Living on the Edge: Unequal Rise of Global Population Exposure on Steep Terrain

Chakshu Gururani , Ugur Öztürk, Thorsten Wagener 

Population growth on steep terrain can increase exposure to slope-related hazards, yet its global distribution and socioeconomic context remain poorly understood. To characterize this exposure using a globally consistent topographic measure, we analyse 1-km gridded population and settlement data on terrain with slope inclination ≥10◦  from 1975-2025, and aggregate selected metrics to topographic catchments (mean area ∼10,000 km2) for spatial comparison. We find that the steep-terrain population increased from approximately 494 to 835 million people, and that this growth was highly unequal across regions and socioeconomic settings. The largest increases occurred in tropical regions, with prominent hotspots in the Kivu Rift, southern Yemen, the Hindu Kush and Southeast Asia. Low- and lower-middle-income countries accounted for more than half of the global increase. Low-income countries had the highest share of their population living on steep terrain in 2025, at 18%, compared with 6.4% in high-income countries. The changing settlement patterns were also reflected in substantial peri-urban growth on steep terrain, particularly in Sub-Saharan Africa and South Asia. Major hotspots of steep-terrain population growth experienced substantial land-cover change and largely overlapped with areas of high landslide susceptibility identified using an independent global dataset. Our results provide a globally consistent baseline for identifying where growing populations on steep terrain coincide with broader patterns of settlement and environmental change relevant to hazard monitoring and risk-informed planning.