The Green Paradox in Resource-Dependent Regions: Heterogeneous Impacts of Environmental Regulation on Carbon Lock-in Subtitle: Evidence from Double Machine Learning in China's Yellow River Basin

Resource-based cities in the Global South universally face a "dual dilemma" of sustaining economic growth while breaking path-dependent carbon lock-in. As a critical energy basin in China, the low-carbon transition of the Yellow River Basin is pivotal for achieving national carbon neutrality goals. However, debate persists regarding whether the "Yellow River Basin Ecological Protection and High-Quality Development Strategy" (implemented in 2019) effectively disrupts this high-carbon dependency. Existing studies often rely on linear models, ignoring the high-dimensional non-linear confounders typical of complex eco-economic systems, potentially masking the true "Green Paradox" effects. Treating this strategy as a quasi-natural experiment, this study employs a Double Machine Learning (DML) causal inference framework on a long-term panel dataset (2000–2023) covering 938 counties. This approach utilizes orthogonalization techniques to effectively eliminate the interference of 75 high-dimensional confounding variables. The findings reveal: (1) Aggregate Effect: The strategy significantly reduced carbon intensity on average (ATE = -0.058, p<0.01). (2) Green Paradox Confirmation: Dynamic analysis reveals that emissions did not decline immediately; instead, a short-term rebound occurred initially (t=0, t=1), confirming the existence of "intertemporal arbitrage" behaviors. (3) Asymmetric Mechanism: Decomposition analysis indicates that emission reductions were primarily "Efficiency-driven" (diluting intensity via innovation, Coef = -0.290) rather than "Structure-driven". Notably, the industrial structure coefficient showed a short-term resilience (Coef = +0.032), suggesting that high-carbon industries were not "washed out" but rather locked in due to structural rigidity. Conclusion: While top-down environmental strategies act as an effective "brake" for expanding economies, declining regions require complementary "Just Transition" mechanisms to avoid falling into a low-carbon poverty trap.