Download Managing arid zone natural resources in Australia for spatial and

CSIRO PUBLISHING
www.publish.csiro.au/journals/trj
The Rangeland Journal, 2008, 30, 15–27
Managing arid zone natural resources in Australia for spatial
and temporal variability – an approach from first principles
Mark Stafford SmithA,C and Ryan R. J. McAllisterB
A
CSIRO Sustainable Ecosystems, PO Box 284, Canberra, ACT 2601, Australia.
CSIRO Sustainable Ecosystems, 306 Carmody Road, St Lucia, Qld 4067, Australia.
C
Corresponding author. Email: [email protected]
B
Abstract. Outback Australia is characterised by variability in its resource drivers, particularly and most fundamentally,
rainfall. Its biota has adapted to cope with this variability. The key strategies taken by desert organisms (and their
weaknesses) help to identify the likely impacts of natural resource management by pastoralists and others, and potential
remedies for these impacts. The key strategies can be summarised as five individual species’ responses (ephemerals, in-situ
persistents, refuging persistents, nomads and exploiters), plus four key emergent modes of organisation involving multiple
species that contribute to species diversity (facilitation, self-organising communities, asynchronous and micro-allopatric
co-existence). A key feature of the difference between the strategies is the form of a reserve, whether roots and social
networks for Persistents, or propagules or movement networks for Ephemerals and Nomads. With temporally and spatially
varying drivers of soil moisture inputs, many of these strategies and their variants can co-exist.
While these basic strategies are well known, a systematic analysis from first principles helps to generalise our
understanding of likely impacts of management, if this changes the pattern of variability or interrupts the process of
allocation to reserves. Nine resulting ‘weak points’ are identified in the system, and the implications of these are discussed
for natural resource management and policy aimed at production or conservation locally, or the regional integration of the
two.
Additional keywords: biodiversity management, deserts, drylands, grazing management, life-history strategy,
rangelands.
Introduction
Natural environments of outback Australia are characterised
by a series of features that demand explicit attention in
designing management and policy (Stafford Smith 2003). At
the foundation of these features is the high degree of climatic
variability at all time scales from intra- and inter-annual through
inter-decadal to longer, and the ways in which this temporal
variability changes in expression spatially at scales from metres
to thousands of km across the continent (Stafford Smith 2008,
this issue). Contention around drought policy (Botterill and
Fisher 2003) is but one example of how the impacts of this
temporal and spatial variability strain conventional approaches
to management and policy in Australia. Past episodes of
degradation in Australian rangelands show that many mistakes
have been made in coping with these drivers, although there
has also been a great deal of collective learning (Stafford Smith
et al. 2007). Since many enterprises for which desert Australia
holds some comparative advantage are based on natural (and
cultural) resources (Jones and James 2006), understanding their
sustainable management is critical. Grazing production systems
remain the most extensive land use on rangelands and alliances
between science, industry and land management agencies have
developed many management guidelines for these systems
© Australian Rangeland Society 2008
(reviewed below). Examples for other production systems or
conservation are few.
The purpose of this paper is thus to review the general
principles for rangelands management that emerge from our
current understanding of how desert organisms respond to
spatial and temporal variability in key drivers of production.
To do so, we undertake a review of the evolution of this
understanding since the landmark works by Noy-Meir (1973,
1974), who articulated the implications of seeing these
environments as pulse-and-reserve systems. From this, we
synthesise several general response strategies for organisms
and communities, and analyse the weak points of each. In
conjunction with a brief review of best-practice management
guidelines, this allows us to provide a systematic framework
for ensuring the comprehensiveness of such guidelines
in the future.
Our focus is on arid and semi-arid rangelands in Australia,
although we draw on data from other arid regions. There are
of course many other elements of holistic good management of
rangelands, including economic, human, social and institutional
issues, but the present paper focuses specifically on those
elements related to the influence of variability on natural
resources.
10.1071/RJ07052
1036-9872/08/010015
16
The Rangeland Journal
M. Stafford Smith et al.
Elements of arid ecosystem functioning
Plants, animals and environments interact in a multitude of ways,
some straightforward (e.g. more production if there is more of
a limiting resource, like rain), others more profound. Climatic
variability is often said to be a dominant driver in arid Australia
(e.g. Friedel et al. 1990). This contrasts with a stronger emphasis
on nutrients (especially micronutrients) and fire in another recent
review that is not so oriented towards management (Orians
and Milewski 2007). This difference may reflect Orians and
Milewski’s (2007) greater emphasis on the semi-arid end of the
continuum, where the present analysis emphasises the arid end.
Thus, while acknowledging that many other factors (e.g. soils,
nutrients, fire, etc.) complicate the picture, we take spatial and
temporal variability of limiting resources as our core analytical
focus in arid systems.
Drivers
In both natural and managed states, arid systems are subject to a
syndrome of causally related drivers (Stafford Smith 2008, this
issue). Here, we focus on the biophysical drivers, particularly
climate and nutrients. Table 1 introduces the main sources of
inputs for different organisms (and for human use of these).
As the ultimate source of soil moisture, rainfall is relatively
low on average, but with high variability over time in pulse
events; it also has high unpredictability in terms of combinations
of these events, and in relation to other weather elements like
temperature. As a result, it exhibits extremes and long return
times for particular combinations of events, with a complex
set of cycles apparently driving this unpredictability, up to and
including multi-decadal patterns (White et al. 2003). There
is also spatial heterogeneity in precipitation at various scales,
between regions, in storm patchiness, and in local redistribution.
Table 1.
Limited and variable amounts of soil moisture are coupled with
generally low levels of a second resource, nutrients, for which
soils are mostly poor on a world scale (Orians and Milewski
2007). However, some soil types are more fertile over large areas,
and redistribution processes (Pickup 1985; Tongway and Ludwig
1994) also create spatial patchiness in this resource.
For Australian arid zones, rainfall, soil moisture and soil
nutrients are all highly variable in space and time. The focus
of the following analysis is on the implications of this variability
for organisms.
Heterogeneity in time: multiple, diverse
pulse-and-reserve cycles
Organism responses in environments where rainfall is
intermittent, and where the amplitude and longevity of soil
moisture pulses are more important than the mean soil water
levels, have long been characterised as a pulse–reserve systems
(Noy-Meir 1973; Westoby 1980; Schwinning et al. 2004).
Importantly, each pulse is recognised as unique (Noy-Meir
1973; Westoby 1980; Stafford Smith and Morton 1990), as
more recently elaborated by Schwinning and Sala (2004) and
in a simulation context by Reynolds et al. (2004). While much
literature conceptualises the responses of arid plants to single
pulses as ephemeral or perennial, in reality organisms face
a probability distribution of pulse sizes and periods between
pulses, and consequent histories of resource storage. Further,
both animal and plant responses may act to buffer both temporal
and spatial variation (see below). These pulse distributions may
be reasonably predictable, as with most Mediterranean-type or
monsoonal climates where rain is more-or-less guaranteed in
a particular season even though its amount may not be. They
may also be highly unpredictable, as is characteristic of central
Drivers of variability for different ecosystem elements (upper section) and a selection of key targets for production (lower section)
in arid lands
Entity/output
Variable input
Comments
Soil moisture
Plant biomass
Rainfall
Soil moisture
(Modulated through run-off/run-on, infiltration rates, soil texture and previous conditions)
Strategies may increase (ephemerals) or decrease (perennials) the variability as expressed by the plants’
production. Often but imperfectly correlated with nutrient inputs
Tends to be naturally pulsed due to native grazers’ (insects, kangaroos) responses to variability in forage supply
and water (this variability is reduced in watered pastoral systems)
Green growth – highly variable, drives ephemeral (including mobile) response. Other active growth resources of
perennials such as sap – more constant permitting persistent strategies, Dead material – very constant,
especially if stored, permitting remarkably stable detritivore populations
Variable/mobile if prey depends on green growth (e.g. locusts or moorhens) but quite stable in certain habitats if
prey dependent on perennial resources (e.g. sap-suckers for insectivorous birds) or detritivore pathway
(e.g. termites for lizards, gryllacridids)
Grazing pressure
‘Herbivore’
biomassA
Food: plant
material
Carnivore
biomassA
Food: other
animals
Sheep/cattle
productivity
Nutritious food
Free water ∼daily
Bush tomato
production
Acacia seed
production
Specialist
timber
AA
Soil moisture
(nutrients/fire)
Soil moisture
Soil moisture
Depends largely on green growth (though can persist poorly with dry matter) hence variable/mobile; for stability,
pastoralist can manage for persistent species, primarily palatable perennial grasses or shrubs
Pastoralist can implement infrastructure to provide water, most easily where there is ground water (else earth
tank dams are ephemeral)
Short-lived perennial hence very variable between years (though fire is an additional factor that can be managed).
‘Enhanced natural harvest’ (applying fire, water, nutrients at critical times) could reduce variability
From longer-lived perennials so less variable annually (depends on flowering strategy), though peaks of
production come from shorter-lived species; could focus on the longer-lived species?
Long-lived perennials, so buffered and stable (but slow growing) if harvest rate is sustainable
few larger animals only are also directly affected by water availability (Stafford Smith and Morton 1990, Proposition 9).
Managing for variability in arid natural resources
Australia for example, where the size distributions both of soil
moisture pulses and of intervening dry periods are very skewed
(Stafford Smith and Morton 1990). The fundamental nature of
this distribution has long been recognised as explaining the lack
of stem succulents in Australia, for example. The stem succulent
strategy can cope with very dry conditions but depends on
reliable re-charge every year, a condition that is safe in the north
and central American deserts but not met in central Australia
(Stafford Smith and Morton 1990). That is, succulents can cope
with great variability, but not great unpredictability.
