CHAPTER 7
Recommendations for the future management and conservation of saltmarshes
in the Peel-Harvey estuarine system
T.H. Rose, A.J. McComb
7.1 Introduction
Estuarine saltmarshes can stimulate a number of senses. In a visual way,
they provide a pleasing vista of procumbent to tall shrubs and trees tinged
with colours ranging from red in autumn to succulent green in spring. This
view is often enhanced by the sight of hundreds of wading birds feeding
and dabbling along the shores and flying low over this interface between
land and water. Saltmarshes also provide a contrasting sense when the rich
productive smells of the marsh are detected. These smells are composed
of decaying sun-baked vegetation mixing with the rotting gases of fetid
muddy land. To some, the landscape features and the close proximity of
open estuarine waters provides a potentially dollar-rich urban development
challenge. With enough fill and re-contouring, these areas could be converted
into expensive waterside homes. To all, however, the swarming mosquito
hazes can drive us into our homes or cars making us wonder why nature has
been so free in creating such a varied environment.
Overall, samphire marshes truly embody a large ecotone
metaphor. On one side is a unique habitat providing an interface and link between
land and water, and on the other side an environment fertile for human cultural
conflict. Unfortunately, humans are an ecotone
species and are drawn to the fringes of estuaries. To reduce conflict and successfully
manage these environments requires an understanding of current land ownership,
reserve status of fringing land, international treaty obligations, the planning
process and the use of practical management plans and structures. It is also
important to recognise the wisdom of using applied management and theoretical
research plans to provide answers to management questions. They are most helpful
if these plans recognise the uniqueness of most saltmarshes and give the public
and estuarine manager the kind of information which allows saltmarshes to be
conserved and sustained well into the future. Ultimately, any management plan
must provide direction to help prevent the degradation of saltmarsh functions,
such as ecologically important biodiversity,
productivity and nutrient storage and release functions.
Successful management of saltmarshes also needs to recognise and plan for future
pressures on these habitats. This pressure may be in the form of increased human
usage from older industries such as peat mining and cattle grazing or from sunrise
industries like ecotourism and permaculture.
The source of such pressure can be simply attributed to the close proximity
of our increasing and more concentrated human populations. In turn, increasing
human proximity and pressure will require careful management of public health
issues, because of the need to control mosquito borne diseases and for the potential
for toxic water quality conditions to arise.
This chapter will outline issues for consideration and provide recommendations
which the community, local authorities and state agencies will need to
consider and hopefully implement, if the saltmarshes of the Peel-Harvey
estuarine system are to be successfully conserved.
7.2 Recognising sources of degradation
There are numerous sources of saltmarsh degradation but these can be divided
into two major ones - natural and human/cultural sources.
7.2.1 Natural sources
Natural activities and impacts created by weather, animals and plants can
change the characteristics of saltmarshes and therefore the susceptibility
of the marsh to human degradation.
The saltmarshes located on the fringes of the basins and tributary rivers of
the Peel-Harvey Estuary are dynamic environments which undergo seasonal and
yearly changes. Estuaries are "ephemeral"
environments and can last, in a geological sense, between several and 20-40
thousand years (Barnes, 1974). The result
is that each saltmarsh can reflect three basic stages or states of development
and maturation, depending on processes determined by geology, the age of the
estuary and human activity in its catchment. For example, saltmarshes can be
accreting or growing; they can be eroding and either be becoming permanently
submerged or disappearing as higher elevation terrestrial
plant communities are established; or lastly, the marsh may be in relative stasis,
with an equal proportion of low and higher elevation plant communities. This
means that nature ultimately determines the longevity of marshes and the uniqueness
of its animal and plant diversity and structure and ecological functions. Nature
strongly influences the propensity for a marsh to become degraded or be resistant
to human impacts, through its overall control of tidal activity, rainfall, hydrology,
river flooding and wind, storm and biological patterns.
