Download Chapter 7: Management template

7
management template
Chapter 1 of the report outlined the wide range of threatening processes that affect mangroves and coastal
saltmarsh in Victoria, and Chapter 2 summarised the legislative and policy frameworks within which these
areas are managed. The discussion below takes those generalised overviews and applies them to a specific
coastal area with extensive coastal saltmarsh: the Barwon River estuary in central-western Victoria, 95 km
south-west of Melbourne.
As mangroves and coastal saltmarsh are under increasing anthropogenic pressures in Victoria, there is an
urgent need to better protect and manage them. Better management involves retaining, rehabilitating and,
where appropriate, revegetating estuarine wetlands by the use of statutory planning mechanisms, combined
with on-ground monitoring programs firmly embedded within a framework of scientific and local knowledge
of mangrove and saltmarsh ecology. As often so little is known about the ecology of estuarine wetlands in
Australia, adaptive management is a useful approach for monitoring the effectiveness of management and
rehabilitation efforts (e.g. see Walters 1986; Gentile et al. 2001; Allan & Stankey 2009). Some literature
tailored to the rehabilitation of Australian coastal wetlands is now available (e.g. Department of Environment
and Climate Change 2008a,b; Adam 2009b). In more general terms, though, the ten basic principles
identified by Zedler (2006) are worth restating for wetland rehabilitation:
• Consider the hydrological, geomorphological and ecological landscape, along with the prevailing climate
• Adopt a dynamic landscape-scale perspective
• Restore or develop naturally variable hydrologic conditions that existed before disturbance
• Where possible, chose to rehabilitate rather than to create wetlands
• Avoid over-engineered structures
• Pay particular attention to soil types, water depths and planting schedules
• Provide suitably heterogeneous topography
• Pay attention to subsurface conditions, including sediment biogeochemistry and groundwater issues
• Consider the complications associated with rehabilitation or wetland creation in seriously degraded sites
• Undertake monitoring early in the adaptive management process.
The management template developed for this part of the report identifies a range of important issues often
confronted by natural resource managers and means by which they can be addressed. Although not all issues
will arise with every mangrove or saltmarsh and not all actions are relevant to every location, the basic aims of
the management of mangroves and coastal saltmarsh are to:
• Allow natural ecological processes to operate as far as possible
• Allow space for future change, especially sea-level rise
• Prevent or minimise human disturbance, including inadvertent changes in hydrology
• Eradicate or control introduced plants and animals.
In one respect the management of mangroves and saltmarshes is probably simpler than of ecosystems that
require periodic reductions in biomass, such as grassland, heathland and some types of woodlands and forest.
These systems need reductions in biomass, usually by processes such as fire, grazing or slashing, to maintain
biodiversity. It is often logistically difficult and expensive to apply such management tools even in terrestrial
environments, especially when the need for follow-up weed control is included. In contrast, mangroves and
coastal saltmarsh, as with a small number of other ecosystems such as temperate rainforest, usually require
no biomass reduction and are best kept in a completely undisturbed condition. On the other hand, however,
mangroves, coastal saltmarsh and other types of estuarine or intertidal wetland are often difficult to access.
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This can pose a serious challenge to management, especially in relation to tidal inundation and passage
through muddy terrain. Nonetheless, management operations are carried out in such difficult situations in
Victoria, with techniques including aerial spraying of *Spartina by helicopter (e.g. Chapter 1.12) and carefully
timed boat access (e.g. Chapter 3).
7.1
What needs to be in a management template?
A natural-area management plan should contain the following elements:
• Good content in terms of an informed and scientific approach to protecting biodiversity, with
information on natural values (which always includes flora and fauna but may include also genetic
diversity, landscape attributes, and ecological function) and clear identification of legal and policy
requirements, management issues and required responses
• Realistic and achievable aims and objectives based on available resources
• Suitable format and appearance with informative maps and illustrations, in order to be readily
understood and implemented.
Although many formats for a management plan are available, the general structure of an effective plan is fairly
basic. Table 7.1 shows the typical contents of a natural-area management plan.
Table 7.1: Typical contents of a natural-area management plan.
Topic
Typical contents
Cover page
Title of plan, authorship; photo optional
Title page
Details of plan publication, date
Acknowledgements
People who contributed to the plan
Contents
Contents page
Introduction
Introduces the management plan, its background and purpose
Management area
Describes the area, its general environment, its legal tenure and management history;
divides the area into management sections for strategy and communication purposes
Natural values
Summarises the geology, geomorphology, flora, fauna, ecology and other significant values
of the area
Legislation and policy
Summarises the relevant laws and government policies that relate to the management area,
with emphasis on any legal obligations to protect and/or manage the area
Management issues and actions
Identifies and discusses management issues and options; includes management actions
individually numbered to facilitate communication and review of effectiveness
References
Includes all cited references; additional references are optional
Appendices
Appendix 1. Flora
List of flora, includes date and sources of most recent record/observation of each species
Appendix 2. Fauna
List of fauna, includes date and source of most recent record/observation of each species
Appendix 3. Management
timetable
Timetable of works over the lifetime of the plan (typically 10 years), budget if appropriate
Figures
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Figure 1. Location
Map of location of management area
Figure 2. Management area
Map of management sections or zones
Figure 3. Natural features
Map of significant flora and fauna occurrences and other significant features
Figure 4. Management information
Map of management information such as weed infestations, material needing removal, etc.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
7.2 Case-study site – Barwon River estuary
The site selected for the management template is the large area of mangrove and coastal saltmarsh in the
Barwon River estuary, one of the largest estuaries in Victoria (Figure 7.1). The estuary extends from the
Barwon River mouth at Barwon Heads to the southern edge of Geelong. Much is located within the 3,300 ha
Lake Connewarre Wildlife Reserve, which includes the Lower Barwon, Lake Connewarre (the largest lake in
central Victoria and tidal), Murtnagurt Swamp, Salt Swamp, Hospital Swamp and Reedy Lake. The remaining
part is on private land.
Figure 7.1: Map of the Barwon River estuary.
The Lake Connewarre Wildlife Reserve, also known as the Lake Connewarre State Game Reserve, is managed
by Parks Victoria. A game reserve is a type of wildlife reserve in which flora and fauna are legally protected,
except for an open hunting season declared on certain duck species in the autumn of certain years. The land
is reserved under the Crown Land (Reserves) Act 1978. The Wildlife Reserve forms an important part of a
Wetland of International Importance and is listed under the Ramsar Convention: Port Phillip Bay (Western
Shoreline) and Bellarine Peninsula. Ramsar sites in Australia are considered matters of national environmental
significance under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.
The Barwon River estuary is an extensive wetland ecosystem which shows a gradual progression from saline
to freshwater conditions from the sea, and is characterised by large areas of native vegetation interspersed
with shallow brackish-water lakes. Much of the estuary is in relatively natural condition, particularly in the
lower section between Lake Connewarre and the river mouth at Barwon Heads (the ‘Lower Barwon’). The
estuary has among the most diverse saltmarsh and estuary vegetation in south-eastern Australia, with major
occurrences of both wet and dry saltmarsh ( Jeff Yugovic, pers. obs.). Table 7.2 shows the area of saltmarsh and
estuarine vegetation in the estuary, based on the mapping described in Chapter 5. In total, there are ~2,008 ha
of saltmarsh and estuarine vegetation, of which 1,351 ha (~67%) are reserved within the wildlife reserve.
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Table 7.2: Saltmarsh and estuarine vegetation of the Barwon River estuary. Areas are based on the mapping described in
Chapter 5.
EVC
(existing or proposed)
Description
Area (ha)
Reserve
Private
Total
EVC 140
Mangrove Shrubland
Avicennia marina shrubland
43
3
46
EVC 10
Estuarine Wetland
Juncus kraussii rushland
113
11
124
EVC 947
Brackish Lignum Swamp
Muehlenbeckia florulenta
shrubland
88
16
104
EVC 196
Seasonally Inundated Sub-saline
Herbland
Wilsonia spp. herbland
80
0
80
Coastal Tussock Saltmarsh
Austrostipa stipoides
grassland
<1
9
10
Gahnia filum sedgeland
355
103
458
Sarcocornia quinqueflora
herbland
246
381
627
Suaeda australis herbland
47
40
87
Hemichroa pentandra
herbland
<1
<1
<1
Atriplex cinerea shrubland
<1
<1
<1
Atriplex paludosa shrubland
2
<1
2
Tecticornia arbuscula
shrubland
76
25
101
Coastal Saline Grassland
Distichlis distichophylla
grassland
88
4
92
Coastal Dry Saltmarsh
Frankenia pauciflora
herbland
22
4
26
Disphyma crassifolium
herbland
1
<1
1
Tecticornia halocnemoides
shrubland
<1
<1
<1
Tecticornia pergranulata
shrubland
52
112
164
Wet Saltmarsh Herbland
Wet Saltmarsh Shrubland
Coastal Hypersaline Saltmarsh
Notes:
1 To obtain area figures, mosaic map polygons (data from this study) were split into equal component units, including 3-way mosaics
of species-based units. Those units differ from our recommended EVCs, so the figures presented here differ slightly from those
presented elsewhere (see Appendix G).
2 Marine EVCs in the reserve/estuary: Sea-grass Meadow
3 Dry coastal EVCs in the reserve/estuary: Coastal Alkaline Scrub, Berm Grassy Shrubland
4 Freshwater wetland EVCs in the reserve/estuary: Lignum Swamp, Tall Marsh, Aquatic Sedgeland, Aquatic Herbland
5 Other EVCs recorded in the reserve/estuary not accepted here: Plains Saltmarsh, Brackish Sedgeland, Brackish Grassland, Floodplain
Riparian Woodland, Cane Grass – Lignum Halophytic Herbland, Plains Brackish Sedge Wetland.
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Information on the vegetation ecology and management of the Barwon River estuary is available in Yugovic
(1985, 2006), Yugovic et al. (2003, 2004), Awal (2006), Ecological Associates (2006), Dahlhaus et al. (2007),
Billows & Gwyther (2008) and Ecology Partners (2008). Most recently, Scally (2010) has completed a
BEnvSci (Hons) thesis on perceptions of climate change and adaptation responses for the Barwon River
estuary. Thus although some valuable knowledge has been obtained to date, the ecology of the estuary is still
not particularly well understood or documented. In response to community concern about water quality and
algal blooms in Lake Connewarre, the Lake Connewarre Values Project is underway to better understand the
ecology and management needs of the lake.
