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Challenging Habitats: Southern Saltmarshes
and Mangroves
The information presented here has been written by staff at the
Marine Discovery Centre, Queenscliff, Victoria.
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4. Habitat Issues / Threats
In the past, mangrove stands were seen as unproductive, smelly areas and were often cleared for farmland, harbour developments, residential and industrial developments.
Oil spills can cover the breathing roots of the mangroves and cause them to suffocate. Mangroves in northern Port Phillip Bay have not recovered after many years from oil spills in the 1950's.
Some events that can adversely affect mangroves include;
- Trampling of pneumatophores by people and cars
- Oil Pollution
- Changed freshwater flows - damming rivers alters water flows
- Nutrient inputs creating excessive algal growth and prevent seedlings from being established
The few remaining stands of the mangroves need to be protected to ensure they continue to play their important role in stabilising the banks of rivers and providing nursery habitat for many species.
Clearing: Saltmarshes have been extensively cleared since European settlement resulting in loss of habitat for many birds, reptiles and invertebrates. We have now lost around 80% of the original saltmarsh areas that carpeted the coast of the Port Phillip Bay.
Although saltmarsh is now considered to be important for a number of reasons (such as habitat provision, erosion and flood control, recreational amenity and scientific and educational research opportunities), saltmarsh plants were considered to be extremely useful for other purposes in times gone by. This was due to their high Potassium content.
Potassium is an element which, in certain forms, is used by living organisms as part of their normal functioning. It is also used as "Potash" by humans involved in making glass.
During the Second World War, supplies of glass from overseas were difficult to obtain, so alternatives were sought. A great deal of saltmarsh was cleared, the plants collected and burnt, and the potash left behind was used in the manufacture of glass for use throughout the region .
Not surprisingly, the unusual combinations of plants found in saltmarshes provide important habitat for a number of animals. The Orange-bellied Parrot is perhaps the most well known bird which relies on coastal saltmarsh. In its winter home, the Orange-bellied Parrot feeds on the seeds, leaves and shoots of a number of saltmarsh plants, including four different types of glasswort, Southern Sea Heath, Rounded Noonflower and Sea Rocket.
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