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3. Wetlands and riparian zones

Summary

Wetlands, rivers, watercourses and their associated riparian zones are essential for maintaining biodiversity, clean water and the long-term sustainability of rural and urban populations. Most rivers and other wetland landscapes in Australia are experiencing problems, with significant degradation and continued decline in ecological condition. Many nationally important wetlands are still in good condition, particularly in northern and central Australia, though in many parts, trend is declining.

This chapter reports on the condition and trend of wetlands listed in A Directory of Important Wetlands in Australia 2001, other wetlands of regional significance and riparian zones.

Wetlands of national importance associated with the majority of subregions (58%) were assessed as being in good condition, meaning that minimum intervention is required to aid their recovery. These principally occur in northern Australia. Encouragingly, the condition of nationally important wetlands in 64 subregions (16%) are near pristine.

In southern Australia, where information was available, many nationally important wetlands (28% of the total assessed) are in fair condition and requiring significant management to bring about their recovery. Wetlands in the AvonWheatbelt in Western Australia, the Darling Riverine Plains and the New South Wales North Coast bioregions, are degraded with recovery unlikely in the medium term.

The trend of most wetlands of national importance is either static (59% of subregions) or declining (37% of subregions). Two subregions are improving—in the Channel Country of Western Queensland and the South Eastern Highlands of New South Wales. In both these areas, sustainable grazing practices and increased reservation within protected areas has contributed to this improvement.

The main threatening processes identified for nationally important wetlands are grazing, feral animals, exotic weeds and changes in hydrological conditions leading to salinisation and other modifications.

Owing to the important role played by other wetlands for the maintenance of biodiversity and ecological processes, wetlands of regional significance were defined and identified where data were available. Approximately, 4700 wetlands of regional significance were identified and assessed.

The condition of riparian zones is degraded across much of southern and western Australia in 31% of the total subregions assessed. A further 38% of subregions have riparian zones in fair condition. The scale of the problem suggests recovery is unlikely in the medium term or without very significant intervention. Only 28% of subregions have riparian zones classed in good condition.

The trend in riparian condition across most parts of Australia is declining (78% of subregions) with the main exceptions being some arid areas, south-west Tasmania and parts of Cape York Peninsula. The most commonly listed threats associated with this decline are: increased fragmentation, overgrazing, feral animals and weeds, changed fire regimes and changed hydrology with many of these threats having a combined impact on riparian zones. Increased fragmentation was a key threat in the highly cleared regions of southern and eastern Australia. Feral animals, overgrazing, exotic weeds and changed fire regimes were identified as key threats in wide ranging environments—from arid inland Australia to the more intensively used bioregions in Victoria and Tasmania. This demonstrates the widespread and pervasive nature of these threats.

These findings for wetlands and riparian zones in conjunction with the Audit's assessments of rivers and estuaries, means that targeted programs are urgently required to maintain these vital natural resources and their associated biodiversity. An Australia-wide program of protective policies and reservation where appropriate is required. This program could be rapidly developed as an Australia-wide partnership and build on existing activities of States and Territories.

Introduction

The Ramsar Convention definition of wetlands includes systems that are man-made or natural, that occur in marine or terrestrial areas, and that have water either permanently or temporarily standing still or flowing, fresh or salty. Consequently, rivers, lakes, swamps, marshes, dams, irrigated lands and coral reefs all qualify as wetlands. This definition is widely used and the diversity of wetlands it encompasses is reflected in A Directory of Important Wetlands in Australia (Environment Australia 2001).

The third edition of A Directory of Important Wetlands in Australia lists 851 wetlands, 56 of which are considered of international importance. Information on the condition and trend of these wetlands was unavailable for many subregions. This highlights the need for more data on these wetlands and on-going monitoring to assess their condition over time.

This Biodiversity Assessment also identifies and assesses wetlands important at the regional level where data were available. Wetlands of regional importance were specifically identified to gain an understanding of the extent and significance of wetlands that have not been listed as nationally important wetlands. Regionally important wetlands are a vital resource for the protection of regional biodiversity and can be easily overlooked and lost through incremental development and other impacts.

