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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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... • Biodiversity conservation. (Sweeney, et al., 2019) • Restoring ecosystem processes. ...
... We consequently include it as a type of nature-based solution in this review. Rewilding should, however, be locally tailored not only within the context of a region or a continent, but also within the context of one single country (Sweeney, et al., 2019), as the number of factors influencing rewilding success may differ spatially. ...
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NbS have gained substantial attention in the academic literature recently as a potential approach for simultaneously tackling environmental issues and addressing societal challenges. Drylands, which are among the world’s most vulnerable areas to the impacts of climate change and cover a little less than the half of the global terrestrial surface, were the focus of this study. We conducted a systematic literature review to explore the potential opportunities for the application of NbS in rural drylands across the globe. We go on to specifically consider the possibility of applying selected NbS approaches in the Aral Sea region of Uzbekistan, as a case study of a dryland ecosystem illustrating major environmental and social challenges. We highlight which NbS show the most promise in the Aral Sea region and conclude with a discussion of existing gaps in the literature on NbS in drylands, and opportunities for further research.
... Rewilding attempts to increase biodiversity and restore natural ecosystem processes by reducing human influence [2]. Considerable interest in rewilding exists throughout the world [3][4][5][6]. One of the most well-known examples of rewilding in North America is the reintroduction of grey wolves (Canis lupus) to Yellowstone National Park, Wyoming, USA. ...
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Rewilding attempts to increase biodiversity and restore natural ecosystem processes by reducing human influence. Today, there is growing interest in rewilding urban areas. Rewilding of the Detroit, Michigan, USA and Windsor, Ontario, Canada metropolitan area, and its shared natural resource called the Detroit River, has been delineated through the reintroduction of peregrine falcons and osprey, and a return of other sentinel species like bald eagles, lake sturgeon, lake whitefish, walleye, beaver, and river otter. Rewilding has helped showcase the value and benefits of environmental protection and restoration, ecosystem services, habitat rehabilitation and enhancement, and conservation, including social and economic benefits. Improved ecosystem health and rewilding have become a catalyst for re-establishing a reconnection between urban denizens and natural resources through greenways and water trails. The provision of compelling outdoor experiences in nature, in turn, can help foster a personal attachment to the particular place people call home that can help inspire a stewardship ethic.
... For example, it could help to establish how ecological characteristics of species interact dynamically with environmental threats to cause initial population declines, a central question in ecology that has never been resolved (Beissinger, 2000;Chichorro et al., 2019). Furthermore, output from these models is likely to provide additional practical biogeographic insights for conservation planning, including providing geographically explicit guidance for establishment and connection of reserves through landscape-scale restoration (Sweeney et al., 2019), along with more accurate assessment of the conservation value of remnant, peripheral populations (Fisher, 2011;Lesica & Allendorf, 1995). Our protocol for advancing conservation biogeography also holds potential for determining where and in what numbers species should be reintroduced (Armstrong & Seddon, 2008), and how these strategies may vary across predator inhabited (e.g. ...
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An emerging research program on population and geographic range dynamics of Australia's mammals illustrates an approach to better understand and respond to geographic range collapses of threatened wildlife in general. In 1788, Europeans colonized an Australia with a diverse and largely endemic mammal fauna, where many species that are now extinct or threatened were common and widespread. Subsequent population declines, range collapses and extinctions were caused by in- troduced predators and herbivores, altered land use, modified fire regimes and the synergies between these threats. Declines in population and range size continue for many Australian mammals despite legislative protection and conservation interven- tions. Here, we propose an approach that integrates museum data and other historical records into process-explicit macroecological models to better resolve mammal distri- butions and abundances as they were at European arrival. We then illustrate how this integrative approach can identify the likely synergistic mechanisms causing mammal population declines across these and other landscapes. This emerging research ap- proach, undertaken with fine temporal and spatial resolution, but at large geographic scales, will provide valuable insights into the different pathways to, and drivers of, extinction. Such insights may, in turn, underpin conservation strategies based on a process-explicit understanding of population decline and range collapse under alter- native scenarios of impending climate and environmental change. Given that similar information is available for other regional biotas, the approach we describe here can be adapted to conserve threatened wildlife in other regions across the globe.
