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

by a common legal and economic framework and differs in shape and extent from all conti- nents and sub-continents (e.g. the European Union). To avoid pitfalls caused by special con- stellations, we recommend using the global scale as a reference area in the following cases: (i) different borderlines for a subcontinent (e.g. Europe including parts of Turkey and Kazakhstan versus an extent based strictly on national borders) [43]), (ii) inclusion or exclusion of parts of a country that are on other continents (e.g., the overseas departments and territories of France), or (iii) countries divided by a sub-continental border (e.g. Russia). Examples of the different tasks during the process of GIS analysis are shown in Figs 1–3 and Figs 5 and 6, while the identification of national responsibilities and conservation priori- ties implemented in the NRA tool is based on the decision tree shown in Fig 4 and the scores or classes derived from them in Table 2. Schmeller et al. [13] reviewed different approaches for determining national responsibilities and suggested a standardized method that is freely scalable and can provide an improved basis for setting conservation priorities. The method is also applicable to habitats or ecosystems [7] and comprises three steps (Fig 4). The expected distribution proportion (DPexp) in the focal area is the ratio of the distribution area of a species inside the reference area (sensu Schmeller et al. [36, 37]) to the total area of the reference area (Eq 1); the observed distribution proportion (DPobs) in the focal area is the ratio

of the distribution area of the species in a focal area to the total area of the focal area (Eq 2) [36, 37, 47]. DPexp ¼ Distribution Area \ Reference Area Reference Area ð1Þ DPobs ¼ Distribution Area \ Focal Area Focal Area ð2Þ To determine conservation priorities, the national responsibility assessment is combined with an assessment of the IUCN threat status of species [36, 48, 49] (Table 2). An advantage of the approaches proposed in [36] is the integration of biogeographical information, such as regions defined by co-occurrence of species, distribution of large biomes, or climatic factors, into the delineation of ecological zones [7, 40] (Figs 5 and 6). Our analysis in this example reveals that France has a high responsibility score for Sorex cor- onatus because most of the distribution of this species is within the territory of France (com- pare Fig 4 and Table 2). For two species (Sorex alpinus, Sorex minutus) France has a low responsibility score. Sorex alpinus shows preferences for alpine habitats that are less common in the focal area (France) but comprise large regions of Switzerland and Austria. For Sorex minutus, Russia scores very high on the responsibility metric because it includes a large seg- ment of this widespread generalist’s range. France has no responsibility for Crocidura sicula, which is endemic in Sicily, Italy. However, because this shrew can be found only on Sicily and a few surrounding small islands, Italy has a high national responsibility score. Description of the National Responsibility Assessment Tool

Structure. The NRA-Tool needs four predefined layers with polygons to allow assess- ments on a national to global scale (S1 File). The four types of basic layers are (i) files showing the geographical distribution of the focal species (FS, e.g. Fig 1), (ii) the physical geographical regions or spatial units that are either described by co-occurrence of floral and faunal elements (biogeographical unit, BU) or by a combination of bioclimatic factors (ecological unit/region; EcU) that substantially determine the distribution (Fig 5), (iii) the borders of the reference 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 4 / 23