Aims and scope The European Alien Species Information Network team (EASIN, http://easin.jrc.ec.europa.eu) of the Joint Research Centre (JRC) requested the European member states on 22 June 2016 at the 6th IAS Committee to verify the baseline distribution data (2017) of invasive alien species of Union Concern (37 species) 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 was to set a representative geographic account of the current distribution of these species at (i) country and (ii) 10km2 grid level and to get feedback from the member states on this. 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_2016). 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 for ias_belgium_t0_2016 was performed based on predefined cut-off dates and record content validation (see further). Data were then joined with GRID10k layer Belgium based on GRID10k cellcodes (ETRS_1989_LAEA). File description The dataset (ias_belgium_t0_2016.zip) contains two types of data: A shapefile (ias_belgium_t0_2016.shp) 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 ias_belgium_t0_2016 data and the EASIN maps. Incorrect data (N) can represent records mapped on wrong 10km2 squares or records that fall outside of the date range applied for ias_belgium_t0_2016. New squares (New) represent previously unpublished data that are currently 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 shapefile (ias_belgium_t0_2016.geojson), converted to WGS84 projection. Date range The baseline distribution should reflect the current status and situation of the IAS of Union concern in each member state. No specific time period was set by EASIN, but most frequently, historical records were not taken into consideration for the baseline. For ias_belgium_t0_2016 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 invasive species observations between January 2000 (2000-01-01) and February 2016 (2016-01-31) and includes both casual data as well as established populations. It also comprises data from eradicated populations in that period. 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_2016. 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_2016, 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 scripta. 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. A visual check was performed on the resulting distribution maps by representatives in the national IAS scientific council. Data in the distribution maps provided by EASIN but not present in ias_belgium_t0_2016 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).

{"references": ["European Union (2014). Regulation (EU) no 1143/2014 of the European parliament and of the Council of 22 October 2014 on the prevention and management of the introduction and spread of invasive alien species. Official Journal of the European Union 4.11.2014, L317: 35-55.", "GBIF Secretariat (2016). GBIF Backbone Taxonomy. Accessed via http://www.gbif.org/dataset/d7dddbf4-2cf0-4f39-9b2a-bb099caae36c on 2017-01-26. doi: http://doi.org/10.15468/39omei", "Katsanevakis, S., et al. (2012). Building the European Alien Species Information Network (EASIN): a novel approach for the exploration of distributed alien species data. BioInvasions Records 1(4): 235-245. doi: http://doi.org/10.3391/bir.2012.1.4.01", "Wieczorek, J., et al. (2012). Darwin Core: an evolving community-developed biodiversity data standard.\" PloS ONE 7(1): e29715. doi: http://doi.org/10.1371/journal.pone.0029715"]}