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An Australian perspective on rewilding: Rewilding


Abstract and Figures

Rewilding is increasingly recognized as a conservation tool but is often context specific, which inhibits broad application. Rewilding in Australia seeks to enhance ecosystem function and promote self-sustaining ecosystems. An absence of large-bodied native herbivores means trophic rewilding in mainland Australia has focused on the restoration of functions provided by apex predators and small mammals. Because of the pervasive influence of introduced mesopredators, predator-proof fences, and establishment of populations on predator-free islands are common rewilding approaches. This sets Australian rewilding apart from most jurisdictions and provides globally relevant insights but presents challenges to restoring function to broader landscapes. Passive rewilding is of limited utility in arid zones. Although increasing habitat extent and quality in mesic coastal areas may work, it will likely be necessary to undertake active management. Because much of Australia's population is in urban areas, rewilding efforts must include urban areas to maximize effectiveness. Thus rewilding is not synonymous with wilderness and can occur over multiple scales. Rewilding efforts must recognize human effects on other species and benefit both nature and humans. Rewilding in Australia requires development of a shared vision and strategy and proof-of-concept projects to demonstrate the benefits. The repackaging of existing conservation activities as rewilding may confuse and undermine the success of rewilding programs and should be avoided. As elsewhere, rewilding in Australia should be viewed as an important conservation tool. © 2019 Society for Conservation Biology.
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An Australian perspective on rewilding
ın F. Sweeney ,1John Turnbull,2Menna Jones,3Mike Letnic,4Thomas M. Newsome,5
and Andy Sharp6
1National Parks Association of New South Wales, Pyrmont, NSW, 2009, Australia
2Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales,
Sydney, NSW, 2052, Australia
3School of Biological Sciences, University of Tasmania, Hobart, TAS, 7001, Australia
4Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney,
NSW, 2052, Australia
5School of Life and Environmental Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
6Natural Resources Northern and Yorke, Clare, SA, 5453, Australia
Abstract: Rewilding is increasingly recognized as a conservation tool but is often context specific, which
inhibits broad application. Rewilding in Australia seeks to enhance ecosystem function and promote self-
sustaining ecosystems. An absence of large-bodied native herbivores means trophic rewilding in mainland
Australia has focused on the restoration of functions provided by apex predators and small mammals.
Because of the pervasive influence of introduced mesopredators, predator-proof fences, and establishment of
populations on predator-free islands are common rewilding approaches. This sets Australian rewilding apart
from most jurisdictions and provides globally relevant insights but presents challenges to restoring function
to broader landscapes. Passive rewilding is of limited utility in arid zones. Although increasing habitat extent
and quality in mesic coastal areas may work, it will likely be necessary to undertake active management.
Because much of Australia’s population is in urban areas, rewilding efforts must include urban areas to
maximize effectiveness. Thus rewilding is not synonymous with wilderness and can occur over multiple
scales. Rewilding efforts must recognize human effects on other species and benefit both nature and humans.
Rewilding in Australia requires development of a shared vision and strategy and proof-of-concept projects to
demonstrate the benefits. The repackaging of existing conservation activities as rewilding may confuse and
undermine the success of rewilding programs and should be avoided. As elsewhere, rewilding in Australia
should be viewed as an important conservation tool.
Keywords: apex predator, conservation fencing, critical weight range mammals, ecosystem function, keystone
species, nature-based solutions, people and conservation, policy
Una Perspectiva Australiana del Proceso de Resilvestrar
Resumen: El proceso de resilvestrar es reconocido cada vez m´
as como una herramienta de conservaci´
pero con frecuencia depende del contexto ambiental, lo que inhibe su aplicaci´
on generalizada. En Australia,
el proceso de resilvestrar busca mejorar la funci´
on ambiental y promover los ecosistemas auto-sustentables.
Una ausencia de herb´
ıvoros nativos corpulentos significa que el resilvestreo tr´
ofico en la isla principal de
Australia se ha enfocado en la restauraci´
on de las funciones que proporcionan los superdepredadores y
los mam´
ıferos peque˜
nos. Debido a la influencia generalizada de los mesodepredadores introducidos, los
cercos contra depredadores y el establecimiento de poblaciones en islas libres de depredadores son estrategias
comunes de resilvestreo. Esto coloca al resilvestreo australiano aparte del que ocurre en muchas jurisdicciones
y proporciona informaci´
on relevante a nivel mundial, pero presenta retos para la restauraci´
on de la funci´
en paisajes m´
as amplios. El resilvestreo pasivo es de utilidad limitada en las zonas ´
aridas. Aunque el aumento
de la extensi´
on del h´
abitat y la calidad en las ´
areas meso-costeras puede funcionar, probablemente sea
Article impact statement: Rewilding in Australia seeks to enhance ecosystem function and promote self-sustaining ecosystems.
Paper submitted October 24, 2017; revised manuscript accepted November 22, 2018.
Conservation Biology, Volume 00, No. 0, 1–9
2019 Society for Conservation Biology
DOI: 10.1111/cobi.13280
necesario emprender un manejo activo. Ya que la mayor´
ıa de la poblaci´
on de Australia se encuentra en
areas urbanas, los esfuerzos de resilvestreo deben incluir a las ´
areas urbanas para maximizar su efectividad.
Por lo tanto, el resilvestreo no es sin´
onimo de la naturaleza y puede ocurrir en m´
ultiples escalas. Los esfuerzos
de resilvestreo deben reconocer los efectos que los humanos tienen sobre otras especies y deben beneficiar a
la naturaleza y a las personas. El resilvestreo en Australia requiere del desarrollo de una visi´
on compartida
y de proyectos con prueba de concepto para demostrar sus beneficios. La reinvenci´
on de las actividades de
on existentes como resilvestreo podr´
ıa confundir y debilitar el ´
exito de los programas de resilvestreo,
por lo que deber´
ıa evitarse. Como en todos lados, el proceso de resilvestrar en Australia deber´
ıa verse como
una herramienta importante de conservaci´
Palabras Clave: cercado de conservaci´
on, especies clave, funci´
on ambiental, mam´
ıferos del rango de peso
ıtico, personas y conservaci´
on, pol´
ıtica, soluciones basadas en la naturaleza
Perceptions of Rewilding
The success of rewilding in capturing public imagi-
nation stems from its framing as a positive activity
(Monbiot 2013). The public appeal of rewilding helps
explain why nongovernmental organizations (NGOs) are
active in rewilding (e.g., Australian Wildlife Conservancy,
Greening Australia, Conservation Volunteers Australia).
