Here, we aim to assess the risk of terrestrial apex predator species from current road infrastructure and to detect impact areas of proposed road development on apex predators. This knowledge can form the base for meaningful engagement between road planning committees, financiers, and local stakeholders to ensure biodiversity is protected while achieving the maximum social and economic benefit. It is essential to establish a deeper understanding of the impact of current and proposed roads on apex predators. Around 90% will occur in developing nations that host critical ecosystems and rich biodiversity areas 14 important for apex predators, such as the Amazon 15, Africa 16 and Southern Asia 17. Over 25 million km of newly paved roads will be constructed globally by 2050 13. Large infrastructure projects such as the Belt and Road Initiative 12, and Africa’s Development Corridors have provided the impetus to shift this trend. Historically, road development has been pervasive in developed countries with high Gross Domestic Product (GDP), such as Northwest Europe and the USA, as well as in more densely populated countries like India and Bangladesh 11. Therefore, conservation of apex predators and their habitats is exceptionally important to ensure the preservation and functionality of entire ecosystems over time 8. The maintenance of ecosystem functioning provided by apex predators is linked to a variety of ecosystem services, including carbon sequestration, water provision, and food security 9, 10. They are simultaneously vital to the structure, functioning, and resilience of ecosystems globally 8, 9, due to their direct and indirect influence on the interactions of lower trophic levels, by displacing mesopredators and regulating large herbivore populations 8. Apex predators are defined here as non-herbivorous terrestrial mammals having an average body mass higher than 13 kg 7, or species that are below that threshold but are main predators in their ecosystems (see Supplementary Table S1).
Roads affect almost all species groups 4, but apex predators are acutely threatened by road development, due to their large spatial ranges, low population densities, low reproductive rates, and intolerance to increased human disturbance for most species 6. Some of the impacts of roaded landscapes for wildlife are direct mortality from wildlife-vehicle collisions (WVC), land clearing driving habitat loss and fragmentation, reduced habitat quality adjacent to roads, increased access for poaching, and barriers to wildlife movement causing population fragmentation and loss of genetic connectivity 4, 5. They commonly drive loss of ecological health and integrity 3, 4 providing human access to otherwise undisturbed areas and affecting ecosystems and wildlife 3. Roads are the most widespread form of landscape modification, developed in pursuit of natural resource exploitation, agricultural, and economic development 1, 2, 2. We advocate the need for rigorous road development planning to apply effective mitigation measures as an urgent priority and to avoid construction in wilderness areas and predator strongholds. Roughly 500 protected areas will be intersected by these roads, threatening core apex predator habitats. We applied this method to proposed road developments in three areas: the Brazilian Amazon, Africa, and Nepal, to locate high-impact road segments. Based on species risk from roads, we propose a widely applicable method to assess the potential impact of future roads on apex predators. The sloth bear suffers the highest risk of all apex predators, followed by the tiger and dhole. Eight of the ten species with the highest risk occur in Asia, although other high-risk species are present in the Americas, Africa and Europe.
Our findings reveal all apex predators are exposed to road impacts.
We reviewed road impacts on 36 apex predator species and assessed their risk from current roads based on road exposure and species vulnerability. This occurs through wildlife-vehicle collisions, habitat loss and fragmentation, reduced genetic connectivity and increased poaching. The global expansion of road networks threatens apex predator conservation and ecosystem functioning.
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