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5.5Mining Activities


The main risk identified for ecosystems surrounding the uranium mine sites in the Alligator River Region is from the dispersion of mine waste waters to streams and shallow wetlands, including contamination with radioactive substances (Supervising Scientist 2002). In particular, high rainfall during the wet season often results in the need to release low-level contaminated runoff stored in on-site water bodies (van Dam et al. 2002a). While toxicity tests have been conducted to investigate the effect of uranium on invertebrate and vertebrate species (van Dam et al. 2002a, Hogan et al. 2005), historical water quality monitoring in Magela Creek showed that uranium concentrations are approximately an order of magnitude lower than the site-specific water quality trigger value (established by the Supervising Scientist), indicating that the risk to the downstream environment from controlled waste water release may be negligible (Hogan et al. 2005).

Since the major tailings water leak from the Ranger mine that occurred in the 1999-2000 wet season (refer Supervising Scientist 2000), a monitoring program using biological, chemical and radiological techniques to monitor and assess impacts upon ecosystems and humans arising from mining activities has been developed and implemented at Ranger and Jabiluka (refer Supervising Scientist 2002). This program has been undertaken since that time with an annual review of key knowledge needs and monitoring. In general, the precautionary approach and extensiveness of the program are such that there is a strong level of confidence that any impacts from tailings water leakage or other impact would be detected and acted upon. Nonetheless, the impacts from mining operations remain a salient threat to the ecological character of Kakadu National Park at least in the short term for the remaining duration of mining activities.

In this context, it is noted that historical mining sites in the South Alligator River region continue to be monitored and rehabilitated, but to date, the general view of the Knowledge Management Committee was that these sites are not thought to represent a threat to future ecological character.

5.6Public Safety and Crocodiles


Following the protection of crocodiles in the 1970s, the abundance of saltwater crocodiles Crocodylus porosus has increased within Kakadu National Park (refer Section 3.3.7), thereby increasing the likelihood of crocodile attacks on humans. However, only two fatal crocodile attacks have occurred within the Park over a period of 27 years during which an estimated 3.5 million people visited the Park (SMH 2004). The emphasis of crocodile management within the Park is to educate visitors about crocodiles and their dangers through brochures, signs and advice. Should an increase in crocodile attacks occur, it is possible that visitor numbers may be affected. This may deter some visitors, but may attract others.

5.7Damage to Archaeological Resources and Rock Art


Archaeological resources and rock art are under threat from natural and human-induced impacts. Human induced impacts include theft, vandalism and inappropriate development and tourism. Weathering, vegetation growth and feral animal, termite and fire damage also threaten to damage rock art and archaeological sites, all of which may be preventable impacts. Natural processes, such as tidal inundation of floodplains and storms, may threaten archaeological sites and rock art, and climate change could amplify the effects of these impacts.

5.8Living Resource Extraction

Although the use of lead shot for hunting is banned in Kakadu National Park, this practice continues in some areas of the park. Lead poisoning through the ingestion of spent lead shot can impact on significant wildlife populations, such as magpie geese Anseranas semipalmata (Director of National Parks 2007). Over-harvesting of popular bush tucker items (for example, magpie geese, turtles) by not following Bininj cultural protocols or practices can impact on the populations of these species and cause social tensions.

Adequate fishing resources are also an important component of maintaining Bininj Traditional Ecological Knowledge and cultural practices. The restriction of some areas of Kakadu National Park to public fishing is important for Bininj to undertake fishing and other cultural practices in private.


6Changes to Ecological Character


‘Ecological character’ is defined as a combination of the wetland ecosystem services/benefits, components and processes that underpin wetland systems at any given point in time. In assessing changes to ecological character for Kakadu National Park Ramsar site, as required by the National Framework (2008), the relevant timescales for the assessment of ecological character are taken to include 1980 and 1989 (when Stages I and II, respectively, were listed as Wetlands of International Importance), 1995 when Stage III wetland components were added to the Stage I area and 2010 (the time of preparation of this first ECD and the extension of the remaining Stage III area).

While there has been a considerable body of research in the Magela Creek catchment and several other areas within the site, comparatively less quantitative information exists at a whole-of-site scale. As such, the analyses below attempt to characterise whole-of-site changes to ecological character but also rely on specific investigations and information about particular areas of the site where relevant.


6.1Ecological Character Change Methods


Based on the National Framework and similar approaches undertaken in other ECDs, a two-step approach has been employed to assess changes in ecological character for the Kakadu National Park Ramsar site as discussed in the sections below. These are:

  1. based on the documentation reviewed and Ramsar Nomination Criteria listed as part of the 1998 RISs, an assessment of whether these listing Criteria continue to apply, and
  2. based on the critical components, processes and services/benefits and LACs identified, whether there has been a measurable change to ecological character that is the likely result of anthropogenic activities in Kakadu National Park.

