed, increasing vulnerability to erosion and sediment input into watercourses. At present, manual removal remains the most effective method of control. Management should be undertaken from upstream locations, as seeds are easily dispersed downstream by flowing water. Control is labour-intensive and requires sustained effort over multiple years to achieve long-term reduction. Research is ongoing into the use of rust fungi, a naturally occurring pathogen, as a biological control option for Himalayan balsam.

Giant hogweed

Giant hogweed is a tall, flowering plant that is now widespread along riverbanks and other disturbed ground. It forms dense stands that can displace native vegetation, leading to reduced biodiversity and a loss of suitable habitats for wildlife. The species is commonly found along watercourses, where it can dominate riparian areas if left unmanaged. The sap of Giant hogweed is phototoxic and can cause serious skin irritation. When exposed to sunlight, contact with the sap may result in blistering and burns, which in some cases can persist for several years. Therefore, due to the risks it poses to both ecosystems and human health, careful management and control of giant hogweed is essential across the Wear Catchment.

Japanese knotweed

Japanese knotweed is a highly invasive perennial plant that can rapidly colonise riverbanks, road verges and other disturbed ground. It outcompetes native vegetation, leading to reduced biodiversity, and its extensive root system can cause damage to built structures such as buildings, flood defences, roads and hard surfaces. Japanese knotweed spreads through fragments of stem and root rather than by seed, meaning even small pieces of plant material can lead to new growth. It is therefore essential that plant material is not moved or spread between sites. Under the Wildlife and Natural Environment Act 2011, it is an offence to plant or otherwise cause Japanese knotweed to grow in the wild.

Skunk cabbage

Skunk cabbage is a distinctive plant that releases a strong odour when in bloom. It is considered an invasive species, particularly within wetland environments, where it can outcompete native vegetation. The plant forms dense colonies that block light from reaching other species, reducing plant diversity and altering habitat structure. Its seeds are readily dispersed by water, allowing it to spread into new areas. Originally introduced as an ornamental plant in the early 1900s, Skunk cabbage has since become established in a range of natural habitats. Once present, it can be difficult to control and may require sustained management to limit its spread and reduce impacts on wetland ecosystems.

American signal crayfish

American signal crayfish were introduced to the UK for farming purposes. They are larger and more aggressive than the native white-clawed crayfish and carry a fungal plague to which the native species is highly susceptible. As signal crayfish continue to spread, white-clawed crayfish populations are increasingly threatened and becoming less common. Signal crayfish are also believed to contribute to bank erosion and may predate fish eggs, further impacting river habitats and associated wildlife.

American mink

The American mink was introduced to Europe for fur farming and subsequently escaped into the wild. It is a carnivorous species that feeds on rodents, fish, crustaceans, frogs and birds. Its presence has been linked to declines in European mink and water vole populations. As an efficient predator, the American mink can have significant impacts on native wildlife across the country. These impacts are most notable for species that rely on river corridors and wetland habitats.

Non-Native Species Strategy & Action Plan

In addition to the priority species highlighted above, we are aware of a range of other invasive non-native species present across the Wear catchment. The distribution and impacts of these species continue to evolve, requiring ongoing monitoring, collaboration and adaptive management.

Wear Rivers Trust works closely with partner organisations across the North East to deliver a coordinated approach to the prevention, early detection, rapid response and long-term management of invasive non-native species. By working collaboratively, we aim to protect native biodiversity, improve biosecurity and build more resilient river catchments.

Our North East Invasive Non-Native Species Strategy and Action Plan 2026–2030, developed in partnership with the North East Biosecurity Partnership, sets out our shared regional approach to tackling invasive species and can be accessed below.

Check, Clean, Dry

At Wear Rivers Trust, we follow the Check, Clean, Dry approach in everything we do. It’s a simple and effective way to help protect the Wear catchment from invasive non-native species and other harmful organisms.

To help safeguard the River Wear and its surrounding environment, please follow the steps below. Whether you’re a volunteer, contractor, landowner, or recreational user, you have an important role to play.

Check your clothes and boots before moving between rivers.

Clean everything thoroughly as soon as you can, paying attention to areas that are damp or hard to access. Use hot water if possible.

Dry everything for as long as you can before using elsewhere as some invasive plants and animals can survive for over two weeks in damp conditions.

Volunteer with Us

Join our volunteers to monitor and control invasive non-native species, helping to protect wildlife and restore river habitats across the Wear catchment.

Report an Invasive

Invasive non-native plants or animals can threaten native habitats and species. Noticing and reporting INNS sightings allows for early action to protect our local ecosystems.

Support Our Work

Report invasive non-native species across the Wear catchment to help us act quickly, protect wildlife, and maintain healthy river habitats.