Restoration of native saltmarshes enhances carbon sequestration and mitigates warming effects following Spartina alterniflora removal

The rapid expansion of exotic Spartina alterniflora has significantly threatened native coastal ecosystems' structure and function, prompting global control efforts. Consequently, native saltmarshes restoration has emerged as a nature-based solution following invasive species removal. However, given that S. alterniflora is a high-carbon invasive species, the impacts of native saltmarshes restoration on coastal blue carbon benefits following its removal remain uncertain. Here, we quantified atmospheric carbon uptake and organic carbon storage among restored native saltmarshes (Phragmites australis and Bolboschoenoplectus mariqueter communities), unrestored bare mudflat following S. alterniflora removal and uncontrolled S. alterniflora communities to assess whether native saltmarshes can compensate for the carbon sinks and the climate effects after invasive species eradication. The results showed that S. alterniflora removal drastically reduced carbon sink, with unrestored mudflat transitioning to a carbon source. While restored native saltmarshes showed lower atmospheric carbon uptake compared to pre-eradication S. alterniflora levels, they exhibited significantly enhanced carbon sequestration relative to unrestored mudflats. Additionally, the organic carbon density of soil (0–50 cm) and vegetation in restored sites exceeded unrestored areas by >1.4 times, recovering >70% of the carbon storage observed in S. alterniflora communities. Sustained global warming potentials (SGWP) analysis over a 100-year timescale revealed that without post-eradication vegetation restoration, saltmarsh could shift from climate cooling to warming effects. Native saltmarsh restoration effectively mitigated this transition, demonstrating substantial climate change mitigation potential. Synthesis and applications. Our findings not only reveal that native saltmarsh restoration is a blue carbon-friendly ecological restoration approach following S. alterniflora removal, but also highlight the critical trade-offs between carbon losses from invasive species removal and the carbon offset achieved through restoring native vegetation, providing actionable guidance for coastal management. These insights are particularly valuable for regions facing similar invasive species challenges, informing the development of integrated strategies that maximize carbon compensation while enhancing coastal sustainability and climate resilience. Future restoration programmes should prioritise multifunctional outcomes that simultaneously address biodiversity conservation and climate mitigation objectives.