Amongst the many threats to Salt marshes is the invasion of mangroves! Swamp wallabies were known to graze on mangrove seedlings, and it is believed that since the decline in their numbers since European settlement, mangroves have been able to spread without this limiting control!
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Conservation
In 1982 the south east Australian bioregions contained only 354 square kilometers of salt marsh, yet it was recognised as the most biodiverse type of salt marsh in Australia, with the greatest species richness and incidence of species endemic to Australia. It can be invaded by mangroves at its wet edge, and by other wetland species and human encroachment at its dry edge, and is thus being sqeezed out! In the Sydney region the decline of the swamp wallaby has been suggested as a contributing factor as they were known to limit the landward encroachment of mangrove seedlings by grazing on them.
Major threats are:
- Infilling for development eg roads, residential, waste disposal, agriculture, industrial and recreational uses
- Modification of tidal flows as a consequence of artificial structures being erected
- Alteration of salinity and increasing nutrient levels resulting from the discharge of stormwater into salt marshes, which favours wetland species (other than salt marsh) that like the ‘freshwater’ input (eg Phragmites)
- Weed invasion especially by Juncus acutus
- Physical damage from human disturbance eg trail bikes, domestic and feral animals
- Invasion by mangroves
- Inappropriate fire regimes
- Dumping of rubbish and pollution from oil or chemical spills from shipping or road accidents, catchment runoff of nutrients and agricultural chemicals
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