SoE 2003 > Biodiversity > 6.6 Aquatic ecosystems

6.6 Aquatic ecosystems

Urban development pressures on coastal wetlands continue, although one-fifth of them are now protected. Inland wetlands and riverine ecosystems are under-reserved and under pressure.

Aquatic ecosystems are of critical ecological, economic and social importance. Inland and coastal wetlands and lakes cover around 4.5 million hectares or approximately 6% of the State. Over 95% of the wetland areas are west of the Great Dividing Range, with 60% in the Western Division.

Wetlands in inland areas are sparsely reserved for conservation and under pressure from agriculture and irrigation. Reservation and protection of inland rivers and other aquatic ecosystems are not as well developed as on the coast, where protected areas are more extensive. Around 18% of all coastal lakes and wetlands are in protected areas and 16% of coastal waters in marine protected areas. Coastal aquatic ecosystems face significant pressures from growth in populations and settlements.

A comprehensive framework to protect aquatic ecosystems has been developed in NSW. Key elements include the NSW Biodiversity Strategy and the water reform process, including implementation of the Water Management Act 2000. Other elements include the creation of marine parks and reserves, intertidal protected areas and critical habitat areas for threatened species. This framework is starting to address the accumulated problems facing aquatic ecosystems in NSW, but the commencement only recently of some of the elements, combined with a continuation of existing pressures, mean that improvements to date have been limited.

NSW Indicators

Importance of the issue

The condition of aquatic ecosystems reflects the environmental impacts from activities on land and water discussed elsewhere in this report. Aquatic ecosystems are very important from an ecological, economic and social perspective (see EPA 2000a).

Wetlands (and riparian zones and foreshores) have particularly high ecological values. They help to prevent erosion which protects downstream areas from the inflow of sediments. They also improve the quality of both surface and ground waters by filtering out sediment, nutrients and other pollutants. The reuse of nutrients by wetlands makes them among the most productive of all ecosystems. Wetlands also hold back floodwaters, moderating the force of floods. Wetlands are the most sensitive aquatic group and most of the information on aquatic ecosystems relates to them.

Aquatic ecosystems are under threat from human activities through loss of habitat, harvesting, pollution, siltation and changes in the hydrology of rivers. Coastal aquatic ecosystems face heavy pressures from development and population growth. In inland areas, they are under significant pressure from the intensification of agriculture and irrigation. Altered flow regimes continue to cause impacts despite improved management approaches.

There are estimated to be 4.5 million hectares of wetlands and lakes in NSW, which equates to approximately 6% of the State (Kingsford et al. 2003). There are also around 120,000 hectares of dams and reservoirs. Map 6.3 shows the location of these wetlands across the State.

Map 6.3: Wetlands of NSW

Source: Derived from ANCA 1996; DUAP data, as at 1999; Environment Australia 2001a; Kingsford et al. 2003

Note: See Kingsford et al. 2003 for definitions of main wetland categories.

Inland wetlands and lakes

Since European settlement, there has been a significant reduction in the extent of natural wetlands, with one estimate suggesting that approximately 50% have been lost over that time (Finlayson & Rea 1999). These figures are consistent with worldwide estimates of wetland loss (Kingsford et al. 2003).

Over 95% of wetlands are in inland NSW, west of the Great Dividing Range (Map 6.3; Kingsford et al. 2003). Most of the wetland area (89%) is floodplain wetland with 46% of this concentrated in the north-western catchments of the Paroo and Warrego rivers and the Bulloo–Bancannia catchments. Most of the States' wetlands are found on private and leasehold land.

The majority of freshwater lake areas are also west of the Great Dividing Range (Map 6.3; Kingsford et al. 2003). Within the Western Division, approximately 10% of lake surface area is almost always covered by water (perennial), 32% is intermittently covered by water, and 58% is mainly dry (Seddon et al. 1997; Seddon & Briggs 1998). Most NSW salt lakes are found in the north-west of the State in the Bulloo–Bancannia, Paroo and Warrego catchments. Although covering a relatively small area of around 18,500 hectares (Kingsford et al. 2003), they can be highly productive for waterbirds and aquatic plants and are important for biodiversity.

The wet-dry nature of inland lakes blurs the distinction between 'lake' and 'wetland', and increases the diversity of environments available to plants and animals. This makes them an important ecological component of the western landscapes of NSW. Despite this, many of the intermittent freshwater lakes in the Western Division are used for lakebed cropping when conditions allow. Most cropping occurs on freshwater lakes that are either mainly dry or subject to intermittent flooding. The ecological impacts of this cropping range from minimal to substantial, depending on its frequency and the cultivation methods used (Seddon & Briggs 1998).