Wetlands are ecologically and hydrologically linked to their surroundings. Riparian land is any land that adjoins, directly influences, or is influenced by a body of water. It can include the land and associated flora and fauna immediately alongside small creeks and rivers, billabongs and floodplains. Riparian corridors can also be a key feature for dispersal of small mammals and birds. Because of these special features, rivers, streams and gullies can have a disproportionate importance for biodiversity conservation compared to the area they occupy.

Australia has a wide diversity of wetland systems - from tidal rivers and estuaries on the coast, to ephemeral wetlands such as Lake Eyre in inland Australia. Lake Eyre is one of the largest areas of internal drainage in the world and only fills a few times each century when the rivers of Queensland's channel country receive enough water to push through the dry maze of channels and billabongs on the edge of the Simpson Desert. Such examples illustrate the critical links between wetlands and their associated catchments, with the Lake Eyre Basin covering one sixth of the Australian continent.

The Gulf of Carpentaria wetlands are internationally significant and demonstrate the role and importance of coastal wetland systems. Catchment boundaries disappear during the wet season with floods exporting sediments and nutrients off the land to the shallow Gulf waters, feeding the important finfish and prawn fisheries and their supporting habitats. During the dry season, nutrient cycling is based on occasional inundation of the supratidal salt marshes, supporting the algae of these salt marshes and through the export of the algae with tidal waters to the estuary, supporting fisheries and their habitats.

There is little doubt that most rivers and other wetland landscapes in Australia are experiencing problems, which have largely come about as a result of poor land and water management practices. It is estimated that across Australia about 50% of wetlands have been destroyed since European settlement. Many other wetlands have been subject to major modification. Changes in condition, particularly in the Murray- Darling Basin, have been linked with declines in waterbird numbers (Box 3.1) and are likely to affect other plants and animals that inhabit wetlands.

Catchment planning to protect these natural values, recognises the importance of focussing on the total catchment, the full suite of native plants and animals dependent on these wetland systems and the critical role that people play in the future of our rivers and other wetlands.

At the national scale, a recent submission on biodiversity to the Prime Minister's Science, Engineering and Innovations Council (Morton et al. 2002) recommended that the Commonwealth Government work with the States and Territories to establish an Australia-wide river and estuary protection program.

This submission noted the opportunities that the near pristine river reaches and estuaries provided for nature conservation and nominated examples of Australia's least impacted rivers. It included suggestions that the Mitchell, Ovens, Georgina, Diamantina, Cooper and Paroo be designated as "Heritage Rivers".

The Assessment

This assessment and findings is divided into three sections:

• a summary the Audit's previous findings for rivers and estuaries (NLWRA 2002a);
• assessment of wetlands, and
• assessment of riparian zones.

Findings

Audit River Assessment

River reaches for Australia's major rivers in the intensive use zone were used to provide a spatial framework for an assessment of river condition and for management and monitoring. A river reach is a section of river with relatively uniform physical characteristics. In Australia's more intensively used catchments, 14,606 reaches over 5km in length have been defined, with a total stream length of 209,118km (Figure 3.1). With further fine tuning to meet State and Territory needs, these reaches will provide the basis for a rigorous and consistent reporting framework for tracking progress in river management.

Aquatic biota, as represented by macro-invertebrate indicator species provides a partial measure of river condition. The collated National River Health Program Australian River Assessment Scheme (AusRivAS) datasets suggest that, based on macroinvertebrates as indicators, little change from apparently natural conditions has occurred in 67% of river reach length. Within the remaining 33% of river length with impaired aquatic biota, almost 25% has lost between one fifth and one half of the macroinvertebrate groups used as indicators of river biodiversity (Figure 3.2).

An assessment of environmental modification provides key insights to management challenges for Australia's rivers. Over 85% of river length was classified as having undergone some environmental modification, including catchment disturbance, reduced riparian vegetation, hydrological disturbance and increases in the load of suspended sediments and nutrients (Table 3.1). New South Wales, South Australia and Western Australia have the greatest amounts of modified river length (97%, 96% and 93% respectively) and the Northern Territory has the smallest amount (34%).

Largely unmodified rivers occur in far north Queensland, eastern Victoria and Tasmania (Figure 3.3). These require protective management to ensure their condition is maintained. Rivers in the most modified condition are in parts of the Murray-Darling Basin, the Western Australian wheatbelt, western Victoria and the South Australian cropping areas.

