Our spatial analysis reveals how 830,500 km of roads (a distance equivalent to circling the Earth 20 times) dissect South America’s protected areas into thousands of fragments, leaving most natural environments highly vulnerable to human stressors. We identify critical patterns of road encroachment to inform infrastructure planning and safeguard ecological integrity.

In many tropical frontier areas, weak law enforcement is allowing illegal and illicit roads to proliferate dramatically, sharply increasing the destruction and degradation of forests resulting from road development. We devised a multivariate road-expansion index to predict which specific areas of the Amazon basin, Congo basin and Asia-Pacific region are most vulnerable to road proliferation and associated forest disruption.

Our study reveals that roads and traffic not only cause direct wildlife mortality but also destabilise entire ecological networks by altering predator-prey interactions. By mapping high-risk areas for disrupted predator-prey interactions across Europe, we highlight the urgent need for tailored measures to reduce roadkill and preserve the integrity of ecological networks.

Poorly planned or maintained roads can have devastating impacts on ecosystems, threatening biodiversity and fragmenting habitats worldwide. To address this, we developed a simple yet effective method to assess global and regional risks of road-related environmental impacts. By leveraging readily available data on road exposure and species-level susceptibility, our approach provides a practical tool for conservation planning and risk assessment. This accessible method empowers researchers, policymakers, and planners to identify high-risk areas and prioritize interventions—making it both impactful and easy to implement.