Predicting the response of coastal wetlands of Southeastern Australia to sea-level rise

Coastal saltmarsh is an endangered ecological community in New South Wales and

sea-level rise has been listed as a key threatening process. Over the previous five

decades moderate rates of sea-level rise have coincided with the invasion of saltmarsh

by mangrove. Surface elevation tables (SETs) were installed in 12 coastal wetlands in

Southeastern Australia to establish elevation and accretion trajectories for

comparisons with mangrove encroachment of saltmarsh and sea-level rise. SETs

confirmed that the elevational response of wetlands is more complex than accretion

alone and elevation changes may also be attributed to below-ground processes that

alter the soil volume such as subsidence/compaction, groundwater volume

fluctuations, and below-ground biomass changes. A simple modelling approach was

employed to establish a relationship between the observed rate of mangrove

encroachment of saltmarsh and relative sea-level rise, which incorporates the eustatic

component of sea-level rise and changes in the marsh elevation. Increasing access to

high resolution digital elevation models will enhance our capacity to predict the

response of coastal wetlands to sea-level rise. Long-term datasets of elevation

dynamics and improved understanding of the feedback mechanisms influencing

marsh elevations will further enhance our modelling capacity.