Conventional infrastructure appraisal in Africa prioritizes short-term economic performance while insufficiently accounting for the environmental conditions that govern long-term sustainability, spatial equity, and development resilience. To address this gap, this study develops an explicitly SDG-oriented spatial–ecological framework to examine how environmental quality conditions the economic returns of large-scale infrastructure investments under corridor-based development. The primary objective is to quantify infrastructure–environment complementarity and identify ecological thresholds regulating spatial spillovers and investment effectiveness along Tanzania’s Belt and Road Initiative (BRI) corridors. High-resolution remote sensing and spatially explicit socioeconomic data for 2012–2023 are integrated within a spatial econometric design. A Spatial Durbin Model (SDM) incorporating the Normalized Difference Vegetation Index (NDVI) is estimated to capture non-linear interaction effects, with economic activity proxied by Night-Time Light (NTL) intensity across 2680 corridor grid cells. The results identify a statistically robust ecological threshold at NDVI = −0.8σ, beyond which infrastructure investments shift from low to high economic effectiveness. A strong positive infrastructure–environment interaction (β = 6.44, p < 0.001) indicates that environmental quality functions as a productive modulating factor rather than a passive constraint. Spatial classification shows that 63% of corridor areas are investment-ready, while 15% require ecological restoration prior to effective infrastructure deployment. Although institutional quality and long-term post-construction dynamics are not explicitly modeled, the framework provides a replicable and policy-relevant decision-support tool, offering actionable guidance for aligning corridor development with SDGs 9, 11, and 13 and advancing sustainable infrastructure planning in the Global South.

Conventional infrastructure evaluation in Africa emphasizes economic performance while overlooking environmental conditions that govern long-term sustainability. This study develops a spatial–ecological framework to quantify how environmental quality modifies the developmental returns of infrastructure investments along Tanzania's Belt and Road Initiative (BRI) corridors. A spatial econometric approach integrating remote sensing and socioeconomic indicators captures infrastructure–environment interactions. Using a Spatial Durbin Model (SDM) with the Normalized Difference Vegetation Index (NDVI), the analysis identifies environmental thresholds and estimates complementarity effects on economic activity, measured through Night-Time Lights (NTL). Results reveal a critical threshold at NDVI = –0.8σ, delineating zones where investments generate high returns from areas where environmental degradation limits effectiveness. A significant NTL–NDVI interaction coefficient (6.44, p < 0.001) indicates that higher environmental quality substantially enhances infrastructure-driven growth. Spatial classification shows 63% of the corridor as high-priority zones with optimal returns and positive spillovers, while 15% requires ecological restoration prior to investment. The model demonstrates high explanatory power (pseudo R² = 0.882). The findings provide a replicable decision-support tool for optimizing investment allocation, aligning infrastructure strategies with SDGs 9, 11, and 13.