Non native species have long been introduced and used as ornamental plants or pets and only a small minority of them are or will become invasive (SNH, 2000). However, the threat from invasive species is growing at an increasing rate assisted by climate change, pollution and habitat disturbance. They are now recognised as the greatest threat to biodiversity next to habitat destruction and they threaten our native plants, animals and habitats.

Globally, INNS have contributed to 40% of the animal extinctions that have occurred in the last 400 years (CBD, 2006). Many countries including Scotland are now facing complex and costly problems associated with invasive species:

  • In the UK Japanese Knotweed is thought to affect an area roughly the size of London and Defra has estimated the total cost of its removal using current techniques at £1.56bn.
  • £25 million is the estimated cost of clearing the invasive Rhododendron ponticum from the Loch Lomond and Trossachs National Park.

The invasive non native species (INNS) to be the main focus of the local biosecurity plans were selected through a process that involved the compilation of a provisional list of INNS that was revised and finalised after comments received from the trusts, SNH, SEPA, the Scottish Government and the GB Non Native Species Secretariat. The final list of 29 species presented below contains high impact species from the Water Framework Directive alien species list, the Species Action Framework and those INNS that are a local priority to a number of the Trusts.

By clicking on the INNS name in the table you will access a summary sheet that has information on, or links to, identification guides, distribution, known impacts, and pathways of introduction and spread.


Terrestrial Plants Aquatic Plants & Algae Invertebrates Vertebrates
Rhododendron (Rhododendron ponticum & hybrids)

Japanese Knotweed (Fallopia japonica)

Himalayan Balsam (Impatiens glandulifera)

Giant Hogweed (Heracleum mantegazzianum)

Common Cord-grass (Spartina anglica)

Water Primrose (Ludwigia grandiflora)

Fanwort (Cabomba caroliniana)

Large Flowered Waterweed (Egeria densa)

Floating Pennywort (Hydrocotyle ranunculoides)

Australian Swamp Stonecrop (Crassula helmsii)

Parrot’s Feather (Myriophyllum aquaticum)

Water Fern (Azolla filiculoides)

Nuttall’s Pondweed (Elodea nutallii)

Canadian Pondweed (Elodea canadensis)

Curly Waterweed (Lagarosiphon major)

Wireweed (Sargassum muticum)

Gyrodactylus salaris

North American Signal Crayfish (Pacifastacus leniusculus)

Zebra Mussel (Dreissena polymorpha).

Chinese Mitten Crab (Eriocheir sinensis).

Slipper Limpet (Crepidula fornicata)

Didemnum Tunicates / Sea Squirts (Didemnum vexillum)

American Mink (Mustela vison)

Asian Topmouth Gudgeon (Pseudorasbora parva)Ruddy Duck (Oxyura jamaicensis)

Minnows (Phoxinus phoxinus)

Ruffe (Gymnocephalus cernuus)

Orfe (Leuciscus idus)

Bullhead (Cotus gobio)


Distribution information was obtained from the National Biodiversity Network (NBN) gateway that records and presents presence of species in 10km2 blocks. Note that the distribution records presented in this site are largely those recorded after 1950.


These have been presented as both ecological and economic and were compiled from a number of different sources (see below).

Sources of Information

The information contained on the species links was obtained from the following sources:

Fisheries Research Services

Non Native Species Secretariat Fact Files

Non Native Species Secretariat Risk Assessments

Invasive Species Project Ireland (Most Unwanted)

Centre for Aquatic Plant Management

European and Mediterranean Plant Protection Organisation

Species Action Framework INNS Descriptions

Species Action Framework Training Toolkit

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