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to a particular disturbance may impair its resilience to others. 69 However,
the knock-on effects of bolstering one feature of an ecosystem cannot be
predicted reliably. 70
Third, and most importantly, it is impossible to reach a level of suf
cient
resilience to externalities. 71 The resilience of an ecosystem is not, as Holling
and Gunderson note,
. 72 Rather, it
is relative to the magnitude of the challenges with which the system is
presented, and its condition at the time a challenge arises. An ecosystem
that is already degraded may undergo a regime shift as a consequence of
external events which, if its resilience had not been eroded, would not have
perturbed it unduly. 73 Conversely, a highly resilient ecosystem may still be
altered if the strength of external forces acting on it is suf
'
a
xed quantity that de
nes a system
'
cient to over-
whelm its capacity for adaptation. In this regard, Brierley and Kingsford
suggest that the resilience of marine ecosystems would need to be
'
very
'
great indeed
to withstand the effects of the temperature increases that are
already seen as an inevitable consequence of climate change. 74
In conclusion, a speci
ed resilience approach may be useful in circum-
stances where known variables of an ecosystem are under threat from
a known stressor. However, it does not assist with sustaining sources
of resilience in ecosystems of which we are ignorant or with addressing
threats of harm to them that could not have been anticipated. In this
regard, the best means of protecting ecosystem functionality against the
unknown is to employ a general resilience approach. This seeks to reduce
risks of regime shifts as far as possible by reducing the cumulative pressures
that human activities place on them. 75 As Walker and Salt observe, it is
69 Walker and Salt,
'
Resilience Thinking
'
,p.121;WalkerandSalt,
'
Resilience Practice
'
, pp. 19,
90; Folke et al.,
'
Resilience Thinking
'
,under
'
Specied and General Resilience
'
; F. Miller et al.,
'
Resilience and Vulnerability: Complementary or Conicting Concepts?
'
(2010) 15(3): 11
Ecology and Society under
'
Dening Concepts: Responses to Stress
'
;B.WalkerandF.Westley,
'
Perspectives on Resilience to Disasters across Sectors and Cultures
'
(2011) 16(2): 4 Ecology
and Society under
'
Trading Risks: Speci ed vs. General Resilience
'
.
70 Gunderson,
'
Ecological Resilience
'
,433.
71
Scheffer et al.,
'
Catastrophic Shifts
'
, 595
-
6; Carpenter,
'
Ecological Futures
'
, 2080
-
1.
72 Holling and Gunderson,
'
Resilience and Adaptive Cycles
'
,p.32.
73 Folke et al.,
, 575.
74 A. S. Brierley and M. J. Kingsford,
'
Regime Shifts
'
'
Impacts of Climate Change on Marine Organisms
(2009) 19 Current Biology, R607.
75 Walker and Salt,
and Ecosystems
'
'
Resilience Practice
'
,pp.18
-
20, 90
-
100; Folke et al.,
'
Resilience
Thinking
. See also the analogy drawn between
a general resilience approach and the call in Rockström et al.,
'
,under
'
Speci ed and General Resilience
'
'
A safe operating space
'
,for
humanity to avoid crossing planetary boundaries in Walker and Salt,
'
Resilience
Practice
'
, pp. 186
-
91.
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