As climatic unpredictability increases, so does the diversity of
pulse and reserve patterns. As this diversity of niches increases,
there is a corresponding expansion in the suite of plant lifehistory strategies that may be able to persist in response to
different events and combinations of events, providing these
combinations occur sufficiently often. Reynolds et al. (2004)
modelled a specified set of strategies and showed how they would
perform differentially in different climates, but did not reverse
the question and ask what strategies in general could succeed and
co-exist in these different probability distributions. This was the
challenge raised long ago by Noy-Meir (1973): ‘An interesting
aspect is the analysis of the different pulse-reserve strategies as
optimised strategies in different environments.’
Animals are similarly exposed to variability (though often
lagged and attenuated) through their use of plant or other
animal resources (Table 1). Furthermore, rainfall is spatially
heterogeneous at scales from individual local storm cells up
to continental patterns. Consequently, many animals have the
option of mobility, using pulses (similar or otherwise) that occur
at different times at different places, essentially escaping in
space (Noy-Meir 1974). Animals may practice local mobility
by expanding their home range to encompass more of a
sparse resource. For example, there is good evidence that
hills provide sparse but reliable resources to dasyurids that
live there, so that hill-dwelling species (e.g. Pseudantechinus
macdonnellensis) survive in bigger home ranges but with less
larger-scale movement than related sandplains-dwelling species
(e.g. Sminthopsis youngsoni) (Gilfillan 2001; Pavey et al. 2003;
Haythornthwaite and Dickman 2006). It is similarly known that
other animals such as dingos, eagles, red kangaroos and camels
have larger home ranges in drier areas or dry times (e.g. Norbury
et al. 1994; Edwards et al. 2001).
True mobility, as defined here, is when animals go well
beyond a normal home range in order to find another location
with higher resource levels. Such movements may be regular
migration (effective where there are strong seasonal correlates
with resource supply; e.g. rainbow bee-eaters [Higgins 1999]),
opportunistic invasion (coming in from outside the arid zone
in good times to exploit the temporary supply of resources,
e.g. many water birds [Roshier et al. 2001; Kingsford and
Norman 2002]), or true nomadism (moving around within the
arid zone, given the scale and lack of spatial correlation in
climatic conditions across the whole continent, as reviewed by
Woinarski [2006]). Again, there is a series of trade-offs between
the investment in travelling reserves for movement (and the rate
of use of resources in making the move), and the probability
of finding another location with active resources, all compared
to the hardship of a low resource availability from staying put.
Different organisms make different trade-offs in relation to the
The Rangeland Journal
17
same resource pulse probabilities in space in a way that is
analogous to their trade-offs in time.
Various animal taxa such as rodents (e.g. Dickman et al.
1999) and locusts (e.g. Clissold et al. 2006) exhibit an additional
strategy, which is to irrupt in plagues in response to good
conditions (modulated by migration and predation; Dickman
et al. 1999). The key to this strategy is survival between
irruptions. Notwithstanding the difficulty of monitoring the low
population phase, survival seems to depend on a continuum
of alternatives between a retreat to better refugial habitat
(e.g. Brandle and Moseby 1999) through to persistence as a
sparse but widespread population (e.g. for locusts).
Heterogeneity in space: landscape redistribution
creates resource flows
Even if rainfall were spatially homogeneous over homogeneous
soils, actual soil moisture in different elements of a landscape
would evolve differently, depending on water movement (NoyMeir 1973; Pickup 1985; Stafford Smith and Morton 1990;
Ludwig et al. 1997; Reynolds et al. 2004). Thus, the probability
distribution of soil moisture events on a run-on area is different
to that of a neighbouring run-off area, adding to the diversity
of niches that might be exploited within a locale; in practice,
the differences are accentuated by (partially correlated) changes
in soil texture and chemistry. Consequently, the vegetation of
an arid-zone floodplain encompasses plants with a different
balance of strategies to the vegetation of the nearby hills
(e.g. Jurado 1990; Kratz et al. 1991; Pantastico-Caldas and
Venable 1993). The degree to which these environments are
differentiated depends on the scale of the run-off/run-on pattern,
with permanent water tables and even semi-permanent desert
wetlands occurring downstream at the largest scales. These
patterns are often accentuated by the frequent correlation of
resource concentrations such as those of nutrients with moving
water, and of soil types with landscape position (Pickup 1985;
Stafford Smith and Morton 1990).
These forms of redistribution happen at many scales from
metres through to whole catchments, but a particular outcome
in arid environments is vegetation patterning at the characteristic
scale of groups of local perennial plants, whether these are
grasses or shrubs (Ludwig et al. 2005). Although a variety
of more complex models have been proposed (Lejeune et al.
1999; Esteban and Fairen 2006), HilleRisLambers et al. (2001)
show that the existence of spatial redistribution and a positive
feedback between local plant density and water infiltration are
the only theoretical requirements for self-organising pattern
formation. However, the mechanisms for both redistribution and
the feedback may vary in detail (e.g. local effects around groups
of perennial grass clumps [Anderson and Hodgkinson 1997] or
individual mulga stems [Dunkerley 2002] may be as important
hydraulically as the overall grove structure).
There are several other aspects of spatial resource
distributions that may interact with water re-distribution at local
(run-on/run-off patches) and regional (river floodplains, water
tables and wetlands) scales. These include spatial patterning
in rainfall inputs at local (chance storm patterns) and regional
(bigger orographic effects, etc.) scales (e.g. Noy-Meir 1973),
transport of dust and nutrients by wind (Hesse and McTainsh
2003), and fire patterns (e.g. Turner et al. 2008, this issue).
18
The Rangeland Journal
While there are some geomorphic controls on aspects of spatial
heterogeneity, all these factors mean that even the spatial pattern
of heterogeneity varies over time.
Heterogeneity modulated by other organisms
Lastly, some emergent relationships among organisms arise as a
result of the sum of all the above (particularly the scale issues). In
particular, some organisms create niches for others, incidentally
or mutualistically, and it seems that this occurs with respect
to protection from resource limitations more frequently in arid
biomes than other ecosystems. For example, Flores and Jurado
(2003) show that records of nurse/protégé plant associations
(where the presence of one plant facilitates the establishment
or growth of another, of the same or, usually, different species)
are far more common in arid environments than any other.
These are strictly commensalisms in which seedlings benefit
from the microenvironment created by adult plants with no
apparent effect for the latter. However, Facelli and Temby (2002)
show mixed facilitatory and inhibitory interactions according
to the net effects of shade and root competition for annuals
and shrubs in South Australia. Anthelme et al. (2007) show
that nurse plant benefits are obtained from living plants in
less arid areas but from dead plants at their most arid sites in
Niger. Both of these studies suggest that once water becomes
limiting, there is a trade-off between microclimate protection and
water competition.
Effects are not limited to plant interactions – Robinson
et al. (2002) discuss the higher densities of protozoa found in
plant generated ‘resource islands’; hydraulic lift by large trees
has been shown to support microclimates for other organisms
(Caldwell et al. 1998); and zebra finches have been seen to
concentrate nest building under active kite and eagle nests,
apparently to reduce predation pressures on themselves (Zann
1996). Some interactions may be true mutualisms, such as the
presence of invertebrates around shrubs creating macropores
that enhance infiltration (Ludwig et al. 2005) and larger
mammals using trees for shade and thereby concentrating
nutrients near them (Eldridge and Rath 2002). At larger
landscape-engineering scales, the resource-capturing vegetation
patterning noted above permits greatly increased diversity within
the vegetation patches in many taxa including lichens and
mosses (Eldridge 1999), plants and animals (Ludwig et al.
2004). Indeed the concept of deliberately supporting natural
ecosystem engineers to reconstruct systems is gaining force with
practical applications in arid zones (Ludwig and Tongway 1996;
Byers et al. 2006).
A variety of other interactions appears to be more common
in arid zones than other systems, but these seem to be driven
more by nutrients than variability in climatic conditions (Orians
and Milewski 2007). These include ant-plant seed harvesting
mutualisms (Giladi 2006); other ant interactions (e.g. Morton
and Christian 1994); nutrient-rich micro-sites for germination
of large-seeded species thanks to passage through a bird’s gut
(e.g. Noble 1991); and higher incidence of nitrogen-fixing
nodules on species that do not normally form these, e.g. in
the Simpson Desert (O’Connor et al. 2001). It is likely that
there are many other complex relationships awaiting discovery
in arid lands, e.g. recent uncovering of the rich thrip fauna
(Mound 2004).
M. Stafford Smith et al.
Finally one may note that plants and animals that persist
through finding a mesic niche that is based on taking resources
from other organisms that are themselves persistent (as in
mistletoes on many arid zone trees, or sap-sucking lerps on
river red gums and mulga, or lizards preying on termites)
represent non-mutualistic interactions which are deleterious
to the prey, but nonetheless contribute to dampening down
the variability signal for many organisms (Stafford Smith and
Morton 1990).
Animals also graze or otherwise prey upon plants, so patterns
of variability in this predation also matter. For most of the
Australian landscape, grazing pressure historically would have
lagged plant growth except in richer niches (even when large
marsupials were around they were probably confined to the richer
parts of the landscape, leaving a legacy of thorny responses only
in plants like Acacia victoriae and Capparis spp. that inhabit
such niches). Cingolani et al. (2005) show that plant life-history
strategies are likely to interact with large grazers in different
ways in Australia compared to continents with long histories of
ungulate grazing.
