Impacts of urban expansion on natural habitats in global drylands

Urban regions are growing rapidly worldwide, threatening surrounding habitats, including in drylands. This study finds that indirect impacts to surrounding drylands are more than ten times greater than direct impacts and that such impacted areas contain almost 60% of threatened species globally. Urban regions across the world have expanded rapidly in recent decades, affecting fragile natural habitats, including in drylands, and threatening the achievement of the UN Sustainable Development Goal 15, 'life on land'. Yet, few studies have comprehensively investigated impacts of urban expansion on natural dryland habitats globally even though these cover 40% of global land area and provide habitats for 28% of endangered species. Here, we quantify at multiple scales the loss of habitat quality directly and indirectly caused by dryland urban expansion. Direct impacts are conversions of natural habitats to urban land. We define indirect impacts as proximate impacts within 10 km around the expanded urban land footprint. We found that although urban expansion from 1992 to 2016 resulted in an average 0.8% loss of dryland habitat quality, the indirect impacts were 10-15 times greater. By considering the coincidence of habitat-quality loss and threatened species ranges, we found that, globally, nearly 60% of threatened species were affected by such indirect impacts of dryland urban expansion. Our findings suggest that strategic management is imperative to mitigate the substantial impacts of dryland urban expansion on biodiversity.