Landscape-scale impacts of transportation infrastructure on spatial dynamics of two vulnerable ungulate species in Ghamishloo Wildlife Refuge, Iran
Introduction
Modern human-dominated environments are subject to frequent and intense environmental perturbations (Mcdonald et al., 2009). Transportation infrastructure that enhances connectivity among human settlements often results in decreased connectivity among remaining natural habitats and wildlife populations (Forman and Alexander, 1998). Habitat fragmentation and the creation of barriers by transportation infrastructures reduce landscape connectivity, which is suspected to be one of the most important factors causing wildlife population declines (Borda-de-Água et al., 2011, Forman et al., 2003). Road networks affect wildlife habitats in different ways. First, road construction directly leads to a habitat loss. Second, maintenance and use of roads reduce habitat quality for wildlife by increasing distance between remaining habitat patches (Goodwin and Fahrig, 2002), and via additive barrier and mortality effects (Ascensao and Mira, 2006, Eigenbrod et al., 2008, Hoskin and Goosem, 2010, Jaeger et al., 2005, Shepard et al., 2008). This may hamper dispersal, which is critical for the long-term population viability of wildlife species (Debinski and Holt, 2000, Laurance et al., 2002, Lienert, 2004). By altering habitat area and spatial distribution of habitat patches, road networks affect the structure and spatial heterogeneity of a landscape. Development of roads in protected areas and ecological sensitive regions can have deleterious effects on wildlife populations (Lian et al., 2011). In addition to these primary impacts, roads may also provoke various secondary effects on protected areas. They may facilitate access to hunters, poachers and uncontrolled tourism (Gratson and Whitman, 2000). In addition new roads commonly promote economic development which may compromise conservation goals.
Far-ranging mammals such as large herbivores are particularly sensitive to habitat fragmentation because they need unrestricted access to large continuous habitat (Bolger et al., 2008). Fragmentation of habitat into small, non-contiguous patches may result in dramatic population declines (Simmons et al., 2010). Furthermore, small and isolated subpopulations are Eigenbrod et al., 2008; vulnerable to demographic, genetic, and environmental stochasticity (Fahrig, 2003).
Not withstanding these negative ecological impacts, road networks grow and get denser worldwide due to increasing socio-economic needs for high mobility (Coffin, 2007, Shanley and Pyare, 2011). In Iran, road construction in ecologically sensitive habitats, i.e. protected areas and national parks, has been increasing during the past decades and ecological impacts have become highly visible (Momen Bellah Fard, 2009, Monavari and Mirsaeed, 2008).
In most cases, the ecological value of existing wildlife habitat has been considered of secondary importance in the face of compelling economic and social arguments for road construction. Assessment of ecological impacts of road construction is commonly hampered by a lack of appropriate data. Thus appropriate studies quantifying habitat loss and landscape pattern changes are essential. Further, there is a lack of studies on their impacts on animal species distribution and migration.
Here we provide quantitative data on habitat loss and landscape fragmentation due to Isfahan's West Freeway, which passes through Ghamishloo Wildlife Refuge, I.U.C.N category IV, Habitat/Species Management Area, in Isfahan Province of Iran. The two key affected species in the study area were goitered gazelle (Gazella subgutturosa subgutterosa) and wild sheep (Ovis orientalis isphahanica), both classified as Vulnerable (VU) on the IUCN Red List (Mallon, 2008, Valdez, 2008). The following questions were investigated in this study:
- (1)
How did habitat changes due to road construction affect the distribution of goitered gazelle and wild sheep?
- (2)
How does an existing freeway affect habitat quality and quantity of the large herbivores in Ghamishloo Wildlife Refuge?
- (3)
How landscape metrics such as MNN (mean nearest neighbor); NP (number of habitat patches) and degree of landscape fragmentation have been changed due to road disturbance effects?
Section snippets
Study area
Our study area, Ghamishloo Wildlife Refuge is located 45 km northwest of Isfahan City, Iran (Fig. 1). Ghamishloo is located at 50°59′43″ to 51°28′09″ eastern longitude and 32°40′05″ to 33′02′24″ northern latitude and covered an area of approximately 113′653 ha. This area is covered with plains, mountains and rolling hills. The climate in this region is semi-arid and continental, with average temperatures ranging from −18.5 to 41.5 °C (hot dry summers, and cold dry winters), and mean annual
Goitered gazelle
Based on a literature review five habitat suitability variables were identified for the goitered gazelle. A final habitat suitability map was prepared based on formula 1, which was adopted from Farmer (1981), Ashley and Berger (1999) and Larson et al. (2003), and classified based on Table 6. Goitered gazelle occurrence in each HSI category before and after freeway construction is shown in Fig. 2A.As shown in Fig. 3A, part of northern and eastern sections of the
Discussion and conclusion
We examined the impact of a freeway passing through Ghamishloo Wildlife Refuge on habitat integrity for G. subgutturosa and O. orientalis isphahanica. Our results demonstrate that the freeway not only reduced the area of the original habitat in the refuge for the two vulnerable ungulate species (Fig. 5, Fig. 6) but also further represents a barrier and restricts gene flow between remaining habitat patches. Remaining habitat patches now represent islands in terms of limited area, isolation and
Acknowledgements
We express our appreciation to the Department of the Environment (DOE), Isfahan Provincial Directorate of Environmental Protection for providing us various information on the study area. We are grateful to guards of Ghamishloo Wildlife Refuge, local people and all volunteers, who helped in the fieldwork.
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