Ecological connectivity in environmental impact assessments: modelling alternative highway bypass scenarios

ABSTRACT Road building is one of the greatest threats to biodiversity globally. This study addressed common challenges for spatially explicit ecological assessments of linear infrastructure EIAs, by first providing an overview of existing approaches and then applying a connectivity model with scenario analysis of alternative road alignments for a road bypass in Beaufort, Australia. The application included an expert-based connectivity model using a combination of least-cost paths, circuit theory, and graph theory to model five conservation targets (four species and one group) with different dispersal abilities and habitat requirements. For each of these targets, we modelled four different road alignments, then assessed mitigation options for the least impactful alignment. The results showed that each target species was dissimilarly impacted, with longer dispersers affected the most. The modelling clearly identified a single alignment with the least overall impact on connectivity and showed how wildlife crossing structures can mitigate impacts through improving overall connectivity for all target species. This real-world case-study demonstrated the potential to apply a transparent and quantitative approach to mainstreaming ecological connectivity modelling in EIAs.