7.2.2 Human sources
Grazing Historically, the saltmarshes of the Peel-Harvey have been grazed by sheep
and cattle. Marshes often provided the only source of late summer and autumn fodder,
particularly in dry hot years and where cattle and sheep owners possessed high
water titles to their land. Grazing activity was prevalent in the Creery and Harvey
Estuary marshes (O.H. Tuckey, pers. comm.).
The result is that many of the saltmarshes found around the fringe of the estuary
have been and are still influenced by cattle and sheep grazing which affects plant
and animal species diversity, the historical productivity of the marsh and its
long term accretion/erosion patterns (Adam,
1993).
Hunting Until recently, duck hunting was legal, and this strongly influenced
the numbers and species diversity in saltmarshes (Adam,
1993; M. Bamford, pers. comm.). Since
duck hunting ended in the late 1980s, duck numbers and diversity appear to have
increased (M. Bamford, pers. comm. and T.
Rose, pers. observ.). The hunting of kangaroos and other mammals has also influenced
the number and diversity of natural marsh grazers, and therefore their impact
on and use of the saltmarsh. Hunting can reduce the numbers of, and even eliminate
common members of the fauna in saltmarshes, so affecting overall biodiversity
and natural grazing patterns.
Feral animals and weeds Human settlement
has introduced feral animals such as rabbits,
cats, foxes and bees into the saltmarshes of the region. European use of saltmarshes,
in the main, has also introduced weeds and non-native plants. For example, Watsonia,
bull rushes and grasses are now common components of the plant communities in
most marshes. Weeds have flourished because of altered water tables due to nearby
human settlement and land uses (such as irrigation and clearing). They have
also flourished because of fire events which generally have not been favourable
to a wide range of native plants. If fire patterns mimic more natural patterns
in terms of frequency and intensity, then a wider variety of native plants is
able to compete with introduced plants and weeds (Pen,
1987). The consequences of feral invasions
are that marshes become altered in structure, productivity and nutrient functions.
These alterations affect other estuarine flora and fauna, including native birds
and other animals.
Direct human use and access In the past, horses and bridal trails have
degraded samphire marshes. However more recently, particularly in the last fifty
years, human access and use of vehicles, notably four-wheel drive vehicles and
trail bikes, have degraded saltmarshes through the creation of wheel ruts, destroyed
vegetation and allowed rubbish to be deposited directly in these environments.
Vehicle access has allowed entry to previously isolated areas and provided opportunities
for trees to be cut down or used for fuel. The creation and construction of
roads and trails, both sealed and unsealed, has led to the fragmentation of
once very extensive and continuous saltmarshes in the region, for example the
Creery wetlands. This kind of degradation, that is slow fragmentation, has been
documented in Chapter Two and affects marshes by altering
hydrology, their ability to resist erosion, the processing and export of nutrients
and the provision of habitat integrity which a variety of plants and animals
require to persist in this habitat. The end result is a breakdown in ecological
function and therefore in their importance to the Peel-Harvey estuarine ecosystem.
Human infilling Infilling has been one of the most common ways by which
saltmarshes have been lost in the Peel region. To secure land from the effects
of regular and occasional flooding, humans have used the importation of sedimentary
fill to raise the level of the land. Infilling immediately smothers and eliminates
saltmarsh. It has been the primary method which has allowed the City of Mandurah
to develop around the Mandurah Entrance Channel. Infilling is also prevalent
in the lower reaches of the Serpentine River and at Yunderup Canals, on the
eastern fringe of the Peel Inlet, where further stages of urban development
are occurring. In addition to the immediate impacts of fill, a lot of fill contains
weeds or weed seeds, and sets in train the invasion of saltmarshes with exotics
with consequent long term degradation. In summary, infilling causes a loss of
vegetation and can alter groundwater hydrology patterns, which may lead to de-stabilisation
of marsh communities.