Governments too embrace rewilding (e.g., European
Commission financially supports Rewilding Europe; state
and federal Australian Government agencies practice or
intend to practice rewilding).
There is a growing consensus that rewilding should
focus on restoring ecosystem processes and species
interactions to promote complexity and self-sustaining
ecosystems (Fern´
andez et al. 2017; Pettorelli et al. 2018),
although several definitions exist (Jørgensen 2015;
Pettorelli et al. 2018). Trophic rewilding usually refers
to environmental change driven by strongly interacting
species (Soul´
e et al. 2003). Rewilding can therefore
include restoration of predatory interactions that trigger
trophic cascades and ultimately affect vegetation (Ripple
& Beschta 2007), but could also encompass restoration
of the ecological functions of ecosystem engineers
such as beavers (Castor spp.) (Law et al. 2016), large-
bodied herbivores (Ripple et al. 2015), and granivores
(Mills & Letnic 2018). In passive rewilding vegetation
encroachment (e.g., via abandonment of pastoral land)
drives changes in fauna and flora species composition
and biodiversity (Regos et al. 2016).
Rewilding means different things in different places
(Seddon et al. 2014), and lack of a fixed definition
(Jørgensen 2015) makes setting goals and evaluating suc-
cess difficult (Nogu´
es-Bravo et al. 2016). Questions exist
as to what ecological state, if any, rewilding efforts should
seek to replicate (Corlett 2016), and empirical evidence
that rewilding works is scarce (Nogu´
es-Bravo et al. 2016).
Some argue trophic rewilding distracts from more urgent
conservation issues (Rubenstein & Rubenstein 2016),
others argue rewilding helps reverse declines of biodi-
versity and ecosystem function in a human-dominated
world (Svenning et al. 2016). Whether rewilding is
relevant to introduction of non-native species outside
their range is unclear (Bradshaw et al. 2006), and intro-
duction of ecological surrogates is controversial (Donlan
In Australia support for rewilding stems from increas-
ing threats to biodiversity (Cresswell & Murphy 2017),
the need for novel approaches to reverse species’ de-
cline, and its complementarity with other conservation
initiatives. However, hurdles remain to successful, broad
application of rewilding in Australia. We considered how
rewilding experiences and approaches in other juris-
dictions are relevant to Australia; compared Australian
rewilding approaches with those used in other parts of
the world; considered future directions for rewilding in
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Sweeney et al. 3
Australia; and identified lessons learned in Australia that
are applicable elsewhere.
Opportunities and Limitations of Trophic
Rewilding in Australia
Restoring predator populations that have undergone
range contractions may be particularly important in Aus-
tralian rewilding. Top-down control by dingoes (Canis
dingo), mainland Australia’s largest terrestrial carnivore,
for instance, is a potentially cost-effective mechanism
to suppress or alter the behavior of introduced invasive
mesopredators, such as the red fox (Vulpes vulpes)and
feral cat (Felis catus) (Brook et al. 2012; Letnic et al.
2012). Such top-down control may also enable improved
coexistence of native and non-native species (Wallach
et al. 2015) and reduce overabundant small- and medium-
bodied native and invasive herbivores (Letnic et al. 2012;
Morris & Letnic 2017), sometimes leading to positive
economic outcomes for farmers (Prowse et al. 2014).
The reintroduction of Tasmanian devils (Sarcophilus har-
risii) to mainland Australia may lower red fox and feral
cat abundance, influence trophic cascades, and benefit
small mammals (Hollings et al. 2014, 2016), although not
all species (Hunter et al. 2015).
Increases in large carnivore populations in Europe
(Chapron et al. 2014) raise concern that there is
insufficient space for large predators and humans to coex-
ist (Rubenstein & Rubenstein 2016). However, mainland
Australia is sparsely populated and Tasmanian devils and
humans coexist in Tasmania, where the species is extant.
Other objections to restoring predators relate to human
safety and livestock depredation (Fleming et al. 2012).
Human injuries from Tasmanian devils or dingoes are ex-
tremely rare, but dingoes and devils could harm livestock,
particularly sheep (Jones et al. 2003; Fleming et al. 2012).
As in parts of Europe, where wolves (Canis lupus)are
culled, societal values will be the primary determinant to
the success of trophic rewilding of predators in Australia.
Australian critical weight range (CWR) mammals
(ground-dwelling species from 35 g to 5.5 kg vulnerable
to extinction; [Burbidge & McKenzie 1989]) are suscep-
tible to predation by red foxes and feral cats because
they lack appropriate antipredator responses (Moseby
et al. 2016). Since European colonization, some ecosys-
tem functions and processes have been reduced or elimi-
nated because of mammal extinctions and range contrac-
tions (Bilney et al. 2010; Fleming et al. 2014; Hayward
et al. 2016) (Fig. 1). Thus, CWR mammals are a priority
for conservation, but ineffective control of red foxes and
feral cats, habitat loss, and altered fire regimes remain key
challenges to trophic rewilding of small mammals (Bilney
et al. 2010; Woinarski et al. 2015).
In Europe, Asia, and North America reintroducing
large-bodied (>100 kg) herbivores (or surrogates) is part
of trophic rewilding. Australia lacks comparable native
herbivores but has horses (Equus caballus), donkeys
(Equus asinus), water buffalos (Bubalus bubalis), and
camels (Camelus dromedaries). These were all intro-
duced and have effects on ecosystems that are gener-
ally perceived as negative. Ecological control of these
species cannot be achieved currently due to a lack of
native predators of sufficient size to exert top-down con-
trol (Forsyth et al. 2018). Introducing surrogates of long-
extinct predators is, in the short term at least, unrealistic
in Australia due to intolerance and persecution of existing
predators. The broader effects of such reintroductions on
other species are also unknown.
Opportunities and Limitations of Passive Rewilding
in Australia
Passive rewilding (broadly letting nature take its course)
in Europe has yielded conservation benefits (Regos et al.
2016), and benefits would likely accrue from passive
rewilding in parts of Australia. Australia has lost approxi-
mately 40% of its forest cover, and much of the remainder
is highly fragmented (Bradshaw 2012) or was previously
logged (Hobday & McDonald 2014). Passive rewilding
would increase forest cover and the density of large trees
and the biodiversity they support (Lindenmayer et al.
