Competition from agriculture for flat land is pushing urbanization uphill, which poses threats to habitats and biodiversity on mountains, hills and plateaus. Writing in Nature Cities, Shi and colleagues assess the effects of hillside urban expansion on terrestrial biodiversity by combining 30-m-resolution spatial landform and land-use maps with vertebrate-species range data. From 2000 to 2020, they found that hillside urban areas have expanded by 11.65 million hectares, which has led to a loss of 6.73 million hectares of habitat (particularly forest and grassland ecosystems). By overlapping hillside urban-expansion dynamics with spatial range data of threatened species from the International Union for Conservation of Nature (IUCN) Red List database (birds, mammals, amphibians and reptiles), they revealed that 35% of hillside urban expansion has occurred in biodiversity hotspots, and affects more than 6,600 species. Furthermore, as compared with urban expansion in plains and lowlands, hillside urban expansion is expected to result in more severe habitat fragmentation and to affect more threatened species. By assessing the extent of projected habitat loss and encroachment upon species ranges from hillside urban expansion under five different socioeconomic pathways, the authors also quantified the potential achievement of a moderate 2050 target from the Global Biodiversity Framework. By 2050, 69% of biodiversity hotspots will probably fail to meet this target across any scenario. Given these threats, the findings highlight the need to integrate biodiversity into urban planning, and to consider policies and solutions that could balance urbanization and conservation, such as compact city designs and the establishment of green belts and land-use zoning that prioritizes irreplaceable habitats.
Original reference: Nat. Cities https://doi.org/10.1038/s44284-025-00316-9 (2025)
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