Catchment-specific studies have clearly demonstrated the pressures on wetlands in NSW. Table 6.8 summarises a number of studies that confirm the extent of impacts on wetlands in NSW. For example, there has been 150 years of water resource development along the lower Murrumbidgee River. This has resulted in the diversion of about 60% of river flows, mostly for irrigation. As a consequence, three-quarters of the wetlands forming the lower Murrumbidgee floodplain have disappeared or been degraded. Extensive dieback of floodplain vegetation has occurred and is expected to continue. In parallel to the loss of vegetation, waterbird populations have collapsed by more than 80% and similar declines are expected in the broader communities of aquatic biota, such as vegetation, invertebrates, frogs and fish. In the early 1990s, the Lower Murrumbidgee floodplain wetlands met most criteria for listing as a wetland of international importance, but would fail most of them now, less than 10 years later (Kingsford & Thomas 2001).

The pressures are also significant in some of the least developed inland catchments. Since the 1990s, about 50% of median flows in the Condamine–Balonne catchment have been diverted for irrigation (Sheldon et al. 2000). This has resulted in a 75% reduction in median natural flows to the Narran Lakes Ramsar site in the State's north-west (DNR 2000).

Table 6.8: Declines in wetlands

Streams, riparian zones and foreshores

There is little consistent, statewide information on the biodiversity status of streams, riparian zones and foreshores. Most knowledge relates to the impacts on aquatic flora and fauna of physical and chemical changes in waters and the flow regimes of waterways (see Water 5.1, Water 5.2 and Water 5.3). Individual studies have focused on freshwater riverine systems and riparian vegetation in some parts of the State, such as in the Barmah–Millewa forest (Bren & Gibbs 1986; Bren 1991).

Movement of fish is important in sustaining populations of Australia's native species. Of the 55 species of native freshwater fish living in NSW, 32 are known to be migratory and require free passage to sustain populations (Thorncraft & Harris 2000). There are 3328 licensed weirs or barriers on NSW waterways, including 1035 floodgates on tidal waterways (Copeland 2000). Nearly every waterway in NSW is affected by barriers. Dams and weirs have caused large declines in native fish stocks and in some areas barriers to fish movement have led to the local extinction of some freshwater species (Harris 1995; DLWC 1999a; NSW Fisheries 2000).

Estuaries and coastal lakes

East of the watershed along the Great Dividing Range, wetlands and freshwater lakes form only a small part of the landscape. Currently, 59% of these areas are estuarine wetlands, 35% are coastal lagoons and lakes, 5% are floodplain wetlands, and 1% are freshwater lakes. (Map 6.3; Kingsford et al. 2003).

The lack of knowledge about the nature and condition of coastal wetlands is substantial. While it is known that human activities such as drainage can cause a decline in in-shore habitats, the extent to which these activities have affected coastal ecosystems has not been comprehensively monitored across NSW. In 2002, the Healthy Rivers Commission reported that 31% of coastal lakes were 'moderately' or 'severely' affected by human pressures (HRC 2002).

Other studies have also shown the degree of change to NSW coastal ecosystems: for example, Bowen et al. 1995 estimates that approximately 60% of coastal wetlands have been lost or degraded over the past 200 years.

Beaches, near-shore environments and marine ecosystems

Beaches and near-shore habitats, such as rocky and coral reefs, and bare substrates support a diverse array of fish, invertebrates and aquatic plants. Information on the condition of these habitats is very limited. Currents, wave action and tides are often able to dilute pollution, which means these areas may be less vulnerable to degradation than other aquatic ecosystems. However, even in well-flushed systems, pollutants can bind to and contaminate marine and estuarine sediments, severely affecting environmental health (see Water 5.7).

Response to the issue

Aquatic ecosystem health is in many respects an indicator of the effectiveness of the programs being used to manage pressures on terrestrial ecosystems. However, a number of special measures are also directly applied to protect aquatic ecosystems. The establishment of aquatic protected areas is a major response. There are also a number of other measures including:

• conservation and rehabilitation programs for specific ecosystems
• managing the taking of fish and marine life and improving fish passage
• controlling development likely to have a direct impact on aquatic ecosystems
• managing river flows in regulated rivers.

The Government is currently revising the NSW Biodiversity Strategy (NPWS 1999a) to incorporate aquatic components (see Biodiversity 6.1).

Aquatic protected areas

There are a number of different categories of aquatic protected areas in NSW, including some coming under national and international reservations. Table 6.9 outlines the main protected areas in NSW and highlights some recent changes to these areas.

Table 6.9: Main aquatic protected areas and recent changes

The national Directory of Important Wetlands lists 186 wetlands in NSW. Thirty-six of the 40 types of wetlands listed in the directory are found in the State. About 21% of the total wetland area of NSW is listed (Kingsford et al. 2003).

Figure 6.4 shows the percentage of various wetland types in reserves in NSW compared with the percentage listed as nationally important. In total, 18% of coastal wetland areas are in NPWS reserves and State Forests while 6% are conserved in inland areas (Kingsford et al. 2003).

Figure 6.4: Wetland areas reserved in NSW

Source: Kingsford et al. 2003

There are several types of marine protected areas under NSW and national legislation. A system of Marine Protected Areas is presently being developed for NSW: the NSW Representative System of Marine Protected Areas. The Marine Parks Authority (MPA) has prepared a framework of guiding principles that will be used to assess, establish and manage the Marine Protected Areas (MPA 2001).

