Integrating spatially realistic infrastructure impacts into conservation planning to inform strategic environmental assessment

Infrastructures such as roads and pipelines have environmental impacts that diffuse far beyond the local development footprint, including fragmenting habitat or changing hydrology. Broad-scale diffuse impacts are challenging to incorporate into conservation planning and strategic environmental assessment due to difficulties in determining how impacts spread across landscapes. We built curves representing expert-elicited magnitudes and spatial extents of direct and diffuse impacts of infrastructure on biodiversity groups, to incorporate these impacts into a spatial conservation prioritization. We demonstrate how different prioritization outputs inform different steps of the impact assessment mitigation hierarchy. In southern Australia we find the diffuse-impact footprint to be four times higher than direct (i.e., local) infrastructure impacts, with >75,000 km2 of spatial priority areas for mitigation and >37,000 km2 of spatial priority areas for offsets potentially missed if diffuse impacts are ignored. Understanding both direct and diffuse infrastructure impacts will avoid inefficient spatial allocation of environmental mitigation, restoration, and offsetting efforts.