Threatened species occurrences, Denmark 1991-2015

Industrial PhD-project 2015-2018 conducted by Erik Buchwald.

Denmark excluding marine and fully aquatic areas. Amphibious species included. The quality-checks (see below) yielded detailed occurrence data (N= 267,556) for 1,378 species in 24,317 localities counted as different 100 x 100 meter grid cells.

Species occurrence records were collected and compiled from all relevant sources available in digital formats (more than 22 million records from e.g. ministry databases, NGO citizen science databases and university & museum databases) supplemented by a few detailed inventory studies on beetles, spiders or lichens which were digitized as part of the project (see Table in separate pdf file http://digit.snm.ku.dk/DanBIF/EBuchwald_GBIF2018DataSources/S1%20Table.pdf ). Only records regarding the study species were used and only if data on at least year and detailed locality were recorded or could easily be extracted from supplementary information. In order to use as up-to-date occurrences as possible without leaving out too many overlooked extant occurrences, records from the last 25 years were used (1991-2015). For birds only certain and probable breeding records were used, delimited by the methods applied in Danish Breeding Bird Atlas I, II & III regarding activity type and dates of breeding season. Locality names and coordinates were cross-checked and corrected in records with more than one type of locality information. Locality names were standardized for typing errors etc. and extended with municipality in order to separate synonymous names. Up to more than 15 different sites had the same name, e.g. Nørreskov (Northwood), which in some cases had led to wrong automatic coordinates being applied by some data providers. The data providers had varying levels of quality assurance of their data, so records were carefully and intensely scrutinized as an extra quality control with focus on regionally extinct and very rare species without proper documentation, and on uncertain or inaccurate localities. More than 1500 records for study species were thus excluded and a similar number corrected. Examples include an almost extinct lake-bottom plant noted from forest floor, and long extinct species recorded outside potential range/habitats and without having comments proving their validity or being published in other ways. Other records were marked with "cf." in GBIFs "identificationVerifier" colomn because of suspicion that the recorded species or location might be incorrect being very rare or outside normal range and with no remarks in the original data about the record being unusual. The errors and suspicions were documented in the files with comments on unused records.

The Danish Nature Agency & Danish Innovation Foundation.