SoE 2009 > Water > 6.3 Wetlands

6.3 Wetlands

The condition of wetlands in inland New South Wales continues to decline, mainly due to the effects of drought, water extraction and altered flow regimes.

Long-term surveys demonstrate a general pattern of decline in the extent and productivity of inland wetlands, which has been exacerbated in the shorter term by the effects of prolonged drought.

The majority of inland floodplain wetlands are still affected by drought and are generally in poor condition. However recent inundation of key floodplain wetlands in the Paroo and Narran Lakes demonstrates the boom and bust nature of wetlands and their capacity to respond rapidly to flooding.

Reduced water availability is the principal cause of wetland decline but habitat degradation as the result of catchment land-use changes, clearing and modified drainage patterns is also a significant pressure.

Ongoing recovery of water for the environment is supplementing the environmental water already allocated through water sharing plans. A range of programs is targeted at improving or restoring the condition of high value wetlands and floodplain ecosystems in NSW.

NSW indicators

Notes: Terms and symbols used above are defined in About SoE 2009 at the front of the report.

Introduction

Wetlands are dynamic by nature and an important part of the natural environment. They are 'hot spots' for plant and animal biodiversity and integral to landscape processes at regional and larger scales. Wetlands moderate the impacts of floods and contribute to regional economies by providing nurseries for estuarine commercial fisheries and supporting sustainable timber production, grazing, apiary and tourism. They provide a cultural focus for many regional communities, including Aboriginal communities.

NSW has 12 'Ramsar' wetlands recognised as internationally important for their biodiversity and ecosystem values under the Ramsar Convention. Wetlands provide vital habitat for the migratory bird species protected under various international agreements, such as the Japan–Australia Migratory Bird Agreement (JAMBA), China–Australia Migratory Bird Agreement (CAMBA) and the Republic of Korea–Australia Migratory Bird Agreement (ROKAMBA).

Status and trends

Wetland extent and condition

Little new statewide or systematic mapping of the extent and condition of wetlands in NSW has become available recently but catchment-specific studies clearly demonstrate an ongoing pattern of significant declines over longer time frames as shown in Table 6.9.

Table 6.9: Declines in significant NSW wetlands

The first statewide map of wetland extent in NSW was published in 2004 (Kingsford et al. 2004a). It found that wetlands cover 4.3 million hectares or 5.6% of the state. This map used satellite imagery from 1984 to 1993 to delineate inland wetlands and satellite imagery from 1994 to 1995 to delineate coastal wetlands.

While no update of the statewide extent of wetlands is available, the Macquarie Marshes have been mapped using Landsat MSS and TM data every year between 1979 and 2006 and the Gwydir wetlands from 1987 to 2006. This mapping shows that the frequency and duration of inundation of both these key wetlands has declined and that areas receiving high frequency inundation have also declined.

In response to this reduced flooding, characteristic wetland vegetation communities of the Macquarie Marshes have declined in condition and some have also reduced in area. The death of more than 30% of the river red gum woodlands in the North Marsh has been attributed to lack of inundation (Bacon 2004), while the area of reed and marsh plants in the Northern Macquarie Marshes Nature Reserve decreased by 33% between 1991 and 2008. A significant invasion by chenopod shrubland has replaced wetland plants as the dominant understorey in the river red gum woodlands (Bowen & Simpson 2008b).

The overall extent of the core wetlands in the Gwydir is estimated to have declined by 25% between 1996 and 2008 (Bowen & Simpson 2008a).

Waterbird surveys

The best long-term data on changes in wetland extent in NSW are available from aerial waterbird surveys of available wetland habitat, which have been conducted annually from 1983 to 2008 (Porter & Kingsford 2008).

The abundance and diversity of waterbirds are useful indicators of wetland condition because they are sensitive to environmental changes (Kingsford 1999; Baldwin et al. 2005). The long-term monitoring program shows that waterbird communities and the area of wetlands are continuing to decline across eastern Australia and many wetland areas within NSW (Kingsford et al. 2003; Kingsford et al. 2004b; Porter & Kingsford 2008).