7.3. Considerations for management
The difficulty of managing saltmarshes in a regional or ecosystem context
is that several strategic political and financial steps need to be taken
at the same time in order to effectively conserve this environment. Co-ordinating
synchrony can be very difficult without a unified community and political
recognition of the need to conserve samphires and the will to do so. Co-ordinating
cultural and political will must be combined with the co-ordination of
various government bodies that can influence the conservation of these
environments. The provision of financial resources is also necessary to
fulfil the following recommendations.
7.3.1 Strategic Steps
The preparation of a comprehensive inventory of the location, number and extent
of saltmarsh habitats would be a helpful first step. Chapter
Two is very helpful in that it has identified current locations of saltmarshes
as well as historical trends in saltmarsh habitat area, whether they are expanding
or contracting. This inventory would need to be combined with the defunct Department
of Conservation and Environment Red Book (1983)
recommendations. Finally, an on-the-ground site assessment for "health" and conservation
value of existing saltmarsh habitats is needed. This survey could categorise all
samphire wetlands into conservation value and would complement or update the Red
Book (1983). The combination of the three documents
into an integrated resource document, a resource catalogue, would provide the
basis for several further steps. However, to minimise controversy over boundaries
which define the location and area of conservation areas, the catalogue needs
high quality maps, be surveyed as accurately as possible and follow prescribed
objective procedures which can be easily replicated.
Other means of conserving samphire marshes are as follows:
1. The creation of an Environmental Protection Policy (EPP)
for samphire-dominated saltmarshes in the Peel Region, which could perhaps
extend over the whole Swan Coastal Plain. This EPP could be a subsection
of the current EPP for Wetlands of the Swan Coastal Plain. Only the Environmental
Protection Authority, through the Department of Environmental Protection,
can underwrite such legislation and undertake the extensive public consultation
required for a regional policy. The EPP would identify areas requiring
high conservation and set a target or minimum surface area for saltmarsh
habitat which could not be exceeded or lost in the region. This should
be based on the preceding resource inventory catalogue.
2. Integrate identified saltmarsh worthy of conservation, based on a
minimum functional size into the Peel Regional Plan and Park (particularly into
a regional structure plan). This should be combined with recognition for RAMSAR,
CAMBA and JAMBA
areas. Any areas identified for bird treaties must be clearly outlined and
marked on maps, and recognised by all interests which can potentially affect
their future. It would be expected that following establishment of the Peel
Regional Park, the saltmarshes identified for acquisition and conservation would
be included in its management boundaries.
3. The Peel Regional Strategy (formerly Peel Regional Plan)
must set the framework for the establishment of an acquisition fund which
would provide funds for acquiring privately-held land containing significant
saltmarsh with conservation potential. This fund would need to be based
on similar principles to the Perth Metropolitan Region Improvement Fund
(MRIF) administered by the WA Planning Commission. This fund could also
acquire land for public amenity, buffer purposes, vegetation and wildlife
corridors and foreshore reserves, all of which would help reduce pressure
on fringing areas of the estuary with saltmarsh.
4. Recognise and implement the recommendations in
the Peel Inlet Management Authority Management Programme (Waterways
Commission, 1992), which has identified a Waterways Protection Precinct.
For example, the Programme recommends the retention and conservation of significant
portions of the Creery Wetlands, Entrance Channel samphire areas, Austin Bay,
Roberts Bay and large portions of the fringing land in the southern Harvey Estuary.
Overall, this Programme recognises the need to conserve and maintain saltmarshes
within the Peel Inlet Management Authority's Management Boundary and should
be used as a minimum protection document for saltmarshes. Furthermore, the Programme
is supported by several regional management plans (e.g. Western Foreshore Management
Plan and Draft Eastern Foreshore Management Plan) which aim to help consolidate
smaller fringing saltmarshes into more functional foreshore reserves and have
identified the most appropriate vestees or managers of this land. The term minimum
is used because many saltmarshes were assessed in the late 1980s while the Programme
was being developed. The recovery and improvement in habitat value of saltmarshes
previously classified as degraded may be considerable and thus make some of
the Programme's recommendations outdated.