7.3
Legislation and policy background
Chapter 2 provided a detailed overview of the policy and legislation relevant to Victorian mangroves and
coastal saltmarsh. A guide to the government legislation, policies and strategies specifically relevant to the
Barwon River estuary is provided in the following text. In general these instruments control the types of
development that can occur within the estuary, but do not oblige the landowner or manager to actively
manage the natural values.
commonwealth legislation
The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) applies to developments
and associated activities that have the potential to significantly impact on Matters of National Environmental
Significance, which include:
• Listed threatened species
• Listed ecological communities
• Listed migratory species
• Wetlands of international importance (Ramsar sites)
• Commonwealth land.
Any person proposing to take an action that may, or will, have a significant impact on a Matter of
National Environmental Significance must refer the action to the Australian Government Minister for the
Environment, Heritage and the Arts for a determination of whether the action is a ‘controlled action’ or not.
The Lake Connewarre Wildlife Reserve is a major part of a Wetland of International Importance listed under
the Ramsar Convention and is therefore subject to the EPBC Act.
The EPBC Act is a stand-alone piece of Commonwealth legislation which has little integration with
Victorian planning and environmental legislation. For major forms of development, the Act works well in
terms of referrals and applications for consent. For smaller developments, however, there is a greater risk of
oversight regarding development referrals under the Act because of its separation from state-based legislation.
For example, a development that may not require a planning permit under the Greater Geelong Planning
Scheme but that may require consent under the EPBC Act raises the risk of failing to comply with the EPBC
Act because there is no obligation for the council to advise or forewarn the proponent of a development of
obligations under the Act. This is a significant legislative gap.
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victorian legislation
The Flora and Fauna Guarantee Act 1988 (FFG Act) provides for the conservation of threatened species and
communities and for the management of potentially threatening processes. A permit from the Department of
Sustainability and Environment is required to take protected flora from public land, but a permit is generally
not required for removal of protected flora from private land. Authorisation under the FFG Act is required
also to catch, possess, keep or sell listed fish. ‘Take’ in the Act has a wide range of meanings.
The Planning and Environment Act 1987 controls the planning and development of land in Victoria,
and provides for the development of planning schemes for all municipalities. Of particular relevance to
development proposals are the native vegetation provisions under Clause 52.17, which require a planning
permit to remove, destroy or lop native vegetation including dead native vegetation, subject to certain
exemptions.
The native vegetation controls under the planning scheme require the responsible authority to consider a
variety of biodiversity and other information, including Net Gain policy, biodiversity values and conservation,
the land-protection role of native vegetation, the quality, condition, location and significance of native
vegetation, and the impact of vegetation removal. The planning scheme defines ‘native vegetation’ as ‘plants
that are indigenous to Victoria, including trees, shrubs, herbs and grasses’ (Clause 72). The need for a permit
to remove native vegetation may be also be triggered by planning overlays.
Two significant gaps between these two pieces of leigislation are the inability of the Flora and Fauna
Guarantee Act 1988 to have a strong influence over private land, and the vagaries of local governments to fully
utilise their powers under the Planning and Environment Act 1987.
The Wildlife Act 1975 provides for protection and management of wildlife in Victoria. The Wildlife
Regulations 2002 of the Act prescribe penalties for certain activities relevant to wildlife, including disturbance
of habitat without appropriate authorisation (Section 9). Authorisation to destroy or possess wildlife may be
required (Sections 41–47) if wildlife needs to be moved or destroyed during development.
The Water Act 1989 provides a framework for the allocation and management of surface water and
groundwater throughout Victoria. It provides a principal mechanism for maintenance of ecosystem functions
including those of aquatic ecosystems. Any construction or maintenance activity that affects beds and banks
of waterways, riparian vegetation, quality or quantity of water, requires a licence, permit or approval from
the relevant authority. The relevant authority for the Barwon River estuary is the Corangamite Catchment
Management Authority. Often, however, permits for works on waterways are focussed on declared waterways
or are retrospective in terms of approving works that have already been undertaken.
The Environment Protection Act 1970 underpins the State Environmental Protection Policies (SEPP) which
provides a legal framework for the protection and rehabilitation of Victoria’s surface-water environments. The
uses and values of the water environment are known as ‘beneficial uses’. Environmental quality objectives and
indicators are defined to protect beneficial uses and an attainment program provides guidance on protection
of the beneficial uses. The beneficial use of most relevance to biodiversity is ‘aquatic ecosystems’. The Policy
requires that aquatic ecosystems be protected. Impacts to surface-water quality must not result in changes that
exceed water-quality objectives specified to protect beneficial uses. Proponents and land managers need to
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ensure that direct and indirect (e.g. runoff ) impacts to surface-water quality do not exceed the water-quality
objectives. The SEPP provides recommendations to ensure that beneficial uses are protected.
State Planning Policy Framework Clause 15.01 (Protection of catchments, waterways and groundwater) states
that planning and responsible authorities must have regard for the objectives of the Corangamite Regional
Catchment Strategy. The Corangamite Regional River Health Strategy provides further recommendations on
the protection of existing high value rivers and creeks that are in good condition and strategic improvement of
other rivers and creeks.
The Catchment and Land Protection Act 1994 (the CaLP Act) provides for a system of controls on noxious
weeds and pest animals. The Act specifies four categories of noxious weeds in Victoria: i) State Prohibited
weeds; ii) Regionally Prohibited weeds; iii) Regionally Controlled weeds; and iv) Restricted weeds.
State Prohibited weeds either do not occur in Victoria but pose a significant threat if they invade, or are
present, pose a serious threat and can reasonably be expected to be eradicated. If present, infestations of a State
Prohibited weed are relatively small. They are to be eradicated if possible from Victoria or excluded from the
state. The Victorian Government is responsible for their eradication, but under Section 70(1) of the CaLP Act
it may direct landowners to prevent their growth and spread.
Regionally Prohibited weeds are not widely distributed in a given region but are capable of spreading further.
It is reasonable to expect that they can be eradicated from a region and they must be managed with that goal.
Landowners, including public authorities responsible for Crown land management, must take all reasonable
steps to eradicate Regionally Prohibited weeds on their land.
Regionally Controlled weeds are usually widespread and are considered important in a particular region. To
prevent their spread, continuing control measures are required and landowners have the responsibility to take
all reasonable steps to prevent the growth and spread of Regionally Controlled weeds on their land.
Restricted weeds includes plants that pose an unacceptable risk of spreading in the state or to other parts of
Australia if they were to be sold or traded in Victoria, and are a serious threat to another state or territory of
Australia. Trade in these weeds and their propagules, as plants, seeds or contaminants in other materials, is
prohibited.
None of the serious weeds within the Barwon River estuary, such as Tall Wheat Grass *Lophopyrum
ponticum or *Spartina spp., are declared noxious in Victoria, so the CaLP Act has little or no relevance to the
management of saltmarsh and estuary vegetation in the study area.
Enforcement action, both in terms of ability and willingness to effectively undertake enforcement of
legislation such as water quality by the EPA or weed management by the Department of Primary Industries, is
often lacking. There are difficulties in ensuring regulations are enforceable and in securing evidence to pursue
enforcement action.
local government
The City of Greater Geelong planning scheme is given effect by the Planning and Environment Act 1987. The
planning scheme contains the Victorian Planning Provisions referred to in Chapter 2, and has local planning
overlays that control development within specific areas. Specified actions, which may include the removal of
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native vegetation, require a planning permit from the City of Greater Geelong. Any permit issued must have
regard to the planning scheme and its overlay provisions.
The Public Conservation Resource Zone (PCRZ) is generally applied over the Barwon River estuary
including Lake Connewarre. The purposes of the PCRZ are to:
• Implement the State Planning Policy Framework and the Local Planning Policy Framework, including
the Municipal Strategic Statement and local planning policies
• Protect and conserve the natural environment and natural processes for their historic, scientific,
landscape, habitat or cultural values
• Provide facilities which assist in public education and interpretation of the natural environment with
minimal degradation of the natural environment or natural processes
• Provide for appropriate resource-based uses.
The zoning of land adjoining the estuary ranges from the Farming Zone around Lake Connewarre to the
Residential Zone at Barwon Heads.
Two planning overlays apply to part or all of the Barwon River estuary: Clause 42.01 and Clause 44.03.
Clause 42.01 – Environmental Significance Overlay (ESO) has as its purposes to:
• Implement the State Planning Policy Framework and the Local Planning Policy Framework, including
the Municipal Strategic Statement and local planning policies
• Identify areas where the development of land may be affected by environmental constraints
• Ensure that development is compatible with identified environmental values.
Under the ESO, the Barwon River estuary is covered by a Schedule to the ESO: ESO2 Environmental
Significance Overlay Schedule 2 (High Value Wetlands and Associated Habitat Protection).
The ESO2 was developed by council to apply to those parts of the municipality covered by the Ramsar
Convention and accordingly it covers those wetlands designated as a Ramsar site including Lake Connewarre,
the lower Barwon River estuary, Swan Bay, and parts of the western shoreline of Port Phillip Bay around Point
Wilson and Avalon. The environmental objectives to be achieved under the ESO2 are to:
• Maintain the ecological character (the sum of the biological, physical and chemical components of the
wetland ecosystem, and their interactions which maintain the wetland and its products, functions and
attributes) of Ramsar wetlands
• Protect natural resources and maintain ecological processes and genetic diversity
• Protect and ensure the long-term future of terrestrial and aquatic habitat for native plants and animals,
including shorebird feeding areas and roosts, and species and communities listed under the Fauna and
Flora Guarantee Act 1988
• Encourage ecological restoration, regeneration and revegetation with indigenous species within the site
and in adjoining areas
• Maintain the function of the wetland or habitat area as part of the broader natural system, including
maintenance of natural flows and flooding regimes
• Prevent further loss of wetland habitat
• Manage the site in order to maintain and/or improve its value as a conservation site for native plants and
animals
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
•
•
•
Protect water quality and prevent water pollution in watercourses, water bodies, wetlands and
groundwater
Protect cultural (including aboriginal and non-aboriginal heritage) values
Protect visual amenity.