Zoning plans within marine parks allow for multiple uses, including commercial and recreational fishing, as well as highly protected 'no take' sanctuary zones, where fishing and collecting are not permitted. Zoning plans for the Solitary Islands and Jervis Bay marine parks have recently been completed after extensive consultation with the community and stakeholders.

The MPA is also conducting biodiversity assessments of the bioregions in NSW waters to identify additional areas that may be needed to protect a comprehensive cross-section of marine ecosystems, habitats and species. Assessment of the Tweed–Moreton bioregion has been completed, and a large, multiple-use marine park has been declared in the Cape Byron area. Assessments of the Manning Shelf, Hawkesbury Shelf, Batemans Shelf and Twofold Shelf bioregions are also under way.

Inland freshwater species and ecological communities are assessed by the independent Fisheries Scientific Committee who determine what level of protection, if any, is required. The committee has identified the lower Murray and the Murrumbidgee rivers as endangered ecological communities and declared a range of freshwater species as threatened, requiring a review of their status and the possible introduction of protection measures. The commercial fishing of freshwater native finfish was banned in 2001, removing one of the direct impacts to these species. The Government is committed to developing management strategies and environmental assessments for the stocking of fish and recreational fishing in NSW, which will assist in protecting freshwater aquatic areas.

Other responses

The NSW Wetlands Management Policy was introduced to provide for the conservation, management and use of wetlands (NSW Government 1996). Between 1996 and 2002, a total of $800,000 was spent on 58 community-based wetland rehabilitation projects. Private landholders have strongly supported wetland conservation through sustainable management practices and the wise use of wetlands.

The NSW Estuary Management Program was established in 1992 to restore and protect estuaries along the coast. Particular emphasis has been given to protecting and rehabilitating tidal wetlands. So far 37 Estuary Management Plans have been completed under the program.

The NSW Fisheries Management Act 1994 allows for the protection of marine vegetation and the declaration of fishing closures to limit potential impacts on important areas of aquatic habitat, including wetland areas. In addition, the Act provides for the listing of threatened aquatic species, populations and communities and identification of key threatening processes.

NSW Fisheries works with a range of agencies and stakeholders to improve the movement of fish through the many structures that are barriers to fish passage in NSW. For example:

• 33 fishways in NSW have been designed with the needs of native fish in mind and another 13 fishways are planned to be upgraded in this way (NSW Fisheries data, as at 2002)
• the Murray–Darling Basin Commission has commenced a five-year program for 11 new fishways on the main stem of the Murray River, providing unencumbered passage for fish from the mouth of the river in South Australia to Lake Hume near Albury
• improved management of 40 priority floodgates on the North Coast has opened 85 kilometres of waterways to fish passage and more natural flows.

A number of planning instruments used by State and local governments are important in the management of aquatic ecosystems and the coastal zone. These include State Environmental Planning Policy 14 – Coastal Wetlands, which covers approximately 1700 coastal wetlands of State significance totalling over 96,900 hectares; and State Environmental Planning Policy 71 – Coastal Protection, which commenced in November 2002 and is a key element of the Government's $11.7-million Coastal Protection Package.

The Water Management Act 2000 aims to protect and enhance water sources and the ecosystems they contain. Improved river regulation and responses to poor water quality have a critical role in contributing to the long-term health and viability of aquatic ecosystems (see Water 5.1, Water 5.2 and Water 5.3).

Effectiveness of responses

The effectiveness of most of the responses is difficult to determine at a State level. It is clear that the protected area system for inland and coastal aquatic ecosystems cannot currently be described as 'comprehensive, adequate and representative' (Ponder et al. 2002). The lack of protected inland wetlands and riverine ecosystems are the biggest gaps in the reserve system.

A growing body of research is indicating that 'no take' protection is necessary to protect the viability of species in many locations (Ponder et al. 2002). It is positive that some of these areas are now starting to appear, but further reserves are needed.

The improved management of weirs, dams and floodgates, and rehabilitation of waterway crossings have all been shown to enhance the passage of fish.

Future directions

Government can continue to protect inland wetlands and riverine ecosystems through drafting and implementing recovery plans for threatened species, populations and communities.

The loss, depletion or degradation of aquatic ecosystems will also be prevented by the continued use of planning controls and the promotion of practices that protect or restore aquatic ecosystems.

Government and landholders should work in partnership to develop better models for protection of aquatic ecosystems on private land.

State and local governments can continue to improve local land-use planning systems so that the type and extent of urban development in the catchments of coastal lakes matches the level of protection desired.

Everyone can take steps to reduce the runoff of litter, sediments and other pollutants into waterways.

Linked issues

2.1 Population and settlement patterns

3.2 Climate change

4.1 Land-use changes

4.3 Induced soil salinity

5.1 Freshwater riverine ecosystem health

5.2 Surface water extraction

5.3 Surface water quality

6.7 Aquatic species diversity

6.9 Aquatic harvesting