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\ua0km GWW, the estimated development footprint is 690\ua0km, of which 67% consists of linear infrastructure and the remainder is ‘hub’ infrastructure. An estimated 150,000\ua0km of linear infrastructure exists in the study area, equating to an average of\ua0~1\ua0km per km. Beyond the direct footprint, a further 4000–55,000\ua0km (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

Linear infrastructure impacts on landscape hydrology

The extent of roads and other forms of linear infrastructure is burgeoning worldwide, but their impacts are inadequately understood and thus poorly mitigated. Previous studies have identified many potential impacts, including alterations to the hydrological functions and soil processes upon which ecosystems depend. However, these impacts have seldom been quantified at a regional level, particularly in arid and semi-arid systems where the gap in knowledge is the greatest, and impacts potentially the most severe. To explore the effects of extensive track, road, and rail networks on surface hydrology at a regional level we assessed over 1000\ua0km of linear infrastructure, including approx. 300 locations where ephemeral streams crossed linear infrastructure, in the largely intact landscapes of Australia's Great Western Woodlands. We found a high level of association between linear infrastructure and altered surface hydrology, with erosion and pooling 5 and 6 times as likely to occur on-road than off-road on average (1.06 erosional and 0.69 pooling features km(-1) on vehicle tracks, compared with 0.22 and 0.12\ua0km(-1), off-road, respectively). Erosion severity was greater in the presence of tracks, and 98% of crossings of ephemeral streamlines showed some evidence of impact on water movement (flow impedance (62%); diversion of flows (73%); flow concentration (76%); and/or channel initiation (31%)). Infrastructure type, pastoral land use, culvert presence, soil clay content and erodibility, mean annual rainfall, rainfall erosivity, topography and bare soil cover influenced the frequency and severity of these impacts. We conclude that linear infrastructure frequently affects ephemeral stream flows and intercepts natural overland and near-surface flows, artificially changing site-scale moisture regimes, with some parts of the landscape becoming abnormally wet and other parts becoming water-starved. In addition, linear infrastructure frequently triggers or exacerbates erosion, leading to soil loss and degradation. Where linear infrastructure densities are high, their impacts on ecological processes are likely to be considerable. Linear infrastructure is widespread across much of this relatively intact region, but there remain areas with very low infrastructure densities that need to be protected from further impacts. There is substantial scope for mitigating the impacts of existing and planned infrastructure developments

Predator activity associated with linear infrastructure, link to files

Roads and other forms of linear infrastructure are rapidly proliferating worldwide, yet little is known about how roads affect the distribution and abundance of predators, particularly in relatively intact landscapes. We used a combination of motion-sensor cameras and spoor surveys to compare dingo, fox and feral cat activity on unsealed vehicle tracks (hereafter: roads) and up to 3 kilometres away, in relatively intact landscapes of the Great Western Woodlands in south-western Australia. We compared predator activity as indicated by independent sightings and spoor observations, in woodlands and shrublands: vegetation types with contrasting permeabilities. Predator activity was observed between 12 and 261 times more frequently on roads compared with off-road for all species studied. Roads also appeared to affect predator activity up to 2.5 km away. Even poorly formed and abandoned roads concentrated predator activity and affected landscape-scale rates of predator observations. The effect of road proximity on predator activity was non-linear and different between vegetation types for dingoes and cats but not foxes. Our results provide new evidence of the effects of roads on predator activity in surrounding landscapes, with interacting effects of vegetation. They also reinforce previous findings e.g. stronger roads preference displayed by dingoes and foxes, than by cats. Roads and other linear infrastructure have strong effects on predator activity within intact landscapes, although further research is needed to characterise the implications for prey species. Road planning or approvals, as well as habitat restoration programs for threatened species, should account for the effects of roads on predator activity

Giovanni Andrea Lumaga

Biografia del mercante e collezionista Giovanni Andrea Lumaga (Piuro? 1607 - Venezia 1672