2014). The loss of hollow-bearing trees is a threat to many
forest-dependent mammals (Woinarski et al. 2014) and
birds (BirdLife Australia & Australian Government Depart-
ment of Environment 2015) because Australia possesses
a disproportionate number of species that use hollows
(Gibbons & Lindenmayer 2002).
However, complex interactions between disturbance
(e.g., logging and fragmentation), invasive plants (Lan-
tana camera), and despotic bell miners (Manorina
melanophrys) have resulted in a phenomenon called bell
miner-associated dieback affecting localized but exten-
sive areas of eucalypt forest (Silver & Carnegie 2017).
Despotic noisy miners (M. melanocephala)stronglyand
negatively affect bird species richness and abundance
in woodland ecosystems (Thomson et al. 2015). Manage-
ment intervention is likely to be required in both systems,
limiting the application of passive rewilding.
Many forest ecosystems in Australia are fire prone,
and historic Aboriginal fire management likely influenced
forest development. Fire management following forest
restoration may be necessary to protect fire-sensitive
ecosystems, such as rainforests, or for hazard reduction.
Fire is also likely to be a management concern in passively
regenerating Mediterranean vegetation types in south-
ern Europe. As climate change alters the profitability of
arid-zone pastoralism, some of these lands may become
available for conservation. However, passive rewilding in
Australia’s arid interior, which retains extensive tracts of
native vegetation, may not stop biodiversity declines if
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Figure 1. (a) Impacts of reduced digging on ecosystem function, (b) consequences of the loss of ecosystem function,
(c) impacts of reduced predation on ecosystem function, and (d) consequences of the loss of ecosystem function.
introduced mesopredators remain present or if intro-
duced weeds (e.g., buffel grass [Cenchrus ciliaris]) prolif-
erate and alter fire regimes. Efforts to restore populations
of native fauna will therefore likely need to be accompa-
nied by pest and weed control to help shift the ecosystem
to a preferred state.
Restoring ecosystem function is no less urgent in
marine ecosystems; trophic cascades commonly occur
(Estes et al. 2011) and predatory fish biomass has been
extensively depleted (Christensen et al. 2014). The
recovery of large predatory fish can occur with minimal
human intervention, through the creation of marine
protected areas (MPAs), but to maximize effectiveness,
MPAs must be large, no take, long established, well
enforced, and isolated by deep water or sand (Edgar et al.
2014). In marine systems, widespread loss of habitat-
forming species, such as oysters and corals, and the
facilitation cascades they support simplifies ecosystems
and threatens biodiversity conservation, and their
restoration may thus be construed as rewilding (Thomsen
et al. 2010; Marzinelli et al. 2016). The restoration of such
structural elements need not be confined to MPAs but
is likely to be promoted within them via restrictions on
fishing and physical damage from human infrastructure.
Fenced Exclosures and Rewilding
Australia’s fauna has been devastated by introduced novel
predators due to its long history of evolutionary isolation
(Medina et al. 2011). In Australia fencing is used to ex-
Figure 2. Fenced exclosures, such as at Arid Recovery,
from which red foxes and feral cats are eradicated
achieve some rewilding objectives (photo by Charlotte
clude introduced mesopredators (red foxes and feral cats)
and lower mortality of predator-na¨
ıve CWR mammals.
Fencing in Africa, in contrast, is used to separate humans
and large predators and in Europe to maintain predator
density in rewilding efforts (Bull et al. 2018). Predator-
proof exclosures are also used in New Zealand to provide
havens for birds, reptiles, and invertebrates threatened by
introduced predators (Pech & Maitland 2016).
Fenced exclosures (Fig. 2) have been used success-
fully in Australia to protect threatened species and in-
crease their populations (Moseby et al. 2009). Current
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Sweeney et al. 5
exclosures range from small to reasonably large (123 km2,
Arid Recovery) and a 1450-km2exclosure is proposed
for Yorke Peninsula in South Australia. Recovery of small
mammal populations influences fungi (Clarke et al. 2015)
and termite assemblages (Coggan et al. 2016), soil prop-
erties (Martin 2003; James et al. 2009), seed dispersal,
and shrub recruitment (Mills et al. 2017). In this regard,
fenced exclosures achieve rewilding objectives at least
for some functions driven by smaller species. Only the
largest exclosures can achieve rewilding of devils and
dingoes (Moseby et al. 2018), and these would need to be
even larger to host self-sustaining populations or multiple
groups of devils and dingos.
Fences are ultimately inconsistent with the goal of rein-
stating self-sustaining ecosystems due to the maintenance
requirements of fences, the need for managed migration
between metapopulations, and the disruptions to ecosys-
tem processes and habitat degradation that may arise with
increasing animal populations contained within fences
(Hayward & Kerley 2009). Without the reintroduction of
native predators, fenced exclosures may exacerbate the
problem of prey na¨
e (Moseby et al. 2016). Fences
may therefore be best viewed as a starting point on a
rewilding continuum toward landscape-scale rewilding
that would be achieved in theory through restoration of
native predator populations, the use of livestock guardian
animals, shifts in pastoral practices, financial incentives to
farmers (Van Eeden et al. 2017), and novel means, such as
promoting conditions for native prey species to coevolve
with introduced predators (Moseby et al. 2016). Concur-
rent efforts to improve outcomes on a landscape scale are
necessary to restore self-sustaining ecosystems and avoid
small mammals being confined to fenced exclosures and
loss of their functions in the broader landscape.
Assisted Colonization
Australian NGO and academic sectors enthusiastically
support Tasmanian devil reintroductions to the Australian
mainland (Ritchie et al. 2012) (Supporting Information)
to improve ecosystem function. Devils were extirpated
from mainland Australia 3000 years ago (White et al.
2018). In the absence of a demonstrated broader func-
tional role, assisted colonization of species as a global
conservation tool (Bradshaw et al. 2006) does not fit
rewilding goals. For example, proposals by the Australian
Rhino Project to bring black (Diceros bicornis)andwhite
(Ceratotherium simum) rhinoceroses to Australia have
not focused on the restoration of ecosystem processes,
but rather on conservation of these species.
People and Rewilding
One criticism of rewilding has been a perceived aim of
excluding human involvement with and influence on na-
ture and ecosystems (Jørgensen 2015). Some rewilding
efforts in Europe do seek to reduce human influence
on modified agricultural landscapes (Ceaușu et al. 2015).
But benefits can accrue to humans from rewilding. These
may accrue directly, such as income derived from wildlife
tourism and dingoes increasing profitability of farming
in some circumstances (Prowse et al. 2014; Johnson &
Wallach 2016), or indirectly through ecosystem services.
