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The potential impact of dryland salinity on the
threatened flora and fauna of New South Wales
By Melanie J. B. Zeppel, Brad R. Murray and Derek Eamus
This paper is based on research currently being
carried out by Brad Murray, Melanie Zeppel
and Derek Eamus from the Institute for
Water and Environmental Resource Management at the University of Technology, Sydney
(Gore Hill, NSW 2065, Australia. Tel: + 61 2 9514
4075,
Fax: +
61
2
9514
4079; email:
[email protected]).The project is part of a
larger research program exploring the impact of
dryland salinity on ecosystem structure and
function.
Summary We used digital map overlays in a geographical information system (GIS) to
quantify the potential impact of dryland salinity on the threatened flora and fauna of New
South Wales (NSW). Geographical areas of conservation priority were identified based on
richness of threatened species with distribution records overlapping dryland salinity. Two
alternative schemes – Interim Biogeographical Regionalization for Australia (regions) and
catchment boundaries (catchments) – were used to subdivide NSW. Sydney Basin, North
Coast and South-western Slopes regions – and Hunter, Sydney, Macquarie, Murrumbidgee
and Lachlan catchments – were identified as priority areas with more than 10 salinityoverlap species present. Five threatened plant species were identified as priority species
due to more than half of their known distributions overlapping areas of dryland salinity.
Threatened animal species of most concern had 10–50% of their records overlapping areas
of dryland salinity. Our findings demonstrate that landscape exposure to dryland salinity
should be used in conjunction with total richness of threatened species for prioritizing conservation of geographical areas with respect to the potential impact of dryland salinity on
threatened species.
Key words biodiversity, conservation, dryland salinity, geographical information system,
threatened species.
Introduction
t has recently been estimated that
180 000 hectares of New South Wales
(NSW) are exposed to or at high risk of
dryland salinity (NLWRA 2000). The risk
that such a vast salinity-affected area poses
to biodiversity has been identified as a
high-priority area of research (ANZECC
2001a). Quantifying the potential impact
of dryland salinity on the large number of
plant and animal species that are currently
threatened with extinction is an important
issue that requires immediate attention
(ANZECC 2001b).
Dryland salinity is caused by accelerated rising water tables mobilizing salt in
the soil (Ghassemi et al. 1995). Substantial
increases in the volume of water entering
groundwater systems, due to large-scale
clearing of deep-rooted perennial native
vegetation, have resulted in transport of
salt to the upper soil profile. Increased salt
concentrations and waterlogging of soils
pose a serious risk to biodiversity as they
can impact negatively on plant growth and
survival (Marcar 1993; Sun & Dickinson
1995) and adversely affect animal species
I
(Shine 1994; Stolley et al. 1999), all of
which have serious ramifications for community structure and ecosystem integrity
(Hart et al. 1991; ANZECC 2001b).
Resources available to commit to conserving threatened species are limited
(Myers et al. 2000). Therefore, to provide
prioritization for cost-effective conservation and management of threatened
species in NSW, we use digital map overlays in a geographical information system
(GIS) to identify:
1 Priority areas where substantial
numbers of threatened species occur
with distribution records overlapping
dryland salinity risk areas.
2 Priority species with a high proportion
of their distribution records overlapping dryland salinity risk areas.
We do not intend to infer causality in
any observed overlap between the incidence of salinity and the occurrence of
threatened species. Factors such as land
clearing and habitat fragmentation among
others have primarily been responsible for
so many species being placed at risk of
extinction. Rather, it is our purpose to
identify the additional threat potentially
posed to imperilled species by dryland
salinity.
Methods
Two alternative schemes were employed
for partitioning NSW to identify priority
areas (Fig. 1). The first method used the
Interim Biogeographical Regionalization
for Australia (IBRA; Fig. 1a) (Environment
Australia 2000). The IBRA framework has
been developed for conservation planning
and sustainable resource management in a
bioregional context. Using a range of continental data on environmental attributes,
85 regions across Australia (17 in NSW)
have been delineated, each reflecting a
unifying set of environmental influences
that shape the occurrence of flora and
fauna and their interaction with the physical environment (Environment Australia
2000). The second method used catchment boundaries (17 in NSW; Fig. 1b).
