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4.3Summary of Limits of Acceptable Change


Table 4 -21 lists the LAC indicators relevant to each critical component process and service/benefit, and Table 4-3 outlines the specific LACs. For each LAC indicator outlined in the Table 4-3, the following information is provided: (i) the degree of acceptable change based on the typology outlined in Table 4 -20 (refer to Appendix B for details); (ii) LAC values describing the degree of allowable change (relative to baseline conditions – see Appendix B) in the short-term (within 20 years of ECD preparation) or the long-term (greater than 20 years of ECD preparation); (iii) the spatial and temporal scale at which measurements must be undertaken to assess the LAC; (iv) data quality rating for baseline data and (v) secondary critical component, process and service/benefits addressed by the LAC. Short-term LACs should be reviewed to determine their potential applicability in subsequent periods (that is, post 2030).

As shown in Table 4-3, in most cases, the LACs in the current study have been subjectively derived (level 3) based on the best scientific judgement of the authors. This is due to:



  • a largely incomplete data set for key parameters such as waterbird usage, fish usage and environment condition (both geographically and temporally) since listing, and

  • the general lack of scientific knowledge about the response of particular species and habitats to multiple stressors (for instance a combination of water flows, salinity and habitat availability).

Further discussion on these information gaps is provided in Section 7.1 of this document.

Table 4 21 Critical components, processes and services/benefits, and relevant LAC indicators



Critical Element

LAC

Critical Components

C1 – Mangroves

1

C2 – Melaleuca Forests

2

C3 – Palustrine Wetlands and Billabongs

3

C4 – Waterfalls, Seeps and Waterholes

4

C5 – Populations of Migratory and Resident Waterbirds

10, 11, 12, 13

C6 – Populations of Freshwater Fish

15

C7 – Populations of Freshwater and Saltwater Crocodiles

16, 17

C8 – Populations of Threatened Sharks

5

C9 – Yellow Chat Populations

8

C10 - Pig-nosed Turtle Populations

6

C11 – Locally Endemic Invertebrate Species

9

Critical Processes

P1 – Fluvial Hydrology

18

P2 – Fire Regimes

20

P3 – Breeding of Waterbirds

19

P4 – Flatback Turtle Nesting

7

Critical Services/Benefits

S1 – Maintenance of Global Biodiversity

5, 6, 7, 8, 9

S2 – Fisheries Resource Values

14, 15

S3 – Contemporary Living Culture

21, 22


Table 4 22 Limits of acceptable change (LAC)

Number

Indicator and Primary critical Component / Process/Service for the LAC


Acceptable Change

(Short term or long term)

Limit of Acceptable Change

Spatial scale/temporal scale of measurements

Underpinning baseline data

Secondary critical components/ processes/services addressed through LAC

1

Reduction in mangrove extent (Component 1).

Large change

(short term)



Mangrove extent will not decline by greater than 25 percent of the following baseline values:

Stage I (1984 closest date prior to 1980 listing)



  • EAR = 21 km2

Stage II (1991 closest date to listing)

  • SAR = 36 km2

  • WAR = 42.5 km2

  • Wildman = 14 km2

Note: An increase in mangrove does not in itself represent a change in character unless other components or services/benefits significantly affected.



    • Minimum three sample events separated by at least two year intervals.

    • Measured over a 20 year period from date of ECD preparation.




1A


Service 3

2

Melaleuca forest extent (Component 2).

Large change

(short term)



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

    • Minimum three sample events separated by at least two year intervals.

    • Measured over a 20 year period from the date of ECD preparation.

2A

Service 3

3

Palustrine wetlands and billabongs (Component 3).

No change

(short term)



No permanent loss of billabongs in the South Alligator River catchment (as mapped by BMT WBM 2009) as a direct result of anthropogenic changes in hydrological or geomorphological processes.

    • As observed on an annual basis.

    • Measured over a 20 year period from the date of ECD preparation.

