A common currency for the different ways in which patches and links can contribute to habitat availability and connectivity in the landscape

Graph structures and habitat availability metrics are two recent and complementary approaches for analysing landscape connectivity. They have gained rapid popularity and provided significant conceptual improvements for decision making in conservation planning. We present a further methodological development of the habitat availability concept and metrics by partitioning them into three separate fractions that quantify the different ways in which individual landscape elements can contribute to overall habitat connectivity and availability in the landscape, including stepping stone effects. These fractions are derived from the same concept, are measured in the same units and can be directly compared and combined within a unifying framework. This avoids the problematic and, so far, usual combination of metrics coming from different backgrounds and the arbitrary weighting of connectivity considerations in a broader context of conservation alternatives. We analyse how the relative importance of each fraction varies with species traits. In addition, we show how the critical patches differ for each of the fractions by analysing various forest habitats in the province of Lleida (NE Spain). We discuss the conceptual and conservation implications of this approach, which can be adapted to different degrees of ecological and spatial detail within the graph while still maintaining a coherent framework for the identification of critical elements in the landscape network.