Models of the response of mangrove forests and saltmarshes to sea-level rise are needed to inform coastal decision making. Zero-dimensional models that simulate evolution of a point are foundational for developing spatially explicit landscape models projecting coastal wetland extents under future sea-level rise scenarios. However, both zero-dimensional and spatially explicit landscape models have suffered from insufficient calibration and inadequate validation. In this study, a zero-dimensional model framework was parameterised using real data from four sub-sites exhibiting varying rates of mineral and organic matter addition and autocompaction. The model was calibrated to correspond to tidal parameters at each sub-site and validation was undertaken across three timescales to assess model efficacy. Short-term validation encompassed the period over which measurements of surface elevation gain were determined using a network of surface elevation tables (~20 years); medium-term validation encompassed the period when higher resolution colour aerial photography was available (~35 years); and long-term validation focussed on the period of landscape evolution occurring since the mid-Holocene. The model performed well at the medium to long-term scale and was within the range of variability arising from surface elevation table measurements. This study demonstrates the critical need for site-specific data, a crucial component that is undervalued, often insufficiently resourced to generate useful data, and commonly addressed by extrapolating parameters generated from elsewhere. Validation has provided the necessary confidence for further model development at the landscape scale that will account for processes operating both vertically and laterally, such as shoreline erosion and tidal creek extension.

Estimates of global carbon stocks in coastal wetlands reveal that these are some of the most efficient carbon-sequestering environments in the world, which has prompted a renewed interest in conservation and restoration programs as an opportunity for greenhouse gas abatement. Accumulation of carbon in coastal wetlands is linked to diverse factors such as the type of vegetation, geomorphic setting, and sediment supply. Feedbacks between these factors and the tidal flow conditions drive the dynamics of carbon accumulation rates. Climate change-induced sea-level rise has been shown to increase the vulnerability to submergence of saltmarsh and mangroves in coastal wetlands, even if accommodation and landward colonization are possible. These potential losses of wetland vegetation combined with the reduced productivity of newly colonized areas will directly affect the capacity of the wetlands to sequester carbon from sediments and root growth. Here, we implement an eco-geomorphic model to simulate vegetation dynamics, soil carbon accumulation, and changes in soil carbon stock for a restored mangrove-saltmarsh wetland experiencing accelerated sea-level rise. We evaluate model outcomes for existing conditions and two different management scenarios aimed at mitigating sea-level rise effects and conserve wetland vegetation. Even though some management measures can result in partial conservation of wetland vegetation, they do not necessarily result in the best option for soil carbon capture. Our results suggest that accelerated sea-level can trigger accelerated wetland colonization resulting in wetland areas with limited opportunities for soil carbon capture from sediment and root mineralization, an issue that has not been considered in previous studies.

Habitat degradation is expected to alter community structure and consequently, ecosystem functions including the maintenance of biodiversity. Understanding the underlying abiotic and biotic assembly mechanisms controlling temporal and spatial community structure and patterns is a central issue in biodiversity conservation. In this study, using monthly time series of benthic fish data collected over a three-year period, we compared the temporal community dynamics in natural and modified habitats in one of the largest river-lake floodplain ecosystems in China, the Dongting Lake. We found a prevailing strong positive species covariance, i.e. species abundance changes in the same way, in all communities that was significantly negatively impacted by water nutrients levels. The positive species covariance, which was consistent for both wet and dry years and among habitat types, had significantly negative effects on community stability, which was measured by the average of aggregated abundance divided by temporal standard deviation. In contrast to species covariance, community stability was significantly higher in modified habitats than in natural habitats. Furthermore, our results demonstrated that the ecological stochasticity (i.e. community assembly processes generating diversity patterns that are indistinguishable from random chance) was significantly higher at natural sites than at the modified sites, suggesting that deterministic processes might control the community composition (richness and abundance) at the modified habitat through reducing species synchrony and positive species covariance observed in the natural habitats. When combined, our results suggest that human habitat modification creates environmental conditions for the development of stable benthic fish community in the highly dynamic floodplains, leading to niche-based community and decrease of temporal β-diversity.