Assessing Environmental Sustainability in <scp>G7</scp> Countries: The Role of Sustainability Uncertainty Index and Energy R&amp;D Expenditures Using <scp>MMQR</scp>

ABSTRACT This study examines the impact of economic growth, Sustainability Uncertainty Index (SUI), energy R&amp;D spending (renewable, nuclear and fossil energy), trade openness, and urbanization on the ecological footprint (EF) in G7 countries over the period 2003–2022. In contrast to previous studies, which often focus on energy consumption or CO 2 emissions, this study introduces the SUI and prioritizes energy R&amp;D spending to provide a new perspective on environmental sustainability. Using the moment quantile regression method, the analysis reveals heterogeneous effects across quantiles and confirms the environmental Kuznets curve hypothesis. The results show that economic growth increases the EF, while SUI, renewable energy R&amp;D, trade openness, and urbanization attenuate it. Conversely, fossil fuel R&amp;D spending increases environmental degradation, and nuclear energy R&amp;D shows no significant effect. Policy recommendations include encouraging investment in renewable energy, developing a G7 SUI index, and facilitating the transfer of green technologies to promote sustainable development in G7 countries.