The impacts of global warming on saltmarsh communities have been reviewed by Hutchings (2001). Increasing temperature is predicted to result in a change in community structure in Australia, through an increasing dominance of Spartina, and with it, presumably, a change in the structure of the associated animal communities. While the invertebrate fauna of saltmarshes in Australia is poorly documented, it appears to be heavily influenced by the type of saltmarsh plant community present (Hutchings 1994a, 1994b). There is some evidence that bird populations also are influenced by plant species composition, with dense beds of Spartina not being preferred habitats (Davis and Moss 1984); this has implications for predation of invertebrates by birds, i.e. both “top down” and “bottom up” impacts from population regulatory processes.

 

Increasing temperatures are also predicted, in most cases, to be associated with rising sea levels. Under natural conditions, the saltmarsh would usually just extend landwards. However, increasingly this landward drift is prevented by man-made structures such as seawalls or other retaining walls. It thus seems likely that the total area occupied by saltmarshes will decline, although measuring this accurately will be difficult as there is, as yet, no detailed inventory of the distribution and extent of saltmarshes in Australia. Such a decline could have consequences in terms of the net export of organic matter into nearby coastal waters, and perhaps a change in the quality of the detritus. Increasing storm activity may also lead to increased levels of erosion of saltmarshes, with the additional suspended matter being washed out onto nearby inshore seagrass beds.

 

Mangrove communities will also be affected, with changes in species composition as temperatures rise, and encroachment onto saltmarshes as sea levels rise.



Copyright © Environment Australia, 2002
Department of Environment and Heritage