11. Invasive non-native species
The 2014 Status Directions require SEPA to take account of a range of listed high impact non-native invasive species when classifying the status of rivers, lochs, estuaries and coastal waters. An alien species is defined by the International Union for Conservation of Nature and Natural Resources as a species introduced "outside its normal past or present distribution". "Invasive" alien species are those which "threaten ecosystems, habitats or species with environmental or socio-economic harm."
A high impact invasive non-native species is expected to have a significant adverse effect on the ecological quality of any part of the water environment in which it becomes established. Waters in which one or more of the species have become established cannot be classed as high ecological status. Instead, they are classed as good, moderate, poor or bad status, depending on the extent and severity of the impact they have on the other plants and animals present.
We are proposing to amend the list of species that we direct SEPA to specifically take into account in classification, adding a number of species and removing one. Our proposals regarding species added to the high impact list are summarised in Table 11.1.
|Common name||Species||Plant/ Animal/Fish||Habitat|
|High Impact||Quagga mussel||Dreissena rostriformis bugensis||Animal||Freshwater|
|Two-leaf water-milfoil||Myriophyllum heterophyllum||Plant||Freshwater|
|Gulf wedge clam||Rangia cuneata||Animal||Freshwater/ Brackish|
|Asian shore crab||Hemigrapsus sanguineus||Animal||Marine|
|Asian shore crab||Hemigrapsus takanoi||Animal||Marine|
|American lobster||Homarus americanus||Animal||Marine|
|Water Fern||Azolla caroliniana||Plant||Freshwater|
|Floating primrose willow||Ludwigia peploides||Plant||Freshwater|
|American skunk-cabbage||Lysichiton americanus||Plant||Freshwater|
|Gunnera manicata & tinctoria||Gunnera spp.||Plant||Riparian|
|Himalayan knotweed||Persicaria wallichii||Plant||Riparian|
|Japanese kelp||Undaria pinnatifida||Plant||Marine|
Elodea canadensis has been moved from the high impact list to the moderate list following risk assessment. The proposals are based on the results of detailed risk assessments undertaken by the Great Britain Non-Native Species Secretariat ("GBNNSS"). Further information about the background to the proposals is available from UKTAG.
Irrespective of whether a non-native species is listed as high impact, there are strict controls designed to prevent introductions into the wild. Further information is available from the Scottish Government. Any further proposals to revise the list will be based on the results of risk assessments undertaken by the GBNNSS.
Implications of the proposal
Table 11.2 shows a comparison of the existing Invasive Non-Native Species (INNS) classification with the new proposed classification following updates to the High Impact non-native invasive species list.
|Class||Existing INNS list classification||New proposed INNS list classification||Net change|
The removal of Elodea canadensis from the high impact list will result in 95 waterbodies reverting to High status, currently at Good. This will result in the overall classification for one waterbody changing from good to high status. It is unlikely that other additions to the high impact list will lead to existing waterbody classifications being downgraded at the present time.