For example, restoring forest ecosystems in catchments
could reduce flood risk and provide clean water. Rewild-
ing thus shares similarities with nature-based solutions to
social problems that deliver both biodiversity and human
benefits (Nessh¨
over et al. 2017).
The importance of community involvement, particu-
larly in trophic rewilding, cannot be overstated. Predator
conservation efforts are likely to be opposed initially by
some, and social impacts of rewilding should be assessed
and made clear (Pettorelli et al. 2018). Predator-friendly
farming, designed to integrate socioeconomic and envi-
ronmental outcomes (Johnson & Wallach 2016), is used
in North America and Africa and may help overcome
aversions to predators in Australia too.
Globally, rewilding is synonymous with large, near-
continental scale projects. Yet in Australia, approximately
70% of the human population live in cities and 85% live
in urban areas. Urban rewilding is therefore a high pri-
ority in Australia to demonstrate tangible outcomes and
increase engagement with nature (Jepson 2016). Urban
programs, such as reintroductions of pollinators, reptiles
or small mammals accepted by humans, should occur
alongside initiatives in rural landscapes with the dual aim
of increasing ecosystem function and engaging the pub-
lic in conservation (Watson & Watson 2015). Rewilding
should therefore occur at multiple spatial scales (Fig. 3)
and seek to increase nonhuman autonomy, rather than
spatially separate humans and nonhumans (Prior & Ward
2016). In urban areas, rewilding will necessarily become a
compromise between restoring ecosystem function and
raising public awareness through species tolerated by
humans. There may also be a need to reduce the key
threats that led to the loss of species in the first place,
which sometimes may not be achievable.
Location is an important consideration in rewild-
ing because some areas and landscapes are more eco-
logically and socially suitable than others (Supporting
Information). In Europe a network of experimental sites
has been proposed to identify priority rewilding areas
(Jepson 2016), which could offer a model for Australia.
Locating rewilding initiatives where they have a good
chance of success and where economic benefits can ac-
crue may provide proof of concept and raise the profile of
rewilding. Success may be more readily achieved in areas
where there are ongoing conservation programs run by
local communities. Indigenous owned and managed land
in Australia offers great potential in this regard, especially
where there are established conservation programs or
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Figure 3. Scales at which rewilding is relevant: (a) wisent (Bison bonasus), a large-bodied herbivore, has a large
trophic influence over landscape scales, (b) beaver dams affect biodiversity at regional and local scales, and (c)
pygmy possum (Cercartetus spp.) have local effects in their home ranges of <1ha.
voluntary conservation agreements such as indigenous
protected areas. Indigenous land covers 52% of the coun-
try, and around three-quarters of Australia’s threatened
terrestrial or freshwater vertebrates occur on these lands
(Renwick et al. 2017).
Restoring Processes Rather than Historic States
Rewilding’s focus on ecological processes means success
should be measured by the degree to which management
actions result in the restoration of desired processes. Pos-
itive relationships between biodiversity and ecosystem
function (Cardinale et al. 2012) suggest restoration of
ecological processes may maintain biodiversity. A pro-
cess focus recognizes that ecosystems are dynamic and
therefore do not have a single historic state (Rohwer &
Marris 2016). A reintroduction of beavers (Castor fiber)
confirmed predictions that restored processes would in-
crease biodiversity (Law et al. 2016; Stringer & Gaywood
2016; Law et al. 2017). The restoration of pre-European
landscapes and species assemblages in Australia is in most
cases unachievable due to extinctions and the difficulties
of removing invasive species. Rewilding should therefore
consider contemporary patterns and processes, including
widespread human settlement, and the effects of human
activities and climate change on abundances and distri-
butions of species.
Policy Implications
Current conservation policy in Australia tends to focus on
species-specific or ecological-community-specific threat
reduction that targets species and ecosystems listed as
threatened by experts. Two projects, Gondwana Link
and the Great Eastern Ranges Initiative, seek to enhance
connectivity on the continental scale, and connectivity
is often an aim of conservation strategies. Strategies also
regularly recognize the need to build human appreciation
of nature. The National Reserve System seeks to achieve
comprehensive, adequate, and representative protection
of ecosystems at a bioregional level.
Rewilding should not replace these approaches, but
could be complementary and assist in meeting goals. For
example, explicitly considering maintenance of identi-
fied ecosystem processes could inform reserve selection
and better identify priorities for private land conserva-
tion. Some agricultural policies (e.g., lethal control of din-
goes and land clearing) are contradictory to both conser-
vation and rewilding goals and will require policy shifts.
Lessons from Rewilding in Australia
Although rewilding in Australia differs from rewilding
on continental landmasses, primarily due to the impact
of introduced mesopredators, there are lessons to be
learned from Australia. For example, the focus on re-
constructing all components of food webs, starting with
small consumers such as small mammals and birds, is
underdeveloped globally. Predator exclosures are used
to good effect in Australia and New Zealand and may
facilitate rewilding by promoting persistence of smaller
species affected by introduced predators.
The development of shared goals and strategies for
rewilding in Australia would provide more clarity of pur-
pose and allow evaluation of success and would clearly
signal to policy makers and funding bodies what con-
stitutes rewilding and help avoid rewilding becoming a
rehash of existing activities, which risks eroding pub-
lic interest. For example, the term rewilding is used
in the context of fairy bell-flower (Homoranthus spp.)
conservation to mean reintroductions following seed col-
lections, with no reference to broader ecosystem bene-
fits (Department of the Environment and Energy 2017).
Translocations of species for conservation purposes dif-
fer from translocations of species for that species to per-
form an ecological role (rewilding) (Seddon et al. 2014)
(Supporting Information).
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Sweeney et al. 7
Developing projects to demonstrate proof of concept
that integrate communities and research into rewilding
actions (Supporting Information) would help answer in-
ternational calls for more evidence (Nogu´
es-Bravo et al.
2016; Svenning et al. 2016). Projects in urban areas
designed to deliver outcomes for humans and nature
and high-profile, achievable landscape-scale rewilding are
clear priorities. Differences among arid, Mediterranean,
and mesic Australia mean rewilding needs to be tailored
to location. Passive rewilding may play a greater role in
coastal areas, but a complete absence of management
is likely impossible. However, the important ecological
role of CWR mammals in Australian ecosystems, and their
widespread declines (Fig. 1), means restoration of their
populations remains a high priority throughout Australia.