The overlay relates to the Lake Connewarre Wildlife Reserve only. A permit is required to construct a
building or to carry out certain works including the removal, destruction or lopping of native vegetation and
to subdivide land.
Clause 44.03 – Floodway Overlay (FO) has as its purposes to:
• Implement the State Planning Policy Framework and the Local Planning Policy Framework, including
the Municipal Strategic Statement and local planning policies; to identify waterways, major floodpaths,
drainage depressions and high hazard areas which have the greatest risk and frequency of being affected
by flooding
• Ensure that any development maintains the free passage and temporary storage of floodwater, minimises
flood damage and is compatible with flood hazard, local drainage conditions and the minimisation of soil
erosion, sedimentation and silting
• Reflect any declarations under Division 4 of Part 10 of the Water Act, 1989 if a declaration has been made
• Protect water quality and waterways as natural resources in accordance with the provisions of relevant
State Environment Protection Policies, and particularly in accordance with Clauses 33 and 35 of the State
Environment Protection Policy (Waters of Victoria) (Environment Protection Authority Victoria 2003)
• Ensure that development maintains or improves river and wetland health, waterway protection and
floodplain health.
The Flood Overlay requires a permit to construct a building or to carry out certain works and to subdivide
land. It is applied to both Lake Connewarre itself as well as some of the adjoining land that may be affected by
inundation.
As outlined in Chapter 2, the zones and overlays that have been used and how they have been applied under
the Greater Geelong Planning Scheme over the Barwon River estuary reflect inherent limitations in the
management framework. The PCRZ is a public land based zone that has been applied correctly over the
public land areas of the Barwon River estuary. However the ESO2 is restricted to being applied only over the
public land area of the Barwon River estuary because it has been applied only to the Ramsar site, which in this
case covers only public land (i.e. the Ramsar site designation does not cover private land). The private land
adjoining the Barwon River estuary do not have any conservation-based zone or overlay. Therefore, the relative
importance of the operation of the EPBC Act increases with regard to regulating the impacts of development
on private land adjoining the designated Ramsar Wetland.
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A better planning configuration for the Barwon River estuary would be as follows:
• Public land component – maintain the manner of application of the PCRZ and ESO2
• Private land component adjoining the Barwon River estuary in rural areas – apply the Rural
Conservation Zone (RCZ) and ESO2 at least to a distance from the high-water mark of 200 m to
adequately cover water quality, direct impacts and climate change induced sea-level rise impacts
• Private land component adjoining the Barwon River estuary in urban areas – apply the ESO2 at least to
a distance from the high-water mark of 200 m to adequately cover water quality, impacts from further
intensification of development, direct impacts and climate change induced sea-level rise impacts.
Finally, the Greater Geelong Planning Scheme influences the lower Barwon River estuary through the
planning policy for the township of Barwon Heads. Clause 21.14 of the council’s Municipal Strategy
Statement (MSS) is the planning policy that covers Barwon Heads and Ocean Grove which recognises that
these places are located within a sensitive natural environment. The Barwon River, Lake Connewarre system
and coastline of Bass Strait form major boundaries to the townships, influencing growth options for the
future. The planning policy for Barwon Heads seeks to maintain a village atmosphere and limit urban growth
despite strong pressures for urban expansion and to avoid impacts on environmental assets such as the Barwon
River and Lake Connewarre from development in both townships.
Council undertook a review of the future of Barwon Heads through the preparation of a structure plan
for the town which was adopted in December 2007 and which has implications for the adjoining coastal
saltmarsh and mangroves within the estuary. The structure plan recognised the importance of the setting of
the town adjacent to the river estuary, and coast. It includes policies to ensure the protection of the coastal
saltmarsh and mangroves as part of the environmental values of the town’s setting. It identifies also the need
to investigate applying an overlay relating to the environmental significance of the coast over parts of the town
and extending across the estuary. Figure 7.2 demonstrates the structure plan’s directions for the environmental
features of Barwon Heads. Although the structure plan has been adopted by council, it does not yet form part
of the Greater Geelong Planning Scheme and an amendment to the planning scheme has been prepared and is
awaiting approval.
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Figure 7.2: Extract from the Barwon Heads structure plan, showing how the plan identifies and outlines policy directions
for the town with respect to the Barwon River estuary and Murtnagurt Lagoon. Source: City of Greater Geelong (2007).
7.4
Management issues
Chapters 1.11–1.13 provided a statewide overview of the main threats to mangroves and coastal saltmarsh.
That summary is expanded in the following section and is illustrated with specific examples drawn from
the Barwon River estuary and the actions that need to be taken to ameliorate the threats. The issues may be
classified into three main categories – planning, catchment and site-management issues:
• Planning issues
○ land-use zoning
○ knowledge base
○ planning for sea-level rise
○ infrastructure syndrome
○ annual program
• Catchment issues
○ freshwater runoff
○ pollution
○ eutrophication
○ sedimentation
○ environmental flows
○ buffer protection
○ landscape protection
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•
Site-management issues
○ landfill
○ foreign geological material
○ physical disturbance
○ tidal restriction
○ estuary entrance opening
○ pest plants
○ pasture improvement
○ pest animals
○ stock grazing
○ shell-grit mining
○ rubbish dumping
○ incursion
○ unauthorised use
○ boat wash
○ boardwalks
○ signage
○ mangrove spread
○ fencing
○ fire
○ visitor management
○ regeneration and revegetation
○ wetland construction
○ enforcement
These issues are discussed in turn below.
land-use zoning
Sensitive and appropriate land-use zoning is essential for the protection of mangroves, saltmarshes and
estuaries. Planning schemes need to reflect the significance of these systems by placing them and, importantly,
their buffers within appropriate land-use zones with protective overlays. The fauna, flora and environments
of saltmarshes and estuaries near human land use can be adversely affected by many factors, including
loss of landscape quality, inputs of fresh water, noise, light, cats, dogs and visitor pressure. The approach
taken towards land use on the edges of mangroves, saltmarshes and estuaries can range from high-density
housing (inappropriate) to dedicated open space (appropriate). Protecting the edges of these natural areas is
fundamental to many of the management issues below.
Example from the Barwon River estuary
The public land (Wildlife Reserve) is zoned Public Conservation and Resource Zone (PCRZ) and has
an Environmental Significance Overlay (ESO), but it has no buffer zone and thus one of Victoria’s largest
estuaries is subject to adjacent land uses and developments that adversely affect its landscape value and
ecology.
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Necessary action
•
Prepare and apply appropriate protective land-use zones and overlays to saltmarshes and estuaries and
their adjoining areas. Dedicated open space is appropriate around estuaries near human habitation.
knowledge base
Good working knowledge of the estuary or saltmarsh and its ecology is necessary for the conservation
management of such a dynamic natural area. The geomorphology of the marsh is important to understand as
it explains much of the vegetation pattern, informs knowledge of the ecological processes, and indicates the
potential direction of erosion and deposition processes. An inventory of the flora and fauna is essential, and
species of significance need to be identified and mapped. The ecological services that the community expects
the wetland to deliver also need to be made explicit.
A vegetation-and-feature map based on recent aerial photography is needed to understand the distribution of
significant ecological features and for management communication purposes. The scale used for the statewide
mapping in the present study – 1:10,000 – necessarily simplifies the vegetation pattern and includes mosaics
that should be resolved to component units for better understanding of the vegetation and more effective
management. A scale of between 1:2,500 (1 mm = 2.5 m on the ground) and 1:5,000 (1 mm = 5 m on
the ground) is usually needed to adequately capture the vegetation pattern (see Chapter 1.15 on mapping
protocols). As this scale is usually sufficient to show the distribution of individual saltmarsh units (e.g. based
on floristic and/or structural differences), it shows those that are rare in the local area, region or state and thus
in need of special management.
Example from the Barwon River estuary
Detailed mapping of vegetation in the Barwon River estuary is not currently available. A vegetation map at
1:18,500 was compiled by Yugovic (1985) which, although apparently complex, is a simplification of the
vegetation pattern. It is also rapidly dating, due to vegetation change including the spread of mangroves up the
river and into the lake. The 1:10,000 mapping in the present study also necessarily simplifies the pattern that
occurs on the ground (see Chapter 5.3).
Necessary action
•
•
•
•
Prepare an inventory of the flora and fauna, identifying species of national, state or regional significance,
and, where possible, including quadrat data.
Map the vegetation at a scale of between 1:2,500 and 1:5,000 using recent aerial photography. Map all
saltmarsh units in order to avoid mosaic map units. Ground truth the mapping.
Map the location of management features such as flora of regional or higher significance, special fauna
habitats and special management zones.
Divide the management area into logical management sections or zones, thus facilitating communication
and direction of management effort. Name or number the management sections.
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planning for sea-level rise
Fundamental to mangrove and saltmarsh conservation is the allowance that must be made for low-lying
vegetation to migrate to higher inland sites with rises in sea level, and where appropriate to recover in areas
that are presently cut off by sea walls (Chapter 1.13). Inland migration zones or buffer zones should be,
and in some cases already have been, clearly identified in state and regional strategies and local planning
schemes (Chapter 2). Within these zones, any further construction activity that would affect topography
and hydrology is not appropriate. Such land-use zones should be formalised for example as public acquisition
overlays and marine inundation overlays in planning schemes.
Example from the Barwon River estuary
The Wildlife Reserve, although currently large, has effectively no room for migration. There is no public land
or overlay zone on private land upstream to accommodate any migration and, in fact, the estuarine perimeter
is often occupied by housing (Figure 7.3). Some areas of saltmarsh on private land near the inland limit
of the estuary are proposed by developers for transfer to public land in association with urban residential
development. The transfer is not for future migration of the estuary but for recreation and drainage and,
indeed, landfill and development may block the possibility of any future migration. Moreover, any saltmarsh
that is retained may be damaged or lost if it becomes a receiving area for urban runoff (see Chapter 1.11).