Responses to variability
The ecological processes discussed above drive a series of well
documented but not recently re-synthesised basic life-history
strategies and multi-species interactions (Ross 1969; Westoby
1980; Barker and Greenslade 1982; Morton and James 1988;
Stafford Smith and Morton 1990; HilleRisLambers et al. 2001),
which we now re-visit in order to seek generalities.
Strategies of individual species
Individuals trade off the rate of use of the resource pulse
while they are active against their rate of use of the resource
while inactive, in such a way as to maximise the chance of
genetic survival over a series of variable pulses. Classically,
the extreme strategies are characterised by (i) a perennial plant
which grows relatively slowly during a pulse because it is
investing substantially in roots to ensure its supply continues
between pulses; and (ii) an ephemeral that invests mostly in
leaf rather than roots so that it grows rapidly but then dies,
after seeding heavily as soon as the limited volume of soil
that its roots can access begins to dry. In reality, there is much
greater diversity in responses than implied by the perennialephemeral dichotomy.
Perhaps the best exposition of the individual species strategies
(though self-admittedly biased to the view of a plant ecologist)
was provided by Imanuel Noy-Meir, who distinguished
annuals, perennial ephemeroids, fluctuating persistents and
stationary persistents among plants (Noy-Meir 1973, pp. 42–44),
and annuals, ephemeroids, opportunistic migrators, refuging
persistents and non-refuging persistents among animals (NoyMeir 1974, pp. 197–199) (as well poikilohydrics among both).
The discussion above shows that there are essentially two
functional elements in the responses of individual organisms:
(i) how to respond to a particular frequency distribution of
resource inputs over time (primarily soil moisture for plants,
but various foods that are themselves influenced by these factors
for animals); and (ii) how that temporal frequency distribution
varies spatially at various scales and whether this creates
additional strategy options. We summarise these into five key
Managing for variability in arid natural resources
functional strategies (Table 2), noting that organisms can adopt
a variety of combinations and intermediates. We omit NoyMeir’s separation of ‘ephemeroids’ and ‘fluctuating persistents’
(which really occupy intermediates between ephemerals and insitu persistents functionally, more inactive in dry times than
leafed perennials but able to respond faster and more often than
true ephemerals in small pulses). We distinguish the functional
difference between nomads, that operate only in the desert, and
exploiters, that come in from outside, again noting that this is
a continuum from deep desert nomadism, through regular use
of the semi-arid margins, to short incursions altogether from
outside. We also observe that plants can be refuging persistents,
but we do not include a separate irruptive strategy for animals,
since its functional attributes are captured on the continua
between ephemerals and persistents, and between refuging
and in-situ persistents during the non-irruptive phase for
different taxa.
Table 2.
The Rangeland Journal
19
It is worth noting that the scale of response of strategies in
time and space is potentially continuous, and also interacts with
the scale of the organism. Small organisms with fast turnover
can exploit more (smaller) niches than large organisms, and have
more opportunities to find a mesic site as a refuge than a large
organism. Since organisms that persist locally need to invest
in extensive resource harvesting structures (e.g. trees, termite
colonies) or home ranges (e.g. dingos), these are usually larger
organisms (including the size of colonies for termites or ants).
So the strategies become confounded with size. This observation
is important, because smaller organisms usually have shorter
life spans and are therefore exposed to variability on a different
characteristic temporal scale to larger organisms.
Multi-species and community-level responses
Beyond the individual strategies, there are two general functional
ways in which individuals of the same or different species
Summary of key response strategies to variability in time and space in desert organisms, emergent multi-species relationships,
and their key weak points
Response to variability
In-situ persistents
Persist by harvesting sparse resources widely, plants through extensive root
systems, animals through large home ranges or social networks or low
metabolism
Refuging persistents
Avoid variability by specialising into (usually small) richer niches, plants
by preferentially occupying watercourses and run-on areas, animals by
becoming very small or occupying home ranges with or in waterholes
Weak points
• Interruption to investment in reserve or harvesting network (especially
in small pulses)
• Decline in density of sparse resources
• Extreme events (beyond ‘insurance’) when propagules or
re-colonisation still needed
• Competition from ‘less expensive’ strategies if variability is lessened
• Damage to niche resources
• Competition from exploiters
Ephemerals
Build reserves to survive poor times in an inactive form, but compensate
by growing fast in larger resource pulses
• Interruption to investment in dormant phase (seeds, etc.)
• Interval between pulses becomes too long for reserve survival
Nomads
Be nomadic within the desert among potentially shifting and widely spread
resource-rich (pulse) locations
• Connectivity or asynchrony between pulse locations disrupted
• Competition from exploiters (e.g. weeds) in pulse locations
Exploiters
Be exploitative of resource–rich locations or times in desert regions
from a base outside the desert
• Must survive between events in competitive environment outside desert
Emergent multi-species modes of organisation
Facilitation
Benefit from effects of (or by harvesting resources from) other persistent
organisms
Self-organising communities
Self-organise to build a greater local concentration of resources – many
individuals of one or (usually) more species structured to trap resources,
particularly through interrupting overland flow of water
• Damage to facilitatory organism
• Disruption to ability to regulate resource flow
• Loss of (usually one) dominant structuring species
• Reduction in resources to point where benefits of flow control become
marginal
• Increase in resources to point that other organisms compete without
flow regulation
Asynchronous co-existence
Species co-existing in the same place at different times due to different
pulse patterns through time
• Reduction in temporal variability
Micro-allopatric co-existence
Species co-existing nearby in different places at the same or different times
due to different pulse patterns in space
• Reduction in variability across space
20
The Rangeland Journal
M. Stafford Smith et al.
may interact to handle variability. These are not evolutionary
strategies but are multi-species modes of organisation from
which additional options emerge for the strategies already
mentioned.
First, one individual may facilitate the existence of the other;
this facilitation may be an incidental commensalism as where
a perennial provides shelter which assists another seedling to
establish with no evident impact on the nurse plant; it may
be a parasitic or predatory interaction, where one organism
benefits from the other; or it may be a true mutualism. A
successful persistent essentially provides a less-variable niche
for another organism; Stafford Smith and Morton (1990) argue
that this results in greater stability than might be expected
for some elements of higher trophic levels, at least at the
scales that permit this, but this is also true for some plants
(such as mistletoes, most obviously). Functionally, whether the
interaction is mutualistic, parasitic, predatory or neutral for the
facilitator, in all cases of facilitation, the facilitated organism
depends on the successful establishment of another, usually
a persistent.
The second type of interaction is more complex, where a
set of individuals self-organise (initially by chance but with
positive feedback) to concentrate the limiting resource in
the environment. This engineering of the environment again
results in the organisms experiencing less variability than
would otherwise be expected, but this time multiple individuals
and usually multiple species (often both plants and animals)
are involved. Although the classic examples of this such as
mulga groves or perennial plant patches involve plants, animals
obviously benefit from these community-scale interactions
(e.g. Schlesinger [2000] found skinks [Ctenotus spp] to do
better in the higher cover provided in mulga groves). Indeed,
animals are often an important part of the community feedback
mechanism, as with macro-pores created by macro-invertebrates
enhancing infiltration around chenopod patches (Ludwig et al.
2005). In a more explicit example, mistletoe birds act as an
agent of under-dispersal for mistletoes, which then creates a
resource rich clump for the birds in a self-reinforcing feedback,
which in turn affects a wider community of mistletoe species,
hosts, and frugivores (Reid and Stafford Smith 2000). It is
harder to think of a purely animal-mediated mechanism with
positive feedback, but this certainly occurs in the realms
of human enterprise in arid regions. The key functional
characteristic of self-organising communities is that there
must be some positive feedback mechanism concentrating
(and usually reducing the variability of) an otherwise
sparse resource.
one or more of the following ways, in which the second
and third are the important emergent modes of organisation
not yet discussed:
• Penecontemporaneous exploitation – coexistence on the same
resource pulse. Chesson et al. (2004) have shown the narrow
outcome that more than one strategy can exploit a single pulse
stably; of course, if this were the only mechanism, it would
still result in very low diversity (omitted from Table 2).
• Asynchronous co-existence, where strategies in the same
location benefit differentially from different types of pulses
(with ancillary effects from temperature, nutrients, etc.) for
active growth, such that no type of pulse is absent for so long
that the reserve phase (seed, root, absent nomad, etc) of each
species is actually destroyed.
• Micro-allopatric co-existence, where different parts of the
landscape favour different strategies because the resource
pulses are expressed differently (though note that this effect
may be more on the relative abundances of strategies than
their absolute presence and absence because most event types
likewise change in frequency rather than absolute occurrence;
hence there will often be more effects on compositional rather
than structural diversity of vegetation).
• Facilitation and self-organised communities, because these
provide support for organisms that would be less successful
if the variability of the resource pulses was not moderated
by the ‘engineering’ effects of the facilitating organism
or self-organised structure (see above); this is the source
of biological (as opposed to physical) niches for refuging
persistents (as well as nomads and exploiters).
Thus, the diversity of pulses over time maintains asynchronous
co-existence, while it is the fine-scale processes of landscape
re-distribution over space that maintain micro-allopatric coexistence. In terms of species interactions, an extensive
international literature (with which Australia was never greatly
involved) argued that variability meant that these systems were
non-equilibrial, so that there were no biotic feedbacks between
predators or grazers and their ‘prey’ (see Behnke and Scoones
1993). However, this was clearly not true in some places at some
times, and the debate has now been resolved in favour of a view
of the systems as dis-equilibrial – that is, continually buffeted
away from an equilibrium but nonetheless with significant
biotic controls (Vetter 2005). This is in line with the view
taken here, where the different strategies, furthermore, are
differentially likely to be subject to such controls over time
and space.
