158
From Examples to Theory
From these four examples, several conclusions can be
drawn. Stressors potentially inducing regime shifts may
affect a system gradually, e.g., decline of top-predator due
to fishing (Baltic Sea and Scotian Shelf regime shifts), or
abrupt and exceptionally, e.g., disease outbreak (Caribbean
coral reef destruction). The examples of the Atlantic cod
stock collapse and the North Sea regime shift showed that
climate change may play and important role in such mechanisms (Beaugrand 2004; Conversi et al. 2015; Yletyinen
et al. 2016). In addition, these examples showed the cumulative effects of different stressors and how they may act
together in synergistic ways. The mechanisms and processes
involved in regime shifts may be induced by top-down and/
or bottom-up regulation (Holling 1973; Beisner et al. 2003;
Conversi et al. 2015; Pershing et al. 2015). Finally, these
examples highlight the importance and necessity to understand regime shifts mechanisms for a sustainable use of
marine resources in order to provide ecosystem services and
benefits for human communities (Doak et al. 2008). Also,
they uncovered some fundamental properties of regime
shifts, e.g., the abruptness of changes and their lack or low
reversibility (Scheffer et al. 2001, 2015; Dakos et al. 2012).
However, due to the complexity and entanglement of the
mechanisms involved, defining regime shifts based on
empirical evidences is challenging. A review of the concepts
associated with regime shifts, which are mostly theoretical
(Levin and Möllmann 2015), is essential to understand the
non-linear mechanisms potentially involved in complex systems dynamics, particularly in a time of pronounced environmental changes.
The Regime Shift Theory
Different mathematical frameworks lead to the development
of the regime shift theory (Jones 1975, 1977; Thom 1975;
Crawford 1991), describing how changes in some controlling factors can lead to huge and abrupt changes in various
systems (e.g., biological, physical, behavioral; Jones 1975;
Carpenter 2001; Scheffer et al. 2001). Marine regime shifts
can be defined as dramatic and abrupt changes in the system
structure and function that are persistent in time, where the
system can range from a single cell to a population or an
ecosystem (Beisner et al. 2003; Scheffer and Carpenter
2003). Due to the high number of terminologies and definitions used in the literature, a glossary was added to this chapter in order to have consistent and clear definitions. All terms
highlighted in italics in the following text can be found in the
glossary section (Box 1).
The easiest way to understand and visualize regime shifts is
the example of the ball-in-cup or ball-in- valley diagram developed from the pioneer work of Poincare in the
1800’s in Crawford 1991; Fig. 1). The ball represents the
study system, for instance the Caribbean coral reef. The system reef (our ball) has certain parameters such as coral abundance, coverage, and biodiversity. The system state is
represented by the valley in which our ball (system) lies
(regime 1 in Fig. 1). The dimension of the valley (width and
height in our two dimensions’ figure) corresponds to the
Box 1: Glossary
Regime shift: dramatic and abrupt change in the
structure and function of a system
causing a shift between two alternate
stable states following discontinuous
non-linear dynamics and exhibiting
three equilibria. There are some
debates about the definition and critical transition or phase shift might be
considered synonyms depending on
the literature.
Resilience:
capacity of the system to absorb disturbances and reorganize in a way
that it retains the same functions,
structure, identity and feedback
mechanisms, potentially impeding a
regime shift.
Regime:
dynamic system configuration maintaining certain structures and functions. It is also known as stable state,
basin of attraction or domain of
attraction.
Tipping point: threshold separating two dynamics
regimes. It is also known as critical
threshold or bifurcation point.
Feedback
mechanism:
ecological mechanisms stabilizing a
regime by amplifying (positive) or
damping (negative) the response to a
forcing. Positive feedbacks (reinforcing) move the system to an alternate
stable state, out of equilibrium.
Negative feedbacks (balancing)
maintain the status of the system,
close to the equilibrium dynamics.
Hysteresis:
phenomenon for which the return
path from regime B to regime A, is
drastically different from the path
that led from regime A to regime B.
