VICTORIA Temperate Wet Winters
Mangroves of Victoria mostly inhabit the low energy environments of bays, inlets and estuaries along the central section of the coast. In this way mangroves cover around 2% of the 2,000 kilometres of coastline. In general, the Victorian coast faces the Southern Ocean in the west, the Tasman Sea/Pacific Ocean in the east, while the majority of the central section of coast faces Bass Strait. Within the central and eastern sections are found the sole mangrove species, Avicennia marina or, as referred to locally, the White Mangrove. Recent estimates indicate there are around 63 square kilometres of mangroves in Victoria. Victorian mangroves are restricted to sheltered shores often in association with saltmarsh species such as Sarcocornia quinqueflora (Beaded Glasswort) and Sclerostegia arbuscula (Shrubby Glasswort).
Highest latitudinal limit in the World
The southern hemisphere and world’s highest latitude mangroves occur at Millers Landing in Corner Inlet, at latitude 38° 45’ S. These mangroves are a uniquely cold-tolerant mangrove variety, called Avicennia marina var. australasica that form a distinct south-eastern Australian to New Zealand population.
Uniform low height and structure
Mangroves show a stunted growth form, sometimes of “bonsai” proportions, and form a distinctive vegetation band within the upper tidal zone seaward of saltmarshes forming heights ranging from 0.3 m to 5 m.
Low biodiversity Avicennia marina forms distinct monoculture stands of low-closed shrublands. These mangroves occur on muddy and fine sandy sediments, although an unusual occurrence is located on basalt rocks in the Jawbone Flora and Fauna Reserve at Williamstown, close to Melbourne City.
- Avicennia marina var. australasica - PB, GP
- Avicennia marina var. australasica
- Photo: Chris Harty
Need for further State guidelines, policy and legislation to specifically protect tidal wetlands, including mangrove and tidal saltmarsh plants.
Rapidly increasing population pressures leading to cumulative impacts from multiple small effects.
Mangroves occur along sheltered sections of the Victorian coast mostly within broad inlets and coastal lakes (modified from Ozestuaries 2006), influenced by cool, continually moist conditions, micro to meso tides and moderate to severe waves. Three regions are based on the types of mangrove habitat determined by the different geological and physiographic settings.
Ocean West (OW) - Exposed Cliffs and Rocky Inlets
Discovery Bay and the Glenelg River, to Anglesea and Thompson Creek – 6 local catchment areas, spanning some of the most exposed and rugged coasts in the country. No mangroves occur in this region.
Port Bays (PB) - Large Sheltered Embayments
Barwon River near Port Phillip Bay, to the Powlett River in Western Port Bay – 6 local catchment areas, characterised by the two large, south facing embayments. Mangroves occur in these two large bays: Port Phillip Bay has three or four mangrove sites, including Barwon Heads within the Barwon River estuary near Geelong, Limeburners Bay and Hovells Creek estuary at Corio, and Williamstown in the Jawbone Flora and Fauna Reserve, at the mouth of Kororoit Creek, and under the West Gate Bridge in the Stony Creek Backwash adjoining the Yarra River estuary around Melbourne; and, mangroves occur throughout Western Port Bay, including French Island and Rhyll and Churchill Islands off Phillip Island. The region has one mangrove species with a total mangrove area of ~38 km2.
Gippsland (GP) - Coastal Lakes and Snowy Mountains
Andersons Inlet to Mallacoota Inlet – 8 local catchment areas, with the largest coastal lake system in the southern hemisphere. Mangroves occur in 3 locations, including: Andersons Inlet near Inverloch in South Gippsland; Corner Inlet and the Nooramunga Marine and Coastal Parks, between Wilsons Promontory National Park and McLoughlins Beach; and, Cunningham Arm, Lakes Entrance - the latter being the eastern-most mangrove site in Victoria. Corner Inlet is the southern-most mangrove stand in Australia, and this site is also the highest latitude site of any mangrove in the world. The region has one mangrove species with a total mangrove area of ~25 km2.
