Degraded coastal agricultural lands hold significant soil carbon stocks and are potential candidates for blue carbon restoration

Iroshaka Gregory Cooray; Gareth Chalmers; David Chittleborough

doi:10.1016/j.envres.2026.123742

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Degraded coastal agricultural lands hold significant soil carbon stocks and are potential candidates for blue carbon restoration

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Degraded coastal agricultural lands hold significant soil carbon stocks and are potential candidates for blue carbon restoration

Iroshaka Gregory Cooray, Gareth Chalmers and David Chittleborough

Environmental Research, Vol.293, pp.1-17

2026

DOI: https://doi.org/10.1016/j.envres.2026.123742

PMID: 41519283

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Abstract

Blue carbon ecosystems, including mangroves, offer nature-based solutions against the impacts of climate change. Degraded coastal agricultural lands that were previously coastal wetlands harbour ancient (>1,000 years) soil organic carbon (SOC) pools and can be potential candidates for coastal wetland restoration. We investigated the SOC storage capacity of coastal wetlands under rehabilitation (CWUR) by measuring the SOC stocks of coastal wetlands under different stages of rehabilitation (Phase 1 and Phase 2 sites) and comparing their stocks to those from well-established mature mangroves (reference sites). The location of our study is on Maroochy River floodplain on the Sunshine Coast, Queensland, Australia. In addition, the contribution of different sources to SOC in mature mangroves and CWUR was investigated using Bayesian stable isotope mixing models. Dating of sediments by 210Pb and 137Cs radionuclides was used to estimate the historical sedimentation and carbon accumulation rates for mature mangroves. CWUR had SOC stocks ranged from 242.6 to 322.2 Mg OC ha-1 m-1 whereas the average SOC stocks of mature mangroves were 461.4 Mg OC ha-1 m-1. Not only are the carbon stocks in mature mangroves higher than those for CWUR but they are also comparable to those from mangroves in subtropical Australia and estuarine settings. Unexpectedly, CWUR had higher SOC stocks compared to SOC stocks for pasturelands from previous studies. The suspended particulate matter (SPM) supplied by tidal and fluvial processes is a main constituent of SOC pools in both mature mangroves and CWUR that we studied. Furthermore, mangrove roots contributed significantly to peat and organic-rich sediment formation in mature mangroves on Maroochy River floodplain. Presence of remnant SOC (>1000 years) and availability of accommodation space for sediment deposition in CWUR are advantageous for blue carbon restoration.

Details

Title: Degraded coastal agricultural lands hold significant soil carbon stocks and are potential candidates for blue carbon restoration
Authors: Iroshaka Gregory Cooray (Corresponding Author) - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
Gareth Chalmers - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
David Chittleborough - University of the Sunshine Coast, Queensland, School of Science, Technology and Engineering
Publication details: Environmental Research, Vol.293, pp.1-17
Publisher: Academic Press
Date published: 2026
DOI: 10.1016/j.envres.2026.123742
ISSN: 1096-0953; 0013-9351
PMID: 41519283
Data Availability: Data will be made available on request.
Grant note: This project was supported by the Regional Partnership Agreement between the University of the Sunshine Coast and The Sunshine Coast Council.
Organisation Unit: School of Science, Technology and Engineering; Sustainability Research Cluster
Language: English
Record Identifier: 991200051002621
Output Type: Journal article

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