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INTRODUCTION
The Biodiversity Series
This report is the fourth in the Biodiversity
S~ries produced by the Department of the
Environment, Sport and Territories. The series
intends to provide information about aspects of
Australia's considerable biodiversity, including
its global and national significance, and its
conservation and management status. Many of
the papers iri the Series will consist of reports
prepared for the Biodiversity Unit on a range of
biodiversity related subjects..
This report has been written by scientists
within the CSIRO Division of Wildlife arid
Ecology under commission to the Biodiversity
Unit. It investigates the significance of refugia
to biodiversity in the arid and semi -arid zones
of Australia, and examines the management
issues confronting them.
Some 70 per cent of Australia is included in the
study area. The area is of vital economic
importance and is also significant as a reservoir
of biodiversity, much of which (particularly
plant and invertebrate diversity) remains to be
discovered. Within this vast dry area pockets
- exist which, because they retain moisture, or
because they have been isolated from climatic
or human-induced changes, act as refugia or
refuges. These refugia contain concentrations
of plants and animals, sometimes in unique
ecosystems. Many of these organisms are relicts
of millennia old faunas and floras and as such
are of very great scientific interest. Many
refugia are places to which populations of
plants and animals retract in the face of adverse
environmental conditions such as Widespread
drought, and still others have acted as refuges
from land clearing and exotic animal invasions
of the last two centuries.
This report examines the 76 refugia which can
be identified in arid and semi-arid Australia
. from all available literature and describes their·
known significance'for biodiversity .
conservation, including endangered species,
species of evolutionary importance, and species·
which are restricted to these areas. Land uses
and management issues are also identified. It is
noteworthy that in s()me regions, fewer refugia
than expected were found in references,
perhaps reflecting a lack of data. An appendix
explores a methodology for identifying
ecological refugia.
The authors have made a significant
contribution to understanding the importance·
of refugia in the drier areas of Australia. This
report is a valuable addition to the Biodiversity
Series.
Department of the Environment, Sport and
Territories
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1. TERMS OF REFERENCE
The report is to consolidate and summarise
information on refugia in Australia's arid and semiarid areas, their value and role in conserving
biological diversity and in maintaining the ecological
sustainability of surrounding areas, and the
management requirements for their long term
.sustainability. The project was designed to cover the
points outlined below.
1.1. Identity of known biological refuges
Location, extent, type (e.g. ephemeral wetland,
mound spring, cave, gorge, .etc.).
,
1.2. Importance for the conservation of
biological diversity
Species known to be endemic to the area.
Rare or endangered 'species found there.
Significant populations.
1.3. Importance for ecological sustainability
of surrounding areas
Importance for maintenance of natural populations,·
including those species which help regulate pest
outbreaks.
Role in reducing land degradation, including role as
seed banks.
1.4. Management requirements
Threats posed: type and extent.
Potential to reverse degradation or eliminate threats.
Current land uses which conflict or may conflict
with biodiversity conservation.
Type of land management.
Gaps in knowledge are delineated. In describing the
importance for the conservation of biodiversity,
estimates of importance are included, and the known
and potential values of each refuge are noted. A
summary 6f management r~quirements is also
provided.
Status as wetland sites of importance (including
Ramsaf), and national or other conservation parksor
reserves.
Importance as refuges in dry years, as areas from
which recolonisation can OCCUf.
Importance for relict species or populations.
Degree of degradation, if any.
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Biological-Refugia in Australia
Refugia are identified by reference numb,ers, eg WA 1; SA 13;
NSW 5 etc, as in text (pages 71-131). See also State maps at
beginning of Sections 4-8.
.
L
WA 13 ((
WA 11
WA
WA19
WA 14.
WA21
WA2
WA2B.
NT2
•
WA1B~WA26
WA30.
. WA23
2111. WA 27
/".
WA 12
•
NT13
•
WA1
•
WA3 WA4:
WA15
•
WA20
•
WA22
•
WA17
SA3
WA~
o,
600
,
Kilometres
8
SYDNEY
·
.