6.1.1Assessment of Listing Criteria


Based on the analysis of the previous and current Nomination Criteria presented in Table 2-6 (refer Section 2.5), Kakadu National Park continues to meet the Nomination Criteria for which the original two sites were listed. In addition, as outlined in Section 2.5, Kakadu National Park Ramsar site is deemed to meet the three additional Ramsar Criteria.

6.1.2Potential Changes to Ecological Character Since Listing


When considering changes in ecological character of the site, the National Framework requires the ECD to examine any changes to character that have occurred since the listing date. In order to do this, a baseline of ecological character at the time of listing must be established.

As described in Section 3.1.2, the Fox et al. (1977) report forms a baseline description of ecological character at the time of listing. The fact that the ‘ecosystem services’ listed by Fox et al. (1977) continue be supported at the present time lends support to the notion that broad scale ecological character changes of the site has not occurred.

Notwithstanding, this information forms only a qualitative basis for assessing ecological character changes since listing and more recent studies, monitoring data as well as the expert views of the Knowledge Management Committee need also to be considered in assessing ecological character changes. Some of the key issues with regard to possible changes to ecological character are discussed below:

Exotic Flora

The prominent weed species of concern in Kakadu National Park are mimosa Mimosa pigra, salvinia Salvinia, para grass Urochloa mutica and olive hymenachne Hymenachne amplexicaulis. In general, weed management within the Park has largely contained or managed impacts of these species on wetland flora and fauna communities since listing (Director of National Parks 2007), although the success of weed management is highly variable and is dependent on resources and opportunities (Walden and Gardener 2008). Impacts from weeds are not considered to have caused a change to the ecological character of the site, with further discussion about each of the key species provided below:


Mimosa

Mimosa is a thorny shrub that was discovered in the Park in the early 1980s (around the time of listing) that grows in coastal floodplain areas of the Northern Territory, favouring seasonally or periodically inundated freshwater wetland habitats (Walden et al. 2004). The principal impacts from mimosa on wetland ecosystems include reduction of biodiversity and vegetation structure and alteration of hydrological regimes by encroaching into waterbodies and increasing sediment deposition. A number of studies assessing the risk of mimosa have been undertaken, the most complete and notable being Walden et al. (2004).

Kakadu National Park has been described as ‘an island in a sea of mimosa’, noting control has been given a high priority with approximately $7 million dollars of Australian Government funding provided to the removal of over 8000 hectares of mimosa during the early 2000s (Walden et al. 2004). This large scale reduction has greatly reduced the immediate risk to Kakadu National Park (Walden et al. 2004). Kakadu remains free from serious infestation by the systematic survey and destruction of new outbreaks, which involves four full-time staff and an annual budget of over $400 000 (Storrs et al. 1999).

Salvinia

Salvinia molesta is a free floating aquatic species discovered in the Kakadu National Park in 1983 and, due to its very fast reproduction rate and seasonal flooding, has now spread throughout the Magela Creek system and also can be found in the East Alligator River and Nourlangie Creek system (Storrs and Julien 1996). Significant financial and operational resources are applied to control the weed including previous trials of the use of the biological control agent Cyrtobagous salvinae (a weevil) (Storrs and Julien 1996). In this context, salvinia is not considered to have caused any notable ecological character changes to the site and is being adequately controlled under current management regimes (S. Winderlich pers. comm. 2009).


Para Grass

Para grass is a highly invasive pasture weed introduced as fodder for domestic livestock at Oenpelli in Arnhem Land in the 1960s. Parks Australia eradicate isolated infestations and note the South Alligator River system is at most risk from future invasion (Walden and Bayliss 2003 cited in Douglas et al. 2008). As per the above, the presence and distribution of para grass is not seen as change in ecological character since listing of the site.



Olive Hymenachne

In more recent times (since 2002), olive hymenachne Hymenachne amplexicaulis has also become a weed species of concern and management aims to control the further spread of this species (for example, refer Douglas et al. 2008, Walden and Gardener 2008). The presence of olive hymenachne is also a contributing factor to saline intrusion as discussed below.


