A chronosequence approach assessing carbon stock and fauna habitat potential of restored coastal wetlands in Southeast Queensland, Australia

Restored coastal wetlands provide key ecosystem services such as climate regulation and habitat for biodiversity. Restoration site maturity is considered as a measure of ecological recovery that can be assessed from monitoring vegetation structure development over time. Carbon stock estimates can be refined from local measurements of root productivity and root mass at different site ages but such data are limited. Moreover, few studies simultaneously assess changes in carbon stocks and biodiversity restoration trajectories and compare these to remnant natural wetlands. Here, using a space-for-time approach, we developed recovery trajectories for vegetation structure, root production, carbon stocks, and insectivorous bat activity as an indicator of fauna habitat, for mangroves, saltmarshes, and supratidal forests in subtropical Southeast Queensland, Australia. Over the chronosequence, aboveground vegetation structure suggested that restored wetlands reach maturity in about 33 years for mangroves, 9 years for saltmarshes, 13 years for Melaleuca and 29 years for Casuarina supratidal forests. Root productivity showed no clear trend with site age for most ecosystems, indicating that carbon sequestration of belowground biomass was strongly influenced by site-specific factors rather than site age. Total ecosystem carbon stocks modelled for mature restored wetlands were within at least ∼76 % of reference values. Bat activity in mangroves increased over the chronosequence and was dominated by the closed foraging guild as stands approached maturity. Overall, restoration trajectories derived from a chronosequence approach can improve modelled estimates of carbon sequestration and biodiversity enhancement delivered by restored coastal wetlands, which in turn, can strengthen predictions on how coastal wetland restoration contributes to climate change mitigation and biodiversity loss reversal.