Combining habitat suitability models and spatial graphs for more effective landscape conservation planning: An applied methodological framework and a species case study

In response to the negative effects of habitat fragmentation on biodiversity, habitat network conservation and restoration has become a central objective in conservation planning. Evaluating landscape functional connectivity and mapping habitat networks are key steps for implementing effective actions, but both remain challenging. Habitat suitability models (HSM) and spatial graphs provide conservation managers with useful information for landscape planning. To tackle their respective drawbacks, we proposed to combine HSM and spatial graphs in a four-step methodological framework: (i) collect and prepare input data; (ii) model habitat suitability using MaxEnt to map the species' habitat suitability index (HSI); (iii) transform the HSI map into spatial graph inputs using GIS; and, (iv) perform spatial graph connectivity analysis using Graphab. The outputs of this species-specific and quantitative approach were maps of the species' habitat network. Habitat patches and dispersal linkages were ranked according to their importance for overall habitat availability and landscape connectivity. This prioritization identified locations where conservation biologists and landscape planners should focus conservation and restoration efforts. This framework is illustrated here with a case study on the woodlark (Lullula arborea) - a bird species - in a French Mediterranean area, and the method's limitations and alternatives are discussed. The quantitative-based graphical outputs of the framework can valuably support decision-making for landscape planning, complement local expert opinion, and encourage appropriate stake-holders to cooperate at regional scale.