Purpose <p>Achieving United Nations Sustainable Development Goal 13, Climate Action, requires strategic policy insights on integrating strong institutions and human capacities in the SSA region. Yet, empirical validation on the combined implications of the triad remains unclear, inconclusive, and fragmented. This study examines the effects of human productive capacities and the extent to which institutional quality mediates climate action performance and ecological reserve in SSA between 2000 and 2024.</p> Methodology <p>The study builds on the assumptions of the Environmental Kuznets Curve and the Stochastic Impacts by Regression on Population, Affluence, and Technology for its theoretical framework. Using novel datasets from the Global Footprint Network, and the World Bank, the study employs the Kernel Regularized Least Squares (KRLS) machine learning estimators to capture non-linearities and marginal impacts. Mediation analysis was also used to quantify how institutional mechanisms filter the human capacities-environment nexus.</p> Findings <p>The study finds that (i) human productive capacities have a negative and significant impact on climate action performance and ecological reserve, and (ii) Institutional quality significantly ameliorates the influence of human productive capacities on environmental sustainability. The mediation analysis indicates that institutional quality mitigates approximately 22% of the overall impact of human capital on climate action performance and 12.3% on ecological reserves.</p> Recommendation <p>Regulators are expected to embark on human capital reforms to integrate green stewardship, training, and technical policies, thereby mitigating their adverse implications on sustainability. Simultaneously, authorities should strengthen institutional frameworks to ensure that human productive capacities are channelled towards low-carbon sectoral pathways to sustainability.</p>