Co-existence of strategies
The five individual strategies may be summarised as tolerating
or avoiding resource shortages, in time or space, while the two
multi-individual responses provide ways in which individual
strategies may cascade to affect others. The diversity of
these with respect to the categories of spatial and temporal
heterogeneity in drivers then largely determines landscape-scale
diversity. The ways in which each strategy is made viable
translate readily in to an analogous analysis of the ways in which
each strategy is most easily threatened (Table 2, column 2).
This then provides an indication of the different ways in which
management is likely to disrupt the system.
The five individual strategies (Table 2) represent the extremes
of alternative responses to variability on various continua, with
well defined trade-offs that determine their relative successes
in the face of different driving (resource inputs, Table 1)
and contextual (landscape structure, other organisms, etc)
conditions. Coexistence, and consequent landscape-scale
genetic diversity, results from facilitation and self-organising
communities, but is additionally determined by the diversity
of these driving and contextual conditions over space and
time. Hence, co-existence at a landscape scale occurs in
Weak points in the system
Managing for variability in arid natural resources
Five actions create weak points (WP) at landscape scales for
organisms adapted to variable environments:
WP1. Disrupt investment in reserves – if persistents and
ephemerals do not invest sufficiently in reserves (root
systems for perennial plants, fat or food storage systems and
social networks for persistent animals, and propagules for
ephemerals) this reduces their ability to survive through a
dry time. More subtly, the competitive advantage of in-situ
persistents is partly built on their ability to be active in small
pulses during otherwise dry times, and harvesting them at this
time can damage this competitive advantage.
WP2. Damage niche resources – for refuging persistents, the
maintenance of their refuge is crucial; in the longer term,
some degree of connectivity between refugia (in space for
animals, in time for plants and their seeds) is required for the
species to persist through inevitable local extinctions.
WP3. Destroy key species – facilitation and self-organising
communities depend on the maintenance of one or a few key
species (usually persistent plants).
WP4. Direct damage to resource flow management – the resource
flow controls can themselves be damaged in the case of the
self-organising community, for example where animal tracks
cut channels through mulga groves.
WP5. Increase mean resources or reduce their variability
– an increase in resources or a stabilisation in their
variability can remove the competitive advantage of the
investments of most strategies (also undermining selforganising communities, and asynchronous and microallopatric co-existence), particularly favouring exploiters
such as weeds and pests. The effects of increased
anthropogenic CO2 may already be changing the effective
availability of water.
These landscape-scale impacts are embedded within larger
scale processes that create four additional weak points.
WP6. Degrade ‘pulse network’ – nomads depend upon the
maintenance of a network of locations where resource pulses
may be occurring; if that network is thinned by the loss of
individual scattered locations, or the connectivity between
locations is degraded, at some point this network quite
suddenly becomes dysfunctional. To a lesser extent, exploiters
also depend on this, although the coherence of the network is
less crucial to them as long as they can fall back outside the
desert regions.
WP7. Reduce mean resources – in-situ persistents obtain their
competitive advantage by living mostly ‘close to the edge’ in
terms of investing in harvesting sparse resources that others
cannot. Hence, relatively small declines in the availability
of these resources can strain their resource harvesting
capabilities too far, whether the decline is caused by climate
change (e.g. slight drying) or management (e.g. moderate but
uniform grazing).
WP8. Extend periods of low resources – both ephemeral and insitu perennials are susceptible to an extension in the return
times of pulses, either through climate change or through
management that alters the return time of pulses (e.g. water
extraction on ephemeral rivers).
WP9. Change spatial asynchrony – nomads must not only have a
network of locations where pulses occur, but these pulses must
The Rangeland Journal
21
also be occurring reasonably asynchronously so that there are
always some resource-rich sites available. Large-scale climate
patterns over arid Australia mean that when eastern Australia
is experiencing drought the west tends to be wetter and vice
versa at present; however, there is some evidence that this
asynchrony has not always occurred (Allan 1991). At least
in principle, this could affect the survival of a pure nomad
strategy.
How do these weak points derived from first principles
intersect with management practices?
Management and policy for desert natural resources
subject to variability
There are two main types of management goals in arid zone
environments, which may be paraphrased as ‘maximising’
production from a small set of products, or ‘maximising’
diversity of (usually) species. In practice, the main example of the
former is pastoral production and the products are beef or wool,
but there is a range of other products to be considered similarly,
including the outputs of specific bush-products industries and
visitor experiences in the tourism industry. Likewise, the main
example of the latter is conservation management, although
one might argue that traditional management of country by
Aboriginal people similarly aimed (deliberately or otherwise) at
maintaining a diversity of resources. These goals are generally
incompatible on a single small block of country, though Morton
et al. (1995b) have argued that they can be resolved at a regional
scale (see below). Here, we will first consider them locally.
The goal of maximising the (long-term) production of
specific products means deliberately trying to reduce the
variability experienced by one set of organisms in order to focus
on their production. Whether these are sheep and cattle, or bush
foods or even tourism (Table 1), the key issue is to understand
what effects management is likely to have on system function
and identify which effects are likely to be deleterious to the
production goal.
Management to maximise sustainable pastoral
production
Sheep and cattle depend on forage and water. Provision of water
has of course been one key to pastoral industry development right
across Australia (James et al. 1999), but is not the focus of this
paper; however, it has resulted in a much more homogeneous
grazing pressure for plants over time, thereby reducing the
variability that they experience (Stokes et al. 2006). In fact the
effects of unmanaged stock persisting on country and seeking
out the best production in space and time can be caricatured
as eating off the perennial plants’ reserves (weak point WP1),
grazing out the refuges (WP2), in some cases eating out key
species (WP3), and removing cover from or trampling channels
through self-organised resource flow systems (WP4). If these
effects happen over wide areas, they will trigger WP5, WP6 and
WP7 as well. The saving grace in the past was that the lack of
surface water meant that this only occurred over some of the
country.
Given drinking water, a stable forage supply is a key influence
on the level and consistency of beef or wool production. The
variability of the forage value of natural pastures is minimised
if palatable perennials are their main component (invoking
22
The Rangeland Journal
M. Stafford Smith et al.
facilitation by these perennials in favour of the livestock).
The alternative of ephemeral pastures is more variable and
necessitates external subsidy (e.g. supplementary feeding) to
obtain the same production consistency (or impracticably rapid
changes in stock numbers to track the forage availability). Thus,
a crucial long-term goal for grazing enterprises is to manage
for the best levels of reasonably palatable perennial pasture
(e.g. Partridge 1999). The major issue with this is that the
perennials grow relatively slowly and need to invest a significant
proportion of their carbon assimilation in roots to maintain their
water harvesting safety net for dry times. The shorter-lived ones
(most forage species) also need to be able to direct significant
resources to their seed reserve. Thus, overgrazing them while
they are making these investments will run down the system
in the long-term (e.g. chenopods [Hunt 2001]; grasses [Hacker
et al. 2006]); indeed it often helps to have a modest proportion of
fast-growing ephemerals mixed with them to take some grazing
pressure during the main growing season.
In terms of long-term pasture composition, even moderate
grazing of palatable perennials also clearly risks disadvantaging
them in comparison to other similar but unpalatable strategists,
whether grasses, shrubs or trees (‘woody weeds’). To balance
this effect, fire management is an important consideration not
extensively covered in this paper. Finally, various introduced
weeds and feral animals are notably successful in rangelands,
for two qualitatively different reasons that point to different
approaches to their management. Some succeed by handling
the existing variability, being competitive because of release
from predators or diseases, or because they have claimed
a niche unoccupied by native species (cats, rabbits, couch
grass [Cynodon dactylon] may be examples of these). Others
succeed because of management and disturbance that upsets
the natural variability, for example because of the availability
of persistent artificial waters or homogeneous grazing pressures
around these waterpoints (e.g. Ward’s weed [Carichtera
annua], Arabian grass [Schismus barbatus]; Landsberg
et al. [2003]). This category parallels native species that
have expanded in the arid zone, such as galahs and various
‘woody weeds’.
Many regional best-practice approaches to grazing
management have implicitly identified such risks – some
examples driven by practitioners are summarised in Table 3.
There are also scientific studies (e.g. Foran et al. 1990; Partridge
1999; Ash et al. 2001; Fisher et al. 2004; Sullivan et al. 2006),
examples embedded in plans for specific regions (e.g. Marree
SCB District Plan 1997), and recent individual property case
studies (e.g. LWA 2006). Some of these are very early – as
long ago as 1896, Peter Waite (cited in Lange et al. 1984)
made the need for spelling clear: ‘the intelligent lessees find it
necessary to spell country after it has been stocked for a time’.
There are also many short treatments in the popular literature –
for example, Cole (1994) sets out the essence of sustainable
grazing: ‘The challenge in the [Riverina] rangelands is to
match pasture production with a stocking rate that will ensure
long-term survival of the important perennial grasses’.