In New Zealand, restoring the ecological functions of
bird pollinators that have declined because of predation
by mammalian predators has been identified as a priority
(Anderson et al. 2011). To our knowledge, few rewilding
efforts in other jurisdictions focus on restoring ecological
functions of small consumers.
Engaging communities should be a fundamental
component of rewilding efforts and could be aided by
focusing initially on species and functions most likely
to be accepted by humans. This approach would help
develop societal support for rewilding before tackling
controversial activities, such as reintroduction of preda-
tors. For trophic rewilding in Australia, a concerted effort
is needed to shift current attitudes—and policy—from
one of predator persecution to one of tolerance. Trial
reintroductions of Tasmanian devils to mainland Australia
(Supporting Information) have yet to gain political
support. In areas of high ecological value, caution is
warranted. But in highly modified areas, more ambitious
policies should be pursued to accelerate rewilding. For
example, there are large parks in many Australian cities
where small mammals could be readily reintroduced and
passive rewilding promoted.
The popular appeal of rewilding means it should not
be dismissed as a conservation tool. For rewilding to be
effective, it is important that it not be used to rebrand
existing activities. Provided use of the term rewilding is
restricted to conservation actions that fit the definition,
it could greatly increase the profile of conservation and
wild nature in general.
Insights in this article resulted from a forum supported
financially by Taronga Conservation Society, the National
Parks Association of NSW, FAUNA Research Alliance, and
Conservation Volunteers Australia. We thank staff and
volunteers from the National Parks Association of NSW
and all participants for the productive and collaborative
manner in which they engaged in the process. Several
reviewers provided valuable feedback on earlier drafts of
this paper.
Supporting Information
Forum participants (Appendix S1), methods (Ap-
pendix S2), and results (Appendix S3) are available on-
line. The authors are solely responsible for the content
and functionality of these materials. Queries (other than
absence of the material) should be directed to the corre-
sponding author.
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... They are currently threatened by reduced habitat availability, widespread invasive predator populations and altered corvid behaviour. Trophic rewilding, involving the reintroduction of extirpated native predators, could provide a novel alternative to traditional conservation interventions, via the suppression of invasive species and overabundant herbivores, thus re-engineering the ecosystem (Sweeney et al. 2019). The original native predators on the islands, including Spotted-tailed Quolls (Dasyurus maculatus), Eastern Quolls (D. viverrinus), and Wedge-tailed Eagles (Aquila audax), likely went extinct due to over-hunting by Europeans shortly after their arrival and the Tasmanian Devil (Sarcophilus harrisii) has been documented in recent fossil evidence on Flinders Island (Peacock et al. 2018). ...
... There are multiple interpretations and definitions of trophic rewilding, but for the purposes of our paper, we define it as the restoration of ecological function, especially trophic interactions, through the introduction of targeted animal species. Since European colonisation, mammal extinctions have led to the reduced function of ecosystems across Australia (Sweeney et al. 2019). By restoring these ecosystem processes and species interactions, the goal is to promote complexity and selfsustaining ecosystems. ...
... Trophic rewilding specifically focuses on creating trophic cascades by introducing strongly interacting species, such as predatory interactions ( Figure 1). For example, rewilding of dingoes (Canis dingo) has been advocated for in areas of mainland Australia, as the top-down control of the species can suppress or alter the behaviour of introduced invasive mesopredators, such as the red fox (Vulpes vulpes) and feral cat (Sweeney et al. 2019). Rewilding has captured the interest of the public and many nongovernmental organisations (NGOs) are active in rewilding programmes. ...
... Due to their spatial and habitat requirements they serve as extremely important indicators. The rewilding movement is growing and having successes in Europe (Fernández et al., 2020), USA (Smith et al., 2003), and Australia (Sweeney et al., 2019); it can be used to improve areas of intact habitat where we know of functional species that have been extirpated. We conceptually disagree with Grantham et al. (2022) that the re-wilding approach is species rather than process focussed. ...
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We thank the authors of the commentary of our paper “Where might we find ecologically intact communities” (Grantham et al., 2022) for their interest in our paper (Plumptre et al., 2021) and their critique of some of the methods and conclusions. We here respond to their commentary, where many of their points have been well-made, with the aim of advancing discussion of what is meant by ecological integrity or intactness.
... In North America, the focus is often on protecting carnivores in large, connected landscapes (Wildlands Network 2020), whereas European approaches focus on passive rewilding on abandoned farmland and on reintroducing large herbivores (Jones and Comfort 2019). In Australia, rewilding projects emphasise the restoration of native predator populations and small mammal communities by controlling invasive predators (Sweeney et al. 2019). Several conservation NGOs have also started to implement rewilding projects (e.g. ...
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More than 30 years after it was first proposed as a biodiversity conservation strategy, rewilding remains a controversial concept. There is currently little agreement about what the goals of rewilding are, and how these are best achieved, limiting the utility of rewilding in mainstream conservation. Achieving consensus about rewilding requires agreeing about what “wild” means, but many different definitions exist, reflecting the diversity of values in conservation. There are three key debates that must be addressed to find a consensual definition of “wild”: (1) to which extent can people and “wild” nature co-exist?; (2) how much space does “wild” nature need? and (3) what kinds of “wild” nature do we value? Depending on the kinds of “wild” nature rewilding aims to create, rewilding policy will be faced with managing different opportunities and risks for biodiversity and people.
... Translocation is very much a conservation tool of the Anthropocene (Corlett 2015), encompassing everything from mitigation translocations and reintroductions to assisted colonization (Lunt et al. 2013) and rewilding (Jørgensen 2015;Sweeney et al. 2019). With bold aspirations comes substantial capacity for unintended consequences for both ecology (May & Spears 2011;Abbott & Haynie 2012;Colman et al. 2014) and evolution (Laikre et al. 2010). ...