Planning for sea-level rise is currently provided for under the Victorian Coastal Strategy 2008, which
establishes as state planning policy under Clause 15.08 of the State Planning Policy Framework. Every
planning scheme, including the Greater Geelong Planning Scheme, has a requirement for planning authorities
to plan for sea-level rise of not less than 0.8 m by 2100 and allow for the combined effects of tides, storm
surges, coastal processes and local conditions such as topography and geology when assessing risks and impacts
associated with climate change. The policy has no specific permit trigger, but is required to be considered for
any land use or development on the coast for which a permit is required.
At present, the Greater Geelong Planning Scheme does not address planning for sea-level rise at a local level
in any comprehensive way. However, the Municipal Strategic Statement (MSS) of the planning scheme has
been reviewed and a revised version is currently awaiting Ministerial approval. The revised MSS does include
additional planning policy statements that recognise and require consideration of the effects of sea-level
rise and the need to buffer the impacts on mangroves and coastal saltmarsh. The City of Greater Geelong is
working on possible amendments to its suite of overlays to better improve the planning response to sea-level
rise. The work includes a review of the Environmental Significance Overlays to improve habitat protection for
the Orange-bellied Parrot, which feeds on coastal saltmarsh.
Necessary action
•
•
•
•
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Undertake land-use planning and rezoning to allow for saltmarsh and estuary migration in response to
sea-level rise.
Formalise inundation zones within state strategies and local planning schemes.
Prevent any further construction activity that would affect topography, hydrology or the potential for
estuary movement within inundation zones.
Undertake environmental works within inundation zones, such as removing structures, removing fill and
levelling surfaces as appropriate.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Figure 7.3: Housing adjacent to mangroves, Barwon River estuary.
infrastructure syndrome
All too often with reserve management, the majority of resources is allocated to infrastructure such as
boardwalks, boat ramps and signage rather than to protecting and managing the natural assets the reserve
was created for. This we term the infrastructure syndrome. Its prevalence is primarily due to lack of knowledge,
compounded by ranking decisions, resourcing limitations and skewed conceptions of the management of
natural areas. Resource management is often feeble or ignored altogether in management plans, especially
when the ecological knowledge base is minimal. Effective vegetation management requires appropriate
knowledge, attitudes, skills and resources, and any of these may be lacking for a given location. In some
reserves, management personnel are unaware of special features, such as the rare dry saltmarsh vegetation type,
that may be present in their area of jurisdiction. Such a lack of understanding can lead to inadvertent loss or
damage to such features by neglect or poorly sited infrastructure.
Example from the Barwon River estuary
Infrastructure in the wildlife reserve includes boardwalks, boat ramps and signage. There has been an emphasis
of infrastructure management but *Spartina survey and spraying and fox control have been undertaken
recently. Further management activity is planned for the future.
Necessary action
•
Give resource management priority over infrastructure management.
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annual works program
An annual works program should be prepared in accordance with the management plan prepared for the
saltmarsh. The program should include achievable objectives and estimated person days and costs. It should
be prepared by the end of June each year, as the vegetation management year coincides with the financial year
( July to June inclusive). Also to be prepared by the end of June is a review or audit of activities undertaken
in relation to the annual program objectives. The need for planning may seem obvious, but lack of forward
planning can result in management inaction and neglect even when resources are available.
Example from the Barwon River estuary
Current management of the wildlife reserve includes visitor and duck-shooter management, infrastructure
management (the boardwalk, boat ramps, etc.), *Spartina mapping and spraying, and fox control to protect
Orange-bellied Parrot. However the overall operational budget for the reserve is low (part of $60,000 in
2009–2010 for the entire Bellarine Peninsula, which has several reserves, Lake Connewarre being the largest)
and Parks Victoria does not have a boat to patrol the river and lake with. Two dedicated Rangers cover the
entire Bellarine Peninsula (recently cut from six Rangers), so management of the Barwon River estuary
is poorly resourced from even the perspective of personnel. Due to resource and time constraints, there
are nature reserves on the Bellarine Peninsula that the Rangers have not visited. Sensitive management of
saltmarsh on private land is negligible or non-existent.
Necessary action
•
•
Undertake an annual review of management.
Prepare an annual works program in advance of the next year in accordance with the management plan,
and make arrangements to implement the program.
freshwater runoff
Excessive freshwater input via drains and runoff is frequently a management issue, and excessive freshwater
inputs can cause major detrimental effects on mangroves and coastal saltmarsh (Chapter 1.11). Too great
a dilution of salinity favours saltmarsh communities at the fresh end of the salinity range, such as Distichlis
grassland, and may result in the replacement of Coastal Saltmarsh by other ecological vegetation classes such
as Estuarine Reedbed, Tall Marsh or even exotic vegetation. Dry saltmarsh communities, especially Tecticornia
pergranulata and Tecticornia halocnemoides shrubland, are likely to be especially badly affected, as they are
restricted to sites with dry hypersaline conditions in summer, the opposite of the conditions provided by highvolume freshwater inputs.
Unnatural freshwater input may arrive from below the topographic level of the saltmarsh via a creek or river
coming from the larger catchment of a saltmarsh. As long as lower saltmarsh receives regular tidal inundation
and can drain readily, any fresh water is soon diluted by sea water. Alternatively, and more commonly, fresh
water may arrive from above the level of the marsh via a drain from the adjacent subcatchment (Figure 7.4).
This type of input is more problematic, as upper saltmarsh requires a lower inundation frequency and higher
salinity than lower saltmarsh (see Chapter 1.5).
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Figure 7.4: Urban stormwater drain with one-way valve to prevent sand blockage,
Barwon Heads.
Example from the Barwon River estuary
Runoff from housing and other developments adjacent to the estuary has affected vegetation, by killing
saltmarsh plants and promoting Typha spp. (in a Tall Marsh EVC) and other types of opportunistic or
introduced vegetation. The drains that were constructed to channel the runoff into the saltmarsh have
modified topography and damaged vegetation.
Murtnagurt Swamp supports highly significant dry saltmarsh vegetation, which is particularly susceptible to
freshwater runoff. A residential development in Barwon Heads adjacent to Murtnagurt Swamp had few or
no environmental requirements regarding its stormwater outfall: the drainage plan does not show where the
drain terminates, and it simply runs off the edge of the development plan map into the wetland ( J. Yugovic,
pers. obs.) The discharge is having ongoing detrimental effects on dry saltmarsh: since construction of the
drain, the eastern area of Murtnagurt Swamp has received considerably larger volumes of water, resulting
in this part of the swamp, which is a basin, remaining flooded for much longer periods. The dieback of the
significant dry saltmarsh shrubs indicates adverse effects on these species in particular.
A later residential development in Barwon Heads directs runoff into a specially constructed irrigation dam
on the Barwon Heads Golf Course rather than into Murtnagurt Swamp, which is preferable for the wetland.
The dam is designed to fill only rarely, in which case it will overflow into the swamp (Yugovic et al. 2004).
It has been operational for 2–3 years and has not overflowed. It represents an unusual and innovative use of
stormwater. Another residential development adjacent to the swamp is proposed and it may not have such a
mitigation measure.
Necessary action
•
•
Prevent all freshwater runoff onto saltmarshes other than natural inputs.
Investigate and implement ameliorative measures where freshwater inputs are damaging saltmarsh
vegetation.
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pollution
Chemical pollution, particularly from oil or fuel spills, is a threat to many areas of mangrove and coastal
saltmarsh (Chapter 1.11). Moreover, industrial contamination of soft sediments near industrial sites is a
major concern and is not possible to remediate, and outfalls from nearby sewage treatments plants can foul
waterways. In the Breamlea Nature Conservation Reserve, seepage and runoff from solid waste mounds enters
ponds within the reserve. In both cases the water is strongly coloured and has an offensive odour. Even the
discharge of treated water to saltmarsh should be prevented, as fresh water and nutrients adversely affect many
aspects of saltmarsh ecology.
Example from the Barwon River estuary
There have been no documented chemical pollution incidents in recent years. Nevertheless, sediments in Lake
Connewarre are known to have high concentrations of arsenic, cadmium and mercury due to past industrial
activities and as a legacy from gold mining in the 19th century (Billows & Gwyther 2008).
Necessary action
•
•
•
•
Prevent chemical pollution of mangroves and coastal saltmarsh.
Prepare a contingency plan for chemical pollution by liaising with relevant agencies such as the
Environment Protection Agency.
Prepare to contain oil spills with booms if they occur near coastal areas, and to contain spills from the
landward catchment.
Ensure that surface-water and groundwater outputs from sewage treatment plants is treated to a
satisfactory licensed standard and does not seep or flow into mangroves or coastal saltmarsh.
eutrophication
Eutrophication is an increase in the concentration of plant nutrients in an ecosystem to an extent that it
increases the rate of primary productivity and the biomass of undesirable plants (see review in Chapter 1.11).
Depending on the degree of eutrophication, subsequent negative environmental effects can include hypoxia
or anoxia and severe reductions in water quality; death of fish and other aquatic organisms can then occur. In
many aquatic systems, excess growth of algae (planktonic, benthic and attached forms) as well as of vascular
aquatic plants is caused by excess nutrients entering from upstream (Figure 7.5). Shifts across vegetation
types are also possible, in which case a switch in states has occurred. Controlling nutrient enrichment is a
complex task relating to management of the entire river catchment. It requires multi-agency coordination and
resourcing and the cooperation of landholders within the catchment.
Example from the Barwon River estuary
Water quality in Lake Connewarre is a community concern (e.g. Geelong Advertiser 3/05/2008, 4/07/2009).
Blooms of blue-green algae (cyanobacteria) often occur in the lake from January to March due to excess
nutrients and low flows from the Barwon River, combined with high water temperature (and thus thermal
stratification of the water column) in the ever-shallowing lake. When algae are detected, Parks Victoria
closes the lake to recreational activity and undertakes a monitoring program. The lake is reopened when
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algal abundances fall below a pre-determined trigger level. Recorded filamentous cyanobacteria include
Oscillatoria and Planktothrix, which are not toxic but do cause skin irritation (S. Willsher, Parks Victoria,
pers. comm.). Algal biomass and decaying aquatic plants accumulate on the north shore of the lake due to
prevailing wind direction. The drying vegetation mats cause localised smothering and death of vegetation,
and the accumulation of rotting plants can develop an offensive odour. In fact, the smell emitting from Lake
Connewarre is known locally as the ‘Leopold pong’ (e.g. Geelong Independent 9/07/2009). There is a proposal
by some landowners to dredge the tidal delta area to increase seawater flushing. Such an action would need
thorough and independent scientific and engineering evaluation, especially with regard to the significant
ecological features of the lake.
