The brown bear (Ursus arctos) is the most widespread member of the Ursidae (Feldhamer et al. 2003). Brown bears are distributed across the northern hemisphere in North America, Europe, and northern and central Asia (McLellan et al. 2017) at elevations ranging from sea level up to 5,000 m above sea level (Sathyakumar 2006). More than 200,000 brown bears are distributed in 44 subpopulations with greater abundance in North America, Europe, and northern Asia, and fewer bears in small, fragmented populations in southern areas. The International Union for Conservation of Nature (IUCN) red list (2017; McLellan et al. 2017) reported that Russia supports the largest population of brown bears, exceeding 100,000; and in southern Asia, brown bears exist in isolated groups, which are poorly studied (Servheen 1990, Garshelis and McLellan 2004). The species is endangered in southern Asia, where mostly small, isolated populations exist in remote and rugged mountainous areas (Servheen 1990). In the Asian region, northern Pakistan supports 6 major populations of brown bear (Nawaz 2007), in the western Himalayan Mountains of Pakistan and India (Sathyakumar et al. 2012, Abbas et al. 2015) and the western Kunlun Shan, and the Tian Shan ranges in southern Asia. Similarly, western China supports a population of ∼6,000 bears and another ∼1,000 bears in the northeast (Gong and Harris 2006). The United States supports 33,000, predominantly in Alaska, and Canada has 25,000 brown bears (Ali et al. 2018). In Europe, the brown bear is distributed in 22 countries in 10 populations (Chapron et al. 2014). Although brown bears are well-studied in North America and Europe, little is known about their status and requirements for survival in Asia (Servheen 1999), which hinders conservation efforts.

The brown bear is cryptic, usually occurs at low densities even within protected areas, and usually avoids humans (Nielsen et al. 2004, Nellemann et al. 2007). Brown bears are threatened by several human-related causes. Climate change has affected range of many species by altering their habitat (Parmesan and Yohe 2003, Parmesan 2006), including that of the brown bear (Su et al. 2018). Further, human-caused mortality is a source of population decline (Schwartz et al. 2006, Lewis 2019). In addition, increasing human population and intrusion into brown bear range has resulted in habitat degradation and loss (Can and Togan 2004, Nawaz 2007). The survival of the brown bear depends on the availability of all survival components within its home range (Bjarvall 1989). Globally, brown bear abundance is stable and large (Swenson et al. 1998, Schwartz et al. 2006), but many populations have become small and fragmented. In Europe, Eurasia, and Asia, populations are being fragmented because of human encroachment on their habitat (Servheen 1990). In Japan, populations of the Hokkaido brown bear (U. a. lasiotus) have become increasingly fragmented as a result of habitat loss and other pressures (Servheen 1990, Moll 1995). Similarly, Macdonald (1995) reported that many European brown bear populations were small, fragmented, and vulnerable to extirpation. Brown bears are listed as a species of Least Concern in the IUCN red list (2017; McLellan et al. 2017).

The historical range of brown bears is poorly documented. Existing range maps from the IUCN red list show extinct (over past 500 yr) and extant ranges, which are of questionable accuracy. An improved understanding of the historical range of the brown bear is important because it shapes the current range of the species. Therefore, the objective of our study was to reconstruct the historical brown bear range (spanning ∼1,000 yr before present) and to compare it with the current range to assess changes in occupancy. We also assess the historical and current range within the context of protected areas (PAs) because such areas are considered secure habitat.

Methods

Past occurrence

We collected data on past occurrence of brown bears from all published resources available including journals articles, books, scientific magazines, newspapers, and dissertations (Fig. 1;  Supplemental material (URSUS-D-23-00020R2. Supplemental Material.xlsx) appendix). We considered the historical range of the species as its natural occurrence in the past 1,000 years, and we attempted to retrieve all authentic records of brown bears. We also collected data on brown bear habitat, vegetation type, and altitude as mentioned in the past literature. We recorded the presence of the brown bear outside the current range along with the date of occurrence. We excluded from analyses sources with inadequate information (e.g., period or location of presence, confirmed sighting). Similarly, in cases of overlapping species (i.e., American black bear [U. americanus] and Asian black bear [U. thibetanus]) that are often confused with brown bears, but particularly so in historical times when people were less aware of species identification, we only retained confirmed brown bear records.

Fig. 1.

Schematic flow sheet diagram of the method tool followed for current analysis of the historical range of the brown bear (Ursus arctos).

Spatial data on the current range of brown bears was retrieved from the current (2017) IUCN red list (McLellan et al. 2017;  http://www.iucnredlist.org) and processed to measuring the range size. We used the World Database on Protected Areas and Protected Areas of Asia ( http://www.protectedplanet.net) to examine which protected areas have lost brown bears since historical times. We also analyzed the historical and current ranges of the brown bear to investigate range contraction or expansion.