2C

Component 5, 6, 7 and 10

Process 1, 3

Service 2 and 3


4

Waterfalls, seeps and waterholes (Component 4)

No change

(short term and long term)



No drying of any perennial seeps and permanent waterholes.

Absolute value.

1B

Component 5, 6, 7, 10 and 11

Process 1

Service 1 and 3


5

Spear-tooth shark and northern river shark distribution and abundance (Component 8).

No change

(long term)



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.



    • Absolute value.

    • Absence of these species during three successive sampling occasions (separated by at least one year intervals) will represent an exceedance of LAC.

3B

Service 1

6

Pig-nosed turtle distribution and abundance (Component 10).

Large change

(short term)





Within the known core habitat of this species (as outlined in Georges and Kennett 1989; see Figure 3-10), the average density of pig-nosed turtle will not fall below 13.5 turtles/ha (30 percent reduction of minimum baseline value of 22.5 turtles/ha). Note that Stage specific data are not available, and baseline values were taken post-Ramsar site listing.

    • Minimum three sample events separated by at least two year intervals.

    • Measured over a 20 year period from date of ECD preparation.

2B

Service 1

7

Flatback turtle nesting (Service 1).

Small change

(short term).



The average number nesting attempts at core turtle nesting areas on Field Island, as measured over a one week period during the peak breeding period, must not fall below 0.8 attempts/night in three successive years (20 percent reduction in the minimum baseline value of one attempt a night during the peak breeding season). NB: baseline values were taken post-Ramsar site listing.

    • Minimum five sample events.

    • Measured over a 20 year period from date of ECD preparation.

2A

Process 4

8

Yellow chat distribution and abundance (Component 9).

Large change

(long term)



Floodplain habitats of the site continues to support yellow chat in the long-term.

    • Absolute value.

    • Absence of yellow chat at known sites on South Alligator River floodplain (north of Arnhem Highway) during three successive dry season sampling events (separated by at least one year intervals) over any 20 year period will represent an exceedance of LAC.

3C

Service 1

9

Local endemic invertebrate species distribution and abundance (Component 11).

No change

(short term or long term)



As a minimum, sites at which each species has previously been recorded will continue to provide habitat for these species, unless it can be demonstrated that the species (i) can re-establish naturally and/or (ii) shows great variability in its presence within a site.

    • Absolute value.

    • Absence of any endemic species during three successive sampling occasions (carried out in appropriate seasons and separated by at least one year intervals) over any 20 year period will represent an exceedance of LAC.

2B

Service 1

10

Waterbird abundance (excluding migratory shorebirds) (Component 5).

Moderate change

(short term, individual floodplain context)





Average abundance of the most common species (magpie geese, wandering whistling-duck and plumed whistling-duck) will not fall below the corresponding minimum recorded seasonal values of Morton et al. (1991) for Magela, Nourlangie and East Alligator River floodplains on more than 30 percent of sampling occasions over a 20 year period.

  • Recommended baseline monitoring program should be based on aerial survey protocols of Morton et al. (1991) for Magela, Nourlangie and East Alligator River floodplains. The survey coverage should be expanded to include the South Alligator River floodplains (esp. Boggy Plains). Based on a ten year cycle, the recommended program should comprise a minimum three annual sampling periods, each separated by at least one year. Each annual sampling period is comprised of one late dry season and one wet season survey.

  • LAC based on at least three annual surveys measured over a 20 year period from date of ECD preparation.

2B

Process 3

11

Waterbird species (greater than one percent threshold; excluding migratory shorebirds) - magpie geese, wandering whistling-duck, plumed whistling-duck, radjah shelduck, pacific black duck, grey teal, brolga, and black-necked stork (Component 5).

