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Natural
Ecosystems -
The Coast
Between
13,000 and 20,000 years ago, at the peak of the last Ice Age, the sea
level was about 100 metres lower than it is today, and Tasmania and the
Bass Strait islands were connected to Victoria. As the ice retreated the
sea level rose, drowning the coastal river valleys and forming the many
bays and inlets that are a feature of the modern Victorian coastline.
Constant exposure to the often gale-force winds that blow from the Southern
Ocean has produced the rugged, eroded landforms that characterise much
of the western coastline. Lashed by wind and waves, the coast is dynamic,
wild, and continually changing: some features appear and disappear in
a matter of months or years, unlike the millennia required for mountains
to form and erode.
The
critical environmental factors affecting the vegetation of the coast are
wind, salt, and the natural instability of many coastal landforms. The
grasses and herbs which colonise the foredunes, and the saltmarsh plants
and mangroves of the mudflats, bind these substrates. Coastal scrubs develop
in the lee of the foredunes and on older, stabilised dunes on the landward
side, usually comprising dense stands of wiry shrubs such as Coast Tea-tree,
Coast Beard-heath, Drooping She-oke and Moonah. In the more protected
swales between and behind the dunes, woodlands of Coast Banksia grow.
The
most prominent group of coast-dwelling animals are the birds: Orange-bellied
Parrots, which migrate from Tasmania and overwinter in coastal saltmarshes;
Little Penguins, which nest in the dunes; and scores of migratory birds
that are regular visitors to our bays and estuaries from Japan, Siberia
and the northern Pacific. Australasian Fur Seals spend most of their life
at sea, but use the coasts and islands to rear their young.
Most
of Victoria’s coastline is reserved for public use, with extensive sections
in national or state parks, so that it is relatively intact compared to
the coasts of most other industrialised countries. Much of this consists
of windswept sandy beaches, rocky shorelines and cliffs. Where the impact
of the waves is reduced in the many embayments along the coast, other
habitats have developed, including seagrass beds, mudflats, mangrove communities
and saltmarsh complexes. The coastal soils are predominantly sandy, although
in some areas, especially where there are cliffs and bluffs, loams and
clay soils occur.
Environmental
weeds are a significant problem in many coastal areas; some exotic species
readily colonise disturbed areas, while some native species have been
able to expand beyond their normal range as a result of altered conditions,
such as the long-term absence of fire. Pest animals such as foxes and
cats are also abundant and can be a significant problem for ground-nesting
birds and small mammals. Increasing coastal recreation and the urbanisation
of coastal and near-coastal areas presents a challenge for the management
of this ecosystem.
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