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Mitigation translocation is a subgroup of conservation translocation, categorised by a crisis‐responsive timeframe and the immediate goal of relocating individuals threatened with destruction. However, the relative successes of conservation translocations with longer timeframes and broader metapopulation and ecosystem level considerations have been used to justify the continued implementation of mitigation translocations, without adequate post‐hoc monitoring to confirm their effectiveness as a conservation management tool. Mitigation translocations now outnumber other conservation translocations, and understanding the effectiveness of mitigation translocations is critical given limited global conservation funding – especially if the mitigation translocations undermine biodiversity conservation by failing to save individuals. We assessed the effectiveness of mitigation translocations by conducting a quantitative review of the global literature. We found that mitigation translocations are not yet achieving their potential as an effective applied science, with most translocations focused predominantly on population establishment level questions, as is often seen in translocations more broadly, and less focus placed upon metapopulation and ecosystem outcomes despite these factors being more likely to influence ultimate success. Only a handful of studies included comparison of different management techniques to facilitate practitioners selecting the most effective management actions for the future. To align mitigation translocations with the relative success of other conservation translocations, it is critical that future mitigation translocations conform to an established experimental approach to improve their effectiveness. Effective mitigation translocations will require significantly greater investment of time, expertise and resources in the future. Article Impact Statement: In the absence of high standards of planning and monitoring, mitigation‐translocation managers may be second‐hand agents of biodiversity loss. This article is protected by copyright. All rights reserved
... However, while the general relationship between wild areas and tourism and recreation opportunities is well noted (Cerqueira et al., 2015;Saarinen, 2016Saarinen, , 2019Saeþórsdóttir & Hall, 2019), there is a surprising lack of specific studies of rewilding and tourism. In addition, urban rewilding provides a number of significant urban ecosystem services including urban biodiversity conservation (Lawton, 2019;Sweeney et al., 2019); ground water recharge and improvements in water, air and soil qualities; and economic and aesthetic services such as greenspace (Anderson & Minor, 2017), health benefits (Mills et al., 2017) and informal recreation (Hall, 2013;Kaae et al., 2019;Nejman, Łepkowski, Wilczyńska, & Gawryszewska, 2018;Rupprecht, Byrne, Garden, & Hero, 2015;Rupprecht, Byrne, Ueda, & Lo, 2015). ...
Rewilding is an increasingly significant normative concept in biological conservation, environmental planning and urban greenspace studies. Originally developed in relation to ecological restoration theory and practice the term has developed over time and has come to be used in a range of environmental discourses. Along with other ecosystem services tourism provides a major economic justification for rewilding, although specific studies on rewilding and tourism are limited. In introducing this special issue of Journal of Ecotourism on tourism and rewilding attention is given to the main definitions and approaches to rewilding, their application, and some of the issues that emerge, including contestation over not only how rewilding is framed but also the implications of the (re)introduction of wild animals. Rewilding therefore provides new opportunities to examine the nature-culture relationship and the ethics, management and policies associated with tourism's embeddedness in ecological restoration practices and the framing of the wild.
... It is important to note that during this time a heated debate erupted in Australia between what was called whole-word or look-and-say and phonics-first advocates (see Holdaway, 1979, Thomas 1985. While both methods were based on principles of behaviourist theory of learning (Skinner, 1957) whole-word pedagogy was underpinned by Gestalt theory that argues that people perceive objects as 'wholes' and can be best summed up with the axiom the "whole is more than the sum of its parts" (Hufnus, n.d.). ...
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Noting that most educators would agree that whole language no longer looks the same, this book collects eight articles written by whole language advocates and practitioners from New Zealand, Australia, and the United States that focus on the changes, growth, and development that have occurred in whole language both in philosophy and practice. They emphasize that whole language continues to have an important place in the literacy education of children. After an introduction by the editors, articles in the book are: "Whole Language: Are We Critical Enough?" (Beth Berghoff, Jerry Harste, and Chris Leland); "This Is Literacy: Three Challenges for Teachers of Reading and Writing" (David Bloome); "Defining Whole Language in a Postmodern Age" (Lorraine Wilson); "Towards a Personal Theory of Whole Language: A Teacher-Researcher-Writer Reflects" (Mem Fox); "Teaching Factual Writing: Purpose and Structure" (David Wray and Maureen Lewis); "They Don't Teach Spelling Anymore--Or Do They?" (Chrystine Bouffler); "Real(ly) Writing in School: Generic Practice?" (Jo-Anne Reid); and "Whole Language and Its Critics: A New Zealand Perspective" (John Smith). (RS)
Common species play a disproportionate role in shaping ecosystem structure and function, but are currently under‐represented in conservation translocation initiatives. This represents a missed opportunity because common species are typically easier to source for restoration projects, and larger numbers of common species can feasibly be translocated without substantially impacting source populations. Reintroduction of common species is an important first step in the faunal restoration of severely impacted habitats, such as urban spaces. Common species typically retain higher genetic diversity than threatened species, but this also means that they may have more to lose via population bottlenecks that can occur from translocation. To inform efforts to translocate common species, we assessed genetic impacts of a reintroduction of the common native bush rat Rattus fuscipes to an urban reserve at North Head, Sydney (Australia). Using single‐nucleotide polymorphism diversity, we found that differentiation between source populations was low. Nevertheless, admixture during reintroduction and follow‐up translocations initially increased standardized observed heterozygosity of North Head‐born bush rats and population NE, with a subtle corresponding decrease in within‐population kinship. For 3 years following the last translocation, we detected a small decline in genetic diversity in the North Head population, although final statistics remained similar to the source populations. Our results indicate that no short‐term interventions are necessary to further promote bush rat genetic diversity at North Head, but that continued genetic monitoring will be important to determine whether a trend in declining diversity continues as the population stabilizes. We conclude that translocation of a large number of individuals from multiple sources presents a suitable option for restoring an extirpated small mammal population whilst minimizing genetic effects typically associated with such management actions. Common species present viable candidates for translocations aiming to return biodiversity to disturbed or fragmented urban ecosystems. Native Australian bush rat Rattus fuscipes identified during a recent survey at North Head, Sydney. Using genomic analysis of the reintroduced bush rat population at the site, our study shows that translocations of common species can successfully maintain population genetic diversity, an important outcome as urban restoration improves ecosystem services and increases opportunities for engagement with nature. Photo credit Angela Raña / Australian Wildlife Conservancy.
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Recent studies suggest that apex predators play a pivotal role in maintaining healthy, balanced ecosystems. However, a criticism of studies investigating the ecological role of apex predators is that understanding does not come from manipulative experiments. Here, we use a before-after-control-impact-paired design to test predictions generated from trophic cascade theory (TCT) and mesopredator release hypothesis (MRH) by experimentally introducing dingoes into a 37km 2 paddock and measuring the resultant effects on mammal assemblages. To increase precision of parameter estimates generated by our experiment, we used a Bayesian framework which included prior information recorded from a mensurative study located in a comparable ecosystem that contrasted indices of mammal abundance where dingoes were common and rare. Results of the mensurative study were consistent with TCT and MRH. When using an uninformative prior, results of the experiment showed that dingo addition only had a negative effect on kangaroo activity. Use of an informative prior reduced uncertainty of the posterior mean parameter estimates from the experiment and suggested that red foxes were affected negatively and small mammals and rabbits were affected positively by dingo introduction. However, the prior had a strong influence on the posterior mean effect sizes for small mammals, rabbits and foxes. Opposite polarity of uninformed and prior parameter estimates for rabbits suggests that the prior was incompatible with the uninformed estimates from the manipulative experiment. Our study shows how use of logical informative priors can help to overcome statistical issues associated with low-replication in large-scale experiments, but the strong influence of the prior, means that our findings were driven largely by the mensurative study.