Exotic Fauna

A variety of non-indigenous fauna species are known to occur within the site and include: pigs Sus scrofa, Asian swamp buffalo Bubalus bubalis, cattle Bos spp., horses Equus caballus, donkeys E. asinus, cats Felis catus, dogs Canis lupus familiaris, black rats Rattus rattus, house mice Mus musculus, cane toads Rhinella marina, flower-pot snake Rhamphotyphlops braminus, house gecko Hemidactylus frenatus, sambar deer Cervus unicolour, various ant species4 and honeybees Apis mellifera (Press et al. 1995b; Director of National Parks 2007; Bradshaw 2008). These species, to varying extents, whether individually or collectively, are thought likely to add pressure to the maintenance of the sites’s values for biodiversity and threatened species, although the relative impact of these on native fauna is likely to vary considerably (Gardner et al. 2002; Finlayson et al. 2006; Bradshaw et al. 2007). The majority of introduced taxa have been widely acknowledged as implicit in the degradation of habitat values for both native fauna biodiversity and threatened species (see Table 6 -26).

Additional exotic fauna species that have a high potential to enter the Park include banteng Bos javanicus and crazy ants Anoplolepis gracilipes (Director of National Parks 2007).

Of the non-indigenous fauna recorded on the site, the greatest threats to fauna habitat values are linked to the presence of large, hard-hoofed herbivorous mammals (buffalo, horses, donkeys and pigs) and cane toads (Director of National Parks 2007; Bradshaw 2008), as discussed in further detail below:



Large Herbivores

The severe and adverse environmental impacts effected by buffalo within the site and the region has been widely reported (for example, Braithwaite et al. 1984; Taylor and Friend 1984; Tulloch and Cellier 1986; Skeat et al. 1996). As a result of a major eradication program implemented in the mid-1980s (and completed in 1997), buffalo numbers within the Alligator Rivers Region were significantly reduced (Gardner et al. 2002; Director of National Parks 2007). Since then, numbers within the site have increased gradually, though buffalo (and horses, donkeys and cattle) remain abundant within neighbouring Arnhem Land and pastoral properties (Director of National Parks 2007; B. Salau pers. comm. 2009).

High buffalo numbers have in the past lead to significant environmental damage in lowland environments, and continue to represent a threat to wetland environments (such as springs, billabongs and riparian vegetation) in the stone country (Simon Ward, pers. comm. 2010). High buffalo numbers can cause severe damage to wetland environments (for example, trampling of nests, eggs and vegetation, increased stream erosion and sedimentation) and cultural resources (that is, damage to rock art, sacred sites and archaeological resources). Specifically, buffalo can damage rock art by rubbing against it, damage sacred sites through trampling and environmental degradation and destroy archaeological resources through trampling, grazing and wallowing in open artefact scatters on the flood plain (Jones 1985, Higgins 1999, D. Lindner pers. comm. 2009).

Both pigs and horses generate physical degradation of habitat, particularly around wetlands (most notably freshwater floodplains, tidal flats and monsoon forests), and are implicated in the spread of some of the most significant weed species within the site (for example, mimosa Mimosa pigra and olive hymenachne Hymenachne amplexicaulis (pigs) and mission grass Pennisetum polystachion, gamba grass Andropogon gayanus and gambia pea Crotalaria goreensis (horses); (Director of National Parks 2007). Pigs are regarded as common throughout the region and Kakadu National Park, and it is considered that pig abundance may have increased concomitantly with the decline in buffalo populations, although there is little quantitative data (Gardner et al. 2002). Pig rooting of floodplain areas, while prevalent, is reported as having a far less deleterious impact than buffalos in terms of channelisation and associated saltwater intrusion. The creation of levees and ruts from the rooting is interpreted by some to be inhibiting tidal flows (Petty et al. 2005). Pig rooting may be impacting on the breeding of pig-nosed turtles and populations of bush-tucker turtles and water chestnut tubers (S. Ward pers. comm. 2010).

Whilst horses are considered relatively common throughout the site, there is anecdotal evidence that both donkeys and horses are comparatively more common in the drier southern and western parts of Kakadu National Park (B. Salau pers comm. 2009).

While all of these species are actively controlled and managed, the broad scale program to eradicate buffalo from the Park in the early 1980s appears to have had the most resoundingly positive effect on the ecological character of the wetlands since listing. Research by Petty et al. (2005) has documented how buffalo were exacerbating the natural processes of tidal channel extension and contraction in the South Alligator floodplain through creation of swim channels. This process had been leading to extensive saltwater intrusion into the freshwater areas of Yellow Water for the decades previous. Although some billabongs in the tidal interface area of the South Alligator have been permanently lost and associated Melaleuca communities degraded by saltwater intrusion, it is reported that much of the ‘pre-buffalo’ character of the tidal interface region has been restored in the past 10 years (Petty et al. 2005).

