# Developing a GIS Model for Identifying Bear Corridors with Open-Source Data: The Romanian Context
## 1 Introduction  
The brown bear (_Ursus arctos_) is part of the _Ursidae_ family, along with seven other species that are widespread on Earth [1]. Historically speaking, brown bears were widespread throughout Europe, North America, northern Mexico, Asia, the Middle East, and North Africa, but prolonged exploitation over the course of several centuries led to the extinction of the brown bear in several countries [2, 3]. Currently, global estimates of the population of _Ursus arctos_ indicate that it exceeds 200,000 specimens. Population appraisals, which are derived primarily from tagging or capturing and appraising the specimens, exist for several areas in North America and Europe [4, 5]. At the European level, the brown bear is present in 22 countries and can be categorized, based on geographical distributionand ecological factors, into 10 subpopulations: Scandinavian, Karelian, Baltic, Carpathian, Dinaric-Pindos, Eastern Balkan, Alpine, Abruzzo, Cantabrian, and Pyrenean [2,6]. The largest subpopulation in Europe is the Carpathian one, exceeding 8000 specimens, most of them dwelling in the Romanian Carpathians according to IUCN data [7] (The International Union for Conservation of Nature). The brown bear belongs to the category of large carnivores, and it can be found in the entire mountain area, where 93% of the population is concentrated, with the remaining 7% in the hilly areas of the Carpathians and Subcarbathians in Romania [8] (Figure 1). The brown bear is both a key and an umbrella species for functional ecosystems [9]. Its presence at the top of the trophic pyramid influences the area ecologically and ethologically, directly and indirectly impacting a variety of species, and has an important role in fauna conservation and the function of the ecosystem [10]. The brown bear population in Romania has grown significantly over time, a change caused by several factors, the most important of which are the absence of sustainable management by the government and anthropogenic development in their habitats. Currently, the population of bears is constantly increasing, exceeding the optimal number of specimens that can be supported by the habitats of Romania, which leads to the emergence of conflicts between bears and the human population. The bears tend to use the highest quality habitats to feed [11], which leads to very high densities in certain areas of Romania, but at the same time there are also habitats of the same quality where the bear density is very low or where bears are not present at all. The reason why the bears do not reach these habitats is due to their fragmentation and by the lack of ecological corridors [12]. These ecological systems were, are, and will be  
Figure 1: Geographical position of the study area. constantly degraded by human development, as the transport infrastructure built up to this moment creates barriers to the movement of bears and other wide-ranging or habitat-specific organisms [13]. This insufficiency leads to the interruption of connectivity between habitats of the same quality and to the creation of barriers in the development of ecosystems, where both the bear population and other plant and animal species remain isolated. At the national and international level, several projects aimed at the ecology of large carnivores have been developed in recent years, addressing, among others, topics related to ecological connectivity [14]. Geographic Information System (GIS) technology provides the necessary tools to be used by researchers to identify habitat fragmentation [15], assess habitat quality [16], establish optimal movement routes for wild animals [17; 18], and to preserve connectivity between favorable habitats. To have a clear vision of the habitats of the brown bear within the study area, geospatial modelling was performed, considering all the factors that make up the habitat of this species using open-source data.