SoE 2006 > Biodiversity > 6.6 Aquatic ecosystems

6.6 Aquatic ecosystems

Coastal and inland wetlands continue to decline due to habitat degradation, regulation of rivers, drought, invasive species and development pressures

Marine ecosystems are generally in good condition as they are well flushed and less vulnerable to degradation.

Historically, coastal wetlands have been extensively cleared and drained for development, and now estuaries and coastal ecosystems are under growing threat as population growth and development intensify along the seaboard. Ongoing pressures include habitat alteration, overfishing, pollution, aquaculture, recreational activities and climate change.

Long-term surveys demonstrate a general pattern of decline in the extent and productivity of inland wetlands. This has been exacerbated by the effects of drought during the reporting period.

While water-sharing plans have begun to address the decline of inland wetlands, further increases in environmental water allocations are likely to be needed to moderate the impacts of river regulation. Government commitments to recover water for the environment, through the purchase of water and infrastructure projects that improve efficiency of use, represent significant progress, with $13.4 million allocated to the rehabilitation of NSW wetlands.

NSW indicators

Introduction

Aquatic ecosystems are important from an ecological, economic and social perspective. The State's freshwater ecosystems provide important 'ecosystem services' including acting as breeding grounds for fish, protecting catchment water quality, recycling nutrients, filtering pollution, providing recreational and educational opportunities, protecting foreshores, mitigating floods, and regulating groundwater.

NSW coastal waters have high biodiversity because of the wide range of oceanic, shoreline and estuarine habitats they contain. These varied environments also provide many important ecosystem services, including absorbing pollution, preventing coastal and seabed erosion, maintaining coastal water quality, and acting as breeding grounds for fish.

Many species depend on healthy aquatic ecosystems from the local through to the international scale. NSW has 11 wetlands that are recognised as internationally significant with their listing under the Ramsar Convention. In addition, many inland and coastal sites support migratory bird species and are therefore protected under various international agreements, such as the Japan–Australia Migratory Bird Agreement (JAMBA) and China–Australia Migratory Bird Agreement (CAMBA).

Internationally, the degradation and loss of wetlands has been more rapid than that of most other ecosystems. The status of both freshwater and coastal wetland species is deteriorating faster than those of other ecosystems (Millennium Ecosystem Assessment 2005b).

Current status and trends

Major issues affecting aquatic ecosystems include:

• alteration of natural flow patterns through water extraction and regulation of rivers by dams and weirs, and drought conditions (see Water 5.1 and Water 5.2)
• catchment management practices, including land clearing, grazing and the use of pesticides, which can have adverse impacts even when they occur some distance from waterways
• habitat loss and degradation through the use of instream structures, such as dams and weirs, and the removal of large woody debris (snags), which affect fish migration and breeding
• cold water releases from major dams, which affect fish breeding (see Water 5.3)
• invasive fish species and weeds, which displace native species and compete for habitat (see Biodiversity 6.9)
• climate change, which in inland NSW is expected to reduce water supply, increase droughts and bushfires, change the temperature of water bodies and, along the coast, cause sea levels to rise, resulting in saline incursions into freshwater lakes and lagoons.

Wetlands in NSW cover 4.3 million hectares (ha) or 5.6% of the State (Kingsford et al. 2004a). Approximately 934,000 ha of this area (approximately 22%) ise listed in the Directory of Important Wetlands in Australia (DEH 2001). Thirty-three of the 40 wetland types in the directory are found in NSW, demonstrating the diversity of the State's wetland ecosystems. These figures do not include rivers and streams (see the Water chapter). Map 6.5 shows the location of NSW wetlands.

Inland aquatic ecosystems

Inland aquatic ecosystems include all non-marine/coastal aquatic ecosystems, such as rivers, streams, lakes, billabongs, wetlands, floodplains, inland saline lakes and groundwater-dependent ecosystems.

Around 96% of wetlands in NSW are found west of the Great Dividing Range with the majority (89%) being floodplain wetlands (see Map 6.5) (Kingsford et al. 2004a). Inland wetlands have a mean annual rainfall below 500 millimetres and over 95% of wetland area is less than 250 metres above sea level. There is also approximately 120,000 ha of dams and reservoirs.

Most NSW salt lakes are located 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 ha (Kingsford et al. 2004a), they can be highly productive for waterbirds and aquatic plants and are important for biodiversity.

Map 6.5: Wetlands of NSW

Source: DEH data 2005; DIPNR data 2003; DEC 2001; Kingsford et al. 2004b

Note: See Kingsford et al. 2004a for definitions of main wetland categories.