The Audit's River Assessment found that riparian and in-stream habitats are key management factors for the health of Australia's rivers. Protection of existing habitat and re-establishment of riparian habitat in most catchments, together with improved catchment management to minimise sediment and nutrient inputs, is essential.

Table 3.1: Table 3.1 River environment index (catchment disturbance, habitat, hydrological disturbance and nutrient and suspended sediment load) for each State and Territory.

	TOTAL LENGTH OF REACH (KM) IN EACH CATEGORY AND PERCENTAGE OF TOTAL IN PARENTHESES				PERCENT OF TOTAL LENGTH WITH DATA
	Largely unmodified	Moderately modified	Substantially modified	Extensively modified
Queensland	8 743 (13)	48 214 (71)	10 599 (16)	0 (0)	93
New South Wales	1 619 (3)	39 232 (68)	17 089 (29)	18 (0)	97
Australian Capital Territory	43 (16)	191 (71)	36 (13)	0 (0)	100
Victoria	3 085 (20)	9 042 (60)	3 099 (20)	0 (0)	97
Tasmania	2 028 (37)	3 250 (59)	194 (4)	0 (0)	98
South Australia	299 (4)	4 666 (61)	2 635 (35)	0 (0)	79
Western Australia	1 487 (7)	15 927 (78)	2 929 (14)	12 (1)	80
Northern Territory	9 165 (66)	4 630 (34)	0 (0)	0 (0)	67
Total	26 468 (14)	125 152 (66)	36 581 (19)	31 (1)	90

Audit Estuary Assessment

Half of Australia's 1000 estuaries were assessed as being in near pristine condition. Of the remaining 50%, a further 22% are largely unmodified, 19% are considered modified and 9% are regarded as extensively modified (Figure 3.4).

Estuaries are valuable ecosystems for fisheries and play a key role in biodiversity. Many fish species and other organisms are estuary-dependent in larval or juvenile phases. Protective management arrangements for Australia's pristine estuaries will deliver multiple benefits. They will also be more effective in the long term obviating the necessity to undertake rehabilitation that may be expensive or even not possible. These pristine estuaries occur in all jurisdictions (Figure 3.5) and could provide a foundation for an effective national estuarine and marine management program.

The number of estuaries assessed is different to the number of rivers assessed. Not all estuaries have river reaches that were part of the river assessment.

Many estuaries assessed are small tidal embayments and strand plain drainage lines. While there is correlation for individual river-riparian-wetland-estuary systems in terms of condition, no comparison should be made between the summary findings associated with each.

Assessment of Wetlands

A Directory of Important Wetlands in Australia (Environment Australia 2001) lists 851 wetlands of which 56 are designated to the List of Wetlands of International Importance of the Ramsar Convention. This section summarises the assessment of the condition and trend of these wetlands and the processes that threaten them. Not all bioregions have been surveyed for wetlands of national significance and there are information gaps in those that have. The identification of significant sites is on-going as there is no systematic national inventory from which wetlands at differing levels of significance have been selected.

The criteria used to identify regionally significant wetlands were consistent with those used to assess nationally important wetlands (Figure 3.6). Data collected on each wetland included the name, location (grid reference), description, special values, condition, trend and threatening processes. For regionally significant wetlands, a reliability assessment for the information collected was made.

Assessing the condition of nationally important wetlands (Figure 3.7) provides a benchmark for their management.

The ranking of condition refers to the median value for wetlands within the subregion. While Victoria contains many wetlands of national importance, the information on the condition of these wetlands was not available.

The condition of the majority of nationally important wetlands was assessed as good (58% of the total assessed), occurring principally in northern and eastern Australia. This means that minimum management intervention is required to aid recovery of the wetlands in these regions. Encouragingly, nationally important wetlands in several subregions were also recorded as near pristine. These occurred on Cape York Peninsula, in Tasmania and parts of the Channel Country.

The nationally significant wetlands in the rangelands and the south-west of Western Australia, and most of New South Wales, are either in fair condition (28% of total wetlands assessed) or degraded (Figure 3.7).

