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the increase over time in large downed
woody fuels (fallen snags), increase the
complexity of modeling landscape
dynamics. The bark beetle/wildfire
interaction is notable for its ubiquity
across western North America, but
analogous questions obtain in other
fire-insect systems (Jenkins et al.
2008).
If we extend the domain of fireecosystem
interactions to other external
and internal drivers, we can then seek
quantitative models that take warming
climate as a primary driver. McKenzie
et al. (2009) built qualitative models of
the effects of warming climate on “stress
complexes,” or cascading interactions
among ecosystem elements that are
intensified by warming temperatures.
Figure 4 shows their model for the
Sierra Nevada mountains in eastern
California, United States. Three external
forcings, all of anthropogenic origin
(global warming, fire exclusion, and
ozone pollution), amplify interactions
among fire, insects, and succession to
accelerate forest compositional change
beyond that expected from global
warming by itself. Proportional changes
in the strength of each “arrow” in the
complex will propagate through the
system cumulatively, with increasing
uncertainty at each step. This fairly
simple thought experiment is illustrative
of the peak in complexity of
fire-ecosystem interactions at the “landscape”
scale.
Adapting to Changing Fire
Regimes
Given the near certainty that Earth will
continue to warm through the 21st century
regardless of global mitigation
policies (Solomon et al. 2009), can protected
areas be managed to adapt
successfully to expected changes in fire
regimes? If so, how will these approaches
differ from adaptation efforts in lands
managed intensively for other resources
(Joyce et al. 2009)? Our work with
public lands managers in the American
West has shown that regardless of land
use mandate, adaptation needs to be collaborative,
local, and flexible to
successfully incorporate regionally
unique factors affecting adaptation strat-
Figure 4—Stress complex in forests of the Sierra Nevada mountains. Adapted from McKenzie et al.
(2009).
26 International Journal of Wilderness APRIL 2011 VOLUME 17, NUMBER 1
egies. At the same time, a broad
conceptual approach to adaptation will
inform the process so that it is proactive
rather than only reactive and so that
common resources and objectives can be
entrained. Millar et al. (2007) provide a
framework for focusing adaptation
efforts that evolves as ecosystem change
accelerates and fewer opportunities
remain for maintaining current conditions.
This framework identifies three
stages: resisting change, promoting resilience
to change, and allowing ecosystems
to respond to change. Table 1 summarizes
local and regional actions associated
with each stage for ecosystems in which
substantial management interventions
are possible. Note that most of these
options are unavailable for protected
areas. Clearly, creative solutions are
required to operate within management
constraints (Miller et al. 2011).
Conclusions
Fire and other disturbances will change
in a warming climate in ways that may
be counterintuitive and relatively
abrupt as the Earth system reacts to the
increased radiative forcing from greenhouse
gas emissions. Wilderness and
other protected areas are especially vulnerable
to fire and other disturbances
because they are small, isolated, and
sensitive to environmental effects from
outside their boundaries, valued by
society in their current “equilibrium”
state, and not available for the substantial
manipulations that may help more
managed ecosystems to adapt. Given
that greenhouse warming is unlikely to
abate soon, we can expect significant
changes in protected areas in which fire
is a dominant ecosystem process, in
other words, most of them. These
changes are expected to be rapid enough
that attempts to maintain stationary
conditions will likely fail, and adaptation
must be dynamic and anticipate
future landscape composition and