Balancing Act on the Third Pole: Three Decades of Ecological-Economic Synergy and Emerging Disparities Along the Qinghai–Tibet Railway, China

The Qinghai–Tibet Plateau (QTP), a critical ecological buffer for Asia, faces intensifying pressures from climate change and infrastructure expansion. The Qinghai–Tibet Railway (QTR), as the world’s highest-altitude railway, traverses this fragile yet economically vital region, where balancing ecosystem integrity and development remains a global sustainability challenge. While previous studies have documented localized environmental impacts of the QTR, systematic assessments of long-term ecological-economic interactions—particularly the synergies and trade-offs between ecosystem service value (ESV) and economic growth—are lacking. This gap hinders targeted policy design to reconcile conservation and development in extreme environments. The present research integrates an enhanced ecosystem service valuation framework with spatial econometric modeling to quantify environmental changes and ecological-economic coordination in the Qinghai–Tibet Railway Region (QTRR) during 1990–2020. The analysis reveals a cumulative ESV increase of USD 54.4 billion over the past 30 years, driven primarily by grassland restoration and regulated land use transitions. Notably, county-level ecological-economic coordination improved significantly, with harmonization indices rising by 32–68% across all jurisdictions. However, latent risks emerged: five counties exhibited severe ecosystem-health-to-economy mismatches by 2020. These findings demonstrate that infrastructure corridors in fragile ecosystems can achieve partial ecological-economic coordination through policy interventions, yet persistent local disparities demand spatially differentiated management. By linking ESV dynamics to governance pathways—including livestock–forage balance mechanisms and green urban zoning—the present study provides a transferable framework for assessing sustainability trade-offs in extreme environments. Broader implications highlight the necessity of embedding adaptive ecological thresholds into infrastructure planning, offering experiences for the Belt and Road Initiative and other high-altitude development frontiers.