The demand for ecological tourism and intensive use of outdoor recreational areas have grown fast due to increasing visitors, leisure time, increased income, facilitated mobility, and consumer demands (Sutherland et al., 2001). Thus, nature tourism activities such as walking and mountain biking which are associated with trails, have been growing faster in developing regions (Eagles, 2014; Newsome et al., 2012). Recreational trails are increasingly created in many areas, including national parks and protected areas (Cole, 2004; Eagles, 2014), as well as urban and semi-urban natural areas (Ballantyne and Pickering, 2015). People of all ages and abilities can use trails with different functions such as access to attractive areas, recreation and wildlife watching (Grimwade et al., 2009; Santarém et al., 2015), sports activities, relaxation, and travel to the destination (Grimwade et al., 2009). Trails are designed to avoid the uncontrolled dispersal of visitors (Olive and Marion, 2009) and provide more infrastructure to allow access to natural areas (Ballantyne et al., 2014). As national Parks and protected areas are major destinations for outdoor recreation, the ecosystems of those areas are being extensively affected by human activities (Chatterjea, 2007). This may result in increased environmental degradation and wildlife habitat disruption by concentrating visitor activities into specified areas like trails and recreation sites (Chatterjea, 2007; Clius et al., 2012; Cole, 2004; Dixon et al., 2004; Farrell and Marion, 2001a; Olive and Marion, 2009).
Trail degradation is one of the most evident consequences of expanding visitor numbers in national parks. The magnitude of trail impacts is contingent on the intensity, frequency, timing, and type of use, as well as environmental conditions (Törn et al., 2009). The environmental impacts of recreational trails have been comprehensively presented worldwide. Trampling on trails changes soil surface compaction, mechanical properties, and hydrophysical behavior of watersheds which leads to greater on-trail erosion and changes in the micro-climate conditions (Chatterjea, 2007). The impacts of trampling activity on water resources, plant communities, and wildlife species are observed in areas where visitor use is intensified, particularly along trails and campsites (Leung and Marion, 2000; Matulewski et al., 2021; Olive and Marion, 2009). It is well observed that new paths generated by visitors and trampling can significantly influence the inhibition of radial growth of trees, increasing trail widening, trail muddiness, soil organic matter removal, and soil particles compacting (Cole, 2004; Hill and Pickering, 2006; Leung and Marion, 2000; Matulewski et al., 2021). The decline in vegetation cover, changes in vegetation height, and introduction of weeds are the other negative impacts of recreation trails on the environment (Barros and Marina Pickering, 2017; Dolan et al., 2006). Therefore, trail development and use are often a major concern of natural area managers and visitors (Leung and Marion, 1996a).
Trail width is used as an indicator of degradation of the recreational trails (Tomczyk and Ewertowski, 2011). Generally, environmental predictor variables influence trail width because they influence human behavior (Wimpey and Marion, 2010). The predictor variables for estimating trail degradation can be referenced to environmental and managerial variables (e.g. elevation, slope, aspect, soil type, soil texture, vegetation type, etc (Nepal and Way, 2007; Spernbauer et al., 2023; Tomczyk and Ewertowski, 2011, 2013). The relationship between predictor variables and trail degradation and their negative impacts on the environment is not linear (Hammitt et al., 2015; Tomczyk and Ewertowski, 2013). Therefore, getting a reliable model for understanding the relationship between the trail width and predictor variables is required for effective tourism management (Farrell and Marion, 2001b; Leung and Marion, 2000). According to various studies in recent years, different predictive machine learning (ML) and deep learning (DL) algorithms were widely used in landslide susceptibility (Orland et al., 2020), soil moisture estimation (Adab et al., 2020) and forest fire vulnerability prediction (Adab, 2017). However, a comparative analysis of different predictive models using GIS techniques is very rare for the estimation of trail width (Nepal and Way, 2007; Spernbauer et al., 2023; Tomczyk and Ewertowski, 2013; Wimpey and Marion, 2010) and the prediction of recreational trail susceptibility (Sahani and Ghosh, 2021). In the context of trail width estimation, a comparative analysis of different predictive techniques has not been considered in the literature. Also, quality research is scarce, and a lack of scientific studies on the estimation of trail width in Iran. The accuracy of the algorithms may differ for the mapping of trail width, and the selection of the best model is important for decision-makers for maneuvering the natural stability of the trail. On the other hand, considerable research has been devoted to the context of local attractiveness for tourism and recreation (Khazaee Fadafan et al., 2022; Meshram et al., 2022) and optimal-designed road network by MCDM-GIS approach in Iran (Talebi et al., 2019) rather less attention has been paid to synthesizing knowledge on spatial optimization of recreational trails and role of human mobility patterns on the degradation (Talebi et al., 2022).
A research gap is found in the context of trail width estimation, as no comparisons have been made between multivariate machine learning models. The present study aims to assess the predictive performance of three multivariate machine learning predictive models for the estimation of trail width along the recreational trail of the Sarigol National Park and Protected Area (SNPP) and its optimization of recreational trails. The findings of this study will provide a foundation of comparative analysis of machine learning algorithms for tourism researchers, and government officials to enhance land management and tourism management.