Katharina Dehnen-Schmutz1 and Kevin Walker2
1Centre for Agroecology, Water and Resilience, Coventry University, UK
2Botanical Society of Britain and Ireland (BSBI), UK
There is an increasing need for the systematic assessment of the impacts of alien species, and criteria for consistent assessments have been developed (Bartz & Kowarik 2019). One widely used scheme is the IUCN EICAT framework (Environmental Impact Classification of Alien Taxa, https://www.iucn.org/theme/species/our-work/invasive-species/eicat ) which has recently been used in an assessment for alien taxa in Great Britain (in preparation). This assessment was conducted at the national level by groups of experts from their knowledge of published evidence, anecdotal knowledge and own field experience. However, at the regional level and from the knowledge of local field recorders, the results could be different.
The division of the British Isles into vice counties, based on a recording scheme devised in 1852 and maintained to this day by the Botanical Society of Britain and Ireland (BSBI) for botanical recording offers a scale suitable for comparative impact assessments at regional scales. Vice counties have an average size of about 2000 sqkm, and volunteer vice county recorders are appointed by the BSBI to keep records for their respective vice county. They are therefore likely to have good knowledge and field experience of alien plant occurrences in their vice county.
In this study, we contacted all vice county recorders and asked them, using the EICAT framework, to name the ten highest scoring alien plants at the level of the vice county they are responsible for. The online survey provided definitions about the different impact categories, confidence scoring as well as a habitat classification scheme. We also asked them to score the ten highest scored species from a GB national impact scoring exercise conducted in 2016 using the same methodology.
An analysis of the responses for 45 vice counties shows that 410 scores for 130 species in total were reported with the most frequent species Fallopia japonica listed by 32 vice county recorders, and other frequent species being Impatiens glandulifera (27), and Rhododendron ponticum (26). In terms of impacts, most records were scored as either having “major” or “moderate” impacts, however, 51 were scored in the highest category of “massive”. Among these, R. ponticum was the most frequent, which is also the only species scored in this category for current impacts in the assessment for Great Britain. Among the species reported were also several species that were not considered in the GB assessment, with some of them scored to have massive impacts at vice county level. This shows that national assessments broken down into several separate regional assessments can also be useful to identify species that are not currently considered as high impacts nationally.
Bartz R. & Kowarik I. (2019) Assessing the environmental impacts of invasive alien plants: a review of assessment approaches. NeoBiota 43: 69–99.