Necessary action
•
•
Prevent or minimise nutrient enrichment of water entering the estuary from the catchment.
Ensure that any water-engineering works to minimise eutrophication have net ecological benefit to an
estuary.
Figure 7.5: Masses of rotting vegetation along the shoreline, Lake Connewarre.
sedimentation
Estuaries are naturally places of gradual infilling by sedimentation, but the rate of deposition is much higher in
catchments subject to extensive clearing of native vegetation than in those with large areas of native vegetation.
The resulting poor vegetation cover at countless potential point sources of erosion makes streams turbid with
suspended sediment, and this sediment is later deposited in the estuary when discharge falls and particles are
precipitated due to increasing salinity. Controlling siltation is a complex task requiring management of the
entire catchment, which requires multi-agency coordination and the cooperation of landholders (Figure 7.6).
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Figure 7.6: Lake Connewarre is becoming increasingly shallow due to sediment
accumulation. Note also the presence of an algal scum floating on the surface.
Example from the Barwon River estuary
Since the clearing of most of the Barwon River catchment, Lake Connewarre has filled with sediment (silty
clay) from the eroding catchment. Originally several metres deep, it was reduced to a depth of ~1 m by the
1970s (Rosengren 1973), and is even shallower now. The lake is now longer navigable by outboard motor
boat. The massive amount of infilling has caused major change in the size and shape of the lake. By comparing
Richard Daintree’s 1869 map of the lake with today, it is apparent that the western side the lake has contracted
due to i) extension of the Barwon River delta into the lake and ii) creation of Hospital Swamp which has been
effectively been cut off from the main body of the lake by vegetated rises. Both result from siltation.
Necessary action
•
Prevent or minimise unnatural sedimentation. It will involve multi-agency programs aimed at reducing
the turbidity of water entering an estuary.
environmental flows
River regulation and extraction upstream necessarily results in the removal of large volumes of water that
would otherwise pass into estuaries (Tilleard et al. 2009). Freshwater flooding, either pure or in mixture with
tidal seawater to form brackish water, is vital for the viability of certain vegetation types such as Estuarine
Wetland (Juncus kraussii rushland) and Distichlis-dominated grasslands. Environmental flows are managed
flows, not directly used for agriculture or drinking water, that are intended to keep river and estuary systems
healthy.
Example from the Barwon River estuary
Diversions from the Barwon River traditionally remove large volumes of water that would otherwise pass
into the lakes and swamps of the estuary. The current low flows are exacerbated by the period of drought since
1996, and there has not been a major flood of the Barwon River for over 10 years. River flooding is vital for
Muehlenbeckia shrubland, Distichlis grassland, Juncus rushland and Wilsonia herbland, and these vegetation
types are visibly under stress, presumably because of salinity-related factors. Algal blooms in Lake Connewarre
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
are related to lack of flushing by freshwater flows. The Barwon River has a recommended environmental flow
determined by the statewide FLOWS method (Corangamite Catchment Management Authority 2005) but,
due to low inflow, it does not receive a environmental flow at present. There is a proposal to in future divert
more water from the Barwon River into Reedy Lake in order to cleanse the lake system, but the amount of
extra water would be relatively small. In any case, Reedy Lake currently receives no water due to low river
flow (S. Willsher, Parks Victoria, pers. comm.). Billows & Gwyther (2008, page 21) concluded that ‘efforts
to provide sufficient environmental flow allocations to the estuary are important to avoid unnaturally high
sedimentation rates within Lake Connewarre’.
Necessary action
•
Ensure that environmental flows to the estuary occur where necessary.
buffer protection
Natural coastal areas benefit greatly from buffer zones in which direct impacts of human activity and indirect
impacts (such as weed invasion) can be absorbed to prevent impact on the natural area itself. The effectiveness
of a buffer zone depends on several factors, including size, vegetation cover, and the type of disturbance being
absorbed. Generally, buffers with native vegetation function best as they intercept nutrients and weeds coming
in from surrounding agricultural catchments, and are consistent with protection of natural landscapes.
Example from the Barwon River estuary
The Barwon River estuary has extremely poor or non-existent buffer zones (Figure 7.7), as the reserve was
created out of what was left after all of the potentially arable land had been selected in the mid 19th century.
Recent urbanisation of the immediate catchment of the estuary further increases the need for buffer zones.
Figure 7.7: Lack of a buffer zone around the western edge of Lake Connewarre.
Necessary action
•
•
Create and manage for their protection buffer zones around saltmarshes and estuaries.
Create environmental significance overlays in planning schemes to protect saltmarsh and estuary buffer
zones.
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landscape protection
Visually imposing buildings on the edges of mangroves, saltmarshes and estuaries detract greatly from
the natural landscape. They are visually intrusive and are point sources of freshwater runoff which may be
detrimental to the saltmarsh below.
Example from the Barwon River estuary
A number of over-dominant buildings are situated on the edge of the Barwon River estuary (Figure 7.8). They
have appeared in the last 25 years with little or no consideration of visual impact on the landscape.
Figure 7.8: Visually dominating buildings, western shore of Lake Connewarre.
Necessary action
•
•
•
Protect the natural landscape amenity value of coastal areas from visual intrusion by poorly sited
buildings.
Prevent the construction of buildings and earthworks on escarpments above saltmarshes and estuaries.
Create landscape protection overlays in planning schemes to protect saltmarsh and estuary landscapes.
landfill
Landfill is a major issue in many coastal areas, as it reduces the area of mangrove and saltmarsh and may affect
drainage patterns. It is unsightly and saltmarsh, in particular, is often destroyed without a planning permit
(Figure 7.9). As outlined earlier, coastal saltmarsh is native vegetation requiring a planning permit from local
government for its destruction.
Example from the Barwon River estuary
Many examples of landfill, major and minor, occur within the Barwon River estuary, on public and private
land. The Barwon Heads tip, for example, was sited on saltmarsh on the Murtnagurt Swamp channel (Taits
Road) but most of the material was later removed. However, rather than restoring the original surface level to
facilitate the re-establishment of saltmarsh, clean fill was placed on the site (raising the surface level above that
of saltmarsh) and it was planted out with locally indigenous (not site indigenous) species.
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Figure 7.9: Building waste used as landfill for a causeway on saltmarsh, eastern
shore of Lake Connewarre.
Necessary action
•
•
Prevent saltmarsh and mangrove areas being used for landfill placement.
Remove landfill from those areas that have been affected in the past and dispose of material safely.
foreign geological material
Foreign geological material is often introduced to saltmarshes, mangroves and estuaries to make or stabilise
infrastructure. Foreign material sometimes cannot be contained and will eventually be spread further from
its original location (Figure 7.10). It is not always appreciated that the protection of natural geology and soil
profiles is an important aim of conservation management within nature reserves.
Figure 7.10: Crushed rock from drain on right spreading into estuary; the natural
surrounding substrata is mud.
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Example from the Barwon River estuary
Much foreign material has been placed on the edges of the estuary as landfill or as stabilising measures, and is
spreading in places such as at The Sheepwash.
Necessary action
•
Prevent or minimise the introduction of foreign geological material into saltmarshes and estuaries.
physical disturbance
Physical disturbance to soils and vegetation is a major problem as it is directly responsible for the loss of plants,
as well as disrupting the natural surface profile, which can lead to permanent change in drainage patterns and
thus vegetation. It may also facilitate weed invasion in upper saltmarsh. A wide range of physical disturbances
may occur in coastal wetlands, ranging from ruts created by passage of vehicles, through damage caused
by machinery digging out spiny rush, soil pugging by domestic stock, to drains cut directly into the marsh
surface.
Vehicle rutting is a particular problem. Ruts are caused by removal of soil material on the wheels of vehicles
and compaction of what remains. Ruts are long lasting and difficult to repair and are best prevented in the first
place. To our knowledge repair has not been attempted, but should be possible. It would require i) levelling
the surface using manual or, if feasible without causing further damage, mechanical methods, and ii) filling
the ruts with substrate material of the same geological material and obtained without detriment to the source
site. Under no circumstances should foreign geological material, such as crushed rock, be introduced as it will
eventually be dispersed widely.
Example from the Barwon River estuary
Disturbance by vehicles is severe in parts of Reedy Lake. Constructed drains are common, particularly on
private land, but are also constructed with or without permission in the reserve (Figure 7.11). Pedestrian
traffic along the banks of the river at The Sheepwash causes observable damage.
Figure 7.11: Constructed drain cut into Reedy Lake.
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mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Necessary action
•
•
•
•
Prevent physical disturbance to soils and vegetation.
Install gates or barriers to prevent vehicle access to sensitive areas.
Ensure that authorised vehicles do not cause rutting, for example, by avoiding vehicle access and
movement when soils are wet.
Do not introduce foreign geological material such as crushed rock or gravel.
tidal restriction
Alteration to the natural frequency of seawater inundation often poses a major management issue, as it affects
the extent of mangroves and saltmarsh, often resulting in reduction in area and, in the case of saltmarshes, can
change the distribution of individual species and plant communities. Sea walls, levees, floodgates and culverts
almost always have serious adverse effects on these coastal wetlands. At The Spit Flora and Fauna Reserve, for
example, tidal restriction by a culverted causeway (Point Wilson Road) has lowered salinity and contributed
to increased weed cover (Carr et al. 2002). In rare cases, sea walls have cut off an open marine embayment or
mudflat which has become colonised by saltmarsh.
