Upstream costs of the energy transition: differentiated mechanisms of economic-environmental synergy in lithium development systems.

As the global energy transition accelerates, the low-carbon benefits realized downstream in new energy supply chains do not mean that upstream resource extraction is environmentally benign. The local ecological costs induced by lithium extraction therefore require renewed scrutiny. Existing studies have largely focused on single regions or single environmental effects, making it difficult to identify the general patterns and context-dependent mechanisms underlying the impacts of lithium development. Methodologically, this study develops an integrated evaluation framework that combines ecosystem service value, development economic performance, and a synergy deviation index to characterize economic-environmental relationships across different lithium development systems. This framework is integrated with XGBoost-SHAP and covariance-based structural equation modeling to examine model-attribution patterns, nonlinear response intervals, and structural pathway associations. This design allows ecological costs, development gains, spatial imbalance, and pathway heterogeneity to be assessed under a unified analytical structure. Empirically, the results show that lithium development is generally accompanied by a pronounced spatial coupling between mining expansion and increasing economic-environmental imbalance. This imbalance does not increase linearly with development intensity but exhibits clear landscape-specific differentiation. In high-intensity development systems, conflict tends to be spatially concentrated; in systems where mining is superimposed on broader development activities, conflict tends to diffuse along networked corridors; and in ecologically sensitive systems, severe imbalance may emerge even at relatively small development scales. Further analysis indicates that resource type alone does not determine the magnitude of upstream costs; ecological baseline and development organization strongly shape how disturbance propagates. These findings suggest that the assessments of critical-mineral sustainability should consider not only extraction intensity and downstream decarbonization benefits but also upstream environmental costs across different development systems. The study provides methodological support and empirical evidence for lithium governance and the sustainability assessment of critical mineral supply chains.