Climate change will exert effects on intertidal vegetation not only via rises in sea level, but also by storm surges, higher air and water temperatures (particularly for temperature-limited species such as mangroves), altered CO2 concentrations (via differential effects on plants with different photosynthetic pathways), altered wind speed, insolation, frequency of hot days and altered freshwater inflows (via effects on soil and water hypersalinity), and changed current patterns (via effects on propagule transport).

We modelled the likely impacts of sea-level rise on mangroves and saltmarshes in Western Port, a large marine embayment on the south coast of Victoria with diverse and extensive estuarine vegetation. In the absence of a holistic dynamic model, we explored only two variables: i) tidal regime; and ii) wave energy. The idea was to define the tidal and wave energy constraints on inter-tidal vegetation from their currently mapped extent within the Bay, then attempt to circumscribe this environmental space in a future with an 0.80 m rise in sea level whilst maintaining constant all the other relevant variables. The simple model showed that current saltmarsh and mangrove distributions are tightly related to sea level. It demonstrated also the broad areas where saltmarsh migration is conceivable, such as on the coastal plains around Tooradin, against those where it is impossible due to steep hinterland terrain, such as along the San Remo coast. Such propositions, however, must be interpreted with great caution, as only the basic topography, a crude measure of relative wave energy, and the tidal range of saltmarsh and mangroves were used in the model. The results, although interesting, are not directly useful for coastal planning in either a nature-conservation or coastal-development context. The predictive limitations of such models need to be – but rarely are – considered during their application to coastal planning and biodiversity conservation.