... Australia and New Zealand have had a significant influence on the corpus (Fig. 6 and 7) and, being geographically isolated from the rest of the world, have faced unique threats to their biodiversity (Fisher et al. 2014), with flowon effects to the implementation of translocation science (Sweeney et al. 2019). Both countries have experienced over 200 years of significant and ongoing declines in their native species since colonisation by Europeans (Innes et al. 2010, Woinarski et al. 2015. ...
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Translocations are an important conservation tool that enable the restoration of species and their ecological functions. They are particularly important during the current environmental crisis. We used a combination of text-analysis tools to track the history and evolution of the peer-reviewed scientific literature on animal translocation science. We compared this corpus with research showcased in the IUCNs Global Conservation Translocation Perspectives, a curated collection of non-peer-reviewed reintroduction case studies. We show that the peer-reviewed literature, in its infancy, was dominated by charismatic species. It then grew in two classical threads: management of the species of concern and management of the environment of the species. The peer-reviewed literature exhibits a bias towards large charismatic mammals, and while these data are invaluable, expansion to under-represented groups such as insects and reptiles will be critical to combating biodiversity loss across taxonomic groups. These biases were similar in the Translocation Perspectives, but with some subtle differences. To ensure translocation science can address global issues, we need to overcome barriers that restrict this research to a limited number of countries.
Australia's biota is species rich, with high rates of endemism. This natural legacy has rapidly diminished since European colonization. The impacts of invasive species, habitat loss, altered fire regimes, and changed water flows are now compounded by climate change, particularly through extreme drought, heat, wildfire, and flooding. Extinction rates, already far exceeding the global average for mammals, are predicted to escalate across all taxa, and ecosystems are collapsing. These losses are symptomatic of shortcomings in resourcing, law, policy, and management. Informed by examples of advances in conservation practice from invasive species control, Indigenous land management, and citizen science, we describe interventions needed to enhance future resilience. Many characteristics of Australian biodiversity loss are globally relevant, with recovery requiring society to reframe its relationship with the environment.
The dual strands for future moth conservation in Australia, as for many taxa elsewhere, are thus the expanded attention to single species (Chap. 8) and the wider need to conserve natural habitats and, where necessary, restore these to the condition in which they can harbour and sustain the largely undocumented—but evidently diverse—moth assemblages present (Chap. 9). Both approaches depend, for success, on sound background information and understanding, and both are limited also by interest, logistic support, time commitment and conflicting priorities, so that informed advocacy for the importance and urgency of moths is a central need. They may be augmented by consideration of priority populations, rather than entire species. In situations where the nature of observed variation in appearance or biology is unclear and/or species boundaries are ambiguous, conservation may be considered on a population-by-population basis in order to conserve the fullest range of genetic variation (Patrick et al. 2015). For the Golden sun-moth (Synemon plana, p. xx), Clarke and O’Dwyer (2000) recommended that each of the five genetically distinct population groups they distinguished should be treated as a separate unit for conservation management. This approach remains rare (and largely impracticable) for moths, but is more widely implicit—and accepted—in the election of many local butterfly ‘subspecies’ as conservation foci.
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Urbanisation is increasing, while global biodiversity is decreasing. Through ‘urban rewilding’ cities could help tackle this biodiversity crisis, while exploiting the benefits of urban nature for residents. Private residential gardens, which have potential to support significant biodiversity, should be a primary focus. Yet their proportion of vegetated space is decreasing through changes made by residents, negatively impacting biodiversity. Small adaptations to private gardens can turn them into wildlife habitat, but understanding residents’ behaviour is critical to developing intervention strategies for this. This paper presents a scoping review of existing literature on understanding intent-orientated, pro-environmental behaviours with a focus on rewilding in urban gardens. The literature is mapped to assess the state of knowledge; it is then coded, using the ‘COM-B’ model of behaviour, to identify the capability, opportunity and motivation factors forming barriers and facilitators to residents engaging in rewilding activity in their gardens. The results show that all COM-B factors need to be considered to understand urban rewilding behaviour, but that opportunity and motivation factors have more influence, particularly reflective motivation. They indicate that facilitators are more significant than barriers and highlight an important body of work that has implications for practice and policy aimed at influencing urban rewilding.