Catchments are increasingly being recognized as functional geographical areas
that integrate a variety of environmental
processes and human impacts on land-
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(a)
(b)
Figure 1. (a) Regions and (b) catchments of NSW recognized in the present study. AA, Australian Alps; BB, Bulloo-Bancannia; BBS, Brigalow
Belt South; BHC, Broken Hill Complex; BR, Border Rivers; CC, Coopers Creek; CH, Coffs Harbour; CHC, Channel Country; CO, Condamine; CP,
Cobar Peneplain; DRP, Darling Riverine Plains; HU, Hunter; LA, Lachlan; LF, Lake Frome; LM, Lower Murray; MA, Macquarie; MDD, Murray Darling
Depression; ML (region), Mulga Lands; ML (catchment), Menindee Lakes; MU, Murrumbidgee; NAN, Nandewar; NET, New England Tableland; NG,
Namoi-Gwydir; NNC, NSW North Coast; NSS, NSW South-western Slopes; RIV, Riverina; SB, Sydney Basin; SEC, South-east Corner; SEH, Southeastern Highlands; SS, Snowy-Shoalhaven; SSD, Simpson Strzelecki Dunefields; SY, Sydney; UM, Upper Murray; WA, Warrego.
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DRYLAND
scapes (Aspinall & Pearson 2000). The
latest available digital versions of region
and catchment boundaries were obtained
from National Parks and Wildlife Service
(NPWS) and Department of Land & Water
Conservation 2001.
Digital dryland salinity data were
obtained from the National Land and
Water Resources Audit, aggregated to
occurrences within 1 km grid cells.
Dryland salinity data were based on
regional-scale risk assessments undertaken by agencies using information on
known incidences of salinity and groundwater levels and trends coupled with soil
characteristics and topography (NLWRA
2000; for a NSW salinity risk map see
http://audit.ea.gov.au/ANRA land/docs/na
tional/Salinity_NSW.html). Land units with
groundwater within 2 m of the surface
were classed as being at high risk of
dryland salinity (NLWRA 2000).
Distribution records for threatened
flora and fauna listed on the Threatened
Species Conservation Act 1995 were
provided by NPWS. Extinct species,
marine mammals and records from Lord
Howe Island were not considered in our
analyses. Only spatially unique records for
each species were used (i.e. temporal
repeats of records at exactly the same location were excluded). Records were up to
date as of August 2001, with a resolution of
1 km grid cells, and are for vascular plants
and primarily vertebrate animals (< 1% of
records were for invertebrates) as so little
of the invertebrate fauna and non-vascular
flora has been studied.
Threatened species richness in relation
to dryland salinity was determined by
recording the occurrence of species in
each region and catchment with distribution records overlapping dryland salinity. Priority areas with high numbers of
salinity-overlap species were identified.
Ten or more species was considered to
be a ‘high’ count. The minimum sets of
regions and catchments with all species
with at least one record overlapping with
dryland salinity were also identified.
For each species we recorded the proportion of distribution records that overlapped with salinity. Species with more
than 50% of their records overlapping
salinity were considered priority species.
SALINITY
Species with between 10 and 50% of their
records overlapping salinity were also
recognized to be of conservation concern.
Because some records in the database
were fairly old (i.e. > 50 years) and species
may no longer occur at these locations,
two sets of analyses were initially carried
out. The first used only records from the
last 50 years, the second used all records in
the database (apart from exclusions noted
above). The qualitative outcomes of both
sets of analyses were virtually identical,
hence only the results of the analysis of
the complete dataset are presented.
Results
At least one threatened plant or animal
species was found in each region and
catchment (Tables 1,2). However, only
nine regions and 10 catchments were
found to have areas exposed to (or at high
risk from) dryland salinity (Tables 1,2).