The best-practice publications provide recommendations in
four broad categories, as noted in Table 3. Categories (iii) and
(iv) have important implications for how grazing affects the
resource base, which can be summarised as delivering an
improved ability to control the timing and regularity of grazing
pressure in space and time. In particular, larger sheep and more
resilient breeds of cattle allow these animals to survive dry
Table 3. Key recommendations about (i) managing the temporal and spatial distribution of grazing pressure, and (ii) direct management
of the natural resource, from a series of sources based mainly on pastoralists’ experiences in different regions of the Australian rangelands
Note: most also had recommendations on (iii) whole property management and planning, financial management and marketing, and (iv) animal husbandry,
breeding and genetics, which are not included in this table. See also Partridge (1999) and related volumes, Campbell and Hacker (2000), Quirk and O’Reagain
(2003), LWA (2006) as more scientific or generalised products that tend to highlight specific elements above
Source
(i) Plant-animal management
(ii) Plant-soil management
Atartinga, southern NT
(Purvis 1986)
• Light grazing
• Spelling (12 months on 5-year cycle)
• Good water distribution
• Ponding and cover to retain water on landscape
• Fire to manage dense shrubs
Middleback, SA
(Lange et al. 1984)
• Conservative stocking rates
• Sub-division, reticulation and controlled
access to water
Goldfields, WA
(NEGKLCD 1993)
• Manage total grazing pressure
• Conservative stocking rates
• Strategic spelling for natural regeneration
• Water-harvesting to restore degraded country
• Fence to land systems
Annean, WA (Morrissey
and O’Connor 1989)
• Conservative stocking rates
• Rotational grazing (spell chenopods in summer,
grasses in winter, occasional 12-month spell)
• Fence on land system boundaries
• Cultivate for water infiltration and plant establishment
Merino Downs Qld
(McCormack 1989)
• Low stocking rates for more wool & lambs/head
• Hay forage stored as a reserve to allow spelling in
summer growing season
• Sheep and cattle rotated (for their different impacts)
• Control run-off with grass cover
Beef-Up Forum, Biloela,
Qld (Schulke 2007)
• Safe utilisation rates (match stocking rates to feed)
• Early growing season spelling
• Manage when and where animals graze
•
•
•
•
Monitor land condition
Fire to manage tree-grass balance
Fence riparian/sensitive areas
Weed prevention
Managing for variability in arid natural resources
and hot times better and to graze over larger areas. Categories
(i) and (ii) relate more directly to the natural resources; the
recommended types of actions in these categories may be
summarised as:
• Maintain conservative stocking rates (with various guidelines
for what this means, especially in terms of appropriate
long-term utilisation rates [Johnston et al. 1996; Hall
et al. 1998]), taking care to count total grazing pressure
including uncontrolled grazers – this particularly addresses
WP1, but also WP2, WP3, and WP4; however steady
stocking rates may trigger WP5 by homogenising grazing
over time.
• Apply spelling and rotational grazing to paddocks (especially
in the early growing season/pulse) – this action particularly
addresses WP1, but must be tailored to the species involved
(see Müller et al. 2007).
• Spread grazing evenly in space, with small herds or flocks
per water point – this helps with WP1 and 2 but triggers WP5
(and possibly WP7).
• Fence on land system boundaries, and fence off riparian
and other sensitive areas – this addresses WP2, but can
exacerbate WP5.
• Control run-off with adequate levels of grass cover – this
addresses WP4 before damage has been done.
• Cultivate soil or build ponding banks for water harvesting and
restoration – this addresses WP4 in particular, especially after
damage has been done.
• Use fire to manage the shrub-grass balance – this helps to
counteract the impacts of WP5.
Many other factors affect the exact ways in which these
practices should be applied locally. Such factors include soil
type, landscape heterogeneity, nitrogen content, and the tradeoff among available perennial species. However, it can be seen
that pastoral best practice should address all weak points (and
codes that do not do this should be suspect), even though some
cannot be resolved solely at a property scale.
Management to maximise other sustainable production
systems
Although other production systems (Jones and James 2006)
are very much in the minority in desert Australia at present,
it is worth asking what lessons might be drawn for them,
particularly the nascent bush-products industry (Salvin et al.
2004; Morse 2005) (Table 1). First, it is apparent that longerlived perennials are a better base for any industry looking
for stability in production over time – an attribute met by
acacia seeds, Quandong and speciality timbers. Such industries
must be aware of the same weak points as for palatable
perennials under grazing – sustainable production will depend
on not disrupting the growth and reserve replenishment cycles
(although in the case of seeds, artificial propagation could
substitute, and indeed sandalwood production is moving to
plantations). Second, in the absence of horticulture of some
sort, industries based on wild harvest of shorter-lived species
such as bush tomatoes will be more variable. These industries
need to be wary of managing the seed supply, or replenishment
of root stocks (evident to Aboriginal wild harvesters as shown
by their practices). Logically one might look to exploit other
sources of less variable production such as termites, lizards,
The Rangeland Journal
23
and parasitic fruits such as those of mistletoes, as indeed
Aboriginal people traditionally did; however these have not
caught on today (other than chocolate-coated honey ants in
small quantities!).
There are few best-practice guidelines for these other systems
(however, see Jones [2001] and the Sandalwood Research
Newsletter [2007] for sandalwood; there is also much active
research on bush foods). As these are developed, the weak
points should be considered, in order that their management may
emerge more rapidly for these uses than the century or so that it
has taken in grazing guides.
Lastly, there are various intensive-production systems such as
irrigation horticulture and mining. These are small in geographic
scale and outside the scope of this paper, but it is notable
and appropriate that restoring natural flow management to the
environment (WP4) has been adopted as a key approach to
assessing best-practice management in mining rehabilitation,
using Landscape Function Analysis (Tongway and Hindley
2004).
Management to maximise diversity for conservation
Management for conservation has (or should have) very different
goals to that of sustainable production. The idealised goal for
conservation is to maintain the full diversity of organisms and
hence life-history strategies, as well as their emergent multispecies modes of organisation. Arid zone conservation must
thus aim to maintain the temporal and spatial variability of
drivers such as rain, fire and grazing, while accounting for the
degree to which the effects of fragmentation and other land
uses reduce this variability, in parallel with recommendations
for forests (e.g. Lindenmayer et al. 2006). Stafford Smith
and Ash (2006) distinguish broad categories of selective
forces maintaining biodiversity regionally, some of which
cannot be maintained on protected areas by themselves. They
therefore identify four complementary approaches to regional
conservation management in rangelands, as:
1. Protecting focal areas, which account for substantial
background biodiversity, and particularly take care of (in our
terminology here) refuging persistents.
2. Maintaining connectivity between focal areas, which allows
nomads (and exploiters) to move to and between reserves, and
on a longer timeframe allows any persistents (or ephemerals,
although these are usually more vagile) that occasionally
become locally extinct to re-invade.
3. Maintaining diffuse selection processes based on landscape
structure; this refers mainly to the factors that allow selforganising communities to establish widely, and supports a
key driver of micro-allopatric co-existence.
4. Maintaining diffuse selection processes based on driver
heterogeneity; this refers to landscape-scale spatial and
temporal diversity in the drivers, particularly rainfall and
fire, but also herbivory and predation; this addresses the
hardest weak point to conceptualise, WP5, and supports
asynchronous co-existence.
The facilitation strategy is not greatly in evidence, perhaps
because it occurs at a scale that is fine enough that general reserve
management is sufficient.
Surprisingly, there seem to be no general operational bestpractice manuals for arid zone conservation comparable to the
24
The Rangeland Journal
grazing manuals. Best practice for conservation reserves is
mostly expressed through the medium of park strategic plans
(e.g. NSW NPWS 1996; DEH 2006, among many others) which
tend to specify actions and goals without often articulating
any underlying principles about how landscapes function. The
key features that these have in common are: more or less
adequate zoning of different land uses; controlling feral animals
and weeds; usually managing fire and erosion; sometimes
management of specific endangered species; as well as a
major emphasis on visitor experience and management, and
increasingly joint management with Aboriginal custodians. In
terms of impacts on organisms’ weak points, these goals on
dedicated reserves translate to:
• Maintaining the diversity of selection pressures, particularly
with regard to variability over time and space (i.e. avoiding
WP5, WP6, WP9) – thus for example, it is undesirable to
regulate flows on river systems such as those of the Lake Eyre
Basin (Jenkins et al. 2005) or permit invasion by buffel grass
(Clarke et al. 2005) or irrigate (large) patches of environment
to support an individual species.
• Avoiding the pressures that occur on pastoral lands (thus
addressing WP1–WP5) – grazing which debilitates the ability
of palatable perennials to establish their reserves, particularly
the very palatable species (necessarily lost on pastoral lands).
This generally means removing feral grazers, and ensuring
that native grazers are subject to natural variability in their
populations. This may not be the case for kangaroos in the
absence of predators such as dingos, and also requires the
closure of most artificial waters.
• Looking after local refugia that are critical to those organisms
retreating to these (WP2); these are generally already a focus
for conservation activity (Morton et al. 1995a), although an
added priority is to focus on organisms (most obviously longlived trees) that provide stabilised environments for many
others.
• Managing the competitive effects of weeds (Grice 2006)
and feral animals for their grazing pressure and predation
(Edwards et al. 2004) (again addressing WP1–WP5); the
difficult issue of setting priorities for these could be assisted
by considering how much they are upsetting the natural
variability of driving forces.
In practice, most conservation reserves contain land
management activities related to Aboriginal traditional owners
and tourists, and anyway are too small to ignore the effects
of surrounding off-reserve land uses. The necessary close
engagement of human use with conservation is beyond this
paper (e.g. see Tremblay 2008, this issue), but must play
out at multiple scales. Within parks, the involvement of land
managers (particularly in joint management with Aboriginal
custodians) as well as land users (particularly tourists) is a rapidly
evolving arena that should take note of principles by which the
environment operates.
