In the Dutch Species Catalog, we use a internally controlled set of codes for the occurence (or presence) status of species. This page contains an overview of these codes in English, for non-Dutch people who downloaded the catalog via GBIF.
The list of established species occurring in The Netherlands comprises those with categories 1a, 2a and 2b.
Reported for The Netherlands, but validity of the observation and status of the taxon have yet to be determined.
0a Reported correctly, to be refined
Reported from The Netherlands based on valid observation(s), but exact status has to be determined.
1 Indigenous (undetermined)
Indigenous to The Netherlands or reached the country on its own. Excact status to be determined.
1a Indigenous: native species
Indigenous to The Netherlands, with at least 10 consecutive years of reproduction. Native species.
1b Indigenous: incidental/periodical species
Reached The Netherlands on its own, with less than 10 consecutive years of reproduction. Includes accidental guests and species which occur(red) periodically (e.g. non-breeding wintering species).
2 Introduced (undetermined)
Introduced by humans, exact status to be determined.
2a Introduced: at least 100 years independent survival
Introduced by humans, and survived independently for at least 100 years after introduction (reproducing in the wild).
2b Introduced: 10-100 years independent survival
Introduced by humans, and has independently survived between 10 and 100 years (reproducing in the wild).
2c Introduced: less than 10 years independent survival
Introduced by humans, and has independently survived for less than 10 years (reproducing in the wild).
2d Introduced: incidental import
Introduced by humans, but not reproducing in the wild. In many cases these species will not be registered.
NB. For long-living species such as trees only 2a (minimum three generations, three locations), 2c and 2d apply.
3a Data deficient
Reported from The Netherlands, but exact status is unclear. Includes species without adequate reference, incidental reports without interpretation, or dubious reports in literature without provided evidence.
3b Incorrectly reported
Reported from The Netherlands, but incorrectly, for example as result of an identification error.
3c To be expected
Not reported from The Netherlands, but might occur here (or can reach the area in the near future), based on observations from neighbouring countries. 3cE is used when this category applies to an introduced species.
3d Incorrectly used name (auct.)
Incorrectly used name, for example as a result of an error in an identification key (auct. nec cases). Only for species that do not occur in The Netherlands. When it is clear that a name has been reported from The Netherlands, status 3b is used instead.
Names that do no directly apply to The Netherlands, but have been included for other reasons.