Inland aquatic ecosystems have been greatly modified over the past 200 years: approximately 50% of wetlands have been lost since European arrival (Finlayson & Rea 1999). These figures are consistent with worldwide estimates of wetland loss (Kingsford et al. 2004a). The National Land and Water Resources Audit found that 50% of the river length it assessed in NSW had impaired aquatic biota while 97% was either significantly or substantially modified (NLWRA 2002b). The audit also estimated that 40–50% of important wetland ecosystems in NSW were either degraded or had disappeared.

Critical to the condition and protection of aquatic ecosystems is the provision of adequate environmental flows and sympathetic management by surrounding landowners. Catchment-specific studies have clearly demonstrated the pressures on wetlands in NSW (Table 6.14). For example, water resource development in the Macquarie Marshes has resulted in the depletion of water available to water-dependent ecosystems: between 1944 and 1993, the area inundated by large floods in the marshes decreased by at least 40–50% (Kingsford & Auld 2005). This situation is exacerbated by the impact of drought.

Table 6.14: Declines in significant NSW wetlands

Environmental releases of water in some river valleys since the changes to river flow rules in 1998 have increased the area inundated and supported some waterbird breeding (see Water 5.2).

Waterbird abundance and diversity, and vegetation health, are useful indicators of wetland condition because they are sensitive to environmental changes and good scientific data is available (Kingsford 1999; Baldwin et al. 2005).

Supported by on-ground observation, long-term and systematic aerial surveys of wetland extent, waterbird numbers and breeding success have been conducted annually since 1983 using 30-kilometre transects across eastern Australia. This has provided a consistent baseline of extent and condition data, against which the decline in wetlands can be tracked over time.

Results of the annual aerial surveys show that numbers and breeding of waterbirds are declining significantly across eastern Australia and many wetland areas in NSW (Figure 6.2). In 2005 total waterbird numbers in eastern Australia were the fifth-lowest in 23 years and six species were at the lowest numbers ever recorded. Few wetland areas held water and waterbirds were strongly clustered on the small number that did, such as the Lowbidgee wetlands with 24% of total numbers in 2005 (Kingsford et al. 1999; Kingsford et al. 2004b; Kingsford et al. 2005a).

Record low numbers of waterbirds were counted in the Macquarie Marshes in 2004 and 2005, with fewer than 10 birds in 2005. The marshes averaged 30,000 birds in the 1980s and previous sightings had never been below 100. A combination of severe drought (as indicated by data from the NSW Department of Primary Industries and the Commonwealth Department of Agriculture, Fisheries and Forests) and river regulation has affected the health of waterbird populations in key wetlands (Kingsford 2000).

The fall in waterbird numbers and the breeding index over the past 23 years demonstrate a reduced resilience in waterbird populations. The rebound effect after rain or environmental flow releases is lower and fewer species are breeding (Kingsford et al. 2005a). This suggests that the combined effects of river regulation, habitat change and drought may have resulted in the more vulnerable species being less able to adapt.

Figure 6.2: Aerial waterbird surveys – combined results for all river and wetland systems sampled, 1983–2005

Source: Porter et al. 2006

Notes: Graphs show the estimated total number of waterbirds and wetland area index in eastern Australia along 10 aerial survey bands, 1983–2005. The results show the combined results for all rivers and wetland systems sampled during this time span.

The horizontal line shows the overall mean value.

Figure 6.3: Waterbird abundance and species richness – regulated vs unregulated rivers

Source: DEC/UNSW Aerial Surveys of Wetland Birds in Eastern Australia 1983–2005

To distinguish the effects of river regulation from drought, long-term data for waterbird abundance and species richness were compared for the regulated Lowbidgee system and the unregulated Paroo Overflow from 1983 to 2005 (Porter et al. 2006) (Figure 6.3). Both areas experienced drought conditions during 2003–05 (DPI 2006). Surveying more rivers would give a fuller picture.

In the regulated Lowbidgee system, declines over time in waterbird abundance and mean species richness were highly significant, whereas in the unregulated Paroo wetlands no significant trends were detected. The results indicate that, while drought affects waterbird numbers in both systems, the pattern of decline over time has only been evident in the regulated river system. Similar declines in waterbird abundance, species richness and breeding success have been documented in other significant wetland systems affected by river regulation and altered flooding regimes, including the Macquarie Marshes (Kingsford & Thomas 1995; Kingsford & Johnson 1999; Kingsford 2000; Kingsford & Auld 2005) and Menindee Lakes (Kingsford et al. 2004b).