Natural erosion of the Barwon River estuary bank, Barwon Heads. A mangrove tree survives precariously after falling into the river due to bank erosion. Photo: Chris HartyA range of natural factors affect mangroves in Victoria. These highlight theimportance of monitoring natural processes to quantify these subtle but significantfactors. Some important influencing factors include:- rising temperatures may resultin mangrove expansion where they have been excluded previously by winter frosts fall below 40 C; sea level rise is expected to cause ‘zonal shift’ with mangroves ‘squeezed’ between rising water levels and barriers restricting their landward migration – as well as in competition with saltmarsh plants, like the Shrubby Glasswort; competition with invasive weeds such as Spartina spp. (Cordgrass); storm-wash wrack smothering breathing roots and seedlings of mangroves; and, erosion causing tree loss by destabilisation of trees, and deposition of fine sediments that causes burial/smothering of breathing roots.
Mangroves, birdlife and urban development co-exist at Williamstown, Melbourne. Photo: Chris HartyVictoria is one of the smaller states although it contains the second largest human population in the country – and, this is growing rapidly. Furthermore, the populated areas are expanding within catchments containing the largest areas of mangroves. The resulting human impacts include:- detrimental cumulative impacts caused by fragmented state legislative protection for mangroves – where land use change and development have occurred without adequate consideration of the effects on mangrove ecosystems; altered hydrology and stormwater flows (e.g., increased freshwater discharge from drainage outlets) have increased nutrients and altered environmental flows within estuarine catchment areas; direct damage associated with clearing for waterfront views, or access to waterways for boating and fishing; pollution discharges from urbanised and industrial catchments, such as oil spills causing reduced mangrove coverage, e.g. in Kororoit Creek, Port Phillip Bay; and, sedimentation in estuaries associated with development upstream causing smothering of mangrove roots and loss of mangrove area.
Community conservation & education
Community involvement has improved greatly since 1994 when Victoria commenced its Coast Action program to raise public awareness and understanding of coastal issues. This incorporates wetland protection with improved access to select field sites and education centres. The highest latitude mangroves in the world can be visited at Millers Landing via a walking track that forms part of the bushwalking network within Wilsons Promontory National Park. Likewise, there are informative boardwalks within mangroves at Tooradin on the South Gippsland Highway, at Rhyll as part of the Phillip Island Nature Park, at Limeburners Lagoon near Geelong as part of an extensive walking trail and at Port Franklin and Toora at Corner Inlet, South Gippsland. Until its recent destruction by fire, one of the better educational resources available was the Marine Education Centre at Tooradin, on the northern shores of Western Port Bay. Current research, focused chiefly on Western Port Bay, includes mangrove and saltmarsh monitoring at selected locations by Dr Neil Saintilan, Australian Catholic University. Other projects are more discrete and related to individual university research projects. Parks Victoria are undertaking additional research into mangroves as fish habitats as part of their declaration of a State network of marine national parks. The following ABC Science Show link highlights community involvement in environmental issues and restoration of mangroves and seagrasses in Western Port bay.
Although 96% of the Victorian coast is in public ownership, inappropriate use of coastal lands in the past has resulted in serious degradation of mangrove areas. Mangroves in Victoria are not protected under specific legislation. Notable efforts over the last decade have begun to amend the situation. Protection of mangroves on private land is possible through local policy and development overlay provisions in municipal planning schemes prepared under the 1987 Planning and Environment Act. However, such protection has been poorly implemented at a local level. Mangroves on coastal crown land are protected through a consent process under the Coastal Management Act 1995. Overarching protection is offered with the Victorian Coastal Strategy 2002, the State Biodiversity Strategy and through policies that protect water quality and manage waste discharges under the Environment Protection Act 1970. Marine National Parks like Yaringa, Churchill and French islands in Western Port Bay provide some fully protected areas under Victoria’s ‘no take’ policy. Marine and Coastal Parks afford protection for those mangroves on public coastal crown land at Corner Inlet and Nooramunga. The Ramsar Convention on designated wetlands protects mangroves on public land around Barwon River, Limeburners Bay, Western Port Bay and Corner Inlet. Principle agencies responsible for mangrove areas include: DSE (Department of Sustainability and Environment), Parks Victoria, DPI (Department of Primary Industries), EPA (Environment Protection Authority), Victorian Coastal Council, Regional Coastal Boards, Victorian Catchment Management Council, Regional Catchment Management Authorities and local government. Victoria has recently adopted an integrated approach to better coordinate planning and management of coastal and marine environments through the establishment of the Victorian Coastal Council and Regional Coastal Boards, whose role is to advise the Minister for Environment on coastal matters.