p.6-7 Complex resource systems are organized from the interactions of a set of ecological, social, and economic
systems across a range of scales. Resilience is central to understanding the dynamics of these systems and their vulnerability
to various shocks and disruptions. Resilience measures the strength of mutual reinforcement between processes, incorporating
both the ability of a system to persist despite disruptions and the ability to regenerate and maintain existing organization.
Resilience allows the system to withstand the failure of management actions.
p.8 We propose that the behavior of complex adaptive systems depends upon four key properties: ecological
resilience, complexity, self-organization, and order. As discussed above, resilience is the extent to which a system
can withstand disruption before shifting into another state. Complexity is the variety of structures and processes that occur
within a system. Self-organization is the ability of these structures and processes to mutually interact to reinforce and
sustain each other. The process of self-organization produces order from disorder, but the interaction of processes across
scales also destroys, and reconfigures, ecological organization, producing complex ecological dynamics.
p.9 Ecosystems are resilient when ecological interactions reinforce one another and dampen disruptions.
p.24 In order to understand complicated systems, it is often convenient to consider a simpler system
that exhibits the type of behavior of interest... Some might argue that a principle of parsimony [JLJ - preference
for the least complex explanation for an observation, parsimony is used as a heuristic (rule of thumb) to guide scientists
in the development of theoretical models rather than as an arbiter between published models.] dictates that such models be
used in the absence of strong evidence to the contrary.
p.44,47 Pimm (1991, p.13) defines resilience as "how fast a variable that has been
displaced from equilibrium returns to it..." In summary, according to Pimm (1991) and according to us, long return
times may be diagnostic for a loss of resilience... A long return time is due to disturbances that bring the system near an
unstable equilibrium, or possibly to a weak repulsion from an unstable equilibrium.
p.52 In this volume, a resilient system is one that tends to maintain a given state when subject
to disturbance
p.54 Collectively, these resilience mechanisms, operating at diverse scales, buffer... ecosystems against
fluctuating inputs... Measurements and scientific analyses of perturbations or resilience are always tied to particular scales
of space and time
p.150 Thus, information, key players, connectivity, and cooperative synergy are likely to be important elements,
not only in the resilience of natural ecosystems, but also within human organizations.
p.166-167 To further highlight the differences between definitions of resilience and stability we'll use
a heuristic model - that of a ball in a cup. Picture a ball or marble sitting in the bottom of a cup on a table
(figure 6.2a). The ball is stable (it doesn't move) and its resting point is at an equilibrium created by a balance of the
downward force of gravity and the upward force of the table and cup. If the cup is shaken, the ball will soon return to an
equilibrium position. This physical model captures the essence of engineering resilience; a global equilibrium with resilience
defined as the time taken for the ball to return to a stationary position.
To understand ecological resilience we must change one ingredient of the model: the cup. In ecological
resilience, the cup is not rigid, nor is there just one cup; there are multiple cups on the table (figure 6.2b), and the cups
morph or change shape over time. In a landscape of multiple, morphing cups, a ball can easily move from one cup to another
- change stability domains. Also, the changing landscape allows for a smaller disturbance to cause the ball to move among
the cups. This is analogous to the loss of resilience in ecological systems. that is, the system is no longer capable of absorbing
a disturbance, and so the disturbance suddenly flips the system into another stability domain. This property is known as adaptive
capacity... Each of the pieces in the cup metaphor represents key variables that operate at different speeds... it
is the dynamics of the slowly changing variables that interact with faster variables (disturbances, and other key structural
elements) which define ecological resilience.
p.255-256 Carpenter and Cottingham (chapter 3), Carpenter et al. (1999), and Scheffer (1998) have used the
heuristic of a ball and a cup to highlight differences between these types of resilience. The ball represents the system state
and the cup represents the stability domain (figure 10.1). The ball sitting at the bottom of the cup depicts equilibrium.
Disturbances (depicted by an arrow) move the marble to a transient position within the cup. Engineering resilience refers
to characteristics of the shape of the cup - the slope of the sides dictate the return time of the ball to the bottom. Ecological
resilience suggests that more than one cup exists, and the resilience is defined as the width at the top of the cup. Implicit
in both of these definitions is the assumption that resilience is a static property of systems. That is, once defined, the
shape of the remains fixed over time. However, the cases in this volume indicate that stability domains are dynamic
and variable.
p.256-257 Many of the manifestations of human-induced changes in ecosystems result from alteration
of the key variables that influence the underlying stability domains. The key variables that configure these stability
domains change at relatively slow rates without human intervention and change at more rapid rates with human intervention...
Using the ball-in-cup heuristic, the shape of the cup is subject to change, altering both stability (return time) and resilience
(width of stability domain)... The property of an ecosystem that describes this change in stability landscapes and resilience
is referred to as "adaptive capacity" (Peterson et al. 1998; Gunderson 2000)... The multiple meanings of resilience
all relate to or are dependent upon a time domain. The first definition (Holling 1973) was based on system dynamics over time...
the chapters by [other authors] introduce the spatial dimension of resilience.
p.257 Ecological resilience and adaptive capacity both suggest interactions across scales. One conclusion
from these treatments is that resilience can only be discussed, analyzed, and measured across scale ranges (either in space
or time or both).
