Atlas Florae Europaeae (AFE) records current and historical presence of native and naturalized alien plants according to grid cells.

The taxonomic scope of mapping is taxa at the level of genera, species and (when distinguishable) subspecies. In exceptional cases infrageneric taxa (e.g. sections) can be mapped. Infraspecific taxa at the level of variety and below are ignored. Unresolved species groups may be mapped as aggregates.

In any case a single occurrence of a species in a grid cell constitutes a record. AFE makes no distinction according to a number of actual records in a grid cell (frequency) or a number of individuals in a certain locality (abundance). Except for particular cases, the background information (position and number of actual records, abundance and other field details) is not collected and not stored by AFE.

The following occurrences are qualified to include in mapping.

Native – Any occurrence which is considered native in a certain locality. A taxon may be native in a certain territory but alien in a particular locality within that territory.

A taxon is classified as native (1) if it arrived in the grid cell without intervention by man, whether intentional or unintentional, having come from an area in which it is native, and if its primary occurrences in the grid cell are in habitats that have been subjected to little or no change by man; or (2) if it has arisen de novo of native parentage in the grid cell.

Archaeophytes (aliens arrived to a certain territory prior to the beginning of botanical records) are classified as native. In the Nordic countries, it is customary to use the year 1700 as the time limit between old and new aliens (i.e. archaeophytes and neophytes), but in more southern Europe the year 1500 has been applied.

Alien – Any occurrence which is considered naturalized alien in a certain locality. A taxon may be native in a certain territory but alien in a particular locality within that territory.

A taxon is classified as alien (1) if it was brought (intentionally or unintentionally) to the grid cell by man; or (2) if it has arrived in the grid cell without man’s intervention, but from an area in which it is alien; or (3) if it has arrived in the grid cell without man’s intervention, but its primary occurrences in the grid cell are in habitats that have been created or strongly modified by man.

A taxon is classified as naturalized alien if it forms established populations or colonies in which generative or vegetative reproduction is taking place.

When original field records have no assessments of the status, for practical purposes the status may be assigned to AFE records by expert assessment or interpolation. In case of difficulties in selection between the status of native or naturalized alien, the status ‘unknown or uncertain’ may be used.

If multiple occurrences of a species in a grid cell have different status, the following priority applies. ‘Native (including archaeophytes)’ has priority over ‘status unknown or uncertain’, and ‘status unknown or uncertain’ has priority over ‘introduction (established alien)’.

Occurrences of casual aliens and cultivated plants, even in natural habitats, are never included in AFE. Persisting occurrence of casual aliens (survival) and cultivated plants (relics of cultivation) without reproduction is contrasted to naturalization and also falls outside the scope of mapping.

AFE makes distinction between current and historical occurrences of mapped taxa. A taxon which has been recorded as resident in the grid cell is regarded as extinct if it is known or judged beyond any reasonable doubt to have disappeared from all its localities, or as probably extinct if there are good grounds for believing that it has disappeared from all its localities. Otherwise the taxon is present. For practical reasons taxa may be considered probably extinct if they were not recorded again since 1950, but this practice is not encouraged when mapping is done on the basis of historical specimens alone.

In case of concurring current and historical occurrences in a grid cell, the following priority applies. ‘Present’ has priority over ‘probably extinct’, and ‘probably extinct’ has priority over ‘extinct’.

To express different combinations of status and presence in a grid cell, mapping symbols are used on the AFE maps.