5. Incorporation of saltmarsh areas found in close proximity
or adjacent to current Department of Conservation and Land Management A
and B Class Reserves should be encouraged. Adequate funding for these reserves
also needs to be addressed once these areas are reserved.
6. Inclusion of conservation marshes with recognised conservation
values and/or significant portions of fringing saltmarsh habitat into local
authority town planning schemes (TPS) would be a very strategic move. Inclusion
can occur either through reservation or through adoption of landscape and
special environment zones which are clearly recognised in the new TPS.
These steps would be most relevant for the City of Mandurah and Shire of
Murray, but have some relevance for the Shires of Jarrahdale-Serpentine
and Waroona and the City of Rockingham.
The use of the Town Planning and structure
planning procedures is critical to laying the foundations for the
future conservation of the Peel-Harvey saltmarshes. Legal instruments such as
by-law legislation in Town Planning Schemes can provide for penalties, and scheduling
clearly defined conforming and non-conforming uses can lay the legal foundation
for future use and conservation of these critical habitats. Furthermore, the
ceding of land free of charge to the Crown under the Town Planning Act of 1928
is a further method of securing portions of saltmarshes. However, to use this
method it must be pre-planned, broadly advertised to all development parties,
and based on the provision of public or Crown access around the fringe of the
estuary, as well as providing recreation and conservation uses. The concept
of ceding land and foreshores for strictly conservation purposes needs to be
explicitly supported by the WA Planning Commission.
7. Determine up-to-date community attitudes to saltmarshes and the potential
for future ecotourism and other sustainable
industries which will use saltmarshes. These studies need to be tightly linked
to tourism and development plans and strategies. They would fit best as components
of the Peel Regional Plan. Such studies need to be rigorously designed and defensible
and would probably be best conducted by qualified university and professional
firms. The results of these surveys and polls would lay the basis for educational
programs and identify target groups that need to be reached. None of the above
steps are likely to succeed if society's perceptions of saltmarshes remains
in continuing to perceive them as worthless habitats best filled in and developed.
7.3 2 Immediate strategic suggestions for conserving saltmarshes
While the above strategic steps should be implemented to plan for the "long term"
strategic conservation of samphire of the Peel-Harvey Estuary, the studies in
this report strongly suggest that several areas could be immediately gazetted
for conservation purposes (see previous Point Four above).
Chapter Two strongly suggests that moves should be made
to reserve and immediately manage the following ecologically significant areas:
• the Goegrup Lakes system on the Serpentine River,
• all of the remaining Creery Wetlands,
• southern Peel Inlet adjacent to Austin and Robert Bays,
• the southern area of the Harvey Estuary, that is area south of Island
and Herron Point across to the Harvey River, including its delta.
The last area, in addition to the Goegrup Lakes system, has already been
targeted for inclusion into a park. However, the process needs to be expedited
urgently. The urgency is based on the fact that development is encroaching
quickly upon these areas, and there is increasing unmanaged access to and
use of the areas. This is contributing to their degradation and threatening
their ecological function.
7.3.3 Practical considerations - the use of plans as a basis for management
The management of reserves, particularly saltmarshes, is usually done by
using formal management plans. They are most effective when a saltmarsh
has been clearly gazetted for conservation or as a multiple-use park. Management
plans have a greater chance of success if they are applied to functional
saltmarsh units and not to those which have been fragmented and cut into
halves or quarters because of arbitrary planning and decision making processes.
Managing saltmarshes which have been fragmented, have altered hydrology
characteristics and are becoming degraded is difficult because the resource
often changes more quickly than the best adaptive management plan.
Applied management plans need to have some of the following components:
Foreshore Management plans
(Structure plans) These
can identify the most appropriate location for fences, access points, trails
and roads, boardwalks, education and information boards and centres, parking
facilities, toilets and maintenance and administrative structures if necessary.
