This study examines the effect of Nigeria’s ecological system, measured through biocapacity, ecological footprint, carbon emissions, green finance, foreign direct investment, renewable energy consumption, government health expenditure, urbanization rate, population, and energy use on sustainable economic development, proxied by GDP per capita, life expectancy, and infant mortality rate, over the period 2000–2024. The study is motivated by a persistent Nigerian paradox: nominal economic growth has continued alongside a widening ecological deficit and stagnant human welfare outcomes, while the specific channels theorised to reconcile this disconnect, including foreign direct investment, green finance, government health expenditure, and urbanization have themselves underperformed or produced ambiguous results. Adopting an ex post facto research design and Ecological Economics Theory as its primary theoretical anchor, the study specifies three ARDL bounds-testing models corresponding to its three dependent variables, using annual secondary data drawn from the Global Footprint Network, the World Bank’s World Development Indicators, and the Central Bank of Nigeria. The ARDL bounds test confirms cointegration in all three models. Long-run estimates show population exerting a positive and significant effect on GDP per capita, while green finance, foreign direct investment, and ecological footprint depress it; urbanisation exerts a significant negative long-run effect on life expectancy, while carbon emissions show a significant positive association, consistent with Nigeria sitting on the rising segment of an Environmental Kuznets Curve; the infant mortality model, despite very strong evidence of a long-run relationship, yields no individually significant long-run coefficients, a result attributed to severe multicollinearity among its regressors. Granger causality tests confirm that biocapacity, ecological footprint, carbon emissions, government health expenditure, urbanisation, and population each Granger-cause infant mortality rate, the study’s clearest causal finding. The study concludes that Nigeria’s ecological system and its economic and welfare outcomes are statistically linked, but that the channels expected to convert ecological and financial resources into sustainable development, green finance and foreign direct investment in particular, are not yet functioning as theorised, and offers corresponding policy recommendations.