Total waterbird numbers in eastern Australia for 2006 were the third-lowest on record and waterbirds were concentrated on relatively few wetlands. Limited wetland habitat was available throughout the survey area as 2006 was one of the driest years on record (Figure 6.4). Most of the wetland habitat that was available in 2006 (66%) was in the south of the Murray–Darling Basin. Many major wetland systems, including the Paroo Overflow, Bulloo Overflow, Macquarie Marshes, Menindee Lakes and most northern rivers in the basin, were dry or almost dry. The total breeding index for all species combined was the lowest ever recorded and restricted to a small number of locations.

Severe and widespread drought conditions in 2007 continued to affect wetlands, floodplains and rivers throughout eastern Australia. Wetland area recorded throughout most of the survey was below average and most significant wetlands in NSW remained dry. Some of the Paroo Overflow lakes held water but hosted relatively few birds. The wetland area index was the lowest on record and total waterbird abundance the second-lowest on record with waterbirds concentrated in a few wetlands (Figure 6.4).

In 2008, there was significant water in the Paroo–Warrego and Narran Lakes, but drought continued to affect wetlands in the remaining areas of eastern Australia. The Paroo Overflow lakes and Cuttaburra channels held water after flooding in December 2007 and more than 50,000 waterbirds were recorded. However, overall waterbird abundance remained well below average (Figure 6.4) and waterbirds were again concentrated on just a few wetlands. Total breeding index (all species combined) was below average but higher than in the two previous years.

Trend analyses indicate overall declines in waterbird abundance, wetland area, breeding abundance and breeding species richness but increases in 2008 compared with the previous five years.

Figure 6.4: Estimated number of waterbirds and wetland area index in eastern Australia, 1983–2008

Source: Kingsford & Porter 2009

Notes: Aerial survey along 10 aerial survey bands, 1983–2008

Threatened species and endangered ecological communities

Wetlands are considered to be among the most endangered ecosystems in the world (Millenium Ecosystem Assessment 2005). Twenty freshwater wetland communities have been listed as endangered ecological communities under the Threatened Species Conservation Act 1995, along with one critically endangered species (the orange-bellied parrot), 150 endangered species and 184 vulnerable species all of which rely on wetland habitats for all or some of their life cycles. Wetlands are also important habitats for a number of fish species that are listed under the Fisheries Management Act 1994.

Reservation of wetlands

Protection of wetlands under the National Parks and Wildlife Act 1974 or through Ramsar listing or other means is desirable to achieve effective conservation of these areas over the longer term. Studies suggest that the size of the protected area and the management of the surrounding catchment are critical for effectively protecting aquatic biodiversity (Nevill 2004; Kingsford et al. 2005). However, the sustainability of wetlands within the reserve system still depends heavily on the provision of adequate environmental flows, as well as sympathetic management of land and water resources by government agencies and surrounding landowners (see Water 6.1).

Table 6.10 shows that, at December 2008, only 3.3% of the area of inland wetlands in NSW was managed within the national parks estate, an increase of 0.9% over the preceding three years. Coastal wetlands are better represented, with nearly 18% now being managed within the formal reserve system, an increase of almost 1% since 2005. This analysis is based on a wetlands compilation map drawn from satellite imagery for the period 1986–95 which is presently the best available statewide representation of wetland distribution in NSW (Kingsford et al. 2004a).

Table 6.10: Extent of wetlands in the NSW national parks estate and additions 2006–08

Source: DECCW data 2009

In 2007, the Paroo River wetlands were listed under the Ramsar Convention as a wetland of international importance for their biophysical and cultural values. The site, consisting of Nocoleche Nature Reserve and the Peery and Mandalay blocks within the Paroo–Darling National Park, is the largest Ramsar site in NSW. It adds a further 138,000 ha to the wetlands protected by Ramsar listing in NSW and brings the number of Ramsar sites in NSW to 12.

