Rangelands are the largest terrestrial ecosystems on the Earth, covering close to 40 % of the world landscape, of which more than 80 % located in arid and semi-arid areas (Branson et al., 1981). Soil is the most important component of rangeland ecosystems. It has an interdisciplinary nature and is associated with biodiversity, biogeochemical cycling, hydrology, human health and social sciences (Brevik et al., 2015). Rangeland soils moreover offer services to the human societies and make the Earth system stable (Keesstra et al., 2012; Berendse et al., 2015). Unfortunately, rangelands have undergone (and continue to undergo) rapid transformations as a result of factors such as overgrazing, deforestation, woody-plant encroachment, and invasion by non-native plant species (Wilcox and Thurow, 2006). Each of these factors has led to a reduction in the quantity and/or nutritional quality of the vegetation available for grazing; this is known as “rangeland degradation” (IFAD, 2003). This also resulted in higher soil and water losses (Cerdà, 1998; Kröpfl et al., 2011; Li et al., 2013).

It is believed that livestock grazing is associated with rangeland degradation. Grazing is the most important factor affecting vegetation and soil in all rangelands of the world, having a critical impact on rangeland biodiversity and species composition (Sharafatmandrad et al., 2014; Angassa, 2014), biological groups (Sharafatmandrad et al., 2014; Tarhouni et al., 2016), structure (Eckert and Spencer, 1987; Noy-Meir, 1979, 1993; Walker and Noy-Meir, 1982), goods and services (Papanastasis et al., 2015), functionality (White, 1979; Sousa, 1984; Hobbs and Huenneke, 1992), soil erosion (Tadesse and Penden, 2002; Palacio et al., 2014; Mekuria and Aynekulu, 2013), nutrient cycling (Frank et al., 1998; Ritchie and Tilman, 1995; Fernandez et al., 2008), and hydrological processes (Cerdà and Lavee, 1999; Hiernaux et al., 1999; Sharafatmandrad et al., 2010). However, there is evidence that grazing-management activity, not grazing, is the main cause of rangeland degradation in arid and semi-arid environments (Gulelat, 2002). Pastoralism is a traditional range-management activity that focuses mostly on natural forage rather than on cultivated fodder (Sandford, 1983).

Pastoralists usually have a wealth of knowledge about their grazing lands, attained through years of observations and experiences in herding practices (Oba and Kotile, 2001; Mapinduzi et al., 2003). To combat rangeland degradation, it is recommended that rangeland management systems integrate community perceptions and practices (Khwarae, 2006). Thus, the indigenous knowledge of the local communities can be used in conjunction with technical knowledge to manage natural resources (Khwarae, 2006). In many developing countries where rangelands are a dominant land type and are critically important in the livelihoods of a significant portion of the population, severe rangeland degradation can create significant social, economic, and environmental problems (Bedunah and Angerer, 2012). Therefore, scientific and indigenous knowledge should be integrated so that local communities are able to realize their capacity for monitoring and responding to the land degradation and environmental changes (Stringer and Reed, 2007). The resulting system for rangeland management would improve community livelihood and decrease rangeland degradation at the same time (Khwarae, 2006). It is interesting that pastoralists and ecologists unanimously agree on most of the rangeland degradation indicators.

If land managers want rangeland-degradation indicators to be applicable to land management, then they must be easy to use by local communities, accurate to assess environmental sustainability, and they must result in conservation (Reed et al., 2008). On the other hand, the involvement of the pastoralists in planning and implementing land conservation programs require conservationists and technicians to be aware of environmental indicators used by pastoralists for assessing rangeland degradation. There are many studies that convey a combination of local and scientific ecological knowledge that may contribute to easy and accurate monitoring and management of natural resource changes by local communities (e.g. Folke et al., 2002; Thomas and Twyman, 2004; Fraser et al., 2006; Reed et al., 2007, 2008).

Bottom-up or local-participation approaches implicate that pastoralists have accumulated a wealth of knowledge over time, based on long-term experiences that can complement scientific knowledge concerning environmental assessment and conservation (Richards, 1980). Recently it has become known that both indigenous knowledge and local management play an important role in natural resource conservation (Warren, 1992; Berkes et al., 2000) and combat land degradation. Additionally, there is growing interest concerning how indigenous ecological knowledge and management practices can be used in collaboration with standard scientific methods for improved understanding of the environment and its changes (Dahlberg, 2000; Reed et al., 2007).

