<p>This study estimates the economic value of biodiversity in South Korea and highlights the importance of integrating ecological considerations into preliminary feasibility studies for infrastructure projects. Using a meta-regression analysis based on contingent valuation studies, I quantify biodiversity values and apply them to a cost–benefit analysis of the Songriwon Dam by transferring the estimated values to the Naeseongcheon River basin. While the dam is expected to deliver diverse benefits, it may also incur significant environmental costs, including biodiversity loss, degradation of protected species’ habitats, and ecological fragmentation. In the case of the Songriwon Dam project, my analysis shows that once biodiversity loss is included as a cost, the benefit–cost ratio falls below the threshold of economic viability, reversing the original feasibility conclusion. These findings underscore the need to incorporate non-market ecological values at the early stages of project evaluation. The proposed approach offers a practical tool for environmental valuation in the absence of primary data and supports institutional reforms in environmental impact assessments. Recognizing ecological costs can enhance infrastructure resilience and contribute to more sustainable development outcomes.</p>