Surveys of river red gum and black box along the River Murray floodplain indicate that there has been a decline in tree health and that both species may be experiencing significant population losses (MDBC 2005). This has occurred over a short period of time (2002–04). If the current decline continues, floodplain trees along a large portion of the Murray may be lost.

An assessment of present-day vegetation classes in NSW has found that more than 70% of montane lakes has been drained or cleared (Keith 2004). Montane peatlands and swamps of the New England Tablelands, NSW North Coast, Sydney Basin, South East Corner, South Eastern Highlands and Australian Alps bioregions have been listed as endangered ecological communities under the Threatened Species Conservation Act 1995 (TSC Act), reflecting the poor condition of these aquatic ecosystems.

Coastal and marine ecosystems

The NSW marine jurisdiction extends three nautical miles seaward of the NSW coastline and islands and includes a variety of subtropical and temperate ecological communities. In general, marine waters are considered to be in better ecological condition than estuaries. However, some specific coastal and aquatic ecosystems, mainly adjacent to urban and industrial areas, are potentially at risk of degradation from urban runoff and stormwater pollution, and intense recreational use.

Only 4% of wetlands and freshwater lakes in NSW are coastal, and this is comprised of 59% estuarine wetlands, 35% coastal lagoons and lakes, 5% floodplain wetlands, and 1% freshwater lakes (Kingsford et al. 2004a) (Map 6.5).

More than 70% of coastal wetlands have been cleared since European arrival (Keith 2004). Most coastal floodplains have been cleared, drained and cultivated for so long that little original vegetation remains. However, some coastal freshwater lagoons still provide an important habitat for waterbirds. All freshwater wetlands of the coastal plains of NSW are listed as endangered ecological communities under the TSC Act.

There has been little monitoring of the condition of estuaries and coastal lakes in NSW. The Healthy Rivers Commission reported that 31% of coastal lakes were 'moderately' or 'severely' affected by human pressures (HRC 2002). A national assessment of estuarine condition found that only 14 of the State's 133 estuaries were in 'near pristine' condition, while 34 were found to be 'extensively modified' (NLWRA 2002b). Eleven coastal aquatic ecosystems are listed as endangered ecological communities under the TSC Act.

Most of the estuaries in NSW are under intense urban development pressure with approximately 80% of the population living near an estuary.

Mangrove forests are scattered along the coast of NSW and are expanding into nearby saltmarsh areas. By the latter part of the last century, 25–30% of the remaining saltmarsh had been lost due to mangrove encroachment (Mitchell & Adam 1989; Saintilan & Williams 1999; Saintilan & Williams 2000). The main driver of mangrove invasion is likely to be regional rises in sea level due to climate change (Rogers et al. 2006). This loss of saltmarshes reduces the area available for birds that would normally make use of this habitat (Straw 1999; Straw 2000; Saintilan 2003).

The total area of coastal saltmarsh in NSW in the mid-1980s was approximately 5700 ha distributed in fragmented patches, usually of less than 100 ha (West et al. 1985). Since this estimate, further reduction and fragmentation have occurred (Adam 2002; Harty & Cheng 2003; Hughes 2003a; Kelleway 2005). Because of their decline, saltmarshes in NSW are now listed under the TSC Act as an endangered ecological community.

Seagrasses play an important role in over 100 NSW estuaries and bays by providing habitat for fish, birds and other flora and fauna, consolidating sediments and providing a major source of primary production (West et al. 1989). There are many examples where declines in area have been recorded, such as in Botany Bay (Larkum & West 1990), Port Hacking (Williams & Meehan 2004), Lake Illawarra (West 2004) and some coastal rivers (West et al. 1989).

Information on the condition of beaches and near-shore habitats, such as rocky and coral reefs, is limited. The most serious threat to rocky shores is the removal or damage of plants and animals by humans. Marine waters are generally considered to be in good condition as currents, wave action and tides are usually able to dilute pollution, making them less vulnerable to degradation. Nonetheless, even in well-flushed systems, pollutants can bind to organic material and sediments, and accumulate in filter feeders and higher order predators with adverse effects on ecosystems and human health (see Water 5.7).

The impacts on water quality from developments and urbanisation, resulting in sedimentation and local pollution from sewage and stormwater overflow, is an issue. Collection and fishing practices may also pose serious threats to the health of some marine and estuarine ecosystems.

Response to the issue

Water-sharing plans made under the Water Management Act 2000 are now in place for the major regulated river systems in NSW (see Water 5.1, Water 5.2 and Water 5.3). These are designed to share water resources between users and the environment. As a result, environmental flows have been set for catchments to protect watercourses and their dependent ecosystems. For example, environmental flows totalling about 84,000 megalitres (ML) were released into the Macquarie Marshes between November 2005 and January 2006 to support the breeding of waterbirds in the marshes.

