Socio-ecological assessment of threats to semi-arid rangeland habitat in Iran using spatial models and actor group opinions

Highlights

• Habitat quality was modeled using the InVEST model and field-geospatial data.

• Relationships between habitat quality and species diversity were assessed.

• Different senarios were spatially analyzed to reveal the most important threats.

• Social value of ecosystem services and disservices were identified across local actor groups.

• Main threats to rangelands were assessed across actor groups.

Abstract

Key to the sustainable management of rangelands is identifying socioeconomic and ecological threats to the structure and function of historically grazed ecosystems. We studied how recent anthropogenic factors associated with globalization and urbanization could affect habitat quality and biodiversity as well as actors in a historically grazed rangeland basin in Iran. We used an approach that integrated field data, a spatially explicit ecosystem service model, and actor group opinions concerning threats to rangelands. We found low habitat quality in downstream areas where agriculture predominates. Significant relationships were also found between the Simpson diversity index and habitat quality; thus corroborating our modeling results. Actors and experts ranked grazing and agricultural activities as the greatest threats to habitat quality. Upstream areas with the highest habitat quality had the highest social value in terms of conservation efforts and ecosystem service provision. Modeling scenarios indicated that agriculture was the main threat to habitat quality, more so than grazing. Our approach shows that the historical legacy of past land use objectives that prioritized increased fodder must now be weighed against other current and future societal needs and management objectives such as food security and dust abatement.

Introduction

Rangelands are ecosystems that provide habitat for both domesticated livestock and wildlife and other functions such as biomass production, water regulation and provision, and biodiversity (Havstad et al., 2007; Sliwinski et al., 2017). Many of these ecosystems and their beneficial functions have been historically degraded and are now under threat by other more modern socioeconomic and ecological factors of global concern (Harris, 2010). Rangeland degradation not only includes the loss of biodiversity, decreased primary productivity, decreased water quality, and lower livestock production (O'Connor and Crowe, 2005); but also the loss of other beneficial ecosystem functions referred to as Ecosystem Services and Goods (ESG; Havstad et al., 2007).

There is also a well-documented relationship between rangeland degradation and increased poverty (Bedunah and Angerer, 2012; Pinto et al., 2014). Similarly, semiarid rangeland habitat quality has historically - and currently - affected ESG provision and overall societal welfare in places such as Australia and North America (Havstad et al., 2007; Greiner et al., 2009; Brown and MacLeod, 2011; Alamgir et al., 2014). However, there are few studies from central Asia regarding historically degraded rangelands and how they have been directly and indirectly affected by conventional social and ecological (e.g., droughts, overgrazing and conflicts) and other more modern socio-economic factors (e.g, growing populations, food security and urbanization; Mofidi et al., 2013; Behmanesh et al., 2015; Farimani et al., 2017; McNeely, 2003; Bedunah and Angerer, 2012).

In the central Asian republic of Iran, semiarid rangelands – as opposed to those of Australia and North America - have experienced 1000s of years of livestock use, overgrazing, pastoral activity, and droughts (Vahidi et al., 2014). Agriculture has also been historically important in supplying key ESG to small and intermediate sized urban centers in Iran (Khorami and Pierof, 2013). More recently, Iran has experienced modern changes that have altered the type and intensity of these socio-ecological disturbances (Kazemipour and Mirzaie, 2005). According to the World Bank (2017), the percent of urban population alone in Iran during 1960–2016 increased from 34 to 74%. With increased population and globalization, demand from growing urban areas has transformed rural populations and ecosystems. Much of this change is due to the increased demand for energy resources, food, and other ESGs such as medicinal and industrial plants (Eriksen and Watson, 2009) and new markets for livestock production and handicrafts from pastoral communities (FAO, 2006).

These changes have prioritized rangeland ecosystem and habitat condition assessments for resource managers in order to restore degraded ecosystems and sustain the supply of ESGs (Thackway et al., 2006; Havstad et al., 2007). Jansen et al. (2004) defined ecosystem condition as, “The degree to which human-altered ecosystems diverge from local semi-natural ecosystems in their ability to support a community of organisms and perform ecological functions”. Accordingly, “habitat quality” is regularly used as a key indicator of ecosystem status and changes that result from human activities (Juan et al., 2011).

An ecosystem condition assessment measures the change or alteration of a given site relative to other reference sites (Zerger et al., 2008). These changes can be monitored and evaluated using biophysical attributes and metrics of the available biophysical resources required for survival, reproduction, and population persistence (Hall et al., 1997). In general, improved habitat quality is found in more “pristine” ecosystems relatively less affected by humans; conversely low habitat quality is often associated with increased anthropogenic activity (McKinney, 2002). However, measuring habitat quality using these definitions in data poor contexts is difficult (Gibson, 1994) and particularly in rangelands that have been overgrazed for millennia such as most semiarid rangelands in Iran (Mesdaghi, 1995). Determining habitat quality and land use activities in these socio-ecosystems is therefore necessary to ensure the stability and continued provision of semi-arid rangeland ESG in historically grazed areas (MA, 2005; Shoyama and Yamagata, 2014; Liao et al., 2013).

Poor management practices are also influential drives of rangeland degradation across the world (Harris, 2010; Petz et al., 2014; van Oudenhoven et al., 2015). Overgrazing, wildfire, and introduction and establishment of invasive species are causing changes in ecosystem structure and forage composition (Daryanto and Eldridge, 2010). But, with increased modernization, globalization, and population growth, there is a growing need for agricultural land, infrastructure, urban development, mining, logging, and water development and as such, these are now considered the main threats to habitats across the world (Wilcove et al., 1998). Overgrazing and drought have been identified and studied as the more conventional causes of degradation in Iran's rangelands (Foltz, 2002; Mesdaghi, 1995). However, Kyriazopoulos et al. (2013) found that urban development and wild fires are the greatest threats to Mediterranean rangelands based on citizen perception. But, there is little information regarding how these more modern social, ecological and economic factors (socio-ecological hereafter) are cumulatively affecting habitat quality and the supply of ESG in historically grazed, semiarid rangelands in Iran.

Rangeland ecosystems are socio-ecological systems that need to incorporate actors, their values and opinions as part of their management (Havstad et al., 2007). For more sustainable management of rangeland ecosystems, the social value that people assign to changing landscapes is a key component for environmental management and planning (Menzel and Teng, 2010). In North America and Australia, socio-cultural valuation is regularly used as part of quantifying and mapping the supply and demand for ESG from rangelands (Havstad et al., 2007; Alamgir et al., 2014).

Therefore, the aim of this study was to better understand how recent anthropogenic factors associated with globalization and urbanization could affect both habitat quality and biodiversity in historically grazed rangeland ecosystems in a representative basin in Iran. To do so, our objectives were three-fold. First, we used the Integrated Valuation of Ecosystem Service and Tradeoff (InVEST) model to map the effects of continued grazing, agricultural land conversion, mining-industrial activities, and roads on habitat quality. Second, we elicited opinions from local actor groups and expert land managers to determine which factors were the greatest threats to ecosystems and what the most beneficial ESGs and detrimental ecosystem disservices (EDs) were. Third, we integrated expert elicitations and the InVEST model to assess and map threat scenarios and their relative effects on habitat quality. We then discuss the opinions of the different actor groups in regards to ESGs, EDs and threats as a means to assess objectives one and two.