CANBERRA
o
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2. EXECUTIVE SUMMARY
Several types of refugia are defined to take into
accounuhe fact that different concepts may be
involved in the idea of a refuge, In evolutionary .
..--tenns, a refuge is a region in which certain organisms
persist during a period in which most of the original
geographic range becomes uninhabitable because of
climatic change. However, the term refuge may be
used in other ways, particularlyto mean a region to
. which sgedes retract for short periods (i.e. for a
numbeiOf years at the most) when large parts of
their preferred habitats become uninhabitable
because of drought or other effects. Yet another type
of refuge comprises regions to which threatened
species have retreated because of enVironmental
changes set in train by European settre;ent. Our
investigations have led us to the following nine
categories:
• . Islands
• Mound springs
•
Caves
• Wetlands
• Gorges
• . Mountain ranges
• Ecological refuges
• Refuges from exotic animals
• Refuges from land clearing
Information on the distribution of plants and animals
in arid and semi-arid Australia was surveyed in order
to determine the identity and location of foci of
biological diversity. Subsequently, this data-set was
usedto identify locations thought to constitute
refugia because they possess unusual aggregations of
species considered endemic, relictual, threatened, or
otherwise significant. The chief refuge valu,e of each
is noted, and comments provided on threatening
processes within the refugia, and on land tenure.
Although the emphasis of the study, by force of
-circumstance, is on the species component of
biological diversity, the refugia that are identified are
likely to incorporate at least some values inherent in
genetic and ecosystem diversity.
An attempt is made to provide a measure of. the
importance of each refuge that might be used to
compare among them. As is the case with most
ranking procedures, this one cannot be considered as
concrete, objeclioe orfinal. It is merely a starting-point
for discussion.
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The number of refugia identified in arid and semiarid Australia was 76; there were 32 in Western
Australia, 13 in South Australia, 14 in the Northern
Territory, 8 in Queensland, and 9 in New South
Wales. Some refugia possessed values appropriate to
more than one category, but when classed according
to their primary characteristics the distribution of
refugia among the categories was as 'follows, Islands,
9; Mound springs, 4; Caves,J; Wetlands, 36;
Gorges, 5; Mountain ranges, 12; EcologicaI.refuges,
2; Refuges from exotic animals, 3; and Refuges from
land clearing, 2. Our attempt to rank the refugia
showed that Wetlands tended to be classed as of
lower importance compared to the other categories
because they possessed fewer notable species.
A preliminary analysis on a test region of central
Australia shows that it would be possible for Landsat
imagery to be used to identify areas of persistent
vegetational greenness; such areas might function as
shortcterm drought refugia for certain organisms.
Management issues affecting refugia are discussed. It
is concluded that they are identical to those facing
arid Australia asa whole, land degradation resulting
from over-grazing by domestic stock and by feral
animals, alterations in hydrology, removal of habitats
by clearing at the fringes of the semi-arid zone,
. depredations by exotic predators, and uncontrolled
fire. Thus, better management of refugia is
dependent upon mitigation of the same forces
operating throughout the landscape, but improved
management isespecially necessary in these refugia
because the organisms within them frequently have
no other home.
3. METHODS
3.1. Definitions - What is a Refuge?
It is imperative that we be clear from the beginning
about what constitutes a refuge in arid and semi-arid
Australia. The Oxford dictionary defines "refuge" as
"place of shelter from pursuit or danger or trouble".
In ecological or conservation terms, though, this
definition needs to be refined in order to encompass
several important varieties of refuge springing from
quite different sources.
In evolutionary terms, a refuge is a region in which .
certain types or suites of organisms are able to persist
during a period in which most of the original
geographic range becomes uninhabitable because of
climatic change. The resulting refuge contains high
frequencies of endemic species, because the species
in it tend to respond to the contraction of ringe by
evolving differences from their original, widespread
stock (e.g. Brown and Gibson 1983). Well-known
examples include patches of tropical forests in many
parts of the world, refugia for plants in the Arctic,
and - of importance to us - organisms confined to
isolated, moist environments in arid regions. Such
ospecies are frequently refe~ed to as relicts. However,
this category of refuges in evolutionary time does
not include all phenomena that we need to describe.
