Geoscience Reference
In-Depth Information
2.2.2 Ecosystems as complex adaptive systems
Ecosystem behaviour is the outcome of multiple interactions between
the system
'
s biotic and abiotic components. This interaction percolates
upwards to produce and in
uence the development of macroscopic
properties of the system.
14
In turn, the way in which systemic properties
evolve feeds back to in
uence lower-level interactions.
15
For example,
Levin notes that the aggregation of components into organisational
structures as a result of interrelationships between them has a profound
in
uence on the further development of an ecosystem as a whole.
16
The enormous complexity of these interactions, subject as they are to
constant internal change as species evolve and to the effects of dynamic
externalities such as the climate system and hydrologic cycles, results
in non-linear behaviour at the systemic level.
17
Non-linearity refers to a
situation in which the reactions of complex systems to disturbances are
not strictly proportional to the event(s) that trigger them.
18
In an
ecological context, it means that it is not possible to predict with cer-
tainty either what the exact responses of a system will be to any inter-
vention or the emergent properties of a system that will arise through
interaction between its components.
19
Gunderson describes the com-
plexity of ecosystems as leading to
'
inherent unpredictabilities
'
in their
behaviour.
20
A second product of their complexity is that ecosystems possess not
one but multiple potential stable states.
21
Because of the dependency of
the path they take on the interconnection between systemic levels and
the effect that external in
uences have on their development, it is natural
14
Levin,
, 431; G. Harris, Seeking Sustainability in an Age of
Complexity (Cambridge: Cambridge University Press, 2007), pp. 25
'
Ecosystems and the Biosphere
'
-
6.
15
16
Levin,
Ibid
.
'
Ecosystems and the Biosphere
'
,432
-
3.
17
Gaichas,
'
Ecosystem-based Fishery Management
'
, 396; Levin,
'
Ecosystems and the
Biosphere
,p.22;B.WalkerandD.Sa ,
Resilience Thinking: Sustaining Ecosystems and People in a Changing World
(Washington, DC: Island Press, 2006), pp. 34
'
, 433; Harris,
'
Seeking Sustainability
'
6.
18
W. Steffen et al., Global Change and the Earth System: A Planet under Pressure (Berlin:
Springer-Verlag, 2004), p. 266.
19
Walker and Salt,
-
'
Resilience Thinking
'
,pp.34
-
5; Harris,
'
Seeking Sustainability
'
,
p. 25.
20
L. H. Gunderson,
'
Ecological Resilience
-
In Theory and Application
'
(2000) 31 Annual
Review of Ecology and Systematics,433.
21
M. Scheffer et al.,
'
Catastrophic Shifts in Ecosystems
'
(2001) 413 Nature,591
-
6; Gunderson,
'
Ecological Resilience
'
,426
-
30, 433; Chapin III et al.,
'
Terrestrial Ecosystem Ecology
'
,
pp. 340
-
1.