C. Sguotti and X. Cormon
From Examples to Theory
From these four examples, several conclusions can be
drawn. Stressors potentially inducing regime shifts may
affect a system gradually, e.g., decline of top-predator due
to fishing (Baltic Sea and Scotian Shelf regime shifts), or
abrupt and exceptionally, e.g., disease outbreak (Caribbean
coral reef destruction). The examples of the Atlantic cod
stock collapse and the North Sea regime shift showed that
climate change may play and important role in such mechanisms (Beaugrand 2004; Conversi et al. 2015; Yletyinen
et al. 2016). In addition, these examples showed the cumulative effects of different stressors and how they may act
together in synergistic ways. The mechanisms and processes
involved in regime shifts may be induced by top-down and/
or bottom-up regulation (Holling 1973; Beisner et al. 2003;
Conversi et al. 2015; Pershing et al. 2015). Finally, these
examples highlight the importance and necessity to understand regime shifts mechanisms for a sustainable use of
marine resources in order to provide ecosystem services and
benefits for human communities (Doak et al. 2008). Also,
they uncovered some fundamental properties of regime
shifts, e.g., the abruptness of changes and their lack or low
reversibility (Scheffer et al. 2001, 2015; Dakos et al. 2012).
However, due to the complexity and entanglement of the
mechanisms involved, defining regime shifts based on
empirical evidences is challenging. A review of the concepts
associated with regime shifts, which are mostly theoretical
(Levin and Möllmann 2015), is essential to understand the
non-linear mechanisms potentially involved in complex systems dynamics, particularly in a time of pronounced environmental changes.
The Regime Shift Theory
Different mathematical frameworks lead to the development
of the regime shift theory (Jones 1975, 1977; Thom 1975;
Crawford 1991), describing how changes in some controlling factors can lead to huge and abrupt changes in various
systems (e.g., biological, physical, behavioral; Jones 1975;
Carpenter 2001; Scheffer et al. 2001). Marine regime shifts
can be defined as dramatic and abrupt changes in the system
structure and function that are persistent in time, where the
system can range from a single cell to a population or an
ecosystem (Beisner et al. 2003; Scheffer and Carpenter
2003). Due to the high number of terminologies and definitions used in the literature, a glossary was added to this chapter in order to have consistent and clear definitions. All terms
highlighted in italics in the following text can be found in the
glossary section (Box 1).
The easiest way to understand and visualize regime shifts is
the example of the ball-in-cup or ball-in- valley diagram developed from the pioneer work of Poincare in the
1800’s in Crawford 1991; Fig. 1). The ball represents the
study system, for instance the Caribbean coral reef. The system reef (our ball) has certain parameters such as coral abundance, coverage, and biodiversity. The system state is
represented by the valley in which our ball (system) lies
(regime 1 in Fig. 1). The dimension of the valley (width and
height in our two dimensions’ figure) corresponds to the
Box 1: Glossary
Regime shift: dramatic and abrupt change in the
structure and function of a system
causing a shift between two alternate
stable states following discontinuous
non-linear dynamics and exhibiting
three equilibria. There are some
debates about the definition and critical transition or phase shift might be
considered synonyms depending on
the literature.
Resilience:
capacity of the system to absorb disturbances and reorganize in a way
that it retains the same functions,
structure, identity and feedback
mechanisms, potentially impeding a
regime shift.
Regime:
dynamic system configuration maintaining certain structures and functions. It is also known as stable state,
basin of attraction or domain of
attraction.
Tipping point: threshold separating two dynamics
regimes. It is also known as critical
threshold or bifurcation point.
Feedback
mechanism:
ecological mechanisms stabilizing a
regime by amplifying (positive) or
damping (negative) the response to a
forcing. Positive feedbacks (reinforcing) move the system to an alternate
stable state, out of equilibrium.
Negative feedbacks (balancing)
maintain the status of the system,
close to the equilibrium dynamics.
Hysteresis:
phenomenon for which the return
path from regime B to regime A, is
drastically different from the path
that led from regime A to regime B.
C. Sguotti and X. Cormon