A review of structural and functional connectivity studies in European forests

Abstract Context Ecological connectivity is key to mitigating global change impacts such as isolation and climate change effects on populations, especially in historically modified biomes such as European forests. The term connectivity is widely used in conservation, but the multiple methods for measuring it, as well as the scales and objects of study to which it can be applied, make it difficult to understand and compare research results. Objectives Our aim was to enhance the understanding of connectivity studies in European forests to inform conservation efforts, guide future research, and identify potential knowledge gaps, through a systematic review of connectivity studies in European forests. Methods We did a systematic review on the literature of connectivity studies in European forests. We classified the studies according to the methods used. Then, we extracted information on study characteristics and context relevant for our purpose. Results Our literature search identified 142 relevant articles, more than half of these studied connectivity through structural measures (based only on landscape attributes). The three most used measures were area-based methods, Euclidean distances, and spatial indices (structural), followed by species and graph theory-based models (functional measures, including species data). Most studies focused on large Western European countries, and birds and mammals as focal taxa. Generally, functional measures were more frequent in publications that had the study of connectivity as a primary objective. Conclusions Research priorities and recommendations to guide future studies were identified such as the inclusion of structural and functional measures to bridge the gap between approaches, retaining the benefits of both and helping to uncover relationships between them; and as the need to address temporal connectivity, especially for less mobile species.