Soil organic carbon stocks and sequestration rates in Western Australia’s mangroves

Le résumé fourni par la source

Mangroves are widely recognized for their contribution to climate change mitigation. This study provides the first comprehensive assessment of top 1-m and 30-cm soil organic carbon (OC) stocks and accumulation rates across Western Australia’s mangroves, spanning multiple bioregions, geomorphological settings, and intertidal positions. The results revealed (mean ± SE) 236 ± 13 Mg and 83 ± 4 Mg OC ha −1 in top 1-m and 30-cm soils, respectively, accumulated at 443 ± 83 and 215 ± 22 kg OC ha −1 yr −1 over the past 100 and 500 years, respectively. Mangroves across Western Australia exhibited up to 3-fold differences in top 1-m stocks, with highest OC stocks in tropical settings (328 ± 54 Mg OC ha −1 ) and lowest in temperate mangroves (138 ± 15 Mg OC ha −1 ). At a landscape scale, mangroves within protected embayments and lower and mid intertidal positions held up to ∼1.5-fold higher OC stocks than those in estuarine settings and upper intertidal positions. Long-term accumulation rates varied up to 6-fold, with highest rates in semiarid bioregions and protected settings. Across 212,000 to 277,000 ha of mangrove extent in Western Australia, total stocks in 1-m soils were estimated at 71–86 Tg OC, accumulated at 94–123 Gg OC per annum. Western Australia’s ongoing mangrove losses have been estimated at 0.27% yr −1 , which could result in 177–232 Gg CO 2-eq yr −1 emissions. This study estimates the contribution of Western Australia’s mangroves to the global carbon cycle and provides the basis for improving current national carbon inventories and crediting frameworks.

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