A GIS-based policy support tool to determine national responsibilities and priorities for biodiversity conservation

create larger polygons by a simple dissolve procedure that aggregates all objects with the same attribute in the next highest level unit relative to the original scale. These new, enlarged poly- gons can then be used as natural reference areas based on biogeographical units. Alternatively, geographical units, such as continental borders, or administrative units, such as the member states of the EU, can be used for the creation of the reference area polygon. Assessing the distributions. When distribution data have been obtained for the selected species, distribution areas are designated as “local,” “regional,” or “wide” based on the number of biogeographical units covered by the distribution area of the selected species. This step fol- lows the recommendations of Schmeller et al. [1, 7]. Alternatively, categorization can be based on the area of overlap with biogeographical units (see S2 File for examples). Two classifications of biogeographical units are available in the NRA-Tool for terrestrial ecosystems: The Terrestrial Ecoregions of the World (TErW, [53]) and the Global Environ- mental Zones (GEnZ, [50]). Both classifications subdivide their first level units (Terrestrial Ecoregions resp. Global Environmental Zones) into sub-regions of a lower geographical extent based on additional regional criteria. Following arguments provided by Schmeller et al. [1], we strongly suggest using GEnZ [50, 54] as biogeographical units for implementation at the conti- nental and global scale. Notably, the NRA-Tool also provides a spatial assessment of conserva-

tion priority in the form of maps and associated attribute tables for all focal areas. Our tool is not limited to analyses of terrestrial ecosystems. The architecture allows for any ecosystem classification, provided the layers consist of a complete set of spatially inclusive and comprehensive polygons fully covering the reference area. Thus, the NRA-Tool can be used to perform global assessments of species living only in freshwater ecosystems or even species that are exclusively marine [55, 56]. Workflow. The workflow (Fig 7) starts with the selection of the taxonomic unit (TU) to be analyzed from the dataset of all taxonomic units. The distribution pattern is then classified as “local,” “regional,” or “wide” based on the shapefiles of the reference area and the focal areas, and the distribution of the taxonomic unit with respect to the focal species. In the second step, the NRA-Tool calculates the expected and observed distribution areas and determines national responsibility scores and conservation priorities for the focal species as described above. As an output, conservation priority classes are assigned to all or selected countries or regions for the focal species. The results are provided as maps (shapefiles) with respective attri- bute tables containing the values of national responsibility scores and/or conservation priority of the assessed focal species. The tool also provides the same information and a short summary in an ASCII text file that can be stored digitally for further analyses or visualization.

The NRA-Tool offers two options for classifying distribution patterns: the Polygon Count- Approach (PC-A) [1, 7] and the Polygon Area-Approach (PA-A). The difference between the Polygon Area-Approach and the Polygon Count-Approach option is the way biogeographic Table 2. Classes of conservation priorities based on scores (in brackets) for national responsibility and IUCN threat status following [36]. IUCN Category National responsibility Very high High Medium Basic Extinct in the wild Class 1 (25) Class 1 (20) Class 2 (17) Class 2 (16) Critically Endangered Class 1 (22) Class 2 (17) Class 2 (14) Class 2 (13) Endangered Class 1 (20) Class 2 (15) Class 3 (12) Class 3 (11) Vulnerable Class 2 (18) Class 2 (13) Class 3 (10) Class 4 (9) Near Threatened Class 2 (16) Class 3 (11) Class 4 (8) Class 4 (7) Least Concern Class 3 (11) Class 4 (6) Class 4 (3) Class 4 (2) Data Deficient Not Evaluated https://doi.org/10.1371/journal.pone.0243135.t002 PLOS ONE GIS-based policy support tool to determine national responsibilities for biodiversity conservation PLOS ONE | https://doi.org/10.1371/journal.pone.0243135 December 3, 2020 11 / 23