Belgian baseline distribution of invasive alien species of Union concern (Regulation (EU) 1143/2014)

Aims and scope The European Alien Species Information Network team (EASIN, http://easin.jrc.ec.europa.eu) of the Joint Research Centre (JRC) requests the European member states to provide and verify the baseline distribution data of invasive alien species of Union Concern (Tsiamis et al. 2017) as provided by the EASIN mapping system (Katsanevakis et al. 2012). These are species with documented biodiversity impacts sensu the European Union Regulation on the prevention and management of the introduction and spread of Invasive Alien Species in Europe (IAS Regulation No 1143/2014) (European Union 2014). The purpose of this baseline is to set a representative geographic account of the distribution of these species at (i) country and (ii) 10km2 grid level before the entry into force of the Regulation (and the listing of species through implementing regulations). This distribution provides the baseline for subsequent reporting by the member states as required by the IAS Regulation. The dataset provides a shapefile on the baseline distribution of the invasive species of EU concern in Belgium based on an aggregated dataset (ias_belgium_t0_xxxx). Data were compiled from various datasets holding invasive species observations such as data from research institutes and research projects (76%), citizen science observatories (23%) and a range of other sources (1%) such as governmental agencies, water managers, invasive species control companies, angling and hunting organizations etc. Data were normalized using a custom mapping of the original data files to Darwin Core (Wieczorek et al. 2012) where possible. Species names were mapped to the GBIF Backbone Taxonomy (GBIF 2016) using the species API (http://www.gbif.org/developer/species). Appropriate selection of records was performed based on predefined cut-off dates (see data range) and record content validation (see validation procedure). Data were then joined with GRID10k layer Belgium based on GRID10k cellcodes (ETRS_1989_LAEA). File description The dataset contains two types of data: Shapefiles (ias_belgium_t0_2016.zip and ias_belgium_t0_2018.zip) providing the presence of the species of EU concern at 10km2 (European Terrestrial Reference System projection - 1989 ETRS_1989_LAEA) level. The attributes table field “ACCEPTED” provides coded information on the distribution validation: correct squares (Y) represent data overlapping between the collated baseline data for Belgium and the EASIN maps. Incorrect data (N) can represent records mapped on wrong 10km2 squares, non-validated records or records that fall outside of the date range applied. New squares (New) represent previously unpublished data that were absent from EASIN. The work was supervised and validated by the Belgian national scientific council on invasive alien species, an official consultative structure coordinating scientific input and data aggregation between Belgian regions and institutions with regards to technical implementation of the Regulation No 1143/2014 on invasive alien species. A geojson version of the same shapefiles (ias_belgium_t0_2016.geojson, ias_belgium_t0_2018.geojson, ias_belgium_t0_2020.geojson), in WGS84 projection. Date range The baseline distribution reflects the current status and situation of the IAS of Union concern in Belgium at 10km2 grid level. Historical records were not taken into consideration for the baseline. The choice of cut-off date was based on an analysis of the relative contribution of a year in defining the total distribution of the species at 1km2 grid level (calculated as [the sum of unique UTM 1km2 grid squares year-1/total number of unique UTM 1km2 grid squares for that species]) based on the complete dataset. The dataset comprises observations of Union List invasive species from 2000 until the entry into force for every species, hence between January 2000 (2000-01-01) and February 2016 (2016-01-31) for the species of the first batch (ias_belgium_t0_2016.zip), between January 2000 (2000-01-01) and August 2017 (2017-08-31) for the species of the first update of the Union List (ias_belgium_t0_2018.zip) and between January 2000 (2000-01-01) and August 2019 (2019-08-31) for the species of the second update of the Union List (ias_belgium_t0_2020.zip). For raccoon dog (Nyctereutes procyonoides), included in the second update (ias_belgium_t0_2020.zip) the date cut-off is 01/01/2000 to 31/01/2019. The data include both casual records as well as established populations and also comprise data from eradicated populations for the period 20002017. Validation procedure Record validation was performed to exclude dubious records, wrong identifications etc. This was done based on the IdentificationVerificationStatus field (to which validation information from original data were mapped) if available. In general, non-validated data were not considered for ias_belgium_t0_xxxx. Data were validated in the original datasets based on evidence (e.g. pictures), on the observer’s experience, or based on a set of predefined rules (e.g. automated validation based on geographic filtering). Data from research institutes were generally considered validated. A few casual records of EU list species that were clearly planted were discarded manually. When the original dataset did not mention any validation status, records were not considered validated and therefore not taken into account for ias_belgium_t0_xxxx, unless for Chinese mitten crab Eriocheir sinensis, ruddy duck Oxyura jamaicensis, raccoon Procyon lotor, Siberian ground squirrel Tamias sibiricus, sacred ibis Threskiornis aethiopicus, and red-eared slider Trachemys spp. For these species, we assumed all records were correct as they originate from dedicated sampling (E. sinensis) within research projects or represent species that are readily recognizable by people in the field. Likewise, for the second batch species, all records of Egyptian goose Alopochen aegyptiaca, Himalayan balsam Impatiens glandulifera, giant hogweed Heracleum mantegazzianum and muskrat Ondatra zibethicus (mostly derived from public eradication services) were considered validated and taken into account. For the third batch species, records of the widespread tree of heaven Ailanthus altissima and pumpkinseed Lepomis gibbosus were also considered validated. For species with less than 10 records (Salvinia molesta, Acridotheres tristis), every record was manually checked. A visual check was performed on the resulting distribution maps by representatives of the Belgian scientific council on IAS and the Belgian Comittee on IAS, two official bodies created in response to the EU Regulation within the framework of a cooperation agreement between the Belgian regions and the Federal Authority. Data in the distribution maps provided by EASIN but not present in ias_belgium_t0_xxxx were carefully checked and kept/rejected accordingly. Data providers The providers of the invasive species data for this exercise (individuals and their respective organizations) are listed in the "data providers" section of the dataset metadata. Much of the primary occurrence data that formed the basis for this aggregated dataset will be published as open data on the Global Biodiversity Information Facility (GBIF) within the framework of the Tracking Invasive Alien Species project (TrIAS, https://osf.io/7dpgr/, 2017-2020)