Threatened species with distribution
records overlapping salinity were present
in all of these areas with the exception of
the Upper Murray catchment. Rankings of
regions and catchments based on richness
of salinity-overlap species were different
to ranks based on either total percentage
coverage of dryland salinity or the total
AND
THREATENED
SPECIES
number of threatened species present in
those areas (Tables 1,2). For example,
North Coast and South-eastern Highlands
regions ranked second and fifth in relation
to salinity-overlap species, but ranked
fourth and last, respectively, based on percentage dryland salinity (Table 1). More
notably, Coffs Harbour catchment ranked
first with respect to the total number of
threatened species present, but ranked
only sixth in relation to salinity-overlap
species (Table 2).
Three regions were identified as priority regions with more than 10 threatened
species with distribution records overlapping dryland salinity (Table 1). The
same three regions emerged as priority
areas when threatened flora and fauna
were considered separately (Table 1). Five
catchments were identified as priority
catchments with more than 10 salinityoverlap species (Table 2). The same five
catchments emerged as priority areas
when threatened fauna were considered
separately. Only the Sydney catchment was
identified as a priority area for threatened
flora with 14 salinity-overlap species.
Six of the nine regions (Sydney Basin,
Brigalow Belt South, NSW North Coast,
NSW South-western Slopes, South-eastern
Highlands, Riverina) and six of the 10
Table 1. Regions of NSW ranked by total richness of threatened species with distribution
records overlapping dryland salinity
Regions
Total
Sydney Basin
North Coast
South-western Slopes
Brigalow Belt South
South-eastern Highlands
Riverina
South-east Corner
Darling Riverine Plains
Nandewar
Australian Alps
Broken Hill Complex
Channel Country
Cobar Peneplain
Mulga Lands
Murray Darling Depression
New England Tableland
Simpson Strzelecki Dunefields
68
19
18
9
4
2
2
1
1
–
–
–
–
–
–
–
–
(259)
(274)
(69)
(69)
(110)
(60)
(100)
(69)
(45)
(29)
(46)
(29)
(59)
(32)
(63)
(116)
(26)
Richness
Flora
21
5
4
2
0
1
1
0
0
–
–
–
–
–
–
–
–
(149)
(147)
(23)
(18)
(50)
(15)
(30)
(21)
(15)
(8)
(13)
(9)
(18)
(9)
(18)
(50)
(4)
Fauna
47
14
14
7
4
1
1
1
1
–
–
–
–
–
–
–
–
(110)
(127)
(46)
(51)
(60)
(45)
(70)
(48)
(30)
(21)
(33)
(20)
(41)
(23)
(45)
(66)
(22)
Dryland
salinity (%)
7.52
1.62
8.22
2.23
1.27
0.72
0.07
0.07
0.43
0
0
0
0
0
0
0
0
‘–’ means that no salinity-overlap species were present in the region. Total richness is also broken
down into flora and fauna components. The number of threatened species (salinity-overlap + nonoverlap species) in each region is provided in parentheses. Also shown is the extent of dryland
salinity as a percentage of total land area in the region.
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Table 2. Catchments of NSW ranked by total richness of threatened species with distribution
records overlapping dryland salinity
Catchments
Total
Hunter
Sydney
Macquarie
Murrumbidgee
Lachlan
Coffs Harbour
Namoi-Gwydir
Snowy-Shoalhaven
Border Rivers
Upper Murray
Bulloo-Bancannia
Condamine
Coopers Creek
Lake Frome
Lower Murray
Menindee Lakes
Warrego
50
36
15
12
11
9
4
2
1
–
–
–
–
–
–
–
–
(159)
(223)
(80)
(96)
(77)
(284)
(88)
(148)
(60)
(33)
(47)
(39)
(7)
(27)
(32)
(84)
(33)
Overlap
Flora
Fauna
7
14
5
2
0
4
1
1
0
–
–
–
–
–
–
–
–
43
22
10
10
11
5
3
1
1
–
–
–
–
–
–
–
–
(60)
(120)
(30)
(32)
(21)
(156)
(25)
(63)
(30)
(5)
(12)
(5)
(1)
(9)
(7)
(27)
(8)
(99)
(103)
(50)
(64)
(56)
(128)
(63)
(85)
(30)
(28)
(35)
(34)
(6)
(18)
(25)
(57)
(25)
Dryland
salinity (%)
10.69
2.91
4.01
2.62
2.54
0.15
0.35
0.05
0.29
0.61
0
0
0
0
0
0
0
‘–’ means that no salinity-overlap species were present in the catchment. Total richness is also
broken down into flora and fauna components. The number of threatened species (salinityoverlap + non-overlap species) in each catchment is provided in parentheses. Also shown is the
extent of dryland salinity as a percentage of total land area in the region.
