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Quantifying spatial resilience
Craig R. Allen
" $, callen3@unl.edu
David G. Angeler
#" $! !, david.angeler@slu.se
Graeme S. Cumming
$ % !
Carl Folke
" $
Dirac L. Twidwell
" $, dirac.twidwell@unl.edu
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Allen, Craig R.; Angeler, David G.; Cumming, Graeme S.; Folke, Carl; Twidwell, Dirac L.; and Uden, Daniel R., "Quantifying spatial
resilience" (2016). " &! . 228.
h>p://digitalcommons.unl.edu/ncfwrusta</228
REVIEW: QUANTIFYING RESILIENCE
Quantifying spatial resilience
Craig R. Allen
1
*, David G. Angeler
2
, Graeme S. Cumming
3†
, Carl Folke
4,5
, Dirac Twidwell
6
and Daniel R. Uden
7
1
U.S. Geological Survey, Nebraska Cooperative Fish and Wildlife Research Unit, School of Natural Resources,
University of Nebraska – Lincoln, Lincoln, NE, USA;
2
Department of Aquatic Sciences and Assessment, Swedish
University of Agricultural Sciences, PO Box 7050, SE - 750 07 Uppsala, Sweden;
3
Percy FitzPatrick Institute, DST/
NRF Centre of Excellence, University of Cape Town, Rondebosch, Cape Town 7701, South Africa;
4
Stockholm
Resilience Centre, Stockholm University, 106 91 Stockholm, Sweden;
5
Beijer Institute, Royal Swedish Academy of
Sciences, Stockholm, Sweden;
6
Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln,
Nebraska 68503-0984, USA; and
7
Nebraska Cooperative Fish and Wildlife Research Unit, School of Natural
Resources, University of Nebraska-Lincoln, Lincoln, Nebraska 68503-0984, USA
Summary
1. Anthropogenic stressors affect the ecosystems upon which humanity relies. In some cases
when resilience is exceeded, relatively small linea r changes in stre ssors can cause relatively
abrupt and nonlinear changes in ecosystems.
2. Ecological regime shifts occur when resilience is exceeded and ecosystems enter a new
local equilibrium that differs in its structure and function from the previous state. Ecological
resilience, the amount of disturbance that a system can withstand before it shifts into an alter-
native stability domain, is an important framework for understanding and managing ecologi-
cal systems subject to collapse and reorganization.
3. Recently, interest in the influence of spatial characteristics of landscapes on resilience has
increased. Understanding how spatial structure and variation in relevan t variables in land-
scapes affects resilience to disturbance will assist with resilience quantification, and with local
and regional management.
4. Synthesis and applications. We review the history and current status of spatial resilience in
the research literature, expand upon existing literature to develop a more operational defini-
tion of spatial resilience, introduce additional elements of a spatial analytical approach to
understanding resilience, present a framework for resilience operationalization and provide an
overview of critical knowledge and technology gaps that should be addressed for the advance-
ment of spatial resilience theory and its applications to management and conservation.
Key-words: alternative states, cross-scale ecology, landscape ecology, regime shift, resilience,
spatial ecology, spatial regime
Introduction
Basic changes in the structure–process relationships in
ecosystems are termed ecological regime shifts and occur
when an ecosystem enters a new local equilibrium, or
stable state, that differs in its structure and function from
the previous state. Ecological resilience, the amount of
disturbance a system can withstand before shifting into an
alternative stability domain (Holling 1973), is an impor-
tant framework for understanding and managing ecologi-
cal systems subject to regime changes (Gunderson, Allen
& Holling 2010). When the resilience of an ecological sys-
tem is exceeded, a regime shift occurs.
In social–ecological systems, people are often the pri-
mary drivers of ecological regime shifts. Anthropogenic
stressors, including biological invasions, habitat loss and
degradation, the emergence of novel diseases and climate
change, affect ecosystems upon which humanity relies. In
some cases, relatively small linear changes in these stres-
sors cause relatively abrupt and large nonlinear changes
in ecosystems (Scheffer et al. 2001). Transitions to novel,
anthropogenically driven regimes, such as the conversion
*Correspondence author. E-mail: allencr@unl.edu
†
Present address: Centre of Excellence for Coral Reef Studies,
James Cook University, Townsville, Queensland 4811, Australia
© 2016 The Authors. Journal of Applied Ecology © 2016 British Ecological Society
Journal of Applied Ecology 2016, 53, 625–635 doi: 10.1111/1365-2664.12634
This document is a U.S. government work and
is not subject to copyright in the United States.
of rain forest to pasture, are typically characterized by
reduced biodiversity and ecosystem services (Folke et al.
2002). The speed and nature of anthropogenically induced
regime shifts are especially concerning in the light of the
global scale at which their underlying driving forces now
operate (Steffen et al. 2015).
Environmental change affects ecosystems and the land-
scapes in which they are embedded. Spatial heterogeneity
in the location, manifestation of, and responses to envi-
ronmental change makes spatially explicit approaches to
management and conservation necessary. Spatial resili-
ence, a crucial component of resilience theory, is at the
forefront of attempts to operationalize and quantify resili-
ence concepts in landscapes. Landscapes exhibit spatially
and temporally complex dynamics, and attempts to under-
stand pattern–process relationships in landscapes have led
to rapid advances in ecological theory and application.
