Water Environment and Water Services (Scotland) Act 2003 implementation: environmental standards - consultation

Consultation seeking views on our proposals for new or updated environmental standards for Scotland’s water environment, and updates to some of the assessment methods used for deriving such standards.

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.

Table 11.1: Additions to the existing list of High Impact non-native invasive species
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[9].

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.

Table 11.2: Comparison of the existing and proposed new Invasive Non-Native Species ( INNS) list classification
Class Existing INNS list classification New proposed INNS list classification Net change
High 0 95 +95
Good 144 49 -95
Moderate 43 43 0
Poor 0 0 0
Bad 0 0 0

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.


Email: eqce@gov.scot

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