Lines in the sand: quantifying the cumulative development footprint in the world’s largest remaining temperate woodland

Context: The acceleration of infrastructure development presents many challenges for the mitigation of ecological impacts. The type, extent, and cumulative effects of multiple developments must be quantified to enable mitigation. Objectives: We quantified anthropogenic development footprints in a globally significant and relatively intact region. We identified the proportion accounted for by linear infrastructure (e.g. roads) including infrastructure that is currently unmapped; investigated the importance of key landscape drivers; and explored potential ramifications of offsite impacts (edge effects). Methods: We quantified direct development footprints of linear and ‘hub’ infrastructure in the Great Western Woodlands (GWW) in south-western Australia, using digitisation and extrapolation from a stratified random sample of aerial imagery. We used spatial datasets and literature resources to identify predictors of development footprint extent and calculate hypothetical ‘edge effect zones’. Results: Unmapped linear infrastructure, only detectable through manual digitisation, accounts for the greatest proportion of the direct development footprint. Across the 160,000 km² GWW, the estimated development footprint is 690 km², of which 67% consists of linear infrastructure and the remainder is ‘hub’ infrastructure. An estimated 150,000 km of linear infrastructure exists in the study area, equating to an average of ~1 km per km². Beyond the direct footprint, a further 4000–55,000 km² (3–35% of the region) lies within edge effect zones. Conclusions: This study highlights the pervasiveness of linear infrastructure and hence the importance of managing its cumulative impacts as a key component of landscape conservation. Our methodology can be applied to other relatively intact landscapes worldwide.