Data processing

We obtained 1,910 total locations of historical occurrence, and we retained 1,141 locations that met our criteria for analysis. We georeferenced the recorded locations in Google Earth software ( https://www.google.com/earth/about/versions/#download pro; Google LLC, Mountain View, California) to obtain latitude and longitude. We obtained the Keyhole Markup Language (KML) file from the locations, which we then exported to Quantum Geographic Information Systems (QGIS; Quantum GIS Development Team 2012) and converted into a shape file.

Brown bears have home range sizes that vary depending upon the study time, area, habitat, and food resources. For example, home ranges of male brown bears in central Sweden in boreal forests were up to 1,600 km² (Swenson et al. 2000) and 6–10 times greater than in a forested area of Croatia where resources were abundant, and home ranges were 128 km² (Huber and Roth 1993). Home ranges of male bears in the interior of Alaska and Canada can reach nearly 7,000 km² and those of females around 2,000 km² (McLoughlin et al. 1999). We used a buffer of 150 km² around each location point to approximate the space use of bears. This was done to avoid underestimation or overestimation of range size. We then used the global topographical data layer of the Google Earth (50-m resolution; downloaded from  http://www.webgis.com/terr_world.html) to remove water bodies within the range of brown bears. We used the QGIS toggle editor feature to fill in range gaps by examining the Google Earth map for any physical barrier such as mountains and rivers, and excluded aquatic areas present in the buffered range. We then joined these buffers to create a continuous polygon of the historical range (Fig. 2) and quantified it using the QGIS.

Fig. 2.

Geographic Information System (GIS) – based map showing historical range of the brown bear (Ursus arctos) on the globe. Red dots show occurrence locations of brown bear on the earth in the past.

Results

Records of the historical range of brown bears revealed a wide distribution in the northern hemisphere including North America, Europe, and Asia, in about 48 countries. Brown bear range data included locations from 420 to 600 AD in Algeria and the 1100s in Poland, but exact location records were unknown, and we excluded these locations from analyses. Thus, the oldest confirmed location was from Romania in 1790. The area of the reconstructed historical range polygon of the brown bear was estimated to be 52.2 million km², including 27.8 million km² in Asia, 9.8 million km² in Europe, and 14.4 million km² in North America (Fig. 2). The current range was estimated to be 30.7 million km² (Fig. 3), with Asia having the largest range of 19.2 million km², Europe with 6.2 million km², and North America with 5.2 million km².

Fig. 3.

Map showing comparison of the historical distribution range of the brown bear (Ursus arctos) with its current range that was retrieved from International Union for Conservation of Nature (IUCN) red list of Threatened species (McLellan et al. 2017;  http://www.iucnredlist.org) and modified for the current study.

A comparison of the historical and current ranges of the brown bear showed that the species was more widely distributed in the past (52.2 million km²) as compared with its present range (30.7 million km²), with a total decrease in area of approximately 21.5 million km² and a range contraction of approximately 41.2% (Fig. 3). In Asia, the range has contracted by a maximum of 8.7 million km² (31.3%), in North America its range was reduced by 9.1 million km² (63.2%), and in Europe the range contraction was 3.7 million km² (37.8%; Fig. 3).

We also compared and analyzed the numbers of protected areas in the historical and current ranges of brown bears. Results showed that 49,118 protected areas were within the historical range, encompassing approximately 3.5 million km². There are 18,300 protected areas in the current range of brown bears, covering an area of approximately 2.3 million km². Overall, our analysis revealed 37.37% contraction by numbers of protected areas and 34.3% contraction by size of protected areas that were present in the historical range of the brown bear.

Brown bears occur in 3 different regions of the world; therefore, for each region, we also overlapped a network of PAs with the historical and current ranges of the species for analysis. In North America, most of the protected areas retained brown bears since historical times; however, brown bears were extirpated from 1 of 10 major PAs (Table 1). In Europe, most of the major protected areas lost the brown bear species that they supported in the past, whereby brown bears were extirpated from 8 of 11 major PAs (Table 2). Similarly, in Asia, some protected areas in Kazakhstan and Russia have lost the brown bear but other protected areas in Asia have been successful in retaining the species, and 2 of 12 major PAs have lost the species (Table 3).

Table 1.

Some of the major (based on their size) protected areas (PAs) in North America that have brown bears (Ursus arctos) in their past and/or current range.

Table 2.

Some major (based on their size) protected areas (PAs) in Europe that have brown bears (Ursus arctos) in their past and/or current range.

Table 3.

Some major (based on their size) protected areas in Asia that have brown bears (Ursus arctos) in their past and/or current range.