The concept of spatial resilience represents the most
recent conceptual advance that seeks to explain the resili-
ence and transformability of heterogeneous and dynamic
systems. Other recent developments include identifying
leading indicators of critical spatial thresholds (K
efi et al.
2014), assessing structural and functional spatial compo-
nents of managed systems in relation to their resilience
(Allen et al. 2014; Angeler et al. 2016), determining the
role of connectivity, dispersal and other movements in
conferring resilience (Underwood et al. 2009), assessing
the relevance of network membership for node resilience
and the relevance of node participation for network resili-
ence (Keitt, Urban & Milne 1997; Moore, Grewar &
Cumming 2016), evaluating the relationship of spatial
landscape metrics to resilience (Cumming 2011b; Uden
et al. 2014), and developing approaches for understanding
cross-scale interactions in social–ecological systems (Cum-
ming et al. 2015). Despite recent progress, ambiguity in
definitions, information gaps and an overall lack of quan-
tification and operationalization remain. In this manu-
script, we: (i) review the history and current status of
spatial resilience in the research literature, (ii) expand
upon existing literature to develop a more operational
definition of spatial resilience, (iii) provide an approach to
quantifying spatial resilience that introduces a spatial ana-
lytical method for understanding resilience, (iv) provide a
roadmap for the application of spatial resilience to ecosys-
tem management and (v) discuss current gaps and oppor-
tunities related to the spatial resilience concept and its
operationalization.
Terminology review and synthesis
Spatial resilience is a subset of resilience theory that has
been defined in several ways. In studies of coral reef and
rain forest disturbance, Nystr
€
om, Folke & Moberg (2000),
Nystr
€
om & Folke (2001) and Elmqvist et al. (2001) intro-
duced the term spatial resilience to refer to the importance
of ecological legacies (i.e. species or habitat characteristics
that persist after disturbance and provide ‘ecological
memory’ during reorganization) and connectivity among
neighbouring systems for withstanding disturbances and
avoiding regime shifts at broader spatial extents than indi-
vidual focal systems. Ecological memory is expected to
increase with geographical extent and to some degree with
landscape heterogeneity and diversity (Berkes & Folke
2002), suggesting that fostering or actively conserving par-
ticular landscape features and structures may provide a
means to enhance the ability of focal systems (e.g. pro-
tected areas) to absorb landscape disturbances such as cli-
mate change. In this context, spatial resilience is simply
defined as ecological resilience at broader spatial scales
(i.e. beyond local habitats) (Obura 2005), or more accu-
rately, the ways in which broader-scale resilience affects
local resilience and vice versa.
Nystr
€
om & Folke’s (2001) emphasis on resilience at
spatial scales greater than the focal system has dominated
subsequent spatial resilience references in research litera-
ture. For example, Bengtsson et al. (2003) focused on the
importance of static and dynamic ecological reserves for
developing spatial resilience against large-scale, long-term
disturbances, and Folke (2006) emphasized the utility of
spatial resilience for considering the influence of interac-
tions among temporal scales, spatial scales and spatial
heterogeneity on multi-stable behaviour (i.e. multiple
basins of attraction) in ecosystems. Additional examples
of the extension of Nystr
€
om & Folke’s (2001) definition
are provided by Peterson (2002), Lundberg & Moberg
(2003), Nystr
€
om et al. (2008), Welsh & Bellwood (2012a)
and Cumming et al. (2013). Numerous other studies do
not explicitly employ the term spatial resilience, but are
still founded in Nystr
€
om & Folke’s (2001) definition of
large-scale ecological memory and among-system connec-
tivity as critical aspects of post-disturbance recovery and
reorganization (e.g. van Nes & Scheffer 2005; and Gil-
mour et al. 2013).
Spatial resilience can also be more explicitly considered
as the spatial arrangement of, differences in, and interac-
tions among internal and external elements of a system
(Cumming 2011a,b). System elements that are internal are
those that are related to one another and/or interact with
each other either structurally or functionally (or both) at
the level of analysis defined by the investigator. Because
interaction strengths often decay with distance in space
and time, rather than being all-or-nothing, analyses may
select a cut-off distance or time period over which to
define study system boundaries. Thus, ‘internal’ may be
defined in social, economic or ecological terms, by a geo-
graphical boundary (e.g. watershed or provincial bound-
ary), by participation in a spatially segregated supply
chain (e.g. timber is harvested in one location, cut in
another, sold in another and bought in yet another) or by
shared elements, such as the movements of individuals
between habitat patches within a metapopulation at time-
scales relevant to a single generation (Table 1). Peterson
(2002) and Cumming et al. (2013) similarly consider resili-
ence and spatial resilience in landscape contexts, and
© 2016 The Authors. Journal of Applied Ecology © 2016 British Ecological Society, Journal of Applied Ecology, 53, 625–635
