Abstract: The indiscriminate expansion of rubber plantations in Southeast Asia has catalyzed extensive tropical primary deforestation, yet its cascading impacts on ecosystem services and the underlying eco-economic trade-offs remain inadequately explained. By integrating multi-source remote sensing data with ecosystem service valuation models, this study unveiled the spatial dynamics, ecological repercussions, and economic costs of primary forests converted to rubber plantations in Southeast Asia from 2001 to 2021. The results showed that 12.7% of the current 14.15 × 10⁶ ha rubber plantations were converted from primary forests, with Indonesia, Thailand, and Cambodia collectively contributing 70% of the conversion area. Cambodia exhibited the highest conversion intensity, with 35.3% of its rubber plantations displacing primary forests. Such land-use transformations precipitated catastrophic ecosystem services degradation in conversion, with 66.3–98.2% of areas experiencing declines. Although rubber cultivation generated 69.3 billion USD in economic benefits in conversion, this amount offset only approximately 1/19 of ecosystem service losses, which were valued at 1,344.9 billion USD. Indonesia, accounting for 46% of aggregate ecological value loss, is the regional degradation epicenter. Benefit-loss ratios remained alarmingly low (< 6%) in major producing countries, exposing considerable imbalances in eco-economic relationships. This study draws the attention of policymakers and researchers to the substantial ecological costs associated with rubber-driven primary forest deforestation and calls for collective efforts to explore balanced pathways for rubber expansion and ecosystem conservation.

Key words: Primary forest deforestation, Rubber plantations, Ecosystem service, Eco-economics, Southeast Asia