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The dingo (Canis dingo or C. familiaris, including hybrids with feral dogs) is the apex carnivore on mainland Australia. Fifteen non-native ungulate species have established wild populations in Australia. Dingoes are managed to reduce impacts on domestic ungulates, and introduced wild ungulates are managed to reduce impacts on natural ecosystems and to minimise competition with domestic ungulates. There is speculation about the extent to which (1) dingoes limit the abundances of introduced wild ungulates, and (2) introduced wild ungulates sustain dingo populations. We reviewed the literature to identify potential ecological interactions between dingoes and introduced wild ungulates, and to synthesise evidence for interactions between dingoes and each ungulate species (including the percentage frequency occurrence (%FO) of ungulates in dingo diets). Eleven of the 15 ungulate species were recorded in the diet of dingoes, with the highest %FO occurrences reported for feral goats (73%) and cattle (60%). Two studies concluded that dingoes reduced ungulate abundances (feral goat (Capra hircus) and feral donkey (Equus asinus)), and two studies concluded that dingoes did not regulate feral pig (Sus scrofa) abundances. A fifth study concluded that dingoes exhibited a Type III functional response to increasing sambar deer (Cervus unicolor) abundances. A sixth study concluded that dingoes made relatively little use of hunter-shot sambar deer carcasses. We propose that interactions between dingoes and introduced wild ungulates depend on the sex-age classes vulnerable to dingo predation, dingo pack sizes, the availability of escape terrain for ungulates and the availability of alternative foods for dingoes. The interplay between environmental conditions and the population growth rate of ungulates, and hence their ability to sustain losses from predation, could also be important. We predict that dingoes will have most impact on the abundance of smaller ungulate species and neonates.
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Functional extinction of once abundant species has frequently preceded understanding of their ecological roles. Consequently, our understanding of ecosystems is prone to shifting baselines because it often relies on observations made on depauperate species assemblages. In Australian deserts, current paradigms are that ants are the dominant granivores, mammals are unimportant seed predators and that myrmecochory in many Australian shrubs is an adaptation to increase dispersal distance and direct seeds to favourable germination sites. Here, we ask whether these paradigms could be artefacts of mammal extinction. We take advantage of a predator-proof reserve within which locally extinct native mammals have been reintroduced to compare seed removal by ants and mammals. Using foraging trays that selectively excluded mammals and ants we show that a reintroduced mammal, the woylie (Bettongia penicillata) was at least as important as ants in the removal of seeds of two shrub species (Dodonaea viscosa and Acacia ligulata). Our results provide evidence that the dominance of ants as granivores and current understanding of the adaptive benefit of myrmecochory in arid Australia may be artefacts of the functional extinction of mammals. Our study shows how reversing functional extinction can provide the opportunity to rethink contemporary understanding of ecological processes.
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Rewilding, here defined as “the reorganisation of biota and ecosystem processes to set an identified social–ecological system on a preferred trajectory, leading to the self-sustaining provision of ecosystem services with minimal ongoing management,” is increasingly considered as an environmental management option, with potential for enhancing both biodiversity and ecosystem services. Despite burgeoning interest in the concept, there are uncertainties and difficulties associated with the practical implementation of rewilding projects, while the evidence available for facilitating sound decision-making for rewilding initiatives remains elusive. We identify five key research areas to inform the implementation of future rewilding initiatives: increased understanding of the links between actions and impacts; improved risk assessment processes, through, for example, better definition and quantification of ecological risks; improved predictions of spatio-temporal variation in potential economic costs and associated benefits; better identification and characterisation of the likely social impacts of a given rewilding project; and facilitated emergence of a comprehensive and practical framework for the monitoring and evaluation of rewilding projects. Policy implications. Environmental legislation is commonly based on a “compositionalist” paradigm itself predicated on the preservation of historical conditions characterised by the presence of particular species assemblages and habitat types. However, global environmental change is driving some ecosystems beyond their limits so that restoration to historical benchmarks or modern likely equivalents may no longer be an option. This means that the current environmental policy context could present barriers to the broad implementation of rewilding projects. To progress the global rewilding agenda, a better appreciation of current policy opportunities and constraints is required. This, together with a clear definition of rewilding and a scientifically robust rationale for its local implementation, is a prerequisite to engage governments in revising legislation where required to facilitate the operationalisation of rewilding. © 2018 The Authors. Journal of Applied Ecology
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The last large marsupial carnivores-the Tasmanian devil (Sarcophilis harrisii) and thylacine (Thylacinus cynocephalus)-went extinct on mainland Australia during the mid-Holocene. Based on the youngest fossil dates (approx. 3500 years before present, BP), these extinctions are often considered synchronous and driven by a common cause. However, many published devil dates have recently been rejected as unreliable, shifting the youngest mainland fossil age to 25 500 years BP and challenging the synchronous-extinction hypothesis. Here we provide 24 and 20 new ages for devils and thylacines, respectively, and collate existing, reliable radiocarbon dates by quality-filtering available records. We use this new dataset to estimate an extinction time for both species by applying the Gaussian-resampled, inverse-weighted McInerney (GRIWM) method. Our new data and analysis definitively support the synchronous-extinction hypothesis, estimating that the mainland devil and thylacine extinctions occurred between 3179 and 3227 years BP.