The Australian marsupial fauna has been devastated in the past 250 years, mainly due to impacts from invasive mammalian predators (cats and foxes), although other threats such as invasive herbivores, habitat loss and fragmentation, changes to fire regimes, and now climate change have played a role. The profound and ongoing impact of invasive predators has driven substantial research and management innovation. Australia has been at the forefront of developing approaches to reduce the density and impacts of introduced predators and implementing novel and ambitious species conservation programs. A large and growing network of islands and mainland fenced areas, free of introduced predators (“havens”), has been critical for avoiding further species extinctions. Outside these havens, advances in toxin presentation and deployment have enabled cat and fox densities to be reduced over large areas. Substantial research and field trials have been carried out to understand how predator-prey interactions, and habitat quality management, can be used to reduce predation impacts on susceptible native species. Synthetic biology offers new opportunities to manage introduced predators, including potentially by using gene drives. Finally, the attenuation of the formerly large continuous ranges of many species to small, isolated population remnants (because of predation or other reasons) has also driven research and improvements in genetic and metapopulation management that will increase the chance of population persistence in the longer term. However, unless Australia continues to invest in research and innovative conservation actions, the plight of its priceless marsupial fauna will remain perilous.
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The importance of positive interactions is increasingly acknowledged in contemporary ecology. Most research has focused on direct positive effects of one species on another. However, there is recent evidence that indirect positive effects in the form of facilitation cascades can also structure species abundances and biodiversity. Here we conceptualize a specific type of facilitation cascade-the habitat cascade. The habitat cascade is defined as indirect positive effects on focal organisms mediated by successive facilitation in the form of biogenic formation or modification of habitat. Based on a literature review, we demonstrate that habitat cascades are a general phenomenon that enhances species abundance and diversity in forests, salt marshes, seagrass meadows, and seaweed beds. Habitat cascades are characterized by a hierarchy of facilitative interactions in which a basal habitat former (typically a large primary producer, e.g., a tree) creates living space for an intermediate habitat former (e.g., an epiphyte) that in turn creates living space for the focal organisms (e.g., spiders, beetles, and mites). We then present new data on a habitat cascade common to soft-bottom estuaries in which a relatively small invertebrate provides basal habitat for larger intermediate seaweeds that, in turn, generate habitat for focal invertebrates and epiphytes. We propose that indirect positive effects on focal organisms will be strongest when the intermediate habitat former is larger and different in form and function from the basal habitat former. We also discuss how humans create, modify, and destroy habitat cascades via global habitat destruction, climatic change, over-harvesting, pollution, or transfer of invasive species. Finally, we outline future directions for research that will lead to a better understanding of habitat cascades.
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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.
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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.
Anthropogenic declines have been reported in all of Australasia's eight larger marsupial carnivores (genera Dosyurus, Sarcophilus, and Thylacinus), One species is now extinct (T. cynocephalis), one subspecies is Endangered (D. moculatus grao7is), one species and one subspecies are classified as VuInerable to extinction (D. geoffroii and D. m. maculatus, respectively), two species are Lower Risk-Near Threatened (D. hallucatus, D viverrinus), two are of unknown conservation status (the New Guinea quolls, D. olbopunctatus and D. sportacus), and only one species is classified as Lower Risk-Least Concern (S. lanianus), A successful recovery program has been executed for one species (D. geoffroii-formerly Endangered), which will shortly be removed from threatened fauna lists. While the causes of decline are multiple and complex, the overriding factor is probably habitat loss, degradation and fragmentation, and the associated factors: loss of protective cover from predators, reduced food availability, and increased contact with humans. Introduced predators, cats (Fefe catus), foxes (Vulpes vulpes) and dingoes (Canis lupus dingo), play a not well understood role. Other important mortality factors include persecution, non-target poisoning and road mortality. In this chapter, we conduct a critical review and summary of I) the causes and correlates of decline, 2) the issues related to trophic level and life history that predispose marsupial carnivores to anthropogenic decline, 3) a range of solutions, some of which are being implemented, and 4) future directions for the large amount of work still to be done
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.
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.