Anthropogenic impacts on carbon accumulation capacity within saltmarsh sediments

Purpose: This study provides a comprehensive global synthesis of total organic carbon (TOC) accumulation in saltmarsh ecosystems, drawing on data from 177 sediment cores. These cores were categorized based on environmental conditions, including non-impacted, sewage-impacted, dam-impacted, deforested, and weather-impacted sites. The analysis aims to assess how various anthropogenic and natural stressors influence TOC storage in saltmarshes, offering valuable insights into their role in carbon sequestration and informing future conservation and restoration strategies in the context of global climate change. Materials and methods: A systematic global review was conducted in accordance with PRISMA guidelines, ensuring methodological rigor, transparency, and reproducibility. This approach enhances the reliability of the findings and supports consistent evaluation across studies, providing a robust foundation for synthesizing data on total organic carbon accumulation in diverse saltmarsh environments. Results and discussions: Significantly higher TOC accumulation was recorded in saltmarshes impacted by sewage effluents (397.5 ± 170.1 g m⁻² yr⁻¹) and dam construction (664.1 ± 275.8 g m⁻² yr⁻¹), representing increases of up to three- and fivefold, respectively, compared to non-impacted ecosystems. However, deforested and weather-impacted ecosystems showed up to fourfold declines in carbon accumulation compared to non-impacted areas. Conclusions: These findings highlight the significant influence of anthropogenic pressures, particularly in rapidly urbanizing regions, on the carbon dynamics of saltmarsh ecosystems. Understanding these impacts is essential for developing effective management and restoration strategies that preserve the carbon sequestration potential of saltmarshes and support their role in mitigating climate change through long-term carbon storage in these environments.