The NSW Wetlands Management Policy 1996 provides for the conservation, management and appropriate use of wetlands by key stakeholders. This policy was revised in 2006 and is due for release in 2007.

The NSW Government has provided $13.4 million for the NSW Wetlands Recovery Plan which aims to deliver long-term and permanent benefits to wetlands in NSW through water efficiency projects, water buy-back and projects to improve wetland management. It will begin by focusing on water efficiency and habitat improvement projects for the critically important Macquarie Marshes and Gwydir Wetlands. Matching funding has been sought from the Commonwealth.

A number of planning instruments used by the State and local governments are important in the management of aquatic ecosystems and the coastal zone:

• State Environmental Planning Policy 14: Coastal Wetlands applies to 1300 NSW coastal wetlands of high natural value outside the Sydney metropolitan area and requires preparation of an environmental impact statement before any land clearing, levee construction, drainage work or filling work is approved.
• State Environmental Planning Policy 71: Coastal Protection aims for appropriate and suitably located development in the NSW coastal zone.

Reservation of aquatic ecosystems is one of the major mechanisms to protect their important values, and a number of aquatic ecosystems, including important wetlands, are protected within the NSW reserve system. However, despite some significant recent additions in under-represented areas (see Biodiversity 6.7), the State's reserve system is far from representative of inland aquatic biodiversity.

NSW RiverBank is a $105-million environmental fund which the NSW Government will use to buy back water rights and re-allocate them as environmental flows to the State's most stressed and valued rivers and wetlands. The scheme, to run from 2006 till 2011, will address the over-allocation and overuse of water within the existing water management framework.

In addition, NSW has contributed $115 million to the Living Murray project to restore flows to wetlands with a high conservation value and has also committed to purchase 80–125 gigalitres (GL) of water for the environment in the Murray–Darling system (see Water 5.2). Other releases include 500 GL to the River Murray in October 2005 to allow watering of wetland, floodplain and forest ecosystems, including the Barmah-Millewa Forest, and 180 ML in the MIA State Forest (February–June 2006).

The NSW Estuary Management Program was established in 1992 to restore and protect estuaries along the coast, with particular emphasis on protecting and rehabilitating tidal wetlands. To date, 37 estuary management plans have been completed under the program.

The Coastal Lands Protection Scheme aims to bring significant coastal lands into public ownership and care. By June 2005, a total of 15,314 ha had been acquired at a cost of $65.4 million to create new coastal national parks and reserves.

The Coastal Lakes Sustainability Assessment project is being undertaken as part of the NSW Comprehensive Coastal Assessment. There will be sustainability assessments of eight priority lakes (Back, Burrill, Coila, Cudgen, Merimbula, Myall, Narrawallee and Wollumboola) followed by the preparation of management strategies. The assessment will also provide data on trends in seagrass distribution.

The statewide natural resource management (NRM) targets relevant to this theme are 'By 2015 there is an improvement in the condition of important wetlands, and the extent of those wetlands is maintained', 'By 2015 there is an improvement in the condition of estuaries and coastal lake ecosystems' and 'By 2015 there is no decline in the condition of marine waters and ecosystems'. The available data may be used as a baseline measure of this target in some parts of NSW, but there is a need for further data on a statewide basis to provide a full picture of progress toward the targets.

Future directions

The existing information on wetlands is broad and generalised. There is a need for a comprehensive inventory of wetland habitats, including their condition and extent, to ensure that rare types are properly identified and protected. A definitive typology is a pre-requisite for conservation planning and wetlands need to be afforded greater protection within the terrestrial reserve system.

Continued commitment to the water reform process is essential. More water needs to be purchased to ensure that sufficient is available for environmental flows when and where needed. Further research is also needed into the management of environmental flows in regulated rivers so that they best replicate natural conditions and maximise ecological benefits.

Planning should commence now for reduced river flows in the future due to climate change, and how to accommodate environmental flows in the changed conditions. The impact on coastal ecosystems of a rise in sea levels should also be factored into future management plans.

Better management of pollution from diffuse sources and stormwater is needed to maintain the condition of coastal lakes and estuaries. New tools and controls are being developed to manage runoff into sensitive coastal ecosystems that are under pressure from population growth along the coast.

The capacity to monitor the status and condition of marine and coastal ecosystems is expected to be enhanced through the NSW Monitoring, Evaluation and Reporting Strategy of the NRM program.