catchments (Hunter, Sydney, Macquarie,
Murrumbidgee, Coffs Harbour, Lachlan)
comprised the minimum sets, which
included all threatened species with some
degree of overlap with dryland salinity.
Totals of 32 threatened plant (13 endangered, 19 vulnerable; Table 3) and 55
threatened animal (9 endangered, 46 vulnerable; Table 4) species were found to
have distribution records overlapping
dryland salinity. Incidences of overlap
occurred within only one region or catchment for most threatened species (plants:
29/32 species for regions, 31/32 for catchments; animals: 34/55 for regions, 29/55
for catchments). There was wide phylogenetic latitude to the species whose
distributions overlapped with salinity
(17 different families for plants, 31 for
animals). On average, threatened plant
species had a larger proportion of their
records overlapping salinity than animal
Table 3. Threatened plant species ranked by the proportion of distribution records overlapping dryland salinity†
Taxa
TS
Family
Salinity overlap
Regions
Catchments
Zannichellia palustris
Persoonia pauciflora
Pultenaea parviflora
Grevillea juniperina var juniperina
Eucalyptus parramattensis ssp. decadens
Eucalyptus pumila
Dillwynia tenuifolia
Persoonia nutans
Swainsona recta
Indigofera efoliata
Micromyrtus minutiflora
Brachyscome muelleroides
Prostanthera discolor
Allocasuarina glareicola
Eucalyptus glaucina
Pimelea spicata
Pterostylis saxicola
Zieria obcordata
Grevillea parviflora
Acacia pubescens
Eucalyptus benthamii
Calotis glandulosa
Eucalyptus kartzoffiana
Epacris purpurascens var purpurascens
Corokia whiteana
Tinospora tinosporoides
Acacia bynoeana
Austrostipa wakoolica
Bothriochloa biloba
Cryptocarya foetida
Cynanchum elegans
Syzygium hodgkinsoniae
E
E
E
V
V
V
V
E
E
E
V
V
V
E
V
E
E
E
V
V
V
V
V
V
V
V
E
E
V
V
E
V
Zannichelliaceae
Proteaceae
Fabaceae
Proteaceae
Myrtaceae
Myrtaceae
Fabaceae
Proteaceae
Fabaceae
Fabaceae
Myrtaceae
Asteraceae
Lamiaceae
Casuarinaceae
Myrtaceae
Thymelaeaceae
Orchidaceae
Rutaceae
Proteaceae
Mimosaceae
Myrtaceae
Asteraceae
Myrtaceae
Epacridaceae
Corokiaceae
Menispermaceae
Mimosaceae
Poaceae
Poaceae
Lauraceae
Asclepiadaceae
Myrtaceae
1.00
0.95
0.70
0.67
0.52
0.40
0.33
0.29
0.29
0.25
0.21
0.20
0.20
0.18
0.18
0.16
0.13
0.13
0.11
0.10
0.10
0.07
0.06
0.04
0.03
0.03
0.02
0.02
0.02
0.01
0.01
0.01
SB
SB
SB
SB
SB
SB
SB
SB
NSS
NSS
SB
NSS
SB
SB
NNC, SB
SB
SB
NSS
SB
SB
SB
BBS
SEH
SB
NNC
NNC
SB
RIV
BBS, SB
NNC
SB
NNC
HU
HU
SY
SY
HU
HU
SY
SY
MA, MU
MA
SY
MU
HU
SY
HU
SY
SY
MA
SY
SY
SY
MA
SS
SY
CH
CH
SY
MU
HU, MA, NG
CH
SY
CH
†Total
(2)
(20)
(66)
(3)
(21)
(5)
(42)
(34)
(14)
(4)
(24)
(5)
(5)
(11)
(51)
(49)
(8)
(8)
(9)
(155)
(21)
(15)
(18)
(28)
(37)
(33)
(84)
(47)
(125)
(71)
(71)
(88)
number of records in parentheses.