Furthermore, floating grass mats (also known as sudds) within the site are thought to be recovering as a result of the reduction in buffalo numbers. Floating grass mats are a habitat found in flow channels, waterholes and billabongs of Kakadu during the wet season. They are typically comprised of a range of submerged plant species including Leersia hexandra and native hymenachne Hymenachne acutigluma, and occur along the banks of billabongs (Finlayson et al. 2006). Studies elsewhere in the Northern Territory in billabongs near the Finnis River south of Darwin noted the importance of these mats for a range of fauna including saltwater crocodile nesting, waterbird feeding and underwater habitat for fish and invertebrate species (Hill et al. 1987). In the context of historical changes to ecological character, studies in the Finnis River showed an accelerated loss of floating mats in the period from 1963 to 1978 which was principally the result of buffalo causing the detachment of mats from the bank. The floating mats present in the Kakadu National Park within billabongs and the Magela Creek are less complex or extensive compared to sites such as the Finnis River or Arafura Swamp (Cowie et al. 2000) and there has not been extensive study of these habitats within the Park to date. However, it is likely that this habitat (and associated ecological values) have also benefited from the removal of buffalo from the site.

Cane Toad

As mentioned in Section 5.2, a recent and notorious introduced species is the cane toad Rhinella marina. The preliminary risk assessment of cane toads prepared by van Dam et al. (2002b) outlined the potential effects of cane toads on Kakadu National Park’s resources which included toxic effects on predators such as reptiles, birds and mammals, potential competition with native frogs, and cultural effects from the loss of important bush tucker species. That work assessed the susceptibility of 151 native species as potential cane toad predators and concluded that ten species were considered likely to be at risk of experiencing population level effects (northern quoll, mangrove monitor, Merten’s water monitor, northern sand goanna, spotted tree monitor, northern death adder, king brown snake, dingo), with a further 12 species (or species groups) at possible risk of experiencing population level effects (leeches, snails, ornate burrowing frog, northern dwarf treefrog, desert tree frog, blue-tongued lizard, carpet python, brown tree snake, slaty-grey snake, freshwater crocodile, black bittern, blue-winged kookaburra). A notable proportion of this higher risk group comprises wetland-dependent species (three snake species, four lizard species, all frog species). Many of the ‘at risk’ species also represent traditional food sources. Loss of traditional food sources can lead to decreased application and transmission of traditional ecological knowledge and other activities often associated with this, including decreased used of Bininj languages and decreased application of traditional land and fire management practices.

It would appear many of these impacts foreshadowed by Van Dam et al. (2002b) have now been realised, with anecdotal reports of declines in the populations of a number of predatory wetland-dependent species such as freshwater crocodiles, goannas, snakes and frog fauna in Kakadu National Park and throughout the broader region (S. Winderlich pers. comm. 2009). There are no empirical estimates of the degree of impact of cane toads on native fauna populations within the site; hence firm conclusions on whether there has been a change in character can not be drawn. This represents a key information gap in the context of this ECD and broader management of Kakadu National Park.

There are presently no effective cane toad control measures. Consequently, no cane toad threat abatement plan has been developed to date.

Table 6 26 A summary of ecological and management issues associated with feral fauna species. (after Bradshaw et al. 2007)

Species

Densities

Habitats

Damage

Control

Issues

Pigs

Densities high close to permanent water; areas with subterranean foods; areas with dense woody or grass shelter.

Floodplains flanked by Melaleuca spp., woodlands, vine thickets and forests; upland palustrine areas.

Digging causing erosion/siltation. Weed dispersal. Predation on native species.

Helicopter shooting. Density reduction difficult.

General agreement on control. Adjacent uncontrolled areas are source of immigrants. Vector of Japanese encephalitis virus, Melioidosis, Brucellosis, Leptospirosis, foot and mouth disease, and Tuberculosis.

Buffalo and cattle

Historically up to 34/sq km (mostly floodplains), now <0.1/sq km at a whole of Park scale. Currently a large population in Arnhem land plateau.

All habitats, but higher in floodplains and channels, lowland forests and seasonally inundated areas.


Formerly one of the greatest threats to the region. Severe damage to waterways (erosion, saltwater intrusion). High food consumption. Altered ground cover and plant diversity.

Approximately 80 000 removed during Brucellosis and Tuberculosis Eradication Campaign (BTEC) using helicopters. 20 000 removed since BTEC. Populations increasing and moving back into region.

Buffalo farm with about 600 animals to provide meat. Important source of food and income for Aboriginals. Full eradication culturally contested Adjacent uncontrolled areas are source of immigrants. Vector of Tuberculosis and Brucellosis.

Horses and donkeys

Less abundant than pigs/buffalo. Densities unknown. Population increase up to 80 percent per year.

Drier areas near sites of previous release. High site fidelity. Can live farther from water than pigs/buffalo.