Moderate change

(short term)



Insufficient current, systematically collected baseline data. Long-term LAC to be confirmed on completion of data collection as part of the recommended baseline monitoring program for Indicator 10 above. The following LAC is recommended in the interim:
Average abundance of each species will not fall below the corresponding minimum recorded seasonal values of Morton et al. (1991) for Magela, Nourlangie and East Alligator River floodplains on more than 30 percent of sampling occasions over a 20 year period.

  • For recommended baseline program, spatial and temporal characteristics as for Indicator 16 above.

  • LAC based on at least three annual surveys measured over a 20 year period from date of ECD preparation. An annual survey comprises a representative dry and wet season event.

2B

Process 3

12

Migratory shorebird distribution and abundance (Component 5).

Moderate change

(short term and long term)



Insufficient current, systematically collected baseline data. Should an adequate baseline be established, limits of acceptable change could be calculated based on the range of variability. In the interim, and as a minimum, sites at which each migratory shorebirds have previously been recorded (as per Chatto 2003) will continue to provide habitat for these species.


Recommended baseline monitoring program should include:

  • A combination of aerial and ground surveys.

  • Representative coverage of primary habitats, i.e. intertidal coastline (including lower estuary areas), floodplain wetlands and grasslands.

A minimum of three annual sampling periods, each separated by at least one year, and within a 20 year period. Each annual sampling period is comprised of two seasonal survey events, i.e. a late dry and a late wet season survey.



2B

Process 3

13

Migratory shorebird species (greater than one percent threshold) - marsh sandpiper, little curlew, common sandpiper, Australian pratincole, and sharp-tailed sandpiper (Component 5).

Large change

(long term)





Average abundance of each species (derived from at least three annual surveys over a 10-year period) does not fall below the 20th percentile baseline value, or below one percent of their relevant flyway population, due to altered habitat conditions within the site.
Until completion of a suitable baseline monitoring program (and determination of LACs), the following interim LAC is recommended: one or more species (whose population is currently known to exceed the one percent threshold) no longer occurs within the site.
For LACs, it must be clearly demonstrated that such changes occur outside of the boundaries of what is considered to be natural variability and/or (and in regards to migratory shorebirds) not underpinned by significant external factors which are known to have impacted on a species within other parts of the flyway for the species (staging sites or breeding grounds).



Recommended baseline monitoring program should target the following areas:

  • Coastline, including lower reaches of major rivers (about 10 km from river mouth) – marsh sandpiper, common sandpiper, and sharp-tailed sandpiper.

  • South Alligator River floodplains (east to Boggy Plains and Billyangardee Spring) - marsh sandpiper, little curlew, Australian pratincole, and sharp-tailed sandpiper.

Recommended program should comprise a minimum three annual sampling periods separated by at least one year (and within a 10 year period). Each annual sampling period is comprised of two seasonal survey events, one during late-March to mid-May (wet season and corresponding to northward migration), and the second, during mid-September to mid-November (late dry-season and corresponding to southward migration).
LAC based on at least three annual surveys measured over a 20 year period from date of ECD preparation. An annual survey comprises a representative dry and wet season event (as described above).

2B

Process 3

14

Barramundi abundance (Service 2).

Large change

(short term)



The average abundance of barramundi will not fall below the minimum recorded values of Humphrey et al. (2005) at both Sandy and Mudginberri Billabongs on more than 50 percent of sampling occasions over a 20 year period.
Note: Population data are available for Yellow Water (estimated population of 6000 fish in 1994). In the absence of information describing temporal patterns in abundance, there is insufficient data to establish an LAC for barramundi population size.

    • Minimum six sample events separated by at least one year.

    • Measured over a 20 year period from date of ECD preparation.

2A

Service 3

15

Freshwater fish abundance in billabongs (Component 6).

Large change

(short term, whole of site scale)




The average abundance of freshwater fish species will not fall below the minimum recorded values of Humphrey et al. (2005) at both Sandy and Mudginberri Billabongs on more than 50 percent of sampling occasions over a 20 year period.

    • Minimum six sample events separated by at least one year.