Pressures

Flow modification and extreme drought

Water availability is the most significant pressure on the health of wetland ecosystems. In NSW, the stresses caused by altered flow regimes due to water resource development over the longer term have been intensified during the state's prolonged drought. Current conditions are among the worst on record, particularly in the southern Murray–Darling Basin and the health of most wetland ecosystems has been affected.

The impacts of water extraction, altered flow regimes and drought on water availability are discussed in greater detail in Water 6.1, while the implications of flow modification and drought for aquatic ecosystems are covered in Water 6.2.

Habitat degradation

A number of processes are responsible for habitat degradation. Clearing of wetlands for development and/or cropping may result in irreparable damage to wetland ecosystems and the loss of biodiversity. Modifications to natural patterns of drainage are often difficult to detect or monitor, particularly during dry spells when the changes are less visible. Over-draining of coastal landscapes is a particular threat to freshwater wetlands that may create acid discharges to rivers.

More diffuse impacts to wetland habitats can be caused by surrounding land uses, pests and weeds. Increased nutrient and sediment loads and turbidity are particular threats to submerged aquatic vegetation in wetlands. Subsidence and cracking of watercourses and upland swamps resulting from long-wall mining can also pose problems for water quality and aquatic ecosystems.

In rural and semi-rural areas, grazing of wetland plants by livestock and pest species, such as rabbits and goats, can have a serious impact on the diversity, distribution and health of wetland plants. Grazing of stock may also lead to soil compaction, increased nutrient levels, the introduction of weed species, trampling of native plants and the ringbarking of mature trees.

Invasive species

Introduced plants, which can change wetland structure and function, are favoured by disturbances such as altered flow regimes, clearing or draining of wetlands, and increased nutrient loads. Significant weed species in NSW wetlands include lippia, salvinia, alligator weed and water hyacinth, which can all rapidly clog waterways when conditions are favourable for them (see Biodiversity 7.4).

Lippia has taken over thousands of hectares of the state's inland watercourse country and has had a major impact on the condition of the Gwydir wetlands. Lippia can out-compete all native vegetation including tree seedlings and it poses a severe threat to watercourses and adjacent grazing lands.

Introduced aquatic species, such as European carp and mosquito fish, can decimate native fish populations in wetlands and affect water quality. Introduced herbivores, such as pigs and goats, have caused extensive damage to the condition of wetland vegetation and soils through grazing, trampling and digging and are also capable of altering the structure of watercourses (see Biodiversity 7.4).

Water quality

Water quality plays an important role in wetland health. Runoff from towns, cities and farms may contain toxic substances or high levels of nutrients and sediments. Where excessive levels of nutrients enter wetlands, they can cause problems, such as eutrophication (which severely depletes dissolved oxygen levels), fish kills or excessive plant growth. Increased turbidity affects the productivity of submerged vegetation and leads to siltation, which may have an impact on the composition and habitat of many dependent species. Increased salinity can affect other characteristics of water quality, contribute to the development of acid sulfate sediments and adversely affect biodiversity.

Acid sulfate soils

Generally acid sulfate soils are regarded as an issue for coastal waterways. If left undisturbed and covered with water, sulfidic material poses little or no threat of acidification. However, when it is exposed to oxygen in the air, the sulfides react to form sulfuric acid which can contaminate waterways. See Land 5.1 for more detail.

River regulation has seen some wetlands used as water storages, causing the loss of their dry phase. Where these wetlands are associated with saline groundwater that is high in sulfur, sulfidic sediments may accumulate in the inundated wetland. The drought conditions have recently led to the drying of many otherwise permanently inundated wetlands in the Murray–Darling Basin, exposing sulfidic material with the potential to cause the acidification of some inland wetlands, as has occurred at Bottle Bend on the Murray River. While some investigations have been conducted (Hall et al. 2006), the full extent of the threat posed by acid sulfate soils to inland wetlands is still unclear and requires further assessment.

