Opportunities for blue carbon restoration projects in degraded agricultural land of the coastal zone in Queensland, Australia

Abstract Restoring degraded agricultural lands to their original coastal wetland cover is an approach for enhancing blue carbon storage. This approach enhances carbon sequestration in biomass and soils whilst reducing greenhouse gas emissions and delivering other conservation benefits such as enhancing biodiversity, improving water quality, and protecting coastlines from sea level rise. In Queensland, Australia, tens of thousands of hectares of coastal land have been converted to agriculture since the 1900s, often through drainage. We evaluated the characteristics of degraded agricultural land to identify opportunities for blue carbon restoration projects. Degraded agricultural land was identified through visual inspection of satellite imagery. Our analysis revealed degradation was associated with historical Melaleuca- dominated wetland vegetation and current land uses other than intensive agriculture. Field sampling of a subset of paired degraded and non-degraded sites found that water content, organic carbon, and electrical conductivity were significantly higher at degraded sites. We also observed standing water, drainage structures, and dead trees at degraded sites. From our analyses, we inferred land degradation is likely caused by waterlogging, salinisation, and land management choices. Degraded land historically vegetated by Melaleuca -dominated wetlands could be targeted for blue carbon restoration projects that protect remaining soil carbon and enhance carbon storage, restore ecosystem services, and provide new income streams for landowners. Further characterisation of the distribution of degraded lands may contribute to prioritisation of sites suitable for restoration.