    • Measured over a 20 year period from date of ECD preparation.

2A

Service 2 and 3

16

Saltwater crocodile abundance (Component 7).

Large change

(long term)



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


    • Minimum five sample events separated by at least one year.

    • Measured over a 20 year period from date of ECD preparation.

3A




17

Freshwater crocodile abundance (Component 7).

Large change

(short term, whole of site scale)




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 20 year period.

    • Minimum six sample events separated by at least one year.

    • Measured over a 20 year period from date of ECD preparation.

2B




18

Surface water flows – annual flows (Process 1).

Large change (short term)

Baseline annual flow values vary over time scales measured in decades, and climate change is predicted to result in further major changes. In the interim the following is recommended until it can be refined:

A greater than 20 percent change in the long-term mean annual flow constitutes an unacceptable change based on the following long-term average values:



  • East Alligator = 6.87 million ML/year

  • South Alligator = 5.75 million ML/year

  • West Alligator/Wildman = 0.815 million ML/year

    • Measured over 20 year period.

    • Values measured at existing gauging stations near mouth of each river.

1A




19

Critical life stage processes (Process 3):

  • Feeding and roosting habitat for 53 waterbird species (including 29 migratory shorebird spp.).

  • Dry weather refuge for large aggregations of waterbirds at the Magela and Nourlangie floodplains.

  • Feeding, breeding and dry weather refuge sites for species listed in Service 3.

Large change (short term)

  • Exceedance of LACs in the Species and Habitat LAC Table; OR

  • Based on expert opinion, the site no longer provides adequate refuge function for important flora and fauna species and populations; OR

Based on expert opinion, critical life-cycle processes identified in column 1 (e.g. known feeding sites, roosting sites, breeding sites, etc) have either substantially diminished (in terms of frequency or extent of usage) or are otherwise no longer being supported (relative to natural variability).



Absolute value.

3C




20

Fire – frequency (Process 2).

Large change (short term)

  • The area of wetland burnt per year within individual habitat types will not exceed maximum recorded baseline values outlined in Gill et al. (2000) more than twice over a 20 year period.

Baseline values may not represent optimal fire regimes. These values should be reviewed to determine whether other elements of ecological character could be affected by through the maintenance of these regimes.



    • 20 year measurement periods from time of ECD preparation.

    • Whole-of-site spatial scale and within plateau, lowland and floodplain habitats.




1A




21

Loss or damage to rock art sites, archaeological sites and materials (potentially due to human interference, feral animal damage, weathering, environmental degradation and natural processes including vegetation growth, storms and tidal inundation of flood plains) (Service 3).

Medium change

(short term)

No change




Changes to the following indicators are considered unacceptable:

  • A greater than 10 percent reduction in the number of recorded sites due to preventable damage (e.g. human interference, feral animal damage, weathering, environmental degradation) (NB: Kakadu National Park has 203 sacred sites recorded on its list of 5000 recorded cultural sites (with possibly another 2000 sites which have not yet been recorded) stored on a cultural database at Kakadu National Park Headquarters).

  • A greater than 10 percent reduction in the number of sites managed/maintained (outlined in the cultural database at Kakadu National Park Headquarters) due to preventable damage.

No damage to representative and high priority sites (to be identified through Kakadu National Park’s Cultural Heritage Program).



Absolute measure.

2B




22

Indigenous ‘living culture’ (including the body of Traditional Ecological Knowledge, Bininj languages, traditional fire and land management practices, traditional resource use) (Service 3).

N/A

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

N/A

N/A



Note that where particular areas have been quantified, these are based on the best available data/mapping and should be revised if a more appropriate baseline dataset is derived.

** These cultural elements could be monitored by Bininj and reported through cultural heritage workshops to discuss indicators of ‘living culture’, including: use and transmission of languages, cultural practices, cultural knowledge; access to land and resources; and the ability to undertake spirituality practices

N/A = no available data



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