E, endangered; TS, threatened status; V, vulnerable.
Regions and catchments where overlap occurs are provided for each species. (See Fig. 1 for description of abbreviations.)
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DRYLAND
SALINITY
AND
THREATENED
SPECIES
Table 4. Threatened animal species ranked by the proportion of distribution records overlapping dryland salinity†
Taxa
TS
Family
Salinity overlap
Regions
Catchments
Meridolum corneovirens
Ardeotis australis
Litoria aurea
Cacophis harriettae
Lathamus discolor
Polytelis swainsonii
Anseranas semipalmata
Erythrotriorchis radiatus
Limicola falcinellus
Limosa limosa
Phascolarctos cinereus
Rostratula benghalensis
Xanthomyza phrygia
Miniopterus schreibersii
Oxyura australis
Phascogale tapoatafa
Stictonetta naevosa
Burhinus grallarius
Chalinolobus dwyeri
Charadrius leschenaultia
Ephippiorhynchus asiaticus
Falco hypoleucos
Grantiella picta
Hamirostra melanosternon
Irediparra gallinacea
Mormopterus norfolkensis
Myotis adversus
Neophema pulchella
Ninox connivens
Petaurus norfolcensis
Saccolaimus flaviventris
Scoteanax rueppellii
Botaurus poiciloptilus
Calidris tenuirostris
Charadrius mongolus
Dasyurus maculatus
Falsistrellus tasmaniensis
Grus rubicunda
Ixobrychus flavicollis
Lophoictinia isura
Miniopterus australis
Nyctophilus timoriensis
Pachycephala inornata
Petrogale penicillata
Pteropus poliocephalus
Ptilinopus superbus
Sterna albifrons
Tyto novaehollandiae
Xenus cinereus
Cacatua leadbeateri
Calyptorhynchus lathami
Ninox strenua
Pandion haliaetus
Petaurus australis
Pseudophryne australis
E
E
E
V
E
V
V
E
V
V
V
V
E
V
V
V
V
E
V
V
E
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
E
V
V
V
V
V
V
V
V
Camaenidae
Otididae
Hylidae
Elapidae
Psittacidae
Psittacidae
Anatidae
Accipitridae
Scolopacidae
Scolopacidae
Vombatidae
Rostratulidae
Meliphagidae
Vespertilionidae
Anatidae
Dasyuridae
Anatidae
Burhinidae
Vespertilionidae
Charadriidae
Threskiornithidae
Falconiidae
Meliphagidae
Accipitridae
Burhinidae
Molossidae
Vespertilionidae
Psittacidae
Strigidae
Petauridae
Emballonuridae
Vespertilionidae
Ardeidae
Scolopacidae
Charadriidae
Dasyuridae
Vespertilionidae
Otididae
Ardeidae
Accipitridae
Vespertilionidae
Vespertilionidae
Pachycephalidae
Macropodidae
Pteropodidae
Columbidae
Laridae
Tytonidae
Scolopacidae
Cacatuidae
Cacatuidae
Strigidae
Pandionidae
Petauridae
Leptodactylidae
0.32
0.25
0.12
0.08
0.07
0.07
0.04
0.04
0.04
0.04
0.04
0.04
0.04
0.03
0.03
0.03
0.03
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.02
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.01
0.00
0.00
0.00
0.00
0.00
0.00
SB
BBS
SB
NNC
NNC, NSS, SB
NSS, RIV, SEH
NNC, SB
NNC
SB
NSS, SB
BBS, NNC, NSS, SB, SEH
SB
BBS, NSS, SB, SEH
NAN, NSS, SB
NNC, SB, SEH
NNC, SB
SB
SB
SB
SB
NNC, SB
NSS
SB
SB
SB
SB
SB
BBS, NSS, SB
BBS, NNC, NSS, SB
SB
SB
SB
SB
SB
SB
NNC, NSS, SB
SB
NSS
SB
NSS, SB
NNC, SB
SB
NSS
BBS, SB
NNC, SB
SB
SB
NNC, SB, SEC
SB
DRP, NSS
BBS, NNC, SB
SB
SB
SB
SB
SY
MA
HU, SY
CH
HU, LA, MU
LA, MA, MU
CH, HU
HU
HU
HU, LA, SY
HU, LA, MA, NG, SY
HU
MU, LA, MA, MU, SY
BR, HU, LA, SY
HU, MU, SY
CH, MU
HU
SY
HU
HU
CH, HU
LA
HU, SY
HU
HU
SY
HU, SY
HU, LA, MA, MU, SY
HU, LA, MA, MU
HU, MU, SY