626 C. R. Allen et al.
Cumming (2011a,b) focus on the importance of asymme-
tries and gradients for resilience, and particularly on the
relevance of gradients as drivers of social–ecological pro-
cesses. Olds et al. (2012) view spatial resilience as an inte-
gration of resilience theory into the framework of
landscape ecology, where resilience is made more tractable
by utilizing location, context, connectivity and other land-
scape ecology concepts and metrics. Spatial resilience can
therefore be more explicitly considered as an emergent
property of the spatial arrangement, differences and inter-
actions among internal elements of resilience (i.e. those
within the focal system), external elements of resilience
(i.e. those outside the focal system) and other spatially rel-
evant aspects of resilience (e.g. adaptations to environ-
mental change) (Cumming 2011a,b). External elements
focus on how landscape metrics beyond the focal scale of
analysis affect resilience (e.g. species migration and disper-
sal between habitat patches; hydrological connectivity
between lakes), including spatial subsidies (e.g. sand-
storms fertilizing low productivity soils elsewhere). Both
internal and external components interact to affect the
spatial feedbacks that either maintain a level of local sta-
bility within a landscape or push it into a different state.
Expanding and operationalizing spatial
resilience
Based on current empirical and theoretical knowledge, a
tractable ‘shorthand’ definition of spatial resilience is as
follows: the contribution of spatial attributes to the feed-
backs that generate resilience in ecosystems and other
complex systems, and vice versa. This definition allows
for the operationalization of spatial resilience in manage-
ment, is consistent with the foundational aspects of resili-
ence described by Nystr
€
om & Folke (2001) and Cumming
(2011b) and builds upon the three spatially relevant
aspects of complexity (i.e. asymmetries, networks and
information processing) discussed by Norberg & Cum-
ming (2008).
APPLICATIONS FROM COMPLEXITY THEORY
To operationalize and quantify spatial resilience, consider-
ation of asymmetries, connectivity and information
processing is warranted (Cumming 2011b). Within com-
plex systems, asymmetries are systematic heterogeneities,
such as soil or climate conditions, that can create gradi-
ents in environmental and biotic variables and drive spa-
tial feedbacks and processes that characterize the regime
(or basin of attraction; processes and feedbacks that
maintain dynamic states of systems) of distinct landscape
units (e.g. ecozones, biogeographical regions and climate
domains) (Norberg & Cumming 2008). Socio-economic
asymmetries, such as urban to rural gradients, variations
in access to public transport or spatial patterns in farming
systems, can also drive processes in social–ecological sys-
tems.
Distinct landscape elements, such as habitat patches,
are connected to one another by a variety of processes.
They can be viewed as nodes in networks that are con-
nected by movement, communication or other processes,
such as nutrient exchanges. Network theory is useful in
this context because it illustrates how spatial resilience
can be influenced by the position of a system (e.g. a wet-
land or a city) and its connectivity within a network of
similar systems (Uden et al. 2014). Network membership
and position have implications for resilience at two scales,
that of the individual node and that of the broader net-
work. In fragmented ecosystems, for example, smaller
patches with no obvious individual ecological significance
may be important stepping stones for movement of organ-
isms across landscapes (Urban & Keitt 2001).
Information processing in complex adaptive systems is
related to information exchange within and across system
elements. System elements can comprise habitat patches
or communities of people or organisms; ecological pat-
terns within and across these patches can be mediated by
dispersing organisms or interconnected ecosystem pro-
cesses; and social–ecological processes such as migration
and communication are integral to socioeconomic dynam-
ics. Thus, spatial elements of a system that relate to meta-
community (Leibold et al. 2004) or meta-ecosystem
(Loreau, Mouquet & Holt 2003) aspects can characterize
information processing from a spatial resilience perspec-
tive. Furthermore, a basic tenet of information exchange
among hierarchical levels is the constraint of lower levels
by higher levels (Allen & Starr 1982). Higher levels estab-
lish boundaries within which lower levels are free to indi-
vidualistically operate and simultaneously constrain even
lower hierarchical levels. An initial application of this
principle to spatial resilience is considering what sur-
rounds the focal system– one of the major emphases of
prior spatial resilience definitions. However, the main con-
tribution of ‘thinking outside the focal system’ to spatial
resilience has so far been in identifying subsidies that may
be available for importation into the focal system during
a post-disturbance reorganization phase. Essentially, this
perspective relates to the lateral information flow among
systems. As proposed by Bengtsson et al. (2003), a
dynamic system of ecological reserves at multiple succes-
sional stages can help maximize ecological memory within
Table 1. Internal and external components of spatial resilience
(Cumming 2011b)
Internal elements External elements
Internal arrangement
of components
Context (area influencing system)
System morphology System footprint (area influenced
by system)
Number and nature
of boundaries
Connectivity
Spatial variation in phase Dispersal of organisms
Properties of location Spatial feedbacks
Spatial subsidies
© 2016 The Authors. Journal of Applied Ecology © 2016 British Ecological Society, Journal of Applied Ecology, 53, 625–635
Quantifying spatial resilience 627