Less visible physical damage compared to pigs/buffalo. Erosion, weed dispersal, and vegetation damage. Possibly affects native herbivore densities.

Damage-density relationship unavailable and controversial. Ground and helicopter shooting controls plausible.

High controversy. Many Aboriginals view as part of landscape; horses are part of cultural heritage as many Bininj were stockmen on cattle stations that were later incorporated into Kakadu National Park. Control questioned by many external groups. Vector of Melioidosis.

Cats
Also see Woinarski and Ward n.d.

Largely unknown. Abundance surveys difficult.

Throughout northern Australia, found in terrestrial and wetland (not fully aquatic) habitats.


Consume wide range of native fauna. May compete with northern quolls, snakes and goannas.

Ground-based opportunistic shooting. Difficult to trap. Poisoning is difficult and trials are currently underway.

Pets provide constant source of feral individuals. Vector of toxoplasmosis causing disease in wildlife and humans.

Dogs

Relatively lower than elsewhere in Australia. No density estimates.

Wide distribution in northern Australia.

Hybridization with dingoes. Competition with and predation on native wildlife. Impacts less than cats.

Tracking surveys, shooting, trapping, poisoning, exclusion fences.

Stray pets a source of feral individuals. Control scrutinized by external groups. Some threat of disease and parasites.

Black rats
(Also see Woinarski and Ward n.d.)

Mary River Ranger station, Upper Wildman River Area, Jabiru (see Woinarski and Ward n.d.)

Common in agricultural land and human settlements.

Increasing numbers of records in ‘natural’ bushlands (S. Ward, pers. comm. 2010).



Moderate pests of agricultural industry. Omnivorous diet. Can displace native species.

Poisoning. Making habitat less suitable. Trapping.

All stakeholders seek control, but lack of information on damage makes justification difficult. Vector of Salmonellosis and leptospirosis.

House mice


Normally low, but “plague” outbreaks can occur. Plagues unlikely in Kakadu National Park but possible after heavy rains in drier regions.

All habitat types, but higher densities in areas of higher disturbance, e.g. human settlements and clearings.

Major pests of agricultural industry. Thought to be greater threat to biodiversity than Black rats.

Baiting with strychnine, but serious side-effects for native wildlife. Possible fertility control.

All stakeholders seek control, but lack of information on damage makes justification difficult. Some threat of diseases to wildlife and humans.

Cane toads

Can exceed 2000/km2 in favourable conditions.

Throughout northern Northern Territory.

Reduction of survival and densities of native reptiles through predation and poisoning. Competition with native wildlife. Changes in plant and animal communities.

Trapping, but time-consuming and expensive. Possibility of fertility control.

All stakeholders seek control, but effective methods are unavailable.. Possible transmission of disease to native amphibians.

Ants

Densities unknown

Wide dispersal capability, but generally localised outbreaks. Highly invasive.

Threats to invertebrate diversity. Agricultural and urban pests.

Eradication campaign in Kakadu National Park successful using poisons. Ongoing monitoring vital to identify new outbreaks.

Little community or government interest in control.


Honey bees

Many feral colonies in northern Australia. Densities unknown.

Range in Kakadu National Park unknown.

Competition with native bees and birds. Reduction of “sugar bag” harvested by Aboriginal people.

Changes in pollination patterns of native plant species.



Control through destruction of hives, poisoning, insecticide strips, but less effective in fragmented landscapes.

Proposals to limit distribution of commercial hives not implemented. Damage generally ambiguous, so control difficult to justify.

Recovery of Saltwater Crocodile Populations

The prohibition of the culling of crocodiles in the 1970s, while pre-dating listing of the Ramsar site, has led to a positive change in the character of the site through the recovery of the saltwater crocodile Crocodylus porosus population over the intervening period from listing to the current time (refer Section 3.3.7).

However, this increase in saltwater crocodile numbers together has had a corresponding negative impact on the populations of freshwater crocodiles Crocodylus johnstoni. Parks Australia has noted saltwater crocodiles to be increasingly moving into areas previously inhabited by freshwater crocodiles, with the freshwater crocodiles often killed as a result of the interaction (S. Winderlich pers. comm. 2009). The increasing presence of saltwater crocodiles further upstream within the catchments of the Park also has had a negative impact on tourism and recreational usage of the site’s freshwater areas with swimming in iconic areas such as Twin Falls and Maguk are no longer permitted due to the risk of crocodile attack.

