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

Abstract

Citation for this articleRaiter, K.G., Prober, S.M., Hobbs, R.J., Possingham, H.P., 2017. Lines in the sand: quantifying the cumulative development footprint in the world's largest remaining temperate woodland. Abstract ContextThe 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. ObjectivesWe 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). MethodsWe 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'. ResultsUnmapped linear infrastructure, only detectable through manual digitisation, accounts for the greatest proportion of the direct development footprint. Across the 160,000 km 2 GWW, the estimated development footprint is 690 km 2 , 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 km 2 . Beyond the direct footprint, a further 4,000-55,000 km 2 (3-35% of the region) lies within edge effect zones. ConclusionsThis 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.

Vehicle tracks are predator highways in intact landscapes

“…This region is the largest and most intact temperate woodland remaining on Earth at 16 million hectares in size; and comprises a refuge to over 300 vertebrate species, including many that have declined or become locally extinct elsewhere (Watson et al 2008). Apart from a few small towns, the region has remained largely uncleared and undisturbed except for the effects of pastoralism (approximately one-third of the region) and extensive resource extraction operations, along with changing fire regimes and the effects of invasive species (Prober et al 2012;Raiter et al 2017). The Great Western Woodlands offers a model system for investigating the effects of roads within natural habitats on predator activity, as it has an extensive network of roads surrounded by relatively undisturbed landscapes (Raiter et al 2017).…”

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

“…A key advance of our approach is expert elicitation to build distance–decay curves of infrastructure impacts on biodiversity (such estimates are available for very few places; Raiter, Prober, Hobbs, & Possingham, ). Implementing expert‐predicted infrastructure impacts into conservation prioritization re‐ranked the region's conservation priorities (Figure ).…”

“…A key advance of our approach is expert elicitation to build distance-decay curves of infrastructure impacts on F I G U R E 3 Differences in landscape priorities identified by spatial conservation prioritization approaches considering either direct impacts, i.e., ignoring diffuse infrastructure impacts and assuming homogenous responses of biodiversity, or diffuse impacts, incorporating expert-elicited functions of impact spread across the landscape and assuming heterogeneous responses of biodiversity. Showing (a) the difference in priorities for minimizing/restoring impacts when diffuse impacts (scenario 2) versus direct impacts biodiversity (such estimates are available for very few places; Raiter, Prober, Hobbs, & Possingham, 2017). Implementing expert-predicted infrastructure impacts into conservation prioritization re-ranked the region's conservation priorities (Figure 3).…”

Linear infrastructure impacts on landscape hydrology

“…Lastly, we used a quantification of linear infrastructure across the GWW by Raiter et al (2017) to estimate erosional and pooling features, and linear infrastructure impacts on ephemeral streamlines within the region. The quantification combined 23 unique existing datasets of linear infrastructure and further digitised unmapped disturbance features that were visible in aerial imagery across 24 stratified near-random sample areas.…”

“…This scenario is likely caused by concentration of flows along and by the track, and may also have been exacerbated by cattle that have often been observed along tracks in this area, which is a pastoral station. 3.6 Significance of impacts across the study area Raiter et al (2017) estimated that a total of 149, 820 km of linear infrastructure exist in the GWW, of which 138,311 km are major or minor tracks. Assuming that there is consistency in the formation of such features (i.e.…”