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1. Rewilding is a strategy for ecological restoration that uses reintroductions of animals to re-establish the ecological functions of keystone species. Globally, rewild-ing efforts have focused primarily on reinstating the ecological functions of charismatic megafauna. In Australia, rewilding efforts have focused on restoring the ecological functions of herbivorous and omnivorous rodents and marsupials weighing between 30 and 5,000 g inside of predator-proof exclosures. 2. In many arid ecosystems, mammals are considered the dominant seed predators. In Australian deserts, ants are considered to be the primary removers and predators of seeds and mammals unimportant removers and predators of seeds. However, most research on granivory in Australian deserts has occurred in areas where native mammals were functionally extinct. 3. Here, we compare rates of seed removal by mammals and ants on shrub seeds and abundance of shrub seedlings in two rewilded desert ecosystems (Arid Recovery Reserve and Scotia Wildlife Sanctuary) with adjacent areas possessing depauperate mammal faunas. We used foraging trays containing seeds of common native shrubs (Acacia ligulata and Dodonaea viscosa) to examine rates of seed removal by ants and mammals. We quantified the abundance of A. ligulata and D. viscosa seedlings inside and outside of rewilded areas along belt transects. 4. By excluding ants and mammals from foraging trays, we show that ants removed more seeds than mammals where mammal assemblages were depauperate, but mammals removed far more seeds than ants in rewilded areas. Shrub seedlings were more abundant in areas with depauperate mammal faunas than in rewilded areas. 5. Our study provides evidence that rewilding of desert mammal assemblages has restored the hitherto unappreciated ecological function of omnivorous rodents and bettongs as seed predators. We hypothesize that the loss of omnivorous mammals may be a factor that has facilitated shrub encroachment in arid Australia. 6. We contend that rewilding programs aimed at restoring ecological processes should not ignore consumers with relatively lower per capita consumptive effects. This is because consumers with low per capita consumptive effects often occur at high population densities or perform critical ecological functions and thus may have significant population level impacts that can be harnessed for ecological restoration. 2 | Functional Ecology MILLS et aL.
The Action Plan for Australian Mammals 2012 is the first review to assess the conservation status of all Australian mammals. It complements The Action Plan for Australian Birds 2010 (Garnett et al. 2011, CSIRO Publishing), and although the number of Australian mammal taxa is marginally fewer than for birds, the proportion of endemic, extinct and threatened mammal taxa is far greater. These authoritative reviews represent an important foundation for understanding the current status, fate and future of the nature of Australia. This book considers all species and subspecies of Australian mammals, including those of external territories and territorial seas. For all the mammal taxa (about 300 species and subspecies) considered Extinct, Threatened, Near Threatened or Data Deficient, the size and trend of their population is presented along with information on geographic range and trend, and relevant biological and ecological data. The book also presents the current conservation status of each taxon under Australian legislation, what additional information is needed for managers, and the required management actions. Recovery plans, where they exist, are evaluated. The voluntary participation of more than 200 mammal experts has ensured that the conservation status and information are as accurate as possible, and allowed considerable unpublished data to be included. All accounts include maps based on the latest data from Australian state and territory agencies, from published scientific literature and other sources. The Action Plan concludes that 29 Australian mammal species have become extinct and 63 species are threatened and require urgent conservation action. However, it also shows that, where guided by sound knowledge, management capability and resourcing, and longer-term commitment, there have been some notable conservation success stories, and the conservation status of some species has greatly improved over the past few decades. The Action Plan for Australian Mammals 2012 makes a major contribution to the conservation of a wonderful legacy that is a significant part of Australia’s heritage. For such a legacy to endure, our society must be more aware of and empathetic with our distinctively Australian environment, and particularly its marvellous mammal fauna; relevant information must be readily accessible; environmental policy and law must be based on sound evidence; those with responsibility for environmental management must be aware of what priority actions they should take; the urgency for action (and consequences of inaction) must be clear; and the opportunity for hope and success must be recognised. It is in this spirit that this account is offered. Winner of a 2015 Whitley Awards Certificate of Commendation for Zoological Resource.
Predators with Pouches provides a unique synthesis of current knowledge of the world’s carnivorous marsupials—from Patagonia to New Guinea and North America to Tasmania. Written by 63 experts in each field, the book covers a comprehensive range of disciplines including evolution and systematics, reproductive biology, physiology, ecology, behaviour and conservation. Predators with Pouches reveals the relationships between the American didelphids and the Australian dasyurids, and explores the role of the marsupial fauna in the mammal community. It introduces the geologically oldest marsupials, from the Americas, and examines the fall from former diversity of the larger marsupial carnivores and their convergent evolution with placental forms. The book covers all aspects of carnivorous marsupials, including interesting features of life history, their unique reproduction, the physiological basis for early senescence in semelparous dasyurids, sex ratio variation and juvenile dispersal. It looks at gradients in nutrition—from omnivory to insectivory to carnivory—as well as distributional ecology, social structure and conservation dilemmas.
More than 300 species of Australian native animals — mammals, birds, reptiles and amphibians — use tree hollows, but there has never been a complete inventory of them. Many of these species are threatened, or are in decline, because of land-use practices such as grazing, timber production and firewood collection. All forest management agencies in Australia attempt to reduce the impact of logging on hollow-dependent fauna, but the nature of our eucalypt forests presents a considerable challenge. In some cases, tree hollows suitable for vertebrate fauna may take up to 250 years to develop, which makes recruiting and perpetuating this resource very difficult within the typical cycle of human-induced disturbance regimes. Tree Hollows and Wildlife Conservation in Australia is the first comprehensive account of the hollow-dependent fauna of Australia and introduces a considerable amount of new data on this subject. It not only presents a review and analysis of the literature, but also provides practical approaches for land management.
The use of fences in conservation can be controversial, as artificial barriers constrain natural behaviour and ecological dynamics. However, in the case of large predators inhabiting protected areas within a hostile human‐dominated landscape, predators may remain at low densities if they face high mortality upon leaving the reserve. In turn, this may compromise the potential for density‐dependent effects such as top‐down regulation of prey species abundance. We simulate the hypothetical reintroduction of gray wolves Canis lupus to reserves in their former range (Scottish Highlands), with the objectives of identifying parameters that allow a viable wolf population and the potential for direct top‐down forcing of red deer Cervus elaphus densities. We examine the extent to which the number of dispersing wolves leaving the protected area influences whether these objectives are achieved. Our simulations confirm that source‐sink population dynamics can result in a self‐perpetuating wolf population, but one that never achieves densities needed for strong top‐down forcing. When wolf density is weakly controlled by intraspecific competition, strong top‐down forcing occurs when 20% of dispersing wolves or less leave the population. When 20% to 35% of dispersing wolves leave, the strength of top‐down forcing is highly variable. The wolf population remained viable when 35% to 60% of dispersing wolves left, but then did not exert strong top‐down forcing. Wolves were vulnerable to extinction at greater than 60% disperser loss. Despite their negative connotations, fences (including semi‐permeable ones) could increase the potential for interspecific density‐dependent processes in some cases, thereby facilitating trophic rewilding.