Saltwater Intrusion into Freshwater Wetland Areas

The processes and extent of saltwater intrusion into freshwater meadows of the low lying floodplains adjacent to the shores of the Van Diemen Gulf were presented by Bayliss et al. (1997) as ‘the major coastal management problem in the Alligator Rivers Region and adjacent areas’, with the problem present in both the East Alligator River-Magela Creek System and South Alligator River systems within the Park and the nearby Mary River (outside of Kakadu National Park).

Saltwater intrusion in these areas is a natural process but has been recognised as increasing over the past 50 years principally through landward extension of tidal creeks. While the presence of buffalos in these environments and motorised boat traffic (through scour) are both highlighted in the literature as having contributed to the proliferation and expansion of tidal channels in the floodplain (for example, Petty et al. 2005), interactions between very large magnitude meteorological and oceanographic processes are the likely primary drivers of saltwater intrusion across the northern portion of the Park. These processes include wet and dry season differences in the relative intensities of sea level, tide and flood conditions with flood channels scoured in the wet season and dominated by tidal processes and sedimentation through the natural formation of levees in the dry season (Cobb et al. 2007).

While the removal of buffalo has been a major improvement to floodplain health, boat traffic and olive hymenachne Hymenachne amplexicaulis remain contributing factors to saltwater intrusion. Boat traffic within the waterways of floodplain areas cause indirect impacts by creating small channels that scour in the wet season and channelise flows rather than allowing sheet flow across the floodplain. Olive hymenachne has readily established in these channels and has been shown to exacerbate the channelisation effect from boat traffic by reducing the width of navigational channels. The growth of native hymenachne Hymenachne acutigluma was previously controlled by feeding buffalo but has also flourished as a result of reduced floodplain fire management practices (Petty et al. 2005).

The effect of saltwater intrusion in the floodplain areas of the Park has had the effect of changing the spatial characteristics and distribution of tidal creeks and associated mangrove environments over a long time period, often at the expense of predominantly freshwater systems. This includes the loss of several freshwater billabong environments located proximal to the tidal channels and at the fresh-salt interface areas of the major river systems, noting that these features have both ecological and cultural significance in terms of bush tucker and traditional customary use.

In recognition of these impacts, the intrusion of saltwater has been studied and monitored over time and measures have been implemented by Parks Australia to control impacts. These include the afore-mentioned eradication of buffalo (the program terminated in 1997), continuing efforts by Parks Australia to control and regulate boating traffic in the river systems and in some cases through construction of temporary bunds and other capital works to deter tidal intrusion (refer BMT WBM 2010).

However, the extent to which saltwater intrusion represents an ecological character change is difficult to assess noting that saltwater intrusion into Kakadu National Park’s freshwater wetlands is a continuous natural process. A key factor to be considered is whether the environmental change or the rate of change can be perceived as having an anthropogenic source. In this context, establishing what is ‘natural variability’ in terms of saltwater intrusion is extremely difficult and consideration of longer term trends (for example, before the listing date) have been taken into account in the setting of relevant LACs (see next section in terms of the assessment of ecological character against LACs). As will be discussed below in the context of future threats, the implications of climate change induced sea level rise must also be considered in terms of defining the ‘natural’ rate of change to freshwater wetland systems of Kakadu National Park and their ability to adapt to saltwater intrusion processes.

6.1.3Assessment of Ecological Character Changes Against LACs


In order to be more definitive about changes to ecological character, the National Framework (2008) requires an assessment of whether or not any LACs set as part of the ECD have been exceeded. Drawing upon the discussions above, Table 6 -27 outlines this assessment.

While there has been extensive data gathering and monitoring in the context of the impacts of uranium mining operations at Kakadu National Park for over thirty years, research about wetland environments within the Park undertaken by eriss and monitoring of species and habitats by Parks Australia, the broad information base for an assessment of ecological character change is limited by:



  1. A largely inadequate baseline for the key parameters at the times of listing and extension in 1980/1989/1995/2010.

  2. Limited continuous data sets over the intervening period to the time of ECD preparation for critical components and processes at a landscape scale.

  3. Generally limited understanding of natural variability in some key parameters, noting that tropical wetland environments such as Kakadu National Park can have enormous variation within and between years or decades.

This situation is not uncommon to Ramsar sites around Australia, and is particularly understandable given the size, relative remoteness and diversity of habitats present at Kakadu National Park. With this in mind, the analysis presented in Table 6 -27 should be viewed as a preliminary attempt at characterising changes in ecological character of the site since listing that can be added to and improved as part of future ECD investigations and assessments.

While the level of quantitative information and data needed to provide a more definitive assessment of ecological character change (and to set more definitive LACs sought by the National Framework) are not available, it would appear unlikely that any of the LACs presented in Table 6 -27 have been meaningfully exceeded except that saltwater intrusion processes have possibly degraded freshwater billabongs and other palustrine wetlands and reduced the extent of Melaleuca communities.