Tourism as a land use has characteristics in common with
other production systems – generally seeking a consistent
visitor experience that, in its lowest common denominator
form, involves homogenising impacts just as much as grazing
production. As noted above, the usual solution to this within
parks is thoughtful zoning, based on understanding the weak
points.
M. Stafford Smith et al.
Scaling up to link humans and the environment
Zoning is also recommended by Morton et al. (1995b)
and Biograze (2000) in order to integrate production and
conservation at the regional scale. In terms of the present
analysis, these recommendations aim to:
• Maintain sufficient areas without heavy production pressure
(harvesting, grazing or trampling) so that in-situ persistents
can invest in their reserves;
• Avoid damage to self-organising communities everywhere;
• Protect refugia for refuging persistents; and
• Support connectivity and the maintenance of diffuse
processes at the landscape scale over large areas.
This requires a hierarchical approach to zoning, with
guidelines that are nested and increasingly specific as one moves
from the scale of the region to the ‘property’ (or park, etc.) to
the local management unit (e.g. paddock) scale. The question of
how many resources to invest in the different types of actions
remains a poorly analysed trade-off; Stafford Smith and Ash
(2006) propose an approach to this.
Conclusions
The purpose of this paper has been to systematise what we
already know about the role of variability in arid environments,
with a focus on what variability means for the management of
these environments in Australia. The discussion has perforce
still been in generalities since there has been no successful
systematic effort to model how the responses of specific detailed
strategies to specific temporal distribution patterns of drivers
lead to different optimal strategies in different environments,
an effort that is now underway (McAllister and Stafford
Smith 2006). However, we have seen why certain types of
recommendations are universally important for management
of variable arid environments. Best-practice guidelines already
usually encompass all of these; to be comprehensive in the
future, all these factors should be critically assessed as to their
significance for any given environment, and only omitted after
due consideration.
The basic types of grazing management recommendations
have been around for more than a century and are based on
the fundamental ways in which these environments function.
Yet, there is plenty of evidence that we do not manage
these environments perfectly, whether for production or
conservation. The issue of why some recommendations may
be harder to follow consistently than others is discussed
elsewhere [e.g. long return times, difficulties in monitoring
and attributing changes in variable environments, slow
social learning, the effects of discount rates (Stafford Smith
et al. 2000, 2007)]. However, understanding the functional
significance of the recommendation is part of the raised
awareness needed to counter these difficulties and to identify
the slow variables that are most significant to rangeland
management.
The thesis of this paper has been that highly variable resource
inputs result in particular biotic response strategies; and that
these responses must be understood for successful management
of natural resources in arid lands. In fact, the same diversity of
responses and weak points is likely to be relevant to other entities
dealing with variable inputs, common in dryland environments
Managing for variability in arid natural resources
(Stafford Smith 2008, this issue) whether it is the livelihoods
of small businesses, or the settlements that depend on these, or
many other arid zone institutions. Hence, we may expect similar
approaches to coping with variability by such entities. This will
be the topic of other papers.
Acknowledgements
The work reported in this publication was supported by Land and
Water Australia, CSIRO, and funding from the Australian Government
Cooperative Research Centres Programme through the Desert Knowledge
CRC (www.desertknowledgecrc.com.au); the views expressed herein do not
necessarily represent the views of Desert Knowledge CRC or its Participants.
We are grateful for the review comments of Leigh Hunt, Steve Morton and
Julian Reid. This is Publication No. 2 in the development of a Science of
Desert Living.
References
Allan, R. J. (1991). Australasia. In: ‘Teleconnections linking worldwide
climate anomalies’. (Eds R. Glantz, R. Katz, and N. Nicholls.)
pp. 73–120. (Cambridge University Press: Cambridge.)
Anderson, V. J., and Hodgkinson, K. C. (1997). Grass-mediated capture
of resource flows and the maintenance of banded mulga in a
semi-arid woodland. Australian Journal of Botany 45, 331–342.
doi: 10.1071/BT96019
Anthelme, F., Michalet, R., and Saadou, M. (2007). Positive associations
involving the tussock grass Panicum turgidum Forssk. in the AirTenere Reserve, Niger. Journal of Arid Environments 68, 348–362.
doi: 10.1016/j.jaridenv.2006.07.007
Ash, A. J., Corfield, J. P., and Ksiksi, T. (2001). ‘The Ecograze Project –
developing guidelines to better manage grazing country.’ (CSIRO:
Townsville.)
Barker, W. R., and Greenslade, P. J. M. (1982). ‘Evolution of the flora and
fauna of arid Australia.’ (Peacock Publications: Adelaide.)
Behnke, R. H., and Scoones, I. (1993). ‘Rethinking range ecology:
implications for rangeland management in Africa.’ (Commonwealth
Secretariat, Overseas Development Inst. and International Inst. for
Environment and Development: London.)
Biograze (2000). ‘Biograze: waterpoints and wildlife.’ (CSIRO: Alice
Springs.)
Botterill L., and Fisher M. (2003). ‘Beyond drought in Australia: people,
policy and perspectives.’ (CSIRO Publishing: Melbourne.)
Brandle, R., and Moseby, K. E. (1999). Comparative ecology of two
populations of Pseudomys australis in northern South Australia. Wildlife
Research 26, 541–564. doi: 10.1071/WR97049
Byers, J. E., Cuddington, K., Jones, C. G., Talley, T. S., Hastings, A.,
Lambrinos, J. G., Crooks, J. A., and Wilson, W. G. (2006). Using
ecosystem engineers to restore ecological systems. Trends in Ecology
& Evolution 21, 493–500. doi: 10.1016/j.tree.2006.06.002
Caldwell, M. M., Dawson, T. E., and Richards, J. H. (1998). Hydraulic lift:
consequences of water efflux from the roots of plants. Oecologia 113,
151–161. doi: 10.1007/s004420050363
Campbell, T., and Hacker, R. (2000). ‘The glove-box guide to tactical
grazing management for the semi-arid woodlands.’ (NSW Agriculture:
Sydney.)
Chesson, P., Gebauer, R. L. E., Schwinning, S., Huntly, N., Wiegand, K.,
Ernest, M. S. K., Sher, A., Novoplansky, A., and Weltzin, J. F.
(2004). Resource pulses, species interactions, and diversity maintenance
in arid and semi-arid environments. Oecologia 141, 236–253.
doi: 10.1007/s00442-004-1551-1
Cingolani, A. M., Noy-Meir, I., and Diaz, S. (2005). Grazing effects on
rangeland diversity: a synthesis of contemporary models. Ecological
Applications 15, 757–773. doi: 10.1890/03-5272
The Rangeland Journal
25
Clarke, P. J., Latz, P. K., and Albrecht, D. E. (2005). Long-term changes
in semi-arid vegetation: Invasion of an exotic perennial grass has
larger effects than rainfall variability. Journal of Vegetation Science 16,
237–248. doi: 10.1658/1100-9233(2005)016[0237:LCISVI]2.0.CO;2
Clissold, F. J., Sanson, G. D., and Read, J. (2006). The paradoxical effects
of nutrient ratios and supply rates on an outbreaking insect herbivore,
the Australian plague locust. Journal of Animal Ecology 75, 1000–1013.
doi: 10.1111/j.1365-2656.2006.01122.x
Cole J. (1994). Better pasture plans reviving Hay rangeland. In: ‘The Land’.
(5 May 1994) p. 23. (Rural Press: Sydney.)
DEH (2006). ‘Gawler Ranges National Park management plan.’ (Department
for Environment and Heritage: Adelaide.)
Dickman, C. R., Mahon, P. S., Masters, P., and Gibson, D. F. (1999). Longterm dynamics of rodent populations in arid Australia: the influence of
rainfall. Wildlife Research 26, 389–403. doi: 10.1071/WR97057
Dunkerley, D. L. (2002). Infiltration rates and soil moisture in a groved
mulga community near Alice Springs, arid central Australia: evidence for
complex internal rainwater redistribution in a runoff–runon landscape.
Journal of Arid Environments 51, 199–219. doi: 10.1006/jare.2001.0941
Edwards, G. P., Eldridge, S. R., Wurst, D., Berman, D. M., and Garbin, V.
(2001). Movement patterns of female feral camels in central and northern
Australia. Wildlife Research 28, 283–289. doi: 10.1071/WR00053
Edwards, G. P., Pople, A. R., Saalfeld, K., and Caley, P. (2004). Introduced
mammals in Australian rangelands: future threats and the role of
monitoring programmes in management strategies. Austral Ecology 29,
40–50. doi: 10.1111/j.1442-9993.2004.01361.x
Eldridge, D. J. (1999). Distribution and floristics of moss- and lichendominated soil crusts in a patterned Callitris glaucophylla woodland in
eastern Australia. Acta Oecologica – International Journal of Ecology
20, 159–170. doi: 10.1016/S1146-609X(99)80029-0
Eldridge, D. J., and Rath, D. (2002). Hip holes: kangaroo (Macropus spp.)
resting sites modify the physical and chemical environment of
woodland soils. Austral Ecology 27, 527–536. doi: 10.1046/j.14429993.2002.01212.x
Esteban, J., and Fairen, V. (2006). Self-organized formation of banded
vegetation patterns in semi-arid regions: a model. Ecological Complexity
3, 109–118. doi: 10.1016/j.ecocom.2005.10.001
Facelli, J. M., and Temby, A. M. (2002). Multiple effects of shrubs on annual
plant communities in arid lands of South Australia. Austral Ecology 27,
422–432. doi: 10.1046/j.1442-9993.2002.01196.x
Fisher, A., Hunt, L., James, C., Landsberg, J., Phelps, D., Smyth, A., and
Watson, I. (2004). Review of total grazing pressure management issues
and priorities for biodiversity conservation in rangelands: a resource to
aid NRM planning. Report No. 3. Desert Knowledge CRC and Tropical
Savannas Management CRC, Alice Springs.
