Native-borns and migrants do not contribute equally to domestic CO2 emissions.

While population growth is a known driver of CO2 emissions, prevailing models often treat "population" as a homogeneous factor. This study addresses a critical gap, providing the first comprehensive empirical analysis to disaggregate the contributions of native-born and migrant populations to domestic CO2 emissions. Using an extended STIRPAT model for 172 countries (1990-2022), separated by OECD and non-OECD blocs, we uncover two novel insights. First, native-born populations consistently exhibit a substantially higher emissions elasticity than migrants in both country groups. Second, a dynamic shift occurred in OECD countries: migrants' initially higher per capita emissions impact steadily declined over time, becoming lower than native-born individuals after 2003-2004. This refutes simplistic notions that migration inherently increases emissions. Our findings underscore the urgent need for differentiated, equitable climate policies that acknowledge the heterogeneous and evolving consumption patterns of diverse demographic groups, enabling more efficient mitigation strategies.