Example from the Barwon River estuary
Reedy Lake is highly modified by levees, channels and inlet and outlet structures, which were originally
constructed to create a freshwater wetland for duck shooting (Ecological Associates 2006). Hospital Swamp is
similarly modified by water-engineering works, resulting in dramatic change in vegetation including major loss
of saltmarsh. Curiously, these water-engineering works are described, promoted and sign boarded as wetland
restoration projects. Murtnagurt Swamp was cut off from the estuary by a barrier around 1952 and has not
received a tide from the river since (Figure 7.12). Fortunately, an attempt to hold freshwater in the significant
Salt Swamp by constructing a levee across it, which would have destroyed its unique Wilsonia herbland, was
unsuccessful. The failed levee remains as a scar in the vegetation and landscape of the swamp today.
Figure 7.12: Levee which alienates Murtnagurt Swamp from the Barwon estuary.
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Around 1970 there was a proposal to construct a barrier across the entire Lower Barwon for pasture and to
provide a water storage for irrigation and recreation. That action would have destroyed most of the estuary
and, had it proceeded, it would have been expensive to construct and maintain, and the enlarged Lake
Connewarre, which is already shallow due to deposition of silt from the eroding catchment, would have
rapidly silted up and become choked with reeds, making it unsuitable for water storage (Rosengren 1973, Bird
1993). It appears that with none of the water-engineering works was there any serious consideration of the
natural and economic value of the estuary in its current state, and knowledge of the estuary’s highly significant
and unique ecology was effectively non-existent.
Necessary action
•
•
Prevent tidal restriction of saltmarsh.
Restore tidal connection to saltmarsh where feasible.
estuary-entrance opening
Opening estuaries during periods of low flow brought about by drought and water extraction upstream can
have net ecological benefit if the estuary is cleansed by seawater. There are, however, ‘winners and losers’
among the flora and fauna, and all species need to be considered before taking this action.
Example from the Barwon River estuary
The Barwon River mouth is permanently open, so artificial opening is not an issue.
Necessary action
•
•
Consider opening estuaries where there is a net ecological benefit.
Apply the Estuary Entrance Management Support System or similar model in deciding on whether to
open an estuary.
weeds
As outlined earlier in Chapter 1, weeds are a major threat to saltmarsh because of their capacity to infiltrate
native vegetation and, in some cases, to completely replace it. Lower level or wet saltmarsh presently has few
species capable of invading (other than *Spartina: see Chapter 1.11), probably due to lack of introduction of
saltmarsh species from outside Australia rather than inherent resistance to weed invasion. *Spartina spp. is a
serious weed of wet saltmarsh. Upper level or dry saltmarsh is highly susceptible to weed invasion, particularly
from Mediterranean annual grasses such as Sea Barley-grass *Hordeum marinum. A major weed is Tall Wheat
Grass *Lophopyrum ponticum, which was introduced to Australia (and promoted) as a salt-tolerant pasture
grass, with major management ramifications (Booth et al. 2009). It has invaded many areas in the Connewarre
system (Figure 7.13), and is regarded as the most seriously invasive weed of upper saltmarsh in Victoria
(Booth et al. 2009; see also Chapter 1.11).
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Figure 7.13: Gahnia filum sedgeland (left) invaded by Tall Wheat Grass (right), Salt Swamp.
Weed control involving heavy machinery is damaging to saltmarsh. A single inept operation on Spiny Rush
*Juncus acutus beside the Werribee River has severely damaged saltmarsh vegetation and permanently jumbled
the surface topography of the marsh.
Weeds increased dramatically at The Spit Flora and Fauna Reserve (near Point Wilson) between 1980 and
2002, changing the composition and extent of upper saltmarsh communities. Indigenous saltmarsh annuals
have declined alarmingly with most of the 15 species formerly present now extinct. In contrast, the lower or
wet saltmarsh has few or no weeds. This change is due to tidal restriction, eutrophic water entering the reserve
from the adjacent water treatment plant (both lower salinity) and the withdrawal of sheep grazing (Carr et al.
2002).
Example from the Barwon River estuary
Weeds are widespread within the Barwon estuary, but except for *Spartina, are largely confined to upper
saltmarsh. *Spartina is scattered within the estuary and is currently being mapped and controlled by Parks
Victoria. Parks Victoria is planning to implement control of Tall Wheat Grass at several locations. The
biological control agent rust fungus will be applied via spore water to Bridal Creeper in Coastal Alkaline
Scrub (EVC 858) at Murtnagurt Swamp.
Necessary action
•
•
•
•
•
•
Undertake weed surveys to locate high-threat weeds.
Undertake weed control programs on target weeds.
Undertake weed control programs to protect sensitive areas.
Ensure control programs use appropriate methods and are cost effective.
Inform the local community to minimise the introduction and spread of weeds.
Implement effective monitoring of weed invasions throughout the area, on public and private land.
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pasture ‘improvement’
Pasture ‘improvement’, if it involves introduced salt-tolerant grasses, is a growing issue for the management of
many coastal saltmarshes. The problem with the introduction of Tall Wheat Grass *Lophopyrum ponticum has
been outlined above.
Example from the Barwon River estuary
Tall Wheat Grass is widespread on the edges of the estuary where it is having a major impact, the rare
Estuarine Flats Grassland being particularly vulnerable (Figure 7.14).
Figure 7.14: Pasture ‘improvement’, Salt Swamp.
Necessary action
•
•
•
Prevent the deliberate introduction of salt-tolerant grasses to estuaries.
Eradicate any infestation before it spreads.
Encourage the use of the indigenous species for production if grazing is unavoidable (on private land).
pest animals
Pest (feral) animals can threaten the wildlife of saltmarsh and estuary habitats, either by direct predation or by
habitat modification. A wide range of vulnerable wildlife occurs in such habitats including many waterbirds,
Orange-bellied Parrot Neophema chrysogaster, Swamp Skink Egernia coventryi and Southern Brown
Bandicoot Isoodon obesulus obesulus. Foxes are the main problem.
Example from the Barwon River estuary
Baiting of foxes is being undertaken in the wildlife reserve to protect the Orange-bellied Parrot (Figure 7.15).
Rabbits are also baited within the reserve. Feral deer are being controlled within the Reedy Lake area by the
Australian Deer Association under the supervision of Parks Victoria.
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Figure 7.15: Fox baiting to protect Orange-bellied Parrot, lower Barwon River.
Necessary action
•
•
Undertake pest animal control as appropriate.
Ensure adequate monitoring of pest animal populations and impacts.
mosquito control
Mosquitoes are a human health issue and a cause of pain and irritation in saltmarsh at times. The most
important mosquito in saltmarsh is the Southern Saltmarsh Mosquito Ochlerotatus camptorhynchus, which
occurs along the coast of Victoria and is an important vector of Ross River Virus. Insecticides are used to
control mosquitoes in Victoria (Department of Sustainability and Environment 2004a).
Mosquitoes are an important part of the aquatic food web, with larvae eaten by fish and adults eaten by
birds and bats, but there has been little or no research on the subject. In Victoria, no research has been done
on the sensitivity of critical aquatic species to larvicides, the role of mosquitoes in the food web, or the
impacts of various forms of habitat modification on saltmarsh characteristics. There has been little research
on the environmental impact of control materials and methods under Victorian conditions (Department of
Sustainability and Environment 2004a).
Of prime concern is the lack of information on the environmental impacts of treatments on coastal
saltmarshes in Victoria, many of which are designated as areas of national and international significance.
Data are available from northern states and overseas, but there are no local studies on indicator organisms
and ecosystems subjected to physical, chemical and biological intervention for mosquito management.
Research on the impacts of control chemicals and other materials on fish species of fresh water and marine
environments is also lacking.
Choosing the most appropriate pesticide materials and delivery methods for mosquito management depends
on the environmental sensitivity of a site and the area to be treated (Department of Sustainability and
Environment 2004a). Bacillus thuringiensis and methoprene (a growth inhibitor for larvae) are recommended
for use in areas of very high and high environmental sensitivity. They are the most targeted materials for
larval reduction with studies demonstrating minimal impact on a range of non-target species overseas and in
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Australia. Larvae ingest these materials over the short time (maybe five days) that they are feeding and fail to
develop. Methoprene is used where sites are difficult to monitor and manage and where a longer-term slowrelease treatment (over a month) would be more effective (Department of Sustainability and Environment
2004a).
The use of adulticides to treat mosquitoes is not common in Victoria, except in some cases where significant
disease outbreaks require rapid reductions in mosquito numbers. The insecticides registered for use in
Victoria are mainly malathion and pyrethroids. These chemicals have a more broad-scale impact on non-target
species and may have a much smaller impact on overall mosquito numbers than larvicides (Department of
Sustainability and Environment 2004a).
Some saltmarshes in Australia and overseas have their surface topography modified in order to reduce
mosquito habitat. Runnelling involves linking ponds with the sea enabling better access for predatory fish. It
has the potential to modify saltmarsh hydrology, the chemical characteristics of marsh soil, marsh topography,
and natural vegetation patterns. Of particular concern is the issue of acid sulfate soils that are found in some
estuary sites and that may exposed by channel construction leading to acidification of water (Department of
Sustainability and Environment 2004a).
Example from the Barwon River estuary
Methoprene is applied to parts of the Barwon River estuary by helicopter.
Necessary action
•
Follow Departmental guidelines on the application of mosquito insecticides.
stock grazing
Grazing by domestic stock generally has negative effects on saltmarsh: the surface becomes pugged,
compacted and lowered in elevation, plants are destroyed or damaged, and weeds may be introduced and
spread. Because of their weight, cattle and horses have the greatest impact; sheep usually cause less mechanical
damage and soil compaction. Provided the surface topography is not altered and the hydrology is not altered
(drains or levees are not constructed), there is considerable potential for the recovery of saltmarsh vegetation
following the removal of stock.
Notwithstanding the generally negative impacts of grazing, sheep grazing may lower the intensity of weed
infestations by preventing weeds setting seed. Invasion by mediterranean annual weeds at The Spit Flora and
Fauna Reserve may be in part due to the removal of sheep grazing. In parts of the reserve, the re-instatement of
sheep grazing is likely to control weeds and promote some indigenous species (Carr et al. 2002).
Example from the Barwon River estuary
Stock grazing occurs on most of the private land within the Barwon River estuary. There are many examples
where the vegetation is severely depleted and, in some cases, destroyed (Figure 7.16). Shrub (Tecticornia spp.)dominated samphire communities are particularly vulnerable, as the shrubs are brittle and easily destroyed.