Further information about determining change in ecological character can be found within the recently released ‘National Guidance on Notifying Change in Ecological Character of Australian Ramsar Wetlands (Article 3.2)’ (DEWHA 2009b). As outlined in the document, ‘a breach of an LAC indicates that a component, process or benefit/service has changed beyond its natural variability and the breach of this feature, by definition, requires a remedial response’. However, it is acknowledged by the Guidance document that there are often extreme ranges of natural variability over time, and until such time that natural variability is determined for the circumstances associated with the breach, a notification of ecological character change under the Convention will be made only where there is confidence that the change exceeds any previous condition, that is, it has not previously been experienced to that degree.

Overall, taking into account the findings of the three assessment approaches, there is no evidence to suggest that the site has experienced an ecological character change since listed.

Table 6 27 Assessment of ecological character changes against LAC

Indicator

LAC Value

LAC exceeded?

Comments

  1. Reduction in mangrove extent.

Mangrove extent will not decline by greater than 25 percent over a 20 year period.

No.

Mangroves have increased between 1950-1991. There is no indication mangrove extent has declined since listing in 1980 (Stage I) and 1989 (Stage II).

There are no documented studies about the impacts of higher sea levels negatively impacting on lower estuary mangroves to date.



  1. Melaleuca forest extent.

The number of Melaleuca trees will not decline by greater than 50 percent of baseline values of Riley and Lowry (2002) for the year 1996 (24 704 trees) at the Magela floodplain over a 20 year period.

Unknown – but possible.

Melaleuca communities have been and continue to be in decline within the Magela floodplain. The lack of a consistent methodology to assess changes over time leads to difficulties in assessing long term patterns and quantification of changes since the time of listing. However, it is noted that the eradication of buffalo has largely returned the floodplain to a near pre-buffalo state. This recovery has occurred in part since listing (both Stage I -1980 and Stage II - 1989).


  1. Palustrine wetland and billabongs extent.

Data deficient.

Unknown – but possible.

In particular areas of the floodplain, billabongs that are traditionally freshwater have been affected by saltwater intrusion. However, the eradication of buffalo has largely returned the floodplain to a near pre-buffalo state. This recovery has occurred in part since listing (both Stage I -1980 and Stage II - 1989).

  1. Permanent waterholes and seeps in stone country.

No drying of any perennial seeps and permanent waterholes in the short and long term.

Unknown – but unlikely.

There is no evidence to suggest that anthropogenic activities have resulted in loss of perennial seeps within the site. However, there is no data to indicate flow patterns in seeps within the site.

  1. Spear-tooth shark and northern river shark distribution and abundance.

The site continues to support spear-tooth shark in the long-term.

Wildman and East, West and South Alligator Rivers continue to support northern river shark in the long-term.



Unknown – but unlikely.

Data deficient due to a lack of surveys. No changes to suitable habitat since listing.

Increased saltwater crocodile abundance since listing may be causing deleterious impacts on shark populations as these species are a prey item.


  1. Pig-nosed turtle distribution and abundance.


The average density of pig-nosed turtle will not fall below 13.5 turtles/ha.

Unknown – but unlikely.

Data deficient due to a lack of surveys. No changes to suitable habitat since listing have been recorded, nor are they likely to have occurred.

  1. Flatback turtle nesting.

The average number nesting attempts measured over a one week period during the peak breeding period must not fall below 0.8 attempt/night in three successive years.

Unknown – but unlikely.

Parks Australia monitoring has shown turtle nesting occurs on Field Island and along the northern foreshore. Data collection in more recent times does not provide a baseline for assessment since listing. However, no impacts have been recorded in these habitats or evidence of a decline in nesting usage since commencement of annual monitoring.

  1. Yellow chat distribution and abundance.

Flood plain habitats of the site continue to support yellow chat in the long-term.

No.

Yellow chat have recently been recorded at the site by Parks Australia, therefore this LAC is met.

  1. Local endemic invertebrate species distribution and abundance.

As a minimum, sites at which each species has previously been recorded will continue to provide habitat for these species.

Unknown – but unlikely.


Data deficient due to a lack of surveys. No changes to suitable habitat since listing.


  1. Waterbird abundance – resident species

Average abundance of the most common species (magpie geese, wandering whistling-duck and plumed whistling-duck) will not fall below the minimum recorded seasonal values of Morton et al. (1991) on more than 30 percent of sampling occasions over a 10 year period.

Unknown – but unlikely.

The absence of systematically collected data over appropriate spatial and temporal precludes an assessment of this LAC. Major changes in bird populations are not however thought to have occurred since listing.

