With more mammal species entering the “Species at Risk” and “Endangered Species” lists across the world, there is a growing urgency to mitigate ecological declines caused by habitat fragmentation (Fremier et al., 2015; Hebblewhite, 2017). An increasingly widespread technique used for combating decreasing populations is the implementation of ecological corridors throughout fragmented landscapes (Samways et al., 2010). Ecological corridors are defined as areas or structures that enable and ensure that migratory land animals have adequate ecosystem ranges for migration, spreading, and exchange of species between core habitat zones (Ferretti and Pomarico, 2012). Ecological corridors are of extreme importance due to their ability to decrease the impact to dispersal capacity, biodiversity, ecosystem services, gene pool, food accessibility, population, and edge effects associated with fragmented landscapes (Ferretti and Pomarico, 2012; Pierick et al., 2016; Samways et al., 2010). As human activity, such as urbanization and intensive agriculture, continue perpetuating fragmentation, a key challenge for conservation organizations is determining the most suitable pathways for ecological corridors within increasingly complex landscapes.
Important considerations in establishing ecological corridors include providing proper habitat and land use requirements, avoidance of anthropogenic land uses, avoidance of roads where possible, and ensuring flatter terrain where possible. First, the degree of naturalness to a land use area is a good indicator of its habitat suitability because it is most akin to the state of the area before human intervention. Thus, the most natural areas are favoured highest when siting the corridor, and land use types that contain more anthropogenic elements than natural are restricted completely from corridor siting (Ryan and Hartter, 2012). Second, avoidance of roads as much as possible is integral to successful migration, and minimizing corridor cost. Noise from vehicular engines acts as a deterrent to animal progression through a corridor, and the cost to construct ecological bridges to ensure safe passage increases the overall cost of corridor development (Mellinger 2016). Last, minimizing slope increases the chances of successful migration by allowing for the greatest travel distance with the least amount of energy expenditure for the animal of focus (Proulx, 1982). By adhering to these considerations, the suitability of the corridor for the animal of focus is increased, which in turn increases the likelihood for successful animal migration.
Integration of Geographic Information System (GIS) tools for assessing the variables necessary to make clear decisions ensures that the corridor has the highest impact and suitability possible. Niedziałkowska et al.(2012) found that GIS was integral in determining an ecological corridor for Red Tailed Deer in Poland because of its ability to provide spatial context to the different deer densities collected, as well as the ability to relate those densities to many specific spatial habitat variables, such as forest type and roaming space. Once correlations between densities and habitat variables were established, each cell was given a suitability value based on transformation of the variables to a universal evaluation scale. Beazley et al. (2005) discuss how GIS was used in Nova Scotia to analyze an area's degree of naturalness using a Multi-Criteria Evaluation (MCE). The MCE included variables such as natural cover, age of forests, and road density that were combined through creation of a GIS suitability surface layer, to determine the most suitable areas within the study area. In addition to the MCE, Larkin et al. (2004) used a Least Cost Pathway (LCP) analysis with a cost surface layer consisting of five black bear habitat categories that were classified based on dispersal capacity for West-Central Florida black bear populations. This allowed for a cell by cell analysis of the study area to determine the most probable dispersal path based on selection of a focus cell, and an evaluation of each adjacent cells cost, to pinpoint the cell of least cost. The cell of focus then shifted to that newly identified least cost cell and the process repeated until a best single pathway was formed.
The ability of GIS tools to assess movement through space based on an array of varying types of data, and its ability to consider movement on a cell by cell basis, deem it an important component in corridor establishment (Larkin et al. 2004). Furthermore, due to the complexities of real-world spatial relationships, ecological corridor siting is problematic in realistically considering all of the variables involved. Utilizing GIS tools allows for complex analysis which helps maintain realism, but also provides display for this analysis in a simple visual manner for easy user comprehension. For example, the use of exponential transformations in GIS can allow for phenomena that lose its impact over distance, such as noise pollution, to be realistically considered and displayed in a simple stretch colour map (Mellinger, 2016). Thus, the closer the model is to representing real-world conditions, the higher probability the corridor is sited successfully. Therefore, GIS is important in ensuring realistic problems that may be encountered in the real-world corridor establishment, such as noise pollution as a deterrent from migration progression, are resolved within the model, allowing for higher potentials of success when actual establishment occurs.
Purpose of Research
The purpose of this research is to develop a GIS-based Multi-Criteria Evaluation and Least-Cost Pathway in order to identify the most suitable location for an ecological corridor in Adirondack Park.