The inclusion of generic or specific construction standards as well as specific
survey results are also helpful.
Fencing requirements
Fences help prevent urban encroachment, define the saltmarsh, keep out feral
animals and can be modified when they articulate with vegetation corridors to
allow wildlife to pass.
Weed control and eradication
The identification of weeds and the mapping of weed locations is essential
for weed management. Outlining management options to control them is also
essential. For example, fire control, manual and mechanical removal methods,
herbicide and biological control are all part of such a strategy.
Identification of the type and the scale of feral
animal problems is necessary. An adaptive trapping or control program needs
to be outlined.
Fire management
This is critical from both a general safety and biodiversity
point of view. The use of fire needs to be planned so that low fuel buffers
are found around structures, threats of wildfire spreading to surrounding developments
are minimised, and that a mosaic of fire treatments is provided. These mosaics
will need to vary in fire intensity, from cool to hot, and in terms of seasonality,
during spring, summer or autumn. They will also need to vary in their frequency,
once every set period of years. Maintaining mosaics will help to provide a variety
of habitat conditions which allow a wide variety of plants to flourish, contribute
to and help maintain the seed bank in the
ground.
Inventories of land capability, plant and animal communities
These provide the basis for understanding the physical and biological resources
in each specific saltmarsh and outline major management considerations.
Public Health concerns
Identification of nuisance animals and plants and their management in relation
to the specific marsh is necessary. Management methods to control mosquitoes
should identify appropriate biological, chemical and mechanical controls, such
as runnelling or ditching
(Plate 7.1).
Time scale changes
This allows the manager to understand changes which may occur over different time
scales and which will affect the natural resources of the saltmarsh. For example,
awareness of seasonal changes, public use periods and changes in long term tide
and weather patterns. Consideration for the long term effects that the Dawesville
Channel will have on marshes will also be necessary. One prediction is that
there may be a slow march of fringing vegetation out into the estuary, similar
to that which has occurred in Leschenault Inlet since it was opened to the ocean
in 1951 (L. Pen, pers. comm.).
Public expectations of management and access
Provision for local community management committees may be both necessary
and desirable. Consideration of how decisions will be made as well as how
people wish to utilise the marsh is necessary, and this component needs
to be carefully included in any management plan.
Inclusion of a research plan
A list of management questions, and questions about marsh biology and ecology,
which can be answered by research will facilitate the development of appropriate
management methods, and allow management to be responsive and adaptive to community
concerns and changes in resource status, for example shrinking cover or the
health of specific plant species.
7.4 Research Plans
These plans provide for a more rigorous and methodical way of testing management
tools and reviewing the biological, chemical and physical components as
well as the higher order nutrient and productivity processes of the saltmarsh.
The results of such research need to be disseminated at an appropriate
level so that they provide the saltmarsh manager with viable and responsible
alternatives to the management methods and tools used at present. Research
plans can have a strong scientific component or be dominated by more applied
research questions and issues.
7.4.1 Scientific plans
The preceding chapters have stimulated a number of scientific questions which
could be addressed in a comprehensive manner with a properly financed research
budget. These include the compilation of comprehensive species lists for plants
and animals in the saltmarsh (including dry and wet phases), a measure of their
density and biomass and the daily, seasonal
and spatial changes which occur for both individual
species and their communities. In summary, qualitative and quantitative surveys
of the biota over various temporal and spatial
scales are needed. Studies on establishment characteristics of native and weed
plant species would be helpful. Research which measures natural and feral
grazing pressure would also be very valuable.
Aside from the above biological and ecological questions, important information
could be gathered from studying soil chemistry, particularly with regard to
nutrient exchange and flux. Understanding how
inundation by salt and fresh water and for varying periods affects chemistry
is very important from an overall ecosystem perspective. Related to this direction
of study are questions on plant nutrition and their uptake of nutrients.