The wetlands in these regions would require significant management intervention to bring about their recovery and in locations subject to extensive salting may be beyond practical recovery. Generally, it will be less costly to address threats in rangeland areas such as altered fire and grazing regimes compared to threats in the highly cleared regions of eastern Australia. For example, among the most affected areas, the wetlands in the Darling Riverine Plains bioregion are degraded due to the intensification of agriculture in that region. The recovery of nationally important wetlands in this region is considered unlikely in the medium term.

The trend in the condition of nationally important wetlands (Figure 3.8), shows that most are static (59%) but with a significant proportion declining (37%).

Reductions in Australia's waterbird populations reflect the decline in wetland condition. Fifty percent of Australia's inland waterbirds are listed under various legislation as threatened, mainly from loss of wetland and riparian habitat. Identification of management actions to aid recovery is a priority.

An assessment of the distribution of major threatening processes for wetlands of national importance (Figure 3.9) provides some insights into the condition and trend patterns described above. Grazing pressure, exotic weeds and feral animals are listed most frequently as threats. Changed hydrology, pollution and salinity are the next most frequent group of threats in a range of subregions. Dryland salinity is identified as a key threatening process in southern Australia.

Salt water intrusion is a threat to freshwater wetlands in northern Australia. This occurs when the surface or groundwater hydrology of near coastal areas is affected by drainage, groundwater use or other changes to landform (and sea level rise). For example, in the Northern Territory natural banks that separate salt water and freshwater have been broken by feral animals, notably buffaloes. Saltwater intrusion leads to the loss of freshwater native plants and animals and their replacement by those able to tolerate saline conditions.

Changes to fire regimes is a threat mainly in the seasonally dry tropics, the wet tropics and in Tasmania.

The range of threatening processes at the subregional scale for nationally important wetlands is described in detail in the Australian Natural Resources Atlas (Table 3.2).

The Darwin Coastal and Darling Riverine Plains bioregions have been selected to demonstrate the type of information available on the Atlas (Figure 3.10). These regions are subject to a wide range of threats. The data represent the frequency of recorded threats rather than an assessment of relative importance.

Wetlands of regional significance were identified across Australia. In total, approximately 4700 regionally important wetlands were identified. Specific descriptions and an assessment for each wetland can be found in the Atlas. This listing represents a starting point for the identification and recording of regionally important wetlands. Their occurrence and values should be taken into account in regional and local planning, and natural resource management.

The identification of nationally important wetlands is not complete and large data gaps still remain.

Table 3.2: An extract from the Australian Natural Resources Atlas on the nationally important wetlands of the Darwin Coast bioregion (Similiar information is available on the Atlas for regionally important wetlands).

WETLAND NAME	RAMSAR WETLAND	CONDITION	TREND	THREATENING PROCESSES	THREATENING PROCESSES NOTES
Adelaide River Floodplain System (NT020)	No	Fair (Recovery requires significant intervention)	Unknown	Feral animals changed hydrology - salinity; exotic weeds	Extensive saltwater intrusion; large tracts of Mimosa pigra
Daly-Reynolds Floodplain- Estuary System (NT024)	No	Fair (Recovery requires significant intervention)	Unknown	Feral animals; pollution; changed hydrology - salinity; exotic weeds; grazing pressure	Potential from increased cultivation in catchment
Finniss Floodplain and Fog Bay System (NT025)	No	Good (Recovery requires little intervention)	Static	Grazing pressure; changed hydrology - salinity; exotic weeds; feral animals
Moyle Floodplain and Hyland Bay System (NT027)	No	Near pristine	Unknown	Exotic weeds; changed hydrology - salinity	Potential Mimosa pigra and Brachiara mutica; potential saltwater intrusion

Assessment of Riparian Zones

Increasing investment in the management of riparian areas reflects the increasing recognition of the fundamental role that rivers and their riparian zones play in ecosystem function. This assessment of riparian zones, including condition, trend and the processes threatening them, furthers the understanding of the status of these areas and the range of management practices needed.

Riparian zones were most commonly assessed as being in fair condition, where recovery will require significant management investment (38% of subregions) or degraded where recovery is unlikely in the medium term (31% of subregions) (Figure 3.11). Riparian zones in the highly cleared regions of southern and eastern Australia, assessed as degraded, coincide with the cereal regions of south-western Western Australia and western Victoria, as well as the intensively cropped floodplain systems in north-central New South Wales. In southern Queensland they occur across the Brigalow Belt, Mulga Lands and Channel Country bioregions. Many coastal lowland floodplain areas in southern and eastern Australia are degraded.

