The condition of 974 estuaries was assessed as part of the Estuary Assessment 2000. The assessment was done in two stages.
Stage 1: Identification of Australia's near-pristine estuaries based on expert opinion through State-based workshops.
Stage 2: Determining the extent of change for those estuaries no longer considered to be in near-pristine condition through a more quantitative condition assessment based on a pressure-state-response model.
A preliminary classification of the condition of all estuaries was based on expert opinion through State-based workshops to identify Australia's near pristine estuaries. The term 'near-pristine' rather than 'pristine' is used to reflect the fact that most of Australian estuaries have experienced some impacts as a result human activity.
An estuary was classified as near pristine if it had:
- a high proportion of natural vegetation cover in the catchment
- minimal changes to hydrology in the catchment
- no changes to tidal regime
- minimal disturbance from catchment land use
- minimal changes to floodplain and estuary ecology
- low impact human use of the estuary
- minimal impacts from pests or weeds
The other three categories of the assessment - largely unmodified, modified and severely modified were used to indicate increasing levels of change for some or all of these criteria.
Most of the near pristine estuaries are located away from population centres in tropical northern Australia and temperate western Tasmania. Important near pristine estuaries are also found around the developed areas of Australia, often within or near to managed public lands such as national parks and state forests.
Map: The results of the initial qualitative condition assessment of 970 estuaries. Near pristine estuaries are identified by a green dot. Interim Marine and Coastal Regions for Australia have been aggregated on the basis of similar biophysical features.
Near pristine estuaries are valued by the community as:
- habitat for native plants and animals - important for the conservation of biodiversity
- environments that support commercial, traditional and recreational fisheries and tourism
- places for recreation and wilderness experiences
- benchmarks for estuary management
Near pristine estuaries and their catchments require protection and careful management. Catchment protection and management should ensure that land use does not deleteriously affect waterways or estuaries. Estuary use also requires management including:
- declaration of protective zones (eg. fish habitat areas or marine national parks)
- active management including extension, licencing, patrol and enforcement activities for uses such as tourism, commercial and recreational fishing
Regional planning is essential and provides the context for developing appropriate management arrangements in consultation with community and industry.
Restoration of an estuary and its catchment is expensive. Protective management is more cost-effective in the long term.
For further information, click here to download the near pristine estuaries brochure in PDF format (903 KB)
Stage 2: Determining the extent of change for those estuaries no longer considered to be in near-pristine condition
The second stage of the condition assessment sought to determine the extent of change for those estuaries identified as no longer being in near-pristine condition. States and Territories collated and provided as much qualitative and quantitative information on their estuaries as possible in the project timeframe to support the condition assessment. The assessment was limited by difficulties in access to information and data, with only approximately 50 Australian estuaries studied in any detail. The assessment has generated an important national discussion on what is and isn't actually known about our estuaries and their condition. The condition assessment has facilitated the collation of information on Australia's estuaries to provide a baseline understanding of the condition of Australia's estuaries that can be built upon.
A Pressure-State-Response framework was used to assess the modified estuaries. It includes the criteria used in the near pristine estuary assessment but makes an attempt to quantify as much of the information as possible. The 'State' component of the assessment has been derived using an ecosystem health perspective rather than that of any particular individual or group of beneficial uses. The rationale being that a healthy ecosystem can support a number of beneficial uses. The aim of the assessment is to identify estuaries with problems. It is noted that some problems may be inherent as a result of beneficial uses in that estuary and either not social desirable or economically viable to restore.
The 'Pressure' component of the assessment is comprised of the following indices:
- Susceptibility Index
- Utilisation Index
The 'State' component of the assessment is comprised of the following indices:
- Ecosystem Integrity Index
- Water and Sediment Quality Index
- Habitat Condition Index and
- Fish Condition Index
The 'Response' component captures but does not assess management arrangements.
Confidence ratings are recorded for all indices:
A - Confident, supported by data
B - Fairly confident result (based on expert opinion)
C - not confident / best guess
D - no information not assessed
Map: The condition of Australia's estuaries at a glance.
Australian estuaries were found to be:
- 50% near pristine
- 22% largely unmodified
- 17% modified
- 11% severely modified
Lead agency for estuary management
Estuaries lie between the terrestrial and marine spheres of natural resource management. Consequently, their management has often been neglected. Overlapping responsibilities across tiers of government and agencies also make management complex. This is compounded by the various values held and uses demanded by the community.
A lead agency within each State, and attention to how the roles and responsibilities of all tiers of government and their agencies are accommodated, would facilitate improved estuary management.
In recent years, a range of initiatives at local, State and Commonwealth government levels have addressed the needs of waterways, coasts and oceans. An Australia-wide policy and management initiative for estuaries is essential.
The role, breadth and implications of such a policy will be explored as the assessment of Australia's multi-use, modified estuaries progresses.
Community and industry involvement
Government alone will not fulfil estuarine management needs. All natural resource management involves partnerships between community, industry and government. However, community and industry demands on estuarine resources often compete and sometimes conflict. Processes and institutional arrangements that support community and industry involvement and action need to be built into all management activities.
The University of Queensland has developed some simple conceptual models for various estuary uses and their impacts on estuarine ecology. Each diagram shows examples of good and poor estuary management practices.
On the good management practice side, wetlands are preserved and public amenities are carefully designed to maintain ecological integrity. Speed limits on the water protects the foreshore.
On the poor management practice side, infrastructure along foreshore destroys habitat, public amenities pollute the estuary and litter threatens biota and aesthetic values. High speed water craft disturb other users and wash erodes foreshore. Poor water quality threatens recreational uses.
Urban / industrial and port development
On the good management practice side, nutrients and pathogens are removed from sewage, sewage nutrients are used, and constructed and natural wetlands treat sewage discharge. In the port, ship ballast water is treated to remove pest organisms and dredge is dumped outside tidal areas.
On the poor management side, untreated sewage and pathogens are discharged into estuary, impermeable surfaces cause runoff and foreshore habitat is destroyed. In the port, toxicants enter the estuary (eg. TBT, oil), pest organisms enter the estuary from ballast and hull fouling and dredging occurs within the estuary.
Commercial fishing and aquaculture
On the good management practice side, prawn farms are developed outside wetlands and settling ponds trap suspended sediment. Overstocking and overfeeding is avoided, and medication is only used when a diagnosis is made. There is no trawling inside the sensitive estuarine habitats and alternate, more selective fishing methods are used.
On the poor management practice side, wetlands are destroyed for pond construction. Excess nutrients and antibiotics from overfeeding and overmedicating are discharged into the estuary. Unregulated use of wild-caught larvae reduces wild populations. Indiscriminate trawling within the estuary and fishing during spawning season reduces fish stocks.
On the good management practice side, farm practices reduce erosion and nutrient runoff, stock are fenced off from creeks, there are riparian buffer strips, wetlands are protected, and pesticides are used sparingly.
On the poor management practice side, sediment, nutrient and pesticide runoff from agriculture reaches the estuary directly without riparian vegetation or wetlands.
- Near pristine estuaries brochure (PDF - 903 KB)
- Estuary assessment brochure (PDF - 413 KB)
- Estuary Assessment 2000 report (PDF - 9.5 MB)
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