Infrastructural landscape fragmentation versus occlusion: a sensitivity analysis

Landscape fragmentation, i.e. the process where large habitat patches become smaller and more isolated, has often been accelerated by human activities, such as deforestation, agricultural land conversion, and urbanisation of natural areas. Transport and mobility infrastructures are a major cause of landscape fragmentation. The Infrastructural Fragmentation Index (IFI) is a common measure of landscape fragmentation due to transport and mobility infrastructures and depends, inter alia, on the occlusion coefficient, which accounts for the obstruction to movement. The values of this coefficient mirror well-established conditions, which depend on type of transport and mobility infrastructure and traffic flow. Lack of data affects its values and generates uncertainty in the measurement of landscape fragmentation. In this study, we develop on a sensitivity analysis, by assessing how IFI varies when the occlusion coefficient changes in the case of six landscape units in Sardinia (Italy) and Andalusia (Spain). Our results demonstrate that the IFI is very sensitive to the elimination of national, provincial, and local roads. In addition, we verified that IFI varies linearly versus the occlusion coefficient, i.e. its elasticity is constant. Thus, we advance that, as the uncertainty cannot be eliminated, the most efficient strategy to reduce these biases is to dismiss the absolute values of IFI and adopt difference-based expressions.