The history of pastoralism in Iran dates back several thousand years, but indigenous ecological knowledge of pastoralism is neglected in most studies related to rangelands. Therefore, our main objective was to evaluate pastoralists' knowledge of rangeland degradation assessment, based on their perceptions and experiences. Our research questions were the following.

What are the pastoralists' land evaluation criteria?

Based on a participatory research approach, i.e. integrating ecological knowledge of pastoralists (pastoralists' indicators) and scientific methods (indicators extracted from literature), 17 degradation indicators were identified (Table 1). From 17 indicators, 53 % were classified as vegetative indicators, 35 % were classified as edaphic indicators, and 12 % were classified as other indicators (i.e. indicators related to different aspects of rangelands apart from vegetation and soil). Dasht pastoralists considered nine indicators as the signs of degradation in their rangelands, and five of them (56 %) were considered to be vegetation indicators. Therefore it can be said that Dasht pastoralists focus more on the vegetation indicators than the soil and other indicators. In contrast, Mirza Baylu pastoralists give more importance to soil indicators. They also considered nine indicators to be the signs of degradation, they considered six of them (67 %) to be soil indicators. One indicator was considered by both site pastoralists as a sign of land degradation (i.e. “increase in soil looseness”). To test the soil looseness, pastoralists hold soil crusts between the index finger and thumb. They believe that soil of the rangelands in good condition breaks more easily. One indicator, namely the “increased risk of wildfires”, was exclusively mentioned by Dasht pastoralists and three indicators including “soil muddiness”, “decrease of soil sandiness”, and “increased risk of pest damage” were exclusively mentioned by Mirza Baylu pastoralists. Muddy soils occur in some parts of rangelands with low productivity potential where infiltration rate is low and soil becomes waterlogged. These areas are not suitable for pastoral settlement in wet season. In the Mirza Baylu site, there are large areas on some hills outside of the park that show signs of pests (a certain type of mouse) feeding on the plants roots and making holes in the surface of the soil.

Based on questionnaires filled out by pastoralists, there were significant differences between inside and outside the park for 10 indicators (Table 2). Most significant indicators were vegetative indicators (eight indicators), and only two of them were edaphic indicators. These results show that pastoralists' perceptions of land degradation were mostly based on soil and vegetation conditions. Pastoralists first described rangeland degradation in terms of vegetation indicators. According to pastoralists' assessment, most indicators had the same median inside and outside the park. But the indicators “increase in poisonous plants” and “soil salination” had lower scores inside the park, while “increase in annual plants”, “loss of litter mass”, and “increased risk of wildfires” had higher scores inside the park (Table 2). The areas with high grazing pressure and lower productivity potential were presumed to have more annual plants. This is in contrast with the results. It can be related to high grazing pressure outside the park that removed annual plants. The amount of litter and the risk of wildfire will increase in areas with more annual plants; therefore “increased risk of wildfires” and “loss of litter mass”, respectively, had higher and lower scores inside the park.

Comparing each site separately revealed somewhat different results (Table 3). Indicators “decrease of ground cover”, “increase in the distance between plants”, “soil salination”, “loss of litter mass”, and “increased risk of wildfires” were significant in both sites. Therefore, pastoralists of both sites considered these indicators to be good indicators for assessing and evaluating the degradation of their own rangelands. Vegetation indicators including “decrease of vegetation yield”, “loss of phyto-diversity”, and “removal of palatable plants” were just significant in the Dasht site. In contrast, the indicators “increase in poisonous plants”, “decrease of shrubs”, and “increase in annual plants” were just significant in the Mirza Baylu site (Table 3).

As foregoing, in the areas with high grazing pressure and lower productivity potential presumed to have more poisonous and annual plants than perennial forage plants, accordingly indicators “decrease of shrubs” and “increase in poisonous plants” had higher scores outside the park, but “increase in annual plants” had lower scores outside the park in Mirza Baylu site; this is related to high grazing pressure. Pastoralists believed that in the areas with high productivity potential, forage plants are diverse, which itself increases palatability. Therefore, livestock can find various types of forage.

