The Word Database on Protected Areas uses two identifiers to record protected areas data. The first is the WDPA_ID which is the unique identifier of a protected area and the second is the WDPA_PID or Parcel Identifier which is the unique identifier of any parcels within a given protected area.
The WDPA PID is unique to each record in the WDPA, while the WDPA ID is unique to each protected area.
The WDPA Identifier (WDPA_ID) is a globally unique and persistent identifier for a protected area. The WDPA ID is not unique to the geography of a protected area but to the designation of the protected area. For example, a lake and its shoreline can be a Nature Reserve under a national designation but also an international Ramsar site under the Ramsar convention. This means that for the same place the WDPA will record two WDPA_IDs: one for the national site and another one for the international site.
Parcel ID's are used when in the same protected area different zones have been formally defined and delineated by the data provider e.g. different IUCN management categories.
In the November 2016 release of the WDPA a change was made to the structure of the WDPA Parcel ID (WDPA_PID) field in order to link the parcels to the parent WDPA_ID. The Parcel Identifier will be based upon the WDPA ID for that site with an additional parcel letter added to the code.
The Mexican site Archipiélago de Revillagigedo which has the WDPA_ID of 101412 has two parcels associated with it: parcel 101412_A and parcel 101412_B. The structure of the parcel ids is as follows:
[WDPA_ID], [_], Parcel Letter