Does Regional Development Influence Sedimentary Blue Carbon Stocks? A Case Study From Three Australian Estuaries

Mitigating climate change through the reduction of atmospheric CO2 levels is of interest,particularly through maintaining and re-establishing natural ecosystems that act ascarbon sinks, such as coastal vegetated habitats or “blue carbon” systems. Herewe compare sedimentary blue carbon (C) stocks from 37 sediment cores collectedin pristine (n = 13), agricultural (n = 11), and urban (n = 13) estuaries within thesame geomorphological region, located on the eastern coast of Australia. The meanestimated C stocks for each carbon system (seagrass, mangrove, and saltmarshes)were 402 78, 830 109, and 723 100 Mg C ha􀀀1, respectively, conservativelyestimated up to 3 m depths. Analysis of variance revealed no significant differencebetween C stocks per area (C ha􀀀1) considering each habitat type and between specificestuaries. However, the total estuarine C stocks were found to be greater with increasinglevels of conservation, based on larger areas of blue carbon vegetation. The potentialloss of C to the atmosphere from these small regional estuaries are 500,574 118,635tons of CO2 equivalent (CO2e), based on specific assumptions. The implication of theseresults are that there are large C stocks in small regional estuaries which supports theprotection of blue C systems in developing coastal areas and highlights the uncertaintiesof the CO2 emissions from potential blue C habitat degradation.