Discussion

Brown bear coexistence with humans is a challenge for conservationists throughout the world (Treves and Karanth 2003) because the bears pose a threat to humans and their property (Dickman 2010). In contrast, they are also a key ecosystem component (Ripple et al. 2014). Ecologists agree that the biodiversity is rapidly declining because of increased human population and intervention in ecosystems (Whittaker et al. 2005), and increased extinction risks for megafauna are linked with increased human activity and climate change (Albrecht et al. 2017, Lemoine et al. 2023). Quantification of historical ranges of threatened megafauna is a prerequisite for the development of conservation and restoration policies (Laliberte and Ripple 2004). Our definition of historical range used the occurrence of brown bears anywhere in the world for the past 1,000 years since the glacial retreat about 11,000 years ago that resulted in changes in the range of brown bears (Davison et al. 2011). Similarly, Mahmood et al. (2021) analyzed the historical range and reported contraction of 10 megafauna species, showing severe range contraction for Asiatic lion (Panthera leo; 99.99%), Indian rhino (Rhinoceros unicornis; 99.8%), Sumatran rhino (Dicerorhinus sumatrensis; 99.9%), Javan rhino (Rhinoceros sondaicus; 100%), Asian elephant (Elephas maximus; 95%), tiger (Panthera tigris; 92.9%), Malay tapir (Tapirus indicus; 98%), and common leopard (Panthera pardus; 73%). They highlighted that PAs had lost many of these megafauna species since historical times and many do not harbor one or more large megafauna they once had. Similarly, Mahmood et al. (2019) reported that the range of snow leopards (Panthera uncia) contracted about 69% from 10.47 million km² to its current range of 3.20 million km².

Accurate density and population estimates are needed to manage bear populations (Miller et al. 1997). During the previous century, abundance and range of some Ursidae were reduced by up to 50% of their historical range and abundance (Servheen 1990), and mortality caused by humans was the major source of population decline (Schwartz et al. 2006, Lewis 2019). Similar to our results, brown bear range contracted up to 53% in North American (Laliberte and Ripple 2004). The range reductions were greater in the southern and eastern areas of North America and the species was eliminated from 98% of its historical range during past century in the lower 48 states, one reason being increased human settlement (Mattson et al. 1995). Thirty-one of a total 37 North American brown bear populations present in 1922 were eliminated by 1975, with the greatest reduction during the 1920s to 1930s (Servheen 1999). In Asia, current brown bear range is <50% of its historical range (Servheen 1990).

In the above-mentioned studies, the range records of brown bears were estimated individually in some countries, but data on the global range of the brown bear in historical times are lacking. Therefore, we reconstructed the global historical range of the brown bear using all available information. Our findings report a global historical range of brown bears of approximately 52.6 million km². Spatial data on the current distribution of brown bears from (McLellan et al. 2017) revealed global range of approximately 38.8 km². Our results indicate that the brown bear had a much larger range in the past with a contraction of approximately 14.8 million km² or approximately 28%. Asia (30%) and North America (36%) lost more of the historical range compared with Europe (10%). The contracted brown bear range is similar to that of other megafaunal species, as noted above, and each of these species lost >50% of their historical range. Brown bear range is least studied in Asia, where small, isolated populations exist mostly in remote mountainous areas. Brown bear range loss in Asia was estimated at up to 50% (Servheen 1990, Garshelis and McLellan 2004). Using bioclimatic variables and biophysical data in Central Asia and the Asian highlands, Su et al. (2018) predicted that that brown bear habitat may be further reduced by 11% by 2050. Similar range contractions were notable in France where brown bears were extirpated from most of the country during the 20th century and now only survive in the Pyrénées Mountains, with only 5 bears remaining in the western area in 1995 (Martin et al. 2012). However, European brown bear populations, located in 22 countries, were stable or even slightly expanding (McLellan et al. 2017) as a result of conservation activities (Zedrosser et al. 2001).

Results of historical range analysis of brown bears also showed that the species was present in 62,234 PAs covering approximately 3.89 million km² whereas at present only 33,303 PAs encompassing 2.75 million km² harbor the species, indicating that even PAs have lost the species. However, this result depends on when the bears disappeared and when the areas were protected because brown bears may have been extirpated before a PA was created. In this context, brown bears have been extirpated from approximately 1.14 million km² area under PAs globally, which raises questions about factors that have contributed to the loss. Habitat loss in PAs may cause brown bears to move into nonprotected areas in search of favorable conditions and food, which may result in more human–bear conflicts and increased bear mortalities. However, factors other than human intervention may also be responsible for their extirpation. For example, climatic factors (e.g., temperature and precipitation) and food may have contributed to their loss from the PAs and range contraction. In the long term, planning and management is more effective in ensuring large carnivore conservation in PAs as well as non-PAs if it is based on accurate range information (Minin et al. 2016) because these species have large ranges and spatial requirements (Kojola et al. 2006, Ripple et al. 2014). Nevertheless, PAs have an important role to play in conserving brown bears.