Dirt road density increased markedly since the 1970s in the Daurian grasslands

Abstract

Informal dirt roads are widespread and can increase human access and habitat fragmentation in remote landscapes. However, they are rarely mapped, leaving their ecological effects poorly quantified. We assessed changes in dirt road networks across the Daurian Steppe of Mongolia, Russia, and China from 1972 to 2024 using historical Hexagon KH-9 and recent Maxar WorldView-3 imagery with U-Net CNN. We quantified changes in road extent, density, and landscape fragmentation and compared them with widely used open-access road datasets. We used generalized linear mixed models to estimate how accessibility, terrain roughness, and national context shaped road networks. We compared road density and fragmentation between protected areas and their surrounding landscapes. Absolute and mean pixel-based densities approximately doubled in the study area. Road extent increased by ∼0.6 percentage points, road intensity increased by ∼68%, indicating long-term intensification of existing road corridors. China showed the strongest expansion, Mongolia was most stable, and Russia had substantial spatial reorganization. Fragmentation intensified, with more patches, smaller mean patch area, and higher edge density. Dirt roads remained widespread within protected areas, although strictly protected areas had the lowest densities and buffer zones had the highest. Open-access road datasets captured only 4–20% of the mapped dirt roads. Our findings demonstrate that dirt roads cause persistent, widespread fragmentation, even in protected and sparsely developed landscapes, but are largely missed by broad-scale analyses of human footprints. These results highlight the need to map all infrastructure, including dirt roads, for conservation planning and land management.