HU, SY
HU, SY
HU
HU
HU
HU, MA
HU, SY
MU
HU
HU, MU, SY
HU
HU
LA
NG, SY
HU, SY
HU
HU
HU, SS, SY
HU
CA, MA
CH, HU, MA
HU
HU
HU
SY
(117)
(4)
(246)
(12)
(133)
(518)
(96)
(49)
(28)
(78)
(7703)
(48)
(605)
(626)
(132)
(374)
(154)
(151)
(110)
(46)
(441)
(60)
(120)
(56)
(121)
(133)
(199)
(438)
(284)
(470)
(110)
(285)
(139)
(88)
(81)
(1281)
(369)
(312)
(149)
(286)
(546)
(122)
(191)
(399)
(723)
(106)
(317)
(755)
(68)
(805)
(2620)
(1694)
(681)
(1986)
(376)
†Total
number of records in parentheses.
E, endangered; TS, threatened status; V, vulnerable.
Note that 0.00% means that < 0.01% of records overlap with salinity. Regions and catchments where overlap occurs are provided for each species.
(See Fig. 1 for description of abbreviations.)
ECOLOGICAL MANAGEMENT & RESTORATION VOL 4 SUPPLEMENT FEBRUARY 2003
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species (means with standard deviations,
23.2 ± 26.5% vs 3.2 ± 5.5%). Five threatened plant species were identified as priority species with more than half of their
distribution records overlapping dryland
salinity (Table 3). Sixteen threatened plant
species were considered of concern with
between 10 and 50% of their records overlapping salinity (Table 3). No threatened
animal species had more than 50% of its
distribution records overlapping salinity.
However, three threatened animal species
were considered of concern with between
10 and 50% of their records overlapping
salinity (Table 4).
Discussion
Human activities have contributed to the
extinction of many native species and
placed many more species at risk. Dryland
salinity is a symptom of the massive environmental changes wrought upon the
Australian landscape. Our intention in the
present study was to explore the potential
for dryland salinity to add further to the
substantial amount of biodiversity lost due
to activities such as land clearing for agricultural practices, habitat fragmentation
and the introduction of exotic species.
While these processes continue to contribute to a decline in biodiversity, there
is a paucity of information concerning the
potential risks posed by dryland salinity to
biodiversity and ecosystem structure and
function. Our study is timely, considering
that identifying threatened species most
at risk from dryland salinity has recently
been highlighted as an urgent issue for biodiversity conservation (SRDCC 2002).
Our findings demonstrate that the most
useful prioritization of regions or catchments for the management of the potential
impact of dryland salinity upon threatened
species cannot be based on surrogate
measures such as extent of occurrence of
dryland salinity or total number of threatened species present. Rankings of regions
and catchments based on richness of
salinity-overlap species were different to
ranks based on coverage of dryland salinity
and the total number of threatened
species present in those areas.This point is
further emphasized by the simple fact that
many areas have been reported with no
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record of dryland salinity but with large
numbers of threatened species (e.g. New
England and Murray Darling Depression).