Flores, J., and Jurado, E. (2003). Are nurse-protégé interactions
more common among plants from arid environments? Journal of
Vegetation Science 14, 911–916. doi: 10.1658/1100-9233(2003)014
[0911:ANIMCA]2.0.CO;2
Foran, B. D., Friedel, M. H., MacLeod, N. D., Stafford Smith, D. M., and
Wilson, A. D. (1990). ‘A policy for the future of Australia’s rangelands.’
(CSIRO Division of Wildlife and Ecology: Canberra.)
Friedel, M. H., Foran, B. D., and Stafford Smith, D. M. (1990). Where the
creeks run dry or ten feet high: pastoral management in arid Australia.
Proceedings of the Ecological Society of Australia 16, 185–194.
Giladi, I. (2006). Choosing benefits or partners: a review of the
evidence for the evolution of myrmecochory. Oikos 112, 481–492.
doi: 10.1111/j.0030-1299.2006.14258.x
Gilfillan, S. L. (2001). An ecological study of a population of
Pseudantechinus macdonnellensis (Marsupialia: Dasyuridae) in central
Australia. II. Population dynamics and movements. Wildlife Research
28, 481–492. doi: 10.1071/WR99063
Grice, A. C. (2006). The impacts of invasive plant species on the
biodiversity of Australian rangelands. The Rangeland Journal 28, 27–35.
doi: 10.1071/RJ06014
26
The Rangeland Journal
Hacker, R. B., Hodgkinson, K. C., Melville, G. J., Bean, J., and
Clipperton, S. P. (2006). Death model for tussock perennial grasses:
thresholds for grazing-induced mortality of mulga Mitchell grass
(Thyridolepis mitchelliana). The Rangeland Journal 28, 105–114.
doi: 10.1071/RJ06001
Hall, W. B., McKeon, G. M., Carter, J. O., Day, K. A., Howden, S. M.,
Scanlan, J. C., Johnston, P. W., and Burrows, W. H. (1998). Climate
change in Queensland’s grazing lands: II. An assessment of the impact
on animal production from native pastures. The Rangeland Journal 20,
177–205. doi: 10.1071/RJ9980177
Haythornthwaite, A. S., and Dickman, C. R. (2006). Distribution,
abundance, and individual strategies: a multi-scale analysis of
dasyurid marsupials in arid central Australia. Ecography 29, 285–300.
doi: 10.1111/j.2006.0906-7590.04307.x
Hesse, P. P., and McTainsh, G. H. (2003). Australian dust deposits: modern
processes and the Quaternary record. Quaternary Science Reviews 22,
2007–2035. doi: 10.1016/S0277-3791(03)00164-1
Higgins, P. J. (1999). ‘Handbook of Australian, New Zealand & Antarctic
Birds. Parrots to Dollarbird, Vol. 4.’ (Oxford University Press:
Melbourne.)
HilleRisLambers, R., Rietkerk, M., van den Bosch, F., Prins, H. H. T., and
de Kroon, H. (2001). Vegetation pattern formation in semi-arid grazing
systems. Ecology 82, 50–61.
Hunt, L. P. (2001). Heterogeneous grazing causes local extinction of edible
perennial shrubs: a matrix analysis. Journal of Applied Ecology 38,
238–252. doi: 10.1046/j.1365-2664.2001.00586.x
James, C. D., Landsberg, J., and Morton, S. R. (1999). Provision of watering
points in the Australian arid zone: a review of effects on biota. Journal
of Arid Environments 41, 87–121. doi: 10.1006/jare.1998.0467
Jenkins, K. M., Boulton, A. J., and Ryder, D. S. (2005). A common parched
future? Research and management of Australian arid-zone floodplain
wetlands. Hydrobiologia 552, 57–73. doi: 10.1007/s10750-005-1505-6
Johnston, P. W., Tannock, P. R., and Beale, I. F. (1996). Objective
‘safe’ grazing capacities for south–west Queensland, Australia: model
application and evaluation. The Rangeland Journal 18, 259–269.
doi: 10.1071/RJ9960259
Jones, P. (2001). Sandalwood re-visited in Western Australia. Sandalwood
Research Newsletter 12, 3–4.
Jones, M., and James, C. (2006). Review of desert enterprises reliant on
natural and cultural resources. Report No. 25. Desert Knowledge CRC,
Alice Springs.
Jurado, E. (1990). Seed and seedling biology of central Australian plants.
PhD thesis, Macquarie University, Sydney, Australia.
Kingsford, R. T., and Norman, F. I. (2002). Australian waterbirds – products
of the continent’s ecology. Emu 102, 47–69. doi: 10.1071/MU01030
Kratz, T. K., Benson, B. J., Blood, E. R., Cunningham, G. L., and
Dahlgren, R. A. (1991). The influence of landscape position on temporal
variability in four North American ecosystems. American Naturalist 138,
355–378. doi: 10.1086/285222
Landsberg, J., James, C. D., Morton, S. R., Müller, W. J., and Stol, J. (2003).
Abundance and composition of plant species along grazing gradients
in Australian rangelands. Journal of Applied Ecology 40, 1008–1024.
doi: 10.1111/j.1365-2664.2003.00862.x
Lange, R. T., Nicolson, A. D., and Nicolson, D. A. (1984). Vegetation
management of chenopod rangelands in South Australia. Australian
Rangeland Journal 6, 46–54. doi: 10.1071/RJ9840046
Lejeune, O., Couteron, P., and Lefever, R. (1999). Short range co-operativity
competing with long range inhibition explains vegetation patterns.
Acta Oecologica – International Journal of Ecology 20, 171–183.
doi: 10.1016/S1146-609X(99)80030-7
Lindenmayer, D. B., Franklin, J. F., and Fischer, J. (2006). General
management principles and a checklist of strategies to guide forest
biodiversity conservation. Biological Conservation 131, 433–445.
doi: 10.1016/j.biocon.2006.02.019
M. Stafford Smith et al.
Ludwig, J. A., and Tongway, D. J. (1996). Rehabilitation of semiarid
landscapes in Australia. 2. Restoring vegetation patches. Restoration
Ecology 4, 398–406. doi: 10.1111/j.1526-100X.1996.tb00192.x
Ludwig, J., Tongway, D., Freudenberger, D., Noble, J., and Hodgkinson, K.
(1997). ‘Landscape ecology, function and management: principles from
Australia’s rangelands.’ (CSIRO Publishing: Melbourne.)
Ludwig, J. A., Tongway, D. J., Bastin, G. N., and James, C. D. (2004).
Monitoring ecological indicators of rangeland functional integrity and
their relation to biodiversity at local to regional scales. Austral Ecology
29, 108–120. doi: 10.1111/j.1442-9993.2004.01349.x
Ludwig, J. A., Wilcox, B. P., Breshears, D. D., Tongway, D. J., and
Imeson, A. C. (2005). Vegetation patches and runoff-erosion as
interacting ecohydrological processes in semiarid landscapes. Ecology
86, 288–297. doi: 10.1890/03-0569
LWA (2006). ‘Insights: case studies on how woolgrowers are successfully
managing pastoral country for profit and sustainability.’ (Land and Water
Australia: Canberra.)
Marree SCB District Plan (1997). ‘Marree soil conservation board district
plan.’ (Primary Industries and Resources SA: Adelaide.)
McAllister, R. R. J., and Stafford Smith D. M. (2006). The science of
desert living. In: ‘Proceedings of the 14th biennial Australian Rangeland
Society Conference’. (Ed. P. Erkelenz) pp. 258–261. (Australian
Rangeland Society: Renmark.)
McCormack, J. (1989). Stocking rates and land care: the Merino Downs
case. Australian Rangelands Society Newsletter 89, 12–14.
Morrissey, J. G., and O’Connor, R. E. Y. (1989). 28 years of station
management, ‘fair use and a fair go’. W.A. Dept. of Agriculture Pastoral
Memo (Carnarvon) 13, 2–9.
Morse, J. (2005). Bush resources: opportunities for Aboriginal enterprise
in central Australia. Report No. 2. Desert Knowledge CRC,
Alice Springs.
Morton, S. R., and Christian, K. A. (1994). Ecological observations on the
spinifex ant, Ochetellus flavipes (Kirby) (Hymenoptera, Formicidae), of
Australia northern arid zone. Journal of the Australian Entomological
Society 33, 309–316. doi: 10.1111/j.1440-6055.1994.tb01235.x
Morton, S. R., and James, C. D. (1988). The diversity and abundance of
lizards in arid Australia: a new hypothesis. American Naturalist 132,
237–256. doi: 10.1086/284847
Morton, S. R., Short, J., and Barker, R. D. (1995a). ‘Refugia for biological
diversity in arid and semi-arid Australia.’ (Biodiversity Unit, Department
of the Environment, Sport and Territories: Canberra.)