The riparian zones in many subregions dominated by pastoralism are in only fair condition or are degraded. This is principally due to the impact of stock grazing on riparian vegetation. Overgrazing also leads to increased nutrient and sediment loads, as detailed in the Audit's Australian Agricultural Assessment, (NLWRA 2001b). Very few subregions were classified as having near pristine riparian zones.

The trend in the condition of riparian zones shows that across most of Australia they are declining (73%) (Figure 3.12). Considerable effort is required at the national scale to arrest on-going riparian zone degradation.

The assessment of processes threatening riparian areas at the subregional scale provides some insights into the widespread decline of these systems, Figure 3.13.

The most commonly listed threats are:

• over-grazing;
• exotic weeds;
• changed hydrology;
• increased fragmentation;
• feral animals; and
• changed fire regimes.

The wide distribution of these threatening processes, leading to a declining trend in riparian zones across 73% of subregions, means that additional targeted management initiatives are urgently required.

Rehabilitation would include changes to agricultural practices, replanting and weed control, rationalisation of barrages and levees, and the exclusion of stock and provision of off-stream watering facilities.

The Central Mackay Coast and the Mulga Lands bioregions have been selected to demonstrate the range of processes threatening riparian zones at the subregional scale (Figure 3.14). They provide a contrast between coastal and inland regions and demonstrate the value of a bioregional approach to assessing threats.

Along the Central Mackay Coast, vegetation clearance and fragmentation, changed fire regime and exotic weeds are the major threats identified, with grazing pressure and weeds identified as the key process threatening riparian zones in the subregion away from the coastal strip.

In the Mulga Lands, a wider range of threatening processes on riparian zones exist. Grazing pressure is a threat in all subregions in the Mulga Lands bioregion, with threats from vegetation clearance, feral animals and exotic weeds also widespread. Changed hydrological condition is identified as a threat in the south-east of the Mulga Lands bioregion.

Table 3.3 gives an example of the detailed supporting information available on the Atlas. It shows for riparian zones across each subregion, their condition, trend and threatening processes. A reliability ranking of this assessment is also indicated.

Table 3.3: The average condition, trend and threatening processes for riparian zones in some subregions of the Wet Tropics bioregion. The reliability of the assessment is indicated.

SUBREGION	RIPARIAN CONDITION	RIPARIAN TREND	THREATENING PROCESSES	RELIABILITY OF ASSESSMENT
Herbert (WET1)	Fair (Recovery requires significant intervention)	Declining	Increasing fragmentation and loss of remnants; exotic weeds; changed hydrology	Quantitative and qualitative
Innisfail (WET3)	Fair (Recovery requires significant intervention)	Declining	Increasing fragmentation and loss of remnants; grazing pressure; changed hydrology; pollution	Quantitative and qualitative
Atherton (WET4)	Fair (Recovery requires significant intervention)	Declining	Increasing fragmentation and loss of remnants; pollution; changed hydrology;	Quantitative and qualitative
Paluma - Seaview (WET5)	Degraded (Recovery unlikely in medium term)	Declining	Increasing fragmentation and loss of remnants; changed hydrology; exotic weeds	Quantitative and qualitative
Bellenden Ker - Lamb (WET7)	Fair (Recovery requires significant intervention)	Declining	Increasing fragmentation and loss of remnants; changed hydrology	Quantitative and qualitative

Conclusions

These assessments demonstrate the need for specific programs on rivers, estuaries, wetlands and riparian areas as an Australia-wide priority.

Management priorities and investment strategies will vary between regions and jurisdictions, but will need to include:

• programs for protection through reservation—such as the near pristine estuaries, river reaches and wetlands;
• rehabilitation activities—building on existing works and strategically designed to complement the areas reserved; and
• fine tuning of existing policies and new policies—ensuring a greater level of consideration, protection and integrated natural resource management at scales from local government through to Australia-wide.

Underpinning these strategies is the need for reliable information, and the assessment of the range of aquatic and related habitats here has indicated some of the deficiencies that exist. Continued investment in research and inventory work to document the values and increase awareness of the condition, threatening processes and management opportunities for these vital assets is needed.

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