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| ŠUMARSKI LIST 5-6/2021 str. 68 <-- 68 --> PDF |
Birds and Habitats Directives and Convention on Biological Diversity (Fleurke and Trouwborst, 2014), which resulted in the designation of the European Natura 2000 network. This is comprised of a network of ecologically important sites selected to ensure the long-term survival of Europe’s most valuable and threatened species and habitats. Results of these actions are notable, with evidences of recovery of both large carnivore and herbivore populations (Apollonio et al., 2010; Chapron et al., 2014; Linnell et al., 2016b). The South-eastern Europe is part of the Balkan Peninsula in Mediterranean basin, linking Central Europe with Asia Minor. It is one of the three European glacial refugia, and is a part of one of the world’s 36 biodiversity hotspots (Zachos and Habel, 2011; Noss et al., 2015), with an area-adjusted mammal species richness significantly higher than in the rest of Europe (Kryštufek, 2004). However, the conservation value of transboundary management of wildlife populations in the South-eastern Europe has come under huge pressure since 2015 due to the border fence constructions in response to large influxes of refugees/migrants from Asia and Africa. In the wider region (Fig. 1), in the time when this study was done extensive fences existed between the state borders of Slovenia–Croatia (178 km), Hungary–Croatia (136 km), Hungary–Serbia (175 km), Greece–Turkey (182 km), North Macedonia–Greece (30 km), and Bulgaria–Turkey (233 km) respectively (Linnell et al., 2016b; Pokorny et al., 2017). Fences that reduce movement over a range of spatial scales can be a threatening process for populations of large mammal species (Kowalczyk et al., 2012; Linnell et al., 2016a; 2016b; Pokorny et al., 2017). In the case of large mammals, such barriers can reduce the carrying capacity of habitats (Ben-Shahar, 1993; Forman et al., 2003) and threaten species by limiting access to resources, thereby leading to population decline (Olson et al., 2009; Ito et al., 2013; Olson, 2014). Fences that limit dispersal can alter gene flow, leading to genetic isolation of populations (Martinez et al., 2002; Epps et al., 2005; Daleszczyk and Bunevich, 2009), and compromise the ability of prey species to avoid predation (Davies-Mostert et al., 2013). Fencing also raises animal welfare concerns, as animals may become ensnared in the fence and die in agony (Harrington and Conover, 2006; Olson et al., 2009; Pokorny et al., 2017). Border fences present a significant threat to wildlife due to their large continuous lengths, and the inability to mitigate their effect on wildlife populations without compromising their security (Linnell et al., 2016b). Several studies have investigated conservation issues associated with border fences: for example, earlier extinction is predicted for the ferruginous pygmy owl (Glaucidium brasilianum) population due to the United States–Mexico border fences (Doublet, 2011), gene flow in European bison (Bison bonasus) is impacted by the barrier between Belarus and Poland (Daleszczyk and Bunevich, 2009), and at the Mongolian–Chinese border, Mongolian wild asses (Equus hemionus hemionus) have restricted access to expansive plains of habitat (Kaczensky et al., 2011). Considering Croatia, Safner et al. (2019) did not detect any historical barrier effect of the river Kupa (which might act as a natural barrier along a part of Slovenia–Croatia border) on genetic structure of transboundary population of Northern chamois (Rupicapra rupicapra); however, as the state border along the river Kupa was fenced in 2015, which has caused important additional ungulate mortality (Pokorny et al., 2017), previous free transboundary gene flow may be seriously interrupted by the border fence. At present, more investigation is required to identify threats of border fences to both animal mortality and population connectivity. As the Croatian border is in a large part fenced towards Hungary and Slovenia, and the existence of relevant databases on wildlife (particularly ungulates) mortality enables relevant insight into the issue, we used fences at the Hungary–Croatia border as a relevant case study of the influence of the border fencing on wildlife populations. However, as their construction is relatively recent (started in 2015), we emphasis the short-term impact, i.e. direct mortality of large mammals (ungulates) due to razor-wired fences, with predicting the possible long-term scenarios considering their barrier effect. In this paper, we present the first data on the direct effect of border fences constructed between Hungary and Croatia on wildlife populations. MATERIALS AND METHODS MATERIJALI I METODE Study area – Područje istraživanja Construction of the border fence between Hungary and Croatia began in September 2015 along approximately 136 km of the 355.5 km of the border (Fig. 1). This border fence is dual layered: towards Hungary a permanent 4 m high fence stands erect, whilst adjacent to this on the Croatian side is a razor-wired fence (Fig. 3A). The fence along Hungary–Croatia border loosely follows the rivers Mura and Drava, in Pannonian region with elevations between 63 and 242 m above sea level. Land surrounding the border is largely agricultural, and forests are predominately composed of pedunculated oak (Quercus robur), different poplar (Populus sp.) and willow (Salix sp.) species, and narrow-leafed ash (Fraxinus angustifolia). Ungulates present in the area are red deer (Cervus elaphus), roe deer (Capreolus capreolus), fallow deer (Dama dama), and wild boar (Sus scrofa). The Hungary–Croatia border fence is adjacent to the transboundary Regional park Mura–Drava protected area; nine Special Areas of Conservation |