Their destruction converts Tecticornia shrubland to Sarcocornia or Disphyma herbland and, under the most
severe pressure, can result in the total loss of native vegetation and its replacement with introduced species.
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In 1983 the exotic annual grasses *Polypogon monspeliensis and *Hordeum marinum were invading bare areas
in Salt Swamp where samphire shrubland had been completely destroyed by cattle. There was no sign of
samphire recovery. An associated easement for an electric fence had been colonised by these grasses, resulting
in their introduction to the central area of the swamp. The easement had left a long-term scar in the vegetation
(Yugovic 1985).
Figure 7.16: Damage to saltmarsh caused by stock trampling and grazing.
Necessary action
•
•
Prevent stock grazing in saltmarsh, except in rare cases where sheep grazing may have a net ecological
benefit, for example in terms of weed control.
Carefully monitor any grazing that is permitted for licensing requirements and to gauge environmental
impacts.
shell-grit mining
Shell-grit mining has caused immense damage to the Lonsdale Lakes system, and has permanently destroyed
saltmarsh and altered landforms and vegetation patterns. Most mining occurred between 1959 and 1973,
when the shell-grit was transported by rail to Melbourne for glass manufacture. Lake Victoria and the area
to the north have been particularly affected. There was no attempt to rehabilitate sites by levelling them, so
unsightly mounds and bunds now occur throughout the mined areas. The industry was unsustainable; little
or no mining of saltmarsh occurs in the area at present, and the last operator will cease operation in 6–12
months.
Despite the extensive destruction of saltmarsh and associated vegetation by shell-grit mining in the Lonsdale
Lakes system, mined areas may develop important biodiversity values (see Chapter 1.11). In the proposed
Lonsdale Lakes residential development area – formerly mined with seasonal or permanent ponding of saline
water – now supports 32 ha of Saline Aquatic Meadow, an endangered EVC in the bioregion (Carr et al.
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2005; North et al. 2007). These Saline Aquatic Meadows have the same floristic composition and structure
that characterise the rare natural examples: they are dominated by the submerged macrophytes Ruppia spp.
and Lepilaena spp. and have no exotic plant species. This situation – saltmarsh destroyed and transformed by
shell-grit mining – is analogous to the conversion of saltmarsh to salt production in evaporation pans. These
novel systems may have high biodiversity values, particularly as bird habitats.
Example from the Barwon River estuary
Shell-grit mining has damaged Salt Swamp and has left numerous scars in the landscape (Figure 7.17; see also
Figure 1.34). Murtnagurt Swamp has been severely damaged, with much of the dry saltmarsh destroyed. Salt
pans or sparse Sarcocornia herbland now occur where the original saltmarsh existed.
Figure 7.17: Scar in saltmarsh vegetation created by shell-grit mining, Salt Swamp.
Necessary action
•
•
Protect saltmarsh from all mining activity.
Rehabilitate, where appropriate, those areas that have been mined.
rubbish dumping
Rubbish dumping is often a problem in coastal saltmarsh, especially when the material dumped is hard waste.
It is unsightly and may involve the introduction of foreign geological material such as bricks and concrete, as
well as posing a pollution threat (Figure 7.18).
Example from the Barwon River estuary
Rubbish dumping occurs throughout the Barwon River estuary on private land, presumably by the landowner.
Within the reserve, it is a minor but growing issue as residential development expands.
Necessary action
•
•
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Prevent rubbish dumping within saltmarshes and estuaries.
Remove rubbish where it has been deposited, ensuring that no unacceptable environmental damage
occurs in the process.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
Figure 7.18: Rubbish dumped on saltmarsh, eastern side of Lake Connewarre.
incursion into public lands
Adjacent landowners may attempt to incorporate public land with saltmarsh or saltmarsh buffer into their
property where there is no fencing in the first place, and may install fencing which is not aligned with title
boundaries. The process is termed incursion (Figure 7.19).
Figure 7.19: Large area of reserve illegally fenced and grazed, Salt Swamp.
Example from Barwon River estuary
Some areas of the wildlife reserve are illegally fenced off from the reserve and grazed as if they were private
property. On the north shore of Lake Connewarre, one area is included in a private garden where beach sand
has been imported, probably killing a mature Boobialla Myoporum insulare in the process.
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Some residents in Barwon Heads mow saltmarsh within the reserve adjacent to their property. Another
example of incursion in the reserve is more complex: the constructed fence is not aligned with title
boundaries, and the net result is that more private land is left outside the fence than public land is included
within the fence. Due to resources shortages, Parks Victoria is unable to patrol and review boundaries.
Necessary action
•
•
•
Prevent incursions into reserves.
Fence public land where necessary.
Consider taking no action where, for a particular property, more private land is left outside the fence than
public land is included within the fence. This should be formalised on title if there is any possibility of an
adverse possession claim.
unauthorised use
Unauthorised use of saltmarsh becomes an issue when natural values are threatened. Vehicle access, including
trailbike access, is highly detrimental to soils and vegetation, and interferes with wildlife.
Example from the Barwon River estuary
In at least two cases in the Barwon River estuary, stock have unrestricted access to the wildlife reserve via
constructed gates. There is evidence of stock grazing on the edges of the lake inside the reserve. Damage is
evident also from unauthorised vehicular access (Figure 7.20).
Figure 7.20: Damage to coastal saltmarsh by
vehicle access, The Sheepwash.
Necessary action
•
338
Prevent unauthorised use of saltmarsh.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
boat wash
The wake left by boats may, in some cases, accelerate the erosion of channel banks. Enhanced erosion may
result in loss of substrata and saltmarsh vegetation, inhibited recruitment of mangroves and saltmarsh plants,
and threats to physical infrastructure.
Example from the Barwon River estuary
Boat wash in the Lower Barwon at Barwon Heads (particularly The Sheepwash) is a problem as bank erosion
is exacerbated and expensive stabilisation measures have had to be implemented (Figures 7.21 and 7.22). The
signposted speed limit of 5 knots is not always observed and is not policed effectively. Parks Victoria is not
authorised under the Marine Act 1988 and in any case has no boat in the area; both factors force Rangers
to shout at offenders from the river bank. Marine Safety Victoria is currently undertaking a review and may
declare Barwon Heads a ‘no wash’ zone, meaning that no boat wake is allowed. A decrease in boat wash
could be achieved by lowering the maximum speed limit even further but, as with the current limit, would be
ineffective without adequate enforcement.
Figure 7.21: Erosion and uprooting of
mangroves, The Sheepwash.
Figure 7.22: Bank erosion and collapse accelerated by boats, The Sheepwash.
Necessary action
•
Prevent boat wash by introducing and enforcing boat speed limits.
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boardwalks
Boardwalks in less-sensitive areas of coastal wetlands are appropriate to enable people to gain access to areas of
saltmarsh, mangrove and estuaries. Access may be desirable for passive recreation (e.g. walking, photography,
etc.) or slightly more active pursuits (e.g. fishing). Boardwalks should be elevated structures that do not
interfere with water flow, or else the sensitive hydrology and ecology of the vegetation will be compromised.
Walking tracks constructed on fill, even with culverts, are not acceptable because they cause significant
disruption to the hydrology and thus the vegetation pattern of the marsh. They also create a substratum for
weeds. Boardwalks should not be too high above the ground, as this type of construction requires handrails
to be installed in accordance with Australian design standards. Handrails on wetland boardwalks conflict
with the open landscape and have an over-engineered appearance. There may be a pollution issue also with the
materials used to construct boardwalks, especially the leaching of contaminants such as arsenic from treated
wood (see Chapter 1.11). Sensitive areas such as lagoons should be avoided to prevent wildlife disturbance.
Boardwalks that are well designed in terms of structure, materials and location are appropriate, but poor
design can damage or compromise the natural values the boardwalk is meant to allow access to.
Example from the Barwon River estuary
The boardwalk at The Sheepwash is a well designed, low but elevated structure (Figure 7.23).
Figure 7.23: Well-constructed elevated boardwalk, The Sheepwash.
Necessary action
•
•
•
340
Undertake detailed site assessment during the design stage to prevent impacts on significant species of
vegetation.
Ensure boardwalks are elevated structures that do not impede water flows.
Avoid sensitive areas, especially lagoons, where wildlife may be disturbed.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
signage
In some cases, signs are appropriate to identify reserves, regulate visitor behaviour and inform visitors of the
value of reserves. Signage should not be visually intrusive in itself.
Example from the Barwon River estuary
Signs are installed at many access points around the reserve, but they are ad hoc, not strategic and, in some
cases, have conflicting messages. Some simply state the relevant regulations (Figure 7.24), which may be
appropriate in hunting zones, but the existing signs are uninviting to visitors and uninformative about
conservation values. Signs on the boardwalk at The Sheepwash, for example, inform visitors about the estuary,
but they focus on fauna and contain little or no interesting information on the vegetation. Parks Victoria
proposes to review all signage in the reserve.
Figure 7.24: Regulations on information sign,
Lake Connewarre.
Necessary action
•
Install signs of suitable design in appropriate locations to identify reserves, regulate visitor behaviour, and
inform visitors of the natural value of area under protection.
spread of mangroves
Mangroves are replacing saltmarsh in many places along the New South Wales coast, but the evidence for a
similar spread in Victoria is less clear, in part because suitable studies have not been undertaken (Chapter
1.11). The relatively limited and restricted distribution of mangroves in Victoria, which are at their southern
geopraphical limit, would mean that the occurrences of encroachment and habitat replacement are few.
Interspecies competition provided by Shrubby Glasswort Tecticornia arbuscula would also limit the ability of
mangroves to encroach when the stature of plants are similar (Figure 7.25).
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As global sea levels are rising, it is anticipated that mangroves in some places along the coast will replace
saltmarsh by colonising higher ground. Changes to sedimentation patterns also may affect the relationship
between mangrove and saltmarsh. A shift in vegetation is not necessarily a problem where saltmarsh and
other types of estuarine wetland have inland areas to which they can migrate, such as within large reserves
that lack alienating structures such as sea walls. In more developed regions, however, there are few or no areas
for landward migration and saltmarsh may be squeezed out by mangroves on the seaward side. In some cases,
mangroves have been planted in areas in which they are not indigenous where they potentially reduce the
mudflat foraging area for waterbirds. It is a problem on Mud Islands (Yugovic 1998) and in the Gippsland
Lakes (Darcy Duggan, pers. comm.). The Mud Islands population of mangroves is being eradicated by Parks
Victoria and the Friends of Mud Islands.
