Functional land-use separation reveals the CO₂-emission benefits of compact living spaces in urbanizing China

Rapid urbanization blurs the spatial boundaries between residential living, industrial production, and peri-urban transition zones, complicating assessments of whether compact development reduces carbon emissions. Existing evidence remains mixed because density is often measured over undifferentiated built-up areas that combine commercial-residential and industrial land. We argue that density should be measured within functionally relevant commercial-residential areas. Using a 0.1° gridded panel for 278 Chinese cities from 2013 to 2019, we combine MEIC fossil-fuel CO₂ emissions, WorldPop population data, and POI-based functional zoning to isolate commercial-residential land. A 1% increase in commercial-residential population density is associated with a 0.09% reduction in per capita CO₂ emissions. This relationship is robust to alternative land-use thresholds, spatial restrictions, and city × year fixed effects. The findings suggest that compact commercial-residential development can complement urban carbon-mitigation strategies, while functional land-use separation can improve the interpretation of density–emission relationships in rapidly urbanizing regions.