Climate change

Climate change is likely to affect wetlands through changes in water availability, and higher temperatures and rates of evaporation. These changes are likely to affect wetland condition and productivity, reduce the frequency of waterbird breeding in major wetlands and potentially lead to shifts in wetland distribution or ecosystem types (CSIRO 2008c). For further consideration of this issue, see the Climate Change Chapter, Water 6.1 and Water 6.2.

Responses

Policy framework

State Plan 2006: A new direction for NSW (NSW Government 2006) has the following target under Priority E4: 'By 2015 there is an improvement in the condition of important wetlands and the extent of those wetlands is maintained'. A Monitoring, Evaluation and Reporting (MER) strategy is being implemented to monitor progress towards all E4 targets.

A review of State Plan 2006 commenced in August 2009 and this may adjust some of the plan's priorities and targets.

NSW Wetlands Policy: A Draft NSW Wetlands Policy to update the NSW Wetlands Management Policy 1996 was released for targeted comment in 2008 and is expected to be finalised shortly. This will provide for the sustainable use and management of NSW wetlands and guide investment in ongoing resource management.

Water availability

Water sharing plans provide for greater flows of environmental water to inland and coastal wetlands in order to improve wetland health. These plans are discussed in Water 6.1.

Purchase of water licences increases the amount of water available for the environment, enhancing the levels and patterns of flows to wetlands and is a significant development in improving wetland health. Water 6.1 describes water purchases for the environment.

Adaptive environmental water plans facilitate the delivery of available environmental water to key wetlands. Plans have been approved for the Lachlan, Macquarie and Gwydir valleys and a draft plan prepared for the Murrumbidgee.

Wetland recovery and restoration

The NSW Wetland Recovery Program delivers targeted wetland conservation outcomes in the Gwydir wetlands and Macquarie Marshes. Water recovery, weed control, grazing management, and research are under way to reduce the ecological stresses on these wetlands.

The NSW Rivers Environmental Restoration Program aims to arrest the decline of the most stressed and iconic rivers and wetlands in NSW. It builds on work undertaken through the NSW Wetland Recovery Program in the Macquarie Marshes and Gwydir River system and is also focused on important wetlands in the Lachlan and Murrumbidgee rivers, such as those in Yanga National Park.

Ecological character descriptions are required under the Water Act 2007 (Cwlth) for all declared Ramsar wetlands and other key environmental sites within the Murray–Darling Basin. Descriptions have been prepared for the Gwydir wetlands Ramsar site, the Wilgara component of the Macquarie Marshes Ramsar site, Fivebough and Tuckerbil swamps. Drafts are in preparation for the Macquarie Marshes Nature Reserve, the Paroo River wetlands and the Perricoota–Koondrook red gum forest.

Future directions

NSW remains committed to the water reform process. Water sharing plans and increased environmental flow releases are expected to have a positive impact on wetland ecosystem health once flows return to more usual levels and patterns of variability.

Monitoring of environmental flows will facilitate adaptive management so that environmental flows better replicate natural conditions and optimise the benefits to the health of wetland ecosystems.

Inland rivers and wetlands are not well represented within the national parks estate. The NSW National Parks Establishment Plan 2008 (DECC 2008a) has identified wetlands as a key priority for building the reserve system over the next 10 years.

The implementation of floodplain management plans is expected to provide better protection and management for important wetland ecosystems and processes.

Further research is desirable to determine the likely effects of climate change on wetland ecosystems due to reduced water availability and the possible shifts in community composition that may result from altered seasonality of flows.

There is a need to update information on the extent of NSW wetlands and for more effective monitoring of extent, allowing for the intermittent and unpredictable nature of inundation patterns which vary substantially over longer time frames.

Better information is desirable on the location and types of wetlands found in NSW, particularly the conservation values of the smaller and less well-studied types that may have unique values and not be adequately protected.