How does renewable energy, newborn birth rates, industrialization, and economic growth affect environmental quality? New evidence from 90 Belt and Road countries

Reducing carbon emissions is a critical approach for attaining global environmental sustainability and combating climate change. To investigate how energy, population, industry, and economic structure affect environmental quality. This study collects panel data for 90 Belt and Road (B&R) nations from 1995 to 2021. For the first time, the nonlinear dynamic impacts of renewable energy, newborn birth rate, industrialization, and economic growth on carbon emissions are investigated using a threshold panel model and a panel vector autoregression (PVAR) model. According to the study's findings: (1) models 1–4 demonstrate that all structural factors have substantial threshold impacts on carbon emissions, demonstrating a nonlinear connection. (2) Carbon emissions are negatively impacted by energy structure (renewable energy) and population structure (newborn birth rate). Industrial structure (industrialization) and economic structure (economic growth), on the other hand, have a beneficial influence on carbon emissions. However, when the structural variables grow in size, their threshold effects all increase this contribution. (3) In three groups of nations with varying wealth levels, differences in the influence intensity of structural factors on carbon emissions, particularly renewable energy and economic growth, were detected. The impact of renewable energy on carbon emissions is: middle-income (MI) countries > high-income countries (HI) > low-income countries (LI). The impact of economic growth on carbon emissions is MI countries > LI countries > HI countries. Based on the findings, relevant policy recommendations are provided to the policy makers of the “B&R” countries from the perspectives of structural factors and heterogeneity. It provides certain references for the realization of global environmentally sustainable development strategies and the coordinated development of economic, social and environmental systems.