Finally, higher order research into processes and function is critical to strategic
management of saltmarshes. For example, investigating mechanisms for importing
and exporting nutrients and organic matter is essential. Such research needs
to also include the effect of spatial and
temporal factors on these processes.
7.4.2 Applied management research
Applied research should investigate a range of tools used in the management plan.
For example, investigating the effect of trail and fence locations and determining
the best time to rotate these or if it is even necessary. Methodical investigation
of access and the best kinds of fencing and surface treatment of trails are also
examples of this kind of research. Perhaps the most important are investigations
and monitoring of fire treatments and their impact on the vegetation community.
This could include investigating the seed bank
and determining recovery potential of various areas of the marsh. Reviewing and
monitoring runnels (Plate 7.1) or ditches for mosquito
control and impact on vegetation and birds would also be very important. Ultimately,
research would need to look at resistance of mosquitoes to current use of larvicides
as well as biological controls.
Much of applied research could be included in regular monitoring of the marsh
vegetation and fauna community and the format for such monitoring to allow the
manager to be adaptive and responsive to changes. Monitoring in its various
forms would include overseeing the impact of ecotourism
and making sure related access and use do not detrimentally impact upon the
saltmarsh environment. Applied research could also examine the feasibility and
success of regenerating or rehabilitating degraded marsh.
7.5 Conclusion
Degradation of saltmarshes occurs on a number of different spatial
and time scales. Both natural and human assisted disturbances of the saltmarsh
can vary in time from the very short to decades. Nature contributes an underlying
source of "degradation" and change. This usually occurs on a relatively slow scale
but storm events can occur on very short scales. Unfortunately, human activity
in the saltmarsh is often chronic and occurs over a long time. Human degradation
can also occur in pulses, such as during prawning and fishing seasons. In either
form this degradation can occur over a significant area.
Many of the above recommendations and ideas need to be implemented by
a few key organisations. Because of the value of saltmarshes to the Peel-Harvey
Estuary and the fact that the Peel Inlet Management Authority is a public
statutory body with a line management structure and function with extensive
foreshore management plans, the majority of co-ordination could be done
by this organisation. To a lesser extent, some of the work would also need
to be done by the Department of Conservation and Land Management, with
its role in the management of reserves and other related categories of
land. However, critical further work would need to be done by Local Authorities
on their Town Planning Schemes and by the Conservation Council of Western
Australia to maintain political momentum. All of these organisations could
be strategically directed by an EPA Environmental Protection Policy on
saltmarshes with significant assistance provided by the WA Planning Commission.
The Planning Commission could produce guidelines to advise developers of
the sensitivity of samphire marshes and the manner in which to develop
in the vicinity of them in a sustainable way.
The conservation and preservation of saltmarshes in the Peel-Harvey region
cannot be simply based on the argument that wetlands should just be conserved.
This simplistic approach will be unsuccessful without demonstrating and proving
the benefits of such a policy or proposing alternative ways of meeting community
needs (Adam, 1993). Educating the community
and decision makers on the very valuable role that saltmarshes perform for the
environment and for the economy will be critical. Understanding the insidious
role of the tyranny of small decisions, which defines the process coined by
Adam in the mid 1980s as that of approving small incremental losses without
understanding the cumulative impact this has on ecosystems
and how this has eroded and degraded many saltmarshes in the region, needs to
be squarely faced and understood. Reliance on mitigation procedures to sacrifice
relatively functional or recovering saltmarshes for artificial or "quartered"
habitats is a poor alternative. Overseas experience has shown that this rarely
works unless a degraded area is returned to functionality.
The eventual fate of saltmarshes in the Peel-Harvey will be heavily
influenced by the effects of the Dawesville Channel. This channel will
influence the expansion or contraction of this habitat and will require
managers and the public to realise that the eventual direction of change
will be determined after decades of monitoring and will require flexibility
in saltmarsh management.
