Blue carbon stock of restored mangrove forests is lower than naturally recruited mangroves

Mangrove restoration has become a central strategy in coastal management, driven by the need to mitigate climate change through carbon sequestration and storage in mangrove biomass and soils. However, despite the increase in mangrove restoration projects, the carbon stock of these restored sites is fairly unknown, indicating that most current estimates of carbon offset potential are based on mature naturally recruited mangrove forests. Research is therefore urgently needed to assess carbon accumulation trajectories in restored mangrove systems to evaluate the effectiveness of restoration as a management tool. Here, we used a chronosequence design to evaluate and compare the carbon stock of restored and naturally recruited mangroves of different site ages (5, 6, 9, 10 & 11 years old) in Guyana, South America. We defined the carbon stock based on the above-ground trees and soil carbon, using species-specific allometric equations and formulas to calculate the total carbon stocks. The naturally recruited mangroves had 30.1% higher carbon stock than the restored mangroves. The 6-year-old site had the highest carbon stock for the restored mangroves, while the 5-year-old naturally recruited mangroves had the highest carbon stock. The differences in carbon stock suggest that restored mangroves may take longer to attain the same carbon stock as naturally recruited mangroves. Our results highlight that while restoration enhances carbon accumulation over time, natural regeneration may be more efficient in early carbon recovery. Integrating such findings into mangrove management strategies can improve restoration design, monitoring frameworks, and policy decisions aimed at maximizing carbon sequestration and coastal resilience. • Naturally recruited mangroves stored 30% more carbon than restored sites, showing the efficiency of natural regeneration. • Carbon accumulation varied with forest age, influenced by species composition, sediment, and hydrology. • Mangrove restoration is context-dependent, requiring tailored strategies and monitoring. • Findings inform coastal governance, blue carbon accounting, and adaptive management for effective restoration.