Landscape connectivity for mammalian megafauna along the Iran-Turkmenistan-Afghanistan borderland

Abstract

Habitat fragmentation threatens biodiversity, causes population isolation and reduces the availability of resources. When species ranges span geopolitical borders, management of transboundary populations and securing their connectivity can be compromised by different conservation priorities and juridical efforts. Using a combination of species distribution modelling and circuit theory, we modelled suitable habitats for four conservation-dependent mammalian megafauna in northeastern Iran, bordering Turkmenistan and Afghanistan which is part of the larger Kopet Dag Ecoregion in central Asia. Our multispecies approach aimed to identify key habitats and potential national and international corridors for Persian leopard (Panthera pardus), bezoar goat (Capra aegagrus), urial (Ovis orientalis) and goitered gazelle (Gazella subgutturosa) based on environmental variables. Between 18 to 34% of the study area was identified as suitable habitat for each species with a moderate variability in coverage by conservation network, ranging between 14 to 43%). Importantly, we identified three key landscapes which can enhance the connectivity between main populations of the species in northeastern Iran as well as neighboring countries. Most of the suitable landscapes along the Iran-Turkmenistan borderlands are protected on the Iranian side, providing a source for landscape connectivity across the border. In contrast, the main suitable landscapes for megafauna in northeastern Iran are located far from the Afghan border. Our multispecies approach provided an empirical framework for spatial conservation planning for the mammalian megafauna across the Kopet Dag Ecoregion and can direct future survey efforts to identify critical wildlife areas in Turkmenistan and Afghanistan, two countries with scarce data on biodiversity.

Introduction

Habitat conversion, degradation and fragmentation, mediated by growing pressures from human actions, threaten biodiversity (Tittensor et al., 2014). Future population growth and economic development are forecasted to impose unprecedented levels of extinction risk on many species worldwide, especially large mammals of Africa, Asia and South America (Crist, Mora, & Engelman, 2017; Tilman et al., 2017).

Although geopolitical borderlands are typically rich in biodiversity, protecting these landscapes is often challenging. Borderlands are characterized by dynamic social, political, economic and sometimes even ecological transitions which, at extremes, involve armed conflicts and political instability (McNeely, 2003; Trouwborst et al., 2017). Expansion of border security barriers, particularly across Eurasia is recognized as a threat to wildlife because they can cause mortality, obstruct access to seasonally important resources, and reduce effective population size and viability (Linnell et al., 2016).

Borderlands between Iran-Turkmenistan-Afghanistan, which are part of the larger Kopet Dag Ecoregion (Memariani, Zarrinpour, & Akhani, 2016; Olson & Dinerstein, 1998) is a shared steppe landscape hosting various conservation-dependent mammals, such as Persian leopard (Panthera pardus saxicolor), bezoar goat (Capra aegagrus), urial (Ovis orientalis) and goitered gazelle (Gazella subgutturosa) (Atamuradov, Fet, Fet, Valdez, & Feldman, 1999; Farhadinia, Moll et al., 2018; Kaczensky & Linnell, 2015; Moheb & Bradfield, 2014). Nonetheless, national conservation programs have created a heterogeneous landscape across the border. There is no established network of conservation areas on the Afghan side of the border (Kanderian, Lawson, & Zahler, 2011). In Turkmenistan, many established reserves suffer from limited conservation resources (Kaczensky & Linnell, 2015). On the Iranian side, the expanded network of reserves hosts populations of the mammalian megafauna (Farashi, Shariati, & Hosseini, 2017; Farhadinia, Moll et al., 2018; Ghoddousi et al., 2016) and can potentially play as a source role for the neighbouring countries. As a transboundary biodiversity-rich landscape, the Kopet Dag Ecoregion can benefit from inter-governmental conservation initiatives.

Although some mammalian species move across the border (Farhadinia, Johnson, Macdonald, & Hunter, 2018; Kaczensky & Linnell, 2015), there is no coordinated collaboration for biodiversity conservation. Two mammalian species, Asiatic wild ass (Equus hemionus) and Asiatic cheetah (Acinonyx jubatus venaticus), both assumed to depend on transboundary movement have already disappeared from one side of the border in Iran, and Turkmenistan, respectively (Farhadinia et al., 2017; Kaczensky & Linnell, 2015; Mallon, 2007). Developing a rigorous spatial conservation framework, along with encouraging political willingness, can facilitate a transboundary partnership between the countries.

A protective strategy in environments that are facing fragmentation is creating a network of habitats through connecting corridors (Di Minin et al., 2013; Foster, Love, Rader, Reid, & Drielsma, 2017; Moqanaki & Cushman, 2017). Corridors can improve the connectivity between isolated patches and, therefore, increases the landscape’s capacity to sustain individuals, populations and meta-populations (Haddad et al., 2015; Khosravi, Hemami, & Cushman, 2018). Such a landscape-based conservation initiative requires measures that are supported by accurate information on distribution patterns and dispersal possibilities (Moqanaki & Cushman, 2017). Species Distribution Models (SDM) and circuit theory are increasingly combined to prioritize critical habitat patches and connectivity areas (Ahmadi et al., 2017; Carroll, McRAE, & Brookes, 2012; McRae & Beier, 2007).

Some mammalian megafauna, due to their extensive spatial and habitat requirements, can potentially be an umbrella for conservation planning of co-occurring species (Brodie et al., 2015; Closset-Kopp, Wasof, & Decocq, 2016; Khosravi, Hemami, Cushman et al., 2018). Assessing environmental conditions for multiple umbrella species with various habitat requirements can benefit the functionality of ecological corridors for a wider range of taxa (Brodie et al., 2015; Closset-Kopp et al., 2016; Khosravi, Hemami, Cushman et al., 2018). Accordingly, we tailored this approach to four conservation-dependent mammalian species with various habitat requirements, including Persian leopard, goitered gazelle, bezoar goat and urial which occur at all sides of the borderland between Iran, Turkmenistan and Afghanistan in central Asia.

Using a combination of species distribution modelling and circuit theory, we modelled suitable habitats for the species in northeastern Iran which is part of the larger Kopet Dag Ecoregion. Our study site was limited to Iran because species occurrence data as well as updated environmental layers were unavailable from the Turkmen and Afghan sides. We also assessed landscape connectivity among important habitat patches. Finally, we evaluated the efficacy of the existing conservation network in safeguarding the focal mammalian community in the region. Our modelling approach develops a spatial framework for launching inter-governmental transboundary partnerships across the Kopet Dag Ecoregion and can direct future survey efforts to identify critical wildlife areas in Turkmenistan and Afghanistan, two countries with scarce data on biodiversity.