Carbon dioxide removal through mangrove forest (re-)establishment: Key drivers, uncertainties and challenges for long-term success

Mangrove (re-)establishment, or mangrove reforestation and afforestation, is increasingly recognized as a nature-based carbon dioxide removal (CDR) approach with the potential to contribute to climate change mitigation strategies, while delivering substantial ecological and societal co-benefits. However, their effectiveness as long-term CDR strategies depends on a sequence of interdependent decisions and management actions spanning project design, implementation, and monitoring. This review synthesizes evidence on important key factors impacting carbon sequestration outcomes in mangrove reforestation and afforestation and identifies key challenges for robust quantification of CDR potential. Successful mangrove (re-)establishment begins with the integration of stakeholder perspectives, governance frameworks and local ecological conditions into site selection. Failure to account for these dimensions can reduce carbon sequestration potential, as well as storage permanence, and compromise project success. Long-term success further depends on sustained management interventions, including survival monitoring, pest control, tree thinning, and supplementary planting. Across the (re-)establishment pathway, monitoring, reporting, and verification (MRV) remains a critical challenge, particularly due to the limited availability of pre-restoration baseline data of carbon stocks and fluxes. This deficiency introduces substantial uncertainty for estimating net carbon dioxide removal. Although mangrove restoration can achieve sequestration rates of up to 41 Mg CO₂ ha⁻¹ yr⁻¹ under favorable conditions, strong spatial and temporal variability underscores the need for continuous long-term datasets across diverse tropical regions. We highlight the importance of transdisciplinary collaboration to strengthen empirical evidence, improve process understanding and enhance MRV frameworks. While unlikely to offset hard-to-abate emissions at the scale required as a standalone solution, mangrove reforestation and afforestation represent a valuable component of diversified CDR strategies and provide significant benefits for biodiversity, coastal protection, and local livelihoods.