Pastoralists' indigenous ecological knowledge on rangeland management is the result of their historic environmental management over time (Fernandez-Gimenez, 2000). As is generally known, local knowledge is a rich source of information about land degradation, environmental sustainability, and their respective indicators. Local ecological knowledge of pastoralists has the capability to be used for the management of natural resources. This capability will substantially increase if it is linked to a more general scientific understanding (Reed et al., 2008). The current research tried to integrate indigenous ecological knowledge on rangeland degradation with scientific ecological methods. This research shows that pastoralists can realize the biophysical changes in the rangeland ecosystems caused by livestock grazing. Looking more closely into the indicators list, it can be understood that pastoralists' ecological knowledge on rangeland degradation was based on the connection between people, environmental conditions, and ecosystem productivity (Angassa et al., 2012). Considering both sites as complete, pastoralists focus more on the soil indicators than the vegetation and other indicators as the signs of degradation. Therefore they preferred these indicators for the degradation assessment of their own rangelands during the discussions and interviews (Oba, 2012; Reed et al., 2008).

From indicators taken from literature, four vegetation indicators (i.e. “decrease of shrubs”, “increase in annual plants”, “increase in the distance between plants”, and “decrease of plants height”) were not considered by pastoralists. These indicators are mostly related to grazing influence on vegetation. As the livelihood of pastoralists depends on rangeland vegetation, they always try to deny the negative effects of high grazing pressure on rangelands.

The indicators “soil muddiness” and “decrease of soil sandiness”, which were exclusively mentioned by Mirza Baylu pastoralists, can to some extent be considered the same as the indicators related to erosion in scientific literature such as “soil surface resistance to erosion”, “soil surface loss or degradation”, and “compaction layer” (Pellant et al., 2005).

In the present study, in the Mirza Baylu site, before field assessments and during discussions and interviews, pastoralists believed that there is no clear difference between the areas inside and outside of the park. They believed that to some extent, the area outside the park has better condition and less degradation. They believed livestock grazing makes the plants grow faster and leads to more vegetation diversity, freshness and palatability. In contrast, after field assessments, they had evaluated inside the park to have better condition than outside the park based on their own given scores to the indicators. It shows the difference between holistic and detailed assessments of pastoralists based on the indicators scoring in this area. This can be studied more deeply in further research.

Pastoralists of the Dasht site believed that increased risk of wildfires is a sign of an upward trend in the rangeland condition and indicate the increase in vegetation cover. In fact, pastoralists focus more on ecologic aspect of wildfires.

Based on the results in both sites, the rangelands outside the park, especially the areas around the villages, were degraded in comparison to inside the park. Pastoralists focus on soil indicators in assessing rangeland degradation. During the discussion with pastoralists, it was obvious that they are not seeing indicators related to livestock and their emphasis was given to vegetation, soil, and other indicators. Therefore, this gap can be clearly seen in the indicators list. All pastoralists must be fully involved in planning and managing strategies; they are knowledgeable about the grazing habits of the livestock and the vegetation of their environment and rangelands (Abate et al., 2010). Indigenous knowledge can provide possibility of rapid assessment of rangeland condition (Oba, 2012). Range scientists become more familiar with indigenous knowledge, its concepts and functions (Mapinduzi et al., 2003).

Generally, there are different approaches for assessing land degradation worldwide. There is no single best method to assess land degradation. Many researchers and scientists emphasize that land degradation assessment can be complex because multiple components of degradation may occur in any one place. Therefore, complexity makes it impossible to use the same tools, techniques, and methods for assessing different components of degradation. Many methods have been improved and justified to gather as much useful data as possible. However, the development of any method requires people with good understanding of ecosystems and the socioeconomic drivers of land degradation. Developing and using simple but yet robust methods (e.g. classes of 1–5, very good to bad; simple indicators) are good because they can be easily adapted and used even by non-experts (Kapalanga, 2008). This helps in comparing areas, involves stakeholders as much as possible, and aids in land use and restoration planning and projects prioritizing (Kapalanga, 2008).

The local pastoralists in the both study sites had the knowledge of land degradation assessment in their own rangelands. Pastoralists have many reasons for portraying their own indicators as more practical for rangeland assessments. The pastoralists have a broad knowledge base covering materials from rangelands vegetation and animal habits to land characteristics. Controlling degradation in grazing lands without considering the people whose their livelihoods depend on them will lead to imperfect results. Therefore, matching the scientific land degradation indicators with the ones pastoralists believe in and understand can lead to the successfully control of land degradation. The involvement of pastoralists and the documentation of their knowledge on rangelands can prove to be useful bases for sustainable utilization and the conservation of natural rangelands. We believe that such plans based on indigenous knowledge can be easily accepted by local people.