Morton, S. R., Stafford Smith, D. M., Friedel, M. H., Griffin, G. F., and
Pickup, G. (1995b). The stewardship of arid Australia: ecology and
landscape management. Journal of Environmental Management 43,
195–217. doi: 10.1016/S0301-4797(95)90402-6
Mound, L. A. (2004). Australian Thysanoptera – biological diversity and
a diversity of studies. Australian Journal of Entomology 43, 248–257.
doi: 10.1111/j.1326-6756.2004.00431.x
Müller, B., Frank, K., and Wissel, C. (2007). Relevance of rest periods in
non-equilibrium rangeland systems – a modelling analysis. Agricultural
Systems 92, 295–317. doi: 10.1016/j.agsy.2006.03.010
NEGKLCD (1993). ‘Mulga, merinos and managers: a handbook
of recommended pastoral management practices.’ (North
Eastern Goldfields and Kalgoorlie Land Conservation Districts:
Kalgoorlie.)
Noble, J. C. (1991). On ratites and their interactions with plants. Revista
Chilena de Historia Natural 64, 85–118.
Norbury, G. L., Norbury, D. C., and Oliver, A. J. (1994). Facultative
behaviour in unpredictable environments – mobility of red kangaroos
in arid Western Australia. Journal of Animal Ecology 63, 410–418.
doi: 10.2307/5558
Noy-Meir, I. (1973). Desert ecosystems: environment and producers.
Annual Review of Ecology and Systematics 4, 25–51. doi: 10.1146/
annurev.es.04.110173.000325
Managing for variability in arid natural resources
The Rangeland Journal
Noy-Meir, I. (1974). Desert ecosystems: higher trophic levels. Annual
Review of Ecology and Systematics 5, 195–213. doi: 10.1146/
annurev.es.05.110174.001211
NSW NPWS (1996). ‘Sturt National Park plan of management.’ (NSW
National Parks and Wildlife Service: Sydney.)
O’Connor, P. J., Smith, S. E., and Smith, F. A. (2001). Arbuscular mycorrhizal associations in the southern Simpson Desert. Australian Journal
of Botany 49, 493–499. doi: 10.1071/BT00014
Orians, G. H., and Milewski, A. V. (2007). Ecology of Australia: the effects
of nutrient-poor soils and intense fires. Biological Reviews 82, 393–423.
doi: 10.1111/j.1469-185X.2007.00017.x
Pantastico-Caldas, M., and Venable, D. L. (1993). Competition in two species
of desert annuals along a topographic gradient. Ecology 74, 2192–2203.
doi: 10.2307/1939573
Partridge I. (1999). ‘Managing grazing in northern Australia – a grazier’s
guide.’ (Department of Primary Industries: Brisbane.)
Pavey, C. R., Goodship, N., and Geiser, F. (2003). Home range
and spatial organisation of rock-dwelling carnivorous marsupial,
Pseudantechinus macdonnellensis. Wildlife Research 30, 135–142.
doi: 10.1071/WR03005
Pickup, G. (1985). The erosion cell – a geomorphic approach to landscape
classification in range assessment. Australian Rangeland Journal 7,
114–121. doi: 10.1071/RJ9850114
Purvis, J. R. (1986). Nurture the land: my philosophies of pastoral
management in central Australia. Australian Rangeland Journal 8,
110–117. doi: 10.1071/RJ9860110
Quirk, M., and O’Reagain, P. (2003). Managing grazing lands in a variable
climate. In: ‘Science for drought: proceedings of the national drought
forum’. (Eds R. Stone and I. Partridge.) pp. 101–105. (Queensland
Department of Primary Industries: Brisbane.)
Reid, N., and Stafford Smith, M. (2000). Population dynamics of an arid
zone mistletoe (Amyema preissii, Loranthaceae) and its host Acacia
victoriae (Mimosaceae). Australian Journal of Botany 48, 45–58.
doi: 10.1071/BT97076
Reynolds, J. F., Kemp, P. R., Ogle, K., and Fernández, R. J. (2004).
Modifying the ’pulse-reserve’ paradigm for deserts of North America:
precipitation pulses, soil water, and plant responses. Oecologia 141,
194–210. doi: 10.1007/s00442-004-1524-4
Robinson, B. S., Bamforth, S. S., and Dobson, P. J. (2002). Density
and diversity of protozoa in some arid Australian soils. Journal
of Eukaryotic Microbiology 49, 449–453. doi: 10.1111/j.15507408.2002.tb00227.x
Roshier, D. A., Robertson, A. I., Kingsford, R. T., and Green, D. G. (2001).
Continental-scale interactions with temporary resources may explain
the paradox of large populations of desert waterbirds in Australia.
Landscape Ecology 16, 547–556. doi: 10.1023/A:1013184512541
Ross, M. A. (1969). An integrated approach to the ecology of arid Australia.
Proceedings of the Ecological Society of Australia 4, 67–81.
Salvin, S., Bourke, M., and Byrne, T. (Eds) (2004). The new crop industries
handbook. RIRDC Publ. 04/125. RIRDC, Canberra.
Sandalwood Research Newsletter (2007). Available at: www.jcu.edu.au/
school/tropbiol/srn/ (accessed 30 July 2007).
Schlesinger, C. (2000). The effect of a temporally variable environment
and grazing on ground-active lizards in mulga and shrublands of
central Australia. PhD thesis, Charles Darwin University, Darwin,
Australia.
Schulke, B. (2007). Beefing up grazing land: presentation to Beef-Up
Forum, Biloela, 15 Feb 2007. Meat and Livestock Australia: Brisbane.
Available at: www.mla.com.au/TopicHierarchy/IndustryPrograms/
NorthernBeef/BeefUp+forums/Biloela (accessed 30 June 2007).
27
Schwinning, S., and Sala, O. E. (2004). Hierarchy of responses to resource
pulses in arid and semi-arid ecosystems. Oecologia 141, 211–220.
Schwinning, S., Sala, O. E., Loik, M. E., and Ehleringer, J. R. (2004).
Thresholds, memory, and seasonality: understanding pulse dynamics in
arid/semi-arid ecosystems. Oecologia 141, 191–193.
Stafford Smith, M. (2008). The ‘desert syndrome’ – causally-linked
factors that characterise outback Australia. The Rangeland Journal 30,
3–14.
Stafford Smith, M. (2003). Living in the Australian environment. In: ‘Beyond
drought in Australia: people, policy and perspectives’. (Eds L. Botterill
and M. Fisher.) pp. 9–20. (CSIRO Publishing: Melbourne.)
Stafford Smith, D. M., and Morton, S. R. (1990). A framework for the
ecology of arid Australia. Journal of Arid Environments 18, 255–278.
Stafford Smith, M., and Ash, A. (2006). High conservation value in the
rangelands. Report of a workshop for the Australian Government
Department of the Environment and Heritage. Report No. 19. (Desert
Knowledge CRC: Alice Springs.)
Stafford Smith, M., Morton, S. R., and Ash, A. J. (2000). Towards
sustainable pastoralism in Australia’s rangelands. Australian Journal of
Environmental Management 7, 190–203.
Stafford Smith, D. M., McKeon, G. M., Watson, I. W., Henry, B. K.,
Stone, G. S., Hall, W. B., and Howden, S. M. (2007). Learning from
episodes of degradation and recovery in variable Australian rangelands.
Proceedings of the National Academy of Sciences of USA 104,
20690–20695
Stokes, C. J., McAllister, R. R. J., and Ash, A. J. (2006). Fragmentation of
Australian rangelands: processes, benefits and risks of changing patterns
of land use. The Rangeland Journal 28, 83–96. doi: 10.1071/RJ05026
Sullivan S., Kraatz M., Tapsell S., Tubman W., and O’Donnell K. (2006).
‘Perspectives on managing grazing country: graziers talk about
successfully managing their country, Victoria River District.’ (Tropical
Savannas CRC: Darwin.)
Tongway D. J., and Hindley N. L. (2004). ‘Landscape function analysis
manual: procedures for monitoring and assessing landscapes with
special reference to minesites and rangelands. Version 3.1.’ (CSIRO
Sustainable Ecosystems: Canberra.)
Tongway, D. J., and Ludwig, J. A. (1994). Small-scale resource heterogeneity
in semi-arid landscapes. Pacific Conservation Biology 1, 201–208.
Tremblay, P. (2008). Protected areas and development in arid Australia –
challenges to regional tourism. The Rangeland Journal 30, 67–75.
Turner, D., Ostendorf, B., and Lewis, M. (2008). An introduction to patterns
of fire in arid and semi-arid Australia, 1998–2004. The Rangeland
Journal 30, 95–107.
Vetter, S. (2005). Rangelands at equilibrium and non-equilibrium: recent
developments in the debate. Journal of Arid Environments 62, 321–341.
doi: 10.1016/j.jaridenv.2004.11.015
Westoby, M. (1980). Elements of a theory of vegetation dynamics in arid
rangelands. Israeli Journal of Botany 28, 169–194.
White, W. B., McKeon, G., and Syktus, J. (2003). Australian drought:
the interference of multi-spectral global standing modes and
travelling waves. International Journal of Climatology 23, 631–
662. doi: 10.1002/joc.895
Woinarski, J. C. Z. (2006). Predictors of nomadism in Australian birds:
a re-analysis of Allen and Saunders (2002). Ecosystems 9, 689–693.
doi: 10.1007/s10021-006-0077-2
Zann, R. A. (1996). ‘The zebra finch: a synthesis of field and laboratory
studies.’ (Oxford University Press: Oxford.)
Manuscript received 13 July 2007; accepted 6 September 2007
http://www.publish.csiro.au/journals/trj