This study investigates the impact of converting disturbed Peruvian Amazon forests to smallholder oil palm plantations on carbon stocks. Comparing vegetation structure, species composition, and carbon storage, the study found that oil palm plantations stored 55% less carbon than disturbed forests. This highlights significant ecosystem carbon losses (62.7%) over a 30-year oil palm rotation. Findings emphasize the need for sustainable land-use practices, advocating oil palm expansion on low-carbon degraded lands instead of forested areas to minimize environmental impacts.