Effects of the polycentric spatial structures of Chinese city regions on CO2 concentrations.

• Polycentric structure decreases the mean CO 2 concentrations of city regions. • Significant CO 2 reductions are observed in primary city centers. • Mild CO 2 increases are observed in city subcenters. • This reduction is affected by commuting, industry, and household emissions factors. • Polycentric spatial strategies should be implemented into urban planning practices. The environmental sustainability of polycentric spatial structures in urban planning must be evaluated to ensure the sustainable development of city regions. Given the mixed conclusions of previous studies, as well as the lack of information on reliable methods of assessment and quantifiable mechanisms, a three-year dataset for prefecture-level and above city regions in China and spatial econometric models were used to examine the relationship between regional polycentricity and CO 2 concentrations. After robust testing, we confirmed that polycentric structures decrease the mean CO 2 concentrations of city regions, significantly reducing CO 2 concentrations in primary city centers and mildly increasing those in city subcenters. Further quantitative analyses of the mechanisms underlying these patterns revealed that the CO 2 -reduction effect of polycentric structures is due to the balancing of reductions in commuting duration, transference of industrial CO 2 to neighboring areas, and an increase in household CO 2 emissions. [ABSTRACT FROM AUTHOR]