Figure 7.25: Shrubby Glasswort Tecticornia arbuscula on the left compared with
Avicennia marina on the right. Mangroves would have difficulty in out-competing,
encroaching or replacing the saltmarsh in this situation.
Example from the Barwon River estuary
Mangroves are spreading dramatically in the Lake Connewarre area (Figure 7.26). Twenty-five years ago they
were present only in the tidal delta area as isolated seedlings and stunted shrubs (Yugovic 1985) but now they
are abundant and have formed belts along the edges of the delta islands. The change, along with recent dieback
of Tangled Lignum Muehlenbeckia florulenta, may indicate rising sea levels.
The lake and island shores of Lake Connewarre have always been wet and tidal, and thus apparently suitable
for mangroves in terms of flooding and salinity regimes. Within estuaries mangroves are killed inland by low
salinity and frosts, especially at low tide (Ashton 1971). Both limiting factors are likely to become relaxed
around the lake as a result of climate change: salinity is higher now because of the decrease in river discharge.
The limited water-quality data suggests that the lake has not experienced freshwater conditions in recent years
(Dahlhaus et al. 2007).
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Figure 7.26: Colonising mangroves at the tidal delta, Lake Connewarre.
Necessary action
•
•
Do not remove mangroves from sites they colonise naturally.
Monitor the distribution and extent of mangroves and undertake investigations to determine the cause
of mangrove spread where detected. Removal of mangroves where they do not occur naturally may be
tackling the symptom rather than the cause and hence generate a non-sustainable course of action.
fencing
Fencing is expensive to construct and maintain and, if possible, is best avoided in order to minimise
disturbance and allow wildlife free movement across the landscape. In many situations, however, fencing is
necessary to exclude undesirable impacts arising from grazing by domestic stock, vehicle access or pedestrians.
Fencing may also be installed to protect regenerating or planted vegetation. The Crown is not obliged to pay
for fencing (Fences Act 1968, Section 31).
Example from the Barwon River estuary
Fencing has been necessary throughout the Barwon River estuary to exclude domestic stock and vehicles on
private land from entering the wildlife reserve (Figure 7.27). Fencing is usually undertaken at the cost of the
adjacent landholder, although the Bellarine Ark Project provides some funding.
Protective fencing has been used in the Barwon River estuary to protect naturally established mangrove
seedlings and mangroves planted as a result of a development elsewhere on the estuary (Figure 7.28). Parks
Victoria undertook fencing in 2002 as part of a project to protect the river bank from erosion and to improve
management of pedestrian and recreational fishing access along the river. New boardwalks and fishing
platforms were also erected to better manage human pressure on the river.
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Figure 7.27: An example of effective fencing in restricting stock access along the
boundary of the reserve, Hospital Swamp.
Figure 7.28: Fencing used to protect mangrove seedlings. The fencing has
been successful in not only protecting these mangroves, which have survived
quite well, but also assists in increasing community awareness of their value in
protecting the river environment.
Necessary action
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•
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Construct and maintain fencing to protect natural areas where necessary.
Construct fencing with minimum impact on vegetation.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management
fire
Fire is rare in saltmarshes but can occur at times, and upper level saltmarsh is most likely to burn (see Figure
1.44). Ongoing and future climate change is likely to see an increased incidence and severity of fire. At The
Spit Flora and Fauna Reserve, a fire in 2001 caused high mortality of Gahnia tussocks but reduced the cover
of exotic annuals and stimulated the growth of Distichlis and Sarcocornia, which suggests that fire could have a
useful role in saltmarsh management (Carr et al. 2002).
Example from the Barwon River estuary
Fire is rare within the estuary but does occur occasionally. Fire can move slowly in Gahnia sedgeland, and a
spread rate of 1 m min–1 has been observed at Salt Swamp (Yugovic 1985). The fire had been lit by the adjacent
farmer within an area of the reserve leased for grazing. Yugovic (1985) showed that grazing of saltmarsh by
domestic stock of Gahnia that was regenerating after fire was highly detrimental. A fire originating in Geelong
spread into Reedy Lake between 2005 and 2007 (S. Willsher, Parks Victoria, pers. comm.).
Necessary action
•
•
•
•
Allow fire to burn into saltmarsh; do not construct fire breaks within saltmarsh.
Protect regenerating saltmarsh from disturbance, especially grazing.
Monitor recovery of any burnt saltmarsh vegetation and, in particular, invasion by exotic species or
increases in exotic species.
Undertake weed control if required in fire-affected areas.
visitor management
Visitors are generally desirable around and within saltmarsh and estuary vegetation for community social
health and to increase awareness and support for the protection of natural areas. Even so, visitor pressure may
need to be managed to prevent impacts on natural features, especially those arising from pedestrian passage
through the mangrove or saltmarsh itself. Thus visitor management often requires a range of infrastructure,
including fencing, boardwalks and signage.
Example from the Barwon River estuary
Boardwalks, signage and fencing are placed at various access points around the wildlife reserve, and is
concentrated at The Sheepwash, Barwon Heads. Anglers have access to the river bank by foot and by car. Cars
cause problems especially when they become bogged, and physical damage to saltmarsh results during both
the bogging itself and the subsequent attempts at recovery.
Necessary action
•
•
Undertake measures to manage visitor pressure on natural features.
Provide interpretation material to visitors as appropriate.
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regeneration and revegetation
Revegetation projects are often poorly planned, and plantations purporting to be revegetation can consist of
non-site indigenous species, in which case they are horticulture and not revegetation. Such failures reflect a
general lack of understanding of both saltmarsh ecology and the highly variable and site-specific nature of
wetland vegetation. Such plantings usually do poorly or die, with the result that time and resources are wasted,
community goodwill exhausted, and the integrity of the site’s ecology is compromised. Revegetation is a last
resort to be implemented after all natural recruitment options have been exhausted and should be carried out
using strictly site indigenous plant material.
Example from the Barwon River estuary
A number of plantations purporting to be revegetation occur within the Barwon River estuary, but few are site
indigenous and some include plants not indigenous to the region. There is a general tendency to plant trees
and shrubs below their natural zone on sites that are naturally treeless (Figure 7.29). In many cases, this seems
to be done in order to provide screening for duck shooting. In one plantation Moonah Melaleuca lanceolata
has been planted to provide roosting habitat for Orange-bellied Parrot when the site is below the natural
elevation for this species and the plantation is probably doomed in the long term. The site naturally supports
the shrub Tangled Lignum Muehlenbeckia florulenta which should have been planted instead. Blue-winged
Parrots roost in lignum and the Orange-bellied Parrot is assumed to do likewise. As noted earlier, mangroves
have been planted onto the river bank at The Sheepwash, where they are not site indigenous.
Figure 7.29: Inappropriate planting of locally indigenous but not site-indigenous species at
Salt Swamp, resulting in the almost complete death of young plants.
Revegetation works are often associated with rehabilitation programs, which as mentioned above can often
fail without scientific rigour to support the purpose and design of such works. Mangrove and coastal saltmarsh
rehabilitation projects have now reached a level of sophistication where success has been achieved, such as the
Kooragang Island Restoration Project in Newcastle, NSW. A number of manuals and best-practice guidelines
are now available for New South Wales specifically (e.g. Department of Environment and Climate Change
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2008a,b) and more generally (Adam 2009b). Similar types of guiding documents need to be made available in
Victoria to support both government agencies and the community who are enthusiastic to undertake projects
but require guidance to ensure that projects are appropriate, successful and avoid failure.
Necessary action
•
•
•
•
Facilitate natural regeneration of vegetation.
Undertake revegetation only where natural regeneration cannot occur.
Apply the site-indigenous principle when undertaking revegetation and ensure that the composition and
structure of the vegetation mimics natural models.
Develop best practice guidelines or manuals to assist, facilitate and support rehabilitation projects
involving mangroves and coastal saltmarsh.
wetland construction
Artificial wetlands are sometimes created in coastal saltmarsh to provide habitat for waterbirds, provide
hunting opportunities, or as treatment ponds. Often they are created with little or no regard for the existing
natural vegetation and topography. In one recent case at Williamstown, rare Tecticornia dry saltmarsh
on public land was destroyed for the constructed Paisley-Challis wetlands, allegedly without planning
permission. Adding insult to injury, the wetlands are signed as an environment project with several
government agencies seeking credit for it. To quote from Hobsons Bay City Council (2008):
A feature of the parklands are the Paisley-Challis wetlands, formed in 2002 by restructuring
two stormwater drains to form a filtration wetland, adjacent to the coast. The project embodies
principles of multi-objective planning, bioremediation, habitat consolidation and landscape
enhancement. And it’s produced a shiny new swamp.
Figure 7.30: Outlet structure which controls water levels, Reedy Lake.
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Example from the Barwon River estuary
Large freshwater wetlands have been created from tidal saltmarsh in the Barwon River estuary to provide duck
habitat for hunting. Reedy Lake and Hospital Swamp are managed as freshwater systems, while the attempt
at Salt Swamp failed. Levees, channels, inlet and outlet structures and tracks have been constructed but, to
date, there has been no excavation of wetland basins (Figure 7.30). The artificial wetlands have held little or
no water in recent years due to drought. Waterholes in Salt Swamp were deepened and enlarged when dry to
encourage water retention for duck hunting (Dahlhaus et al. 2007).
Necessary action
•
Prevent construction of ‘wetlands’, especially by excavation, within saltmarsh.
enforcement
A visible presence of management personnel and a willingness to enforce regulations and undertake
prosecution, in court if necessary, is beneficial to natural areas.
Example from the Barwon River estuary
Limited resources are a problem for agencies such as Parks Victoria, which currently does not have a boat with
which to patrol the river and lake.
Necessary action
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Enforce regulations and undertake prosecution as necessary.
mangroves and coastal saltmarsh of victoria: distribution, condition, threats and management