Evidence suggests that salinization of
the soil in the 1–2 m range of the surface
can adversely affect native vegetation
(Ghassemi et al. 1995). The effects of
increased soil salinity and waterlogging on
Australian native plant species overwhelmingly consist of deleterious effects on plant
growth and vigour (e.g. Marcar 1993; Sun
& Dickinson 1995). In addition, only a
small percentage of Australian tree species
occurs naturally in areas subject to prolonged waterlogging (Froend et al. 1987).
Most likely, the overlap between distribution records and dryland salinity described
in the present study suggests that there
will be an overall negative impact on
native biodiversity. However, any threatened halophytic species stand a chance of
benefiting to some degree from increased
salinity levels. An imperative for further
research will be to compare and classify
threatened species for their response to
increased salinity in laboratory and field
experiments. In addition, the lack of resolution below 1 km2 of the data used in our
analysis means that ground-truthing of the
patterns observed here are essential. For
example, threatened plant species may
be growing within patches of upland
remnant vegetation that is not experiencing the effects of dryland salinity further
downslope.
Threatened plant species averaged
higher proportions of their distribution
records overlapping salinity than threatened fauna. This is noteworthy as both
waterlogging and increased soil salinity are
more likely to have an immediate impact
on plants (especially long-lived and slowreproducing species). In general, plant
species are incapable of moving quickly to
unaffected areas given their slow colonization potential. In contrast, most threatened
animal species would have a comparatively simpler task in migrating to unaffected areas. However, there are notable
exceptions (e.g. the Large Land Snail,
Meridolum corneovirens). Loss of plant
species will also undoubtedly impact upon
animal species through loss of habitat.
Distribution data such as those used in
our study for threatened species constitute
ECOLOGICAL MANAGEMENT & RESTORATION VOL 4 SUPPLEMENT FEBRUARY 2003
existing knowledge, but they are biased.
They are not the result of systematic
surveys, and come from areas where more
intensive survey effort has been conducted (Margules & Austin 1994). As more
knowledge accumulates regarding the
extent of dryland salinity and the distribution of threatened species it will be necessary to re-examine the priorities suggested
here. In addition, the areas and species we
have prioritized are based primarily on
well-studied groups in the vertebrate fauna
and vascular flora. How representative are
our patterns for less well-studied groups
such as invertebrates and non-vascular
plants? Although a set of areas in which
one major taxon is well represented can
also represent diversity in unrelated taxa
(Reid 1998), some studies have demonstrated the failure of ‘hotspots’ (areas
particularly rich in species) to correspond
across taxa (Prendergast et al. 1993;
Dobson et al. 1997). Therefore, it is crucial
that systematic biological surveys for
underrepresented taxa covering poorly
known areas are a target for future
research.
Conclusion
Few studies have specifically addressed
the issue of the impact of dryland salinity
on Australia’s biodiversity. Preliminary
work has resulted in the listing of 100
species of flora and fauna as being susceptible to increasing salinity in Victoria
(Ghassemi et al. 1995), while preliminary
studies have estimated that up to 4–8%
and 9–17% of all records of threatened
flora and fauna, respectively, in that State
are predicted to be located in shallow
water-table areas by 2050 (ANZECC
2001b). In the south-west agricultural
region of Western Australia, Keighery et al.
(2000) have shown that 450 endemic
plant species are facing increased salinity
levels.The findings of our study contribute
further to this growing body of evidence
for the potential erosion of Australia’s
unique biodiversity due to dryland salinity.
It is noteworthy that in addition to habitat
destruction, fragmentation, altered fire
regimes and the incursion of exotic
species, native plants and animals must
cope with the potentially devastating
DRYLAND
effects of dryland salinity. Nevertheless, the
opportunity remains to prevent considerable loss of biodiversity by focusing on the
species and geographical regions identified in the present study as warranting
immediate attention.
Acknowledgements
This work was supported by the Department of Agriculture, Fisheries and Forestry
– Australia and Land & Water Australia
(AFFA Science Award to Young People
2001 to BRM), and a UTS Start-Up grant.
We thank Dan Faith, Greg Gowing, Sarah
Kamarudin, and Elijah Price for helpful
discussions, and two anonymous reviewers for constructive comments on an
earlier version of the paper.
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