Abstract
The escalating trend of global hillside urban expansion threatens terrestrial biodiversity and undermines global initiatives, including the Sustainable Development Goals and the Global Biodiversity Framework. This study addresses a critical knowledge gap by examining the impacts of hillside urban expansion on terrestrial biodiversity across multiple scales, integrating multi-source high-resolution data with terrestrial vertebrate species datasets. Our results reveal substantial global hillside urban expansion (11.65 Mha) between 2000 and 2020, with 35% occurring within biodiversity hotspots. It encroaches disproportionately on natural habitat compared to urban expansion in flat areas, significantly exacerbating habitat fragmentation. This has far-reaching consequences for terrestrial biodiversity, directly affecting ~70% of globally threatened species and hindering progress towards biodiversity conservation by 2050. Our findings underscore an urgent need for tailored land-use and urban planning strategies that prioritize biodiversity conservation in ecologically sensitive areas. This study lays the groundwork for the development of more sustainable land-use planning, nature conservation and urban development policies.
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Data availability
All underlying model data are publicly accessible online. The global basic landform unit data can be obtained via Earth System Science Data at https://doi.org/10.5194/essd-2024-401 (ref. 42). The GlobeLand30 data (2000 and 2020) are available at https://www.un-spider.org/links-and-resources/. The GAIA map (2000 and 2020) is available at https://data-starcloud.pcl.ac.cn/iearthdata/13 (ref. 45). The GISA2.0 map (2000 and 2019) is available via Zenodo at https://zenodo.org/record/5136330 (ref. 46). The GISD30 map (2000 and 2020) is available via Zenodo at https://zenodo.org/records/5220816 (ref. 47). Expert-derived polygons of species are available online via the IUCN Red List Portal at https://www.iucnredlist.org/resources/spatial-data-download. GIS country boundaries from Natural Earth are available at https://www.naturalearthdata.com/downloads. The biodiversity hotspot data can be retrieved from https://databasin.org. The future urban expansion dataset based on the five shared socioeconomic pathways is available via Pangaea at https://doi.pangaea.de/10.1594/PANGAEA.905890. Source data are provided via Zenodo at https://doi.org/10.5281/zenodo.15034804 (ref. 49).
Code availability
The code that supports our findings is available via Github at https://github.com/wwwyizhen/HUE.
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Acknowledgements
K.S. acknowledges the support of the National Natural Science Foundation of China (number 42101345) and the Natural Science Research Program of Anhui Universities (number 2023AH020029). B.Y. acknowledges support from the National Natural Science Foundation of China (number 42371332).
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Contributions
Conceptualization: K.S., Y.W., L.G., C.H., B.Y. and B.A.B. Data curation: K.S., Y.W., X.S., Y.C., L.S., Y.C. and Z.C. Methodology: K.S., Y.W., L.G. and B.A.B. Investigation: Z.C., F.F., W.C., L.S., J.M. and C.H. Visualization: K.S., Y.W. and C.H. Funding acquisition: K.S. and B.Y. Writing—original draft: K.S. and Y.W. Writing—review and editing: all authors.
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Nature Cities thanks thanks Antonio T. Monteiro, Chao Yang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Extended data
Extended Data Fig. 1 Spatial distributions of hillside urban expansion globally within 3-km× 3-km grid cells.
a, Hillside urban expansion area; b, Hillside urbanization rate. Maps created with QGIS software. Administrative boundary data from Natural Earth (https://www.naturalearthdata.com).
Extended Data Fig. 2 Heatmap of habitat loss in hillside regions globally within 3-km× 3-km grid cells.
Maps created with QGIS software. Administrative boundary data from Natural Earth (https://www.naturalearthdata.com).
Extended Data Fig. 3 Changes of hillside habitat fragmentation globally within 3-km× 3-km grid cells.
Mean patch size of hillside habitats in a, 2000, and b, 2020. c, Trends in habitat fragmentation from 2000-2020. Note: Grid cells without hillside urbanization are ignored. A higher MPS value indicates greater patch connectivity and a more intact ecosystem, while a lower value suggests severe landscape fragmentation, which may threaten species habitats. Maps created with QGIS software. Administrative boundary data from Natural Earth (https://www.naturalearthdata.com).
Extended Data Fig. 4 Attainment of biodiversity conservation by 2030 and 2050.
The total number of countries (upper panel) and biodiversity hotspots (lower panel) that can meet the target under at least one scenario.
Extended Data Fig. 5 Effects of habitat landscape changes (habitat loss and habitat fragmentation) on threatened species at the national scale.
Trends in plain urban expansion (a, in countries and b, in biodiversity hotspots) and hillside urban expansion (c, in countries and d, in biodiversity hotspots).
Extended Data Fig. 6 Effects of habitat landscape changes (habitat loss and habitat fragmentation) on threatened species on the biodiversity hotspots scale.
Trends in plain urban expansion (a, in countries and b, in biodiversity hotspots) and hillside urban expansion (c, in countries and d, in biodiversity hotspots).
Extended Data Fig. 7 Validation sites of global hillside and plain urban expansion.
a, Global distribution of all validation sites. b–e, Information of selected validation points. Administrative boundary data from Natural Earth (https://www.naturalearthdata.com). Panels b–e: map data in the top three rows from Google Earth.
Supplementary information
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Shi, K., Wu, Y., Sun, X. et al. Extensive terrestrial biodiversity threats from global hillside urban expansion. Nat Cities (2025). https://doi.org/10.1038/s44284-025-00316-9
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DOI: https://doi.org/10.1038/s44284-025-00316-9