  1. Waterbird species (greater than one percent threshold).

As a minimum, sites at which each migratory shorebird has previously been recorded will continue to provide habitat for these species.

Unknown – but unlikely.

See above.

  1. Waterbird abundance – migratiory species (common species)

  2. Waterbird abundance – migratiory species (1% threshold species species)

Sites at which each migratiory shorebird species have been previously recorded (as per Chatto 2003) will continue to provide habitat for these species.

Unknown – but unlikely.

The absence of systematically collected data over appropriate spatial and temporal precludes an assessment of this LAC. Major changes in bird populations are not however thought to have occurred since listing.


  1. Barramundi abundance in billabongs

  2. Freshwater fish in billabongs

The average abundance of barramundi and other fish species will not fall below the minimum recorded values of Humphrey et al. (2005).

No.

Monitoring collected post listing of the Stage I area (1980) and Stage II area (1989) indicates that the populations of these fish are stable and within the bounds of natural variability.

  1. Saltwater crocodile abundance.

The average abundance of saltwater crocodiles will not fall below 35 000 individuals, which represents a 50 percent reduction in the 1994 estimated population.

No.

Monitoring indicates increasing saltwater crocodile abundance within the site since listing.

  1. Freshwater crocodile abundance.

The average abundance of freshwater crocodile will not fall below the minimum recorded values of Parks Australia (Figure 3-18) on more than 50 percent of sampling occasions over a 10 year period.

Unknown – but possible.

Monitoring indicates that there reduced dramatically over the last decade, possibly in response to sampling error, or actual changes in abundance due to such factors as increases in saltwater crocodile or cane toad invasion (noting that sampling is not done using systematic survey methods). There are insufficient data to assess whether there has been a change in populations since listing and whether this constitutes a change in ecological character.


  1. Surface water flows – annual flows and seasonality.

A greater than 20 percent change in the long-term mean annual flow of rivers constitutes an unacceptable change.

No.

There has been limited abstraction and no works to divert water from the freshwater reaches of the major river systems with annual flows within the bounds of natural variability since listing.

  1. Critical life stage processes.




  • The site no longer provide adequate refuge function for important flora and fauna species and populations; OR

  • Critical life-cycle processes have either substantially diminished (in terms of frequency or extent of usage) or are otherwise no longer being supported (relative to natural variability).

Unknown – but unlikely.

Patterns in waterbird usage in particular known breeding, roosting and feeding sites are not identified in the literature and data review as having experienced any significant change since listing (Stage I – 1980 and Stage II – 1989).
See above, re. aquatic species such as turtles and fish.

  1. Fire – frequency – escarpment and lowlands.

  • The area of wetland country burnt per year will not exceed maximum recorded baseline value more than twice over a 20 year period.

No


  1. Rock art, archaeological and other culturally significant sites protected


  • number of sites recorded;

  • number of sites managed/maintained

  • greater than 10 percent sites damaged/lost to preventable damage

  • no damage to representative and high priority sites.




Unknown

Kakadu National Park’s Cultural Database was established in the late 1980s and data has been gradually added until the present date, with most data collected during the 1990s. This does not provide a baseline of data prior to Kakadu National Park’s Ramsar declaration and therefore it is difficult to determine whether changes have occurred since Ramsar listing.

Information is not publicly available from other agencies such as the Northern Land Council and Aboriginal Areas Protection Authority to measure changes to culturally significant sites as recorded under the relevant Acts.



  1. ‘Living culture’ is maintained

Due to the lack of quantitative data regarding ‘living culture’ attributes, the limits of acceptable change are unable to be defined.

However a change in the ability of Bininj to own, occupy, access and use the land and resources of Kakadu National Park could result in a loss of ‘living culture’. A change in the ability of Bininj to use and transmit Bininj cultural practices, knowledge, language and spirituality could also result in a loss of ‘living culture’.




Unknown

Anecdotally, Bininj languages are decreasing in use and some languages (e.g. traditional Jawoyn) are only spoken by a limited number of people.

Half of Kakadu National Park is land under claim and therefore Bininj land ownership remains unclear.


Joint management arrangements continue to enable Bininj to occupy, access and use the land and resources. This facilitates the use and transmission of cultural practices, knowledge and spirituality.


Note: In characterising exceedance of an LAC in the Table, possible responses (based on data availability) include ‘Yes’, ‘No’, or ‘Unknown’. For those LACs where an ‘Unknown’ response is supplied, additional justification is provided based on expert opinion using the following categories: ‘Very Unlikely’; ‘Unlikely’; ‘Possible’; ‘Likely’; ‘Very Likely’.




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