Ecologists frequently use the term refuge in other
ways, particularly to mean a region in which a
species or suite of species persist for short periods
when large parts of their preferred habitats become '
uninhabitable because of unsuitable climatic or
ecological conditions (e.g. drought, flooding or
biologically-driven collapses in food supply). Such
'c, ecological refugia may operate for less than one
.!leneration, or just a few, but may nevertheless be
especially significant in arid Australia because of the
'continent'spropensity to drought. Yet another
;~ategory of refuge comprises regions in which
\
/Jhreatened species occur; in this case, a species has
·fT~.treated because of factors ultimately to do with
;:?~nviro~me~ changes set in train by European
's.ettlement. Por purposes of description, and
···.a.rticularly for management action, it is vital to
i~"ntify the correct category of refuge. Our
'y"stigations hav.e led us to the following set of
leo'ogb.ries, as defined below.
.
..
0
0
'.-'-,------.~--
.\
;,',:-:,
.
"
3.1.1. Islands
Refuges in historical time from introduced predators
and competitors and from changing land-use due to
European use that has otcurred on the adjacent
mainland. Often rich in endangered mammals and
endell)ic species of mammals, reptiles and plants.
Also offshore islands from Barrow Island in the
north-west to Kangaroo Island in the south-east
were refuges from predation by Aborigines and
dingoes in pre-European times (Abbott 1980).
3.1.2. Mound springs
Localised habitat with Regional endemics of aquatic
oinvertebrates (isopods, ostracods, and hydrobiid
molluscs) and fish (where springs form wetlands)..
Springs are areas with concentrations of species with
limited range and specialised habitat requirements;
as more taxonomic work is undertaken, more of the
biota is being recognised as regionally endemic.
They may also provide a localised habitat for
waterbirds that ·is not affected by seasonal variations
in rainfall. The Dalhousie Springs are a well-known
example.
3.1.3. Caves
Provide a refuge in evolutionary time for species that
formerly occupied the litter layer of the forest floor
of rainforest at a time when the climate of Australia
was much
wetter and rainforest extended into areas
/
that are now arid or semi-arid. The Nullarbor caves
constitute examples of such refuges.
3.1.4. Wetlands
Provide permanent or semi-permanent wetland
habitat in arid or semi-arid environments to the
benefit of waterbirds and aquatic fauna and flora.
Includes long-lived pools in river systems as well as
lakes, and can be broadened to incorporate
intermittent wetlands such as Lake Eyre.
3.1.5. Gorges
Provide a specialised microclimate for plants and
animals that allow the continued survival of forms
that were far more widespread in the evolutionary
·past when climates were )Vetter. These;reas often
"provide additional refuge from present-day'
ecological forces such as fire. A well-known example
is Palm Valley in central Australia.
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3.1.6. Mountain ranges
Provide a mixture of refuges in evolutionary 'time
through the presence of sheltered environments and
geographically isolated habitats in which speciation
may take 'place, but also provide run-off water and
plant nutrients which may produce relatively
resource-rich areas functioning a~refugia in
ecological time-frames.
3.1.7. Ecological refugia
As noted in the previous category, the presence of
relatively dependable supplies of moisture and
nutrients may provide n;fugia for animals dependent
upon regular plant production for persistenq; in the
uncertain Australian climate.
3. 1. 8. Refuges from exotic animals
These refuges in historical tiine include sites other
than islands. The refuges have effectively been
created by human activities, and include
environmental zones atJhe edge of the range of
exotic species (e.g. the northern fringes of the ranges
of rabbits and foxes) and localised areas where
species have been able to evade the impact of these
species (e.g. rugged cliff habitat where animals can
escape from the effects of introduced predators and
competitors).
3.1.9. Refuges from land clearing
Areas where species or suites of species have
survived because clearing has been proved
uneconomic due to-aridity or infertility. This
phenomenon is most prominent at the semi-arid
fringes o(the arid zone.
