Abstract
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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.