3.2. Definitions - What Constitutes the
Arid and Semi-Arid Zones?
3.2.1. Boundaries
The arid and semi-arid zones are widely recognised
to constitute those areas which receive less than 250
mm annual average rainfall on the southern margin
and, in the north where evaporation is greater, less
than 500 mm (Williams and Calaby 1985; Figure
3.1). We adopt this definition and the boundaries
shown by Williams and Calaby.
3.2.2. Subdivisions
Some geographic structure is crucial as a basis for
discussion of refugia within the vast area constituted
by arid and semi-arid Australia. Rather than create
our own sub-divisio'ns, or use older regions such as
those of Beard (1969) even though they may be
established in the literature, we chose to use the
Interim Biogeographic Regionalisation for Australia
(!BRA) ofThackway and Cresswell (1994). The'
advantage of doing so, i.e. of presenting the
information in a context in which future discussion
of it can readily proceed, far outweighs the slight
disadvantage that may spring from forthcoming
minor adjustments to the boundaries of the Interim
Regions. Nevertheless, it should be borne in mind
.. ·that these Regions are still subject to modification
and refinement, and are best considered as a
con';enienl framework for discussion rather than as
absolute environmental categories. The !BRA was
derived by compiling the best available data and
information about each State and Territory,
including field knowledge, published resource and
environmental reports, and biogeographic
regionalisations, as well as continental data sets. The
!BRA was developed specifically for the National
Reserves System Cooperative Program, and the
focus is on continental landscape assessments. It is
acknowledged that such a regionalisation cannot be
the sole criterion for allocating conservation
priorities. The Biogeographic Regions occurring in
, arid and semi-arid Australia are shown in Figure'3.1.
3.3. ALiterature Survey Designed to
Identify Foci of Biological
Diversity and to Determine the
Location of Refugia
We approached the task of describing refugia by
scanning as much scientific and technical literature
as possible within the time available to us. For each
Biogeographic Region, we accumulated references
on natural history and ecology and extracted from
them information relevant to potential,foci of
biological diversity. We made p~rticular efforts to
obtain material from the "grey literature" represented
by publications of very limited distribution but
which frequently contain much detailed survey or
ecological information. 'The information sought
concerned:
12
"
,
•
species listed as endangered (E) or vulnerable (V)
by ANZECC (hom that shown in Australian
Nature Conservation Agency 1994);
•
species that are thought to be endemic to the
Region under consideration;
•
relict populations (whatever the cause of
relictuality);
•
other populations considered by authors of the
material to be si.gnificant;
•
and geographic areas identified by the authors as
constituting refugia.
This material is presented, Region-by-Region and
State-by-State, in sections 4-8, in the order Western
Australia, South Australia, Northern Territory,
Queensland, and New South Wales.
When this material was brought together, we
inspected it to determine whether significant records
of species or groups of species fell into a pattern that
might reflect the presence of any of the categories of
refuges specified in section 3.1. These data were
then summarised into identification of the refugia
occurting in each Region, again grouped according
to State or Territory, in sectio'ns 10-14.. Our
assessment has been inclusive rather than critical;
instead of excluding doubtful cases, we have tended
to list them. This approach has been adopted
because we envisage this Report as a starting point
for more detailed field assessment of the refuges
identified herein 'purely from a literature survey..
Sections 15 and 16 discuss some general aspects of
the refugia and of the management issues emerging
. from our analysis. Finally, an Appendix (section 18)
examines the possibility'-.of using satellite imagery to
identify dependably productive areas that may
function as short-term refugia for certain types of
organisms. If imagery could be analysed in this way,
it might expedite the identification of ecologically
significant parts of the landscape requiring special
management.
Figure3.1.
The Australian continent showing the boundary of
the arid and semi-arid region (heavy line; from
Williams and Calaby 1985) and the relevant
Biogeographic Regions (from Thackway and
Cresswell 1994).
Interim Biogeographic Regionalisation for Australia
Regions are shown which fall wholly or partly within the arid a.nd
<om'_,r,rl zones (indicated by the heavy black line).
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