Agriculture Reference
In-Depth Information
in MTC regions differ in timing with potential effects on predictability of extreme
fires (see
Box 1.3
). The mistral winds in the Mediterranean Basin are distributed in
summer and autumn and thus they often occur at times of moderate fuel moisture
content, reducing their likelihood of leading to major fires. Likewise, Berg winds
in the Cape region of South Africa are autumn and winter winds and thus do not
always coincide with low fuel moisture conditions. In contrast, the Santa Ana
winds of southern California are absent in the summer and concentrated in late
autumn when fuel moistures are at their lowest levels.
Unusually long droughts contribute to major fires by leading to very low live
fuel moisture content at the time of fire, and by increasing the dieback of vegeta-
tion, thus producing rapid changes in dead fuel loads. In California major fires
have been preceded by 1-2-yr droughts, and substantial droughts in the first
decade of the twenty-first century correlate with a doubling of large fire events
with catastrophic impacts on local human communities (Keeley & Zedler
2009
).
Droughts are likewise implicated in major destructive fires in Greece (Viegas
2004
)
and Australia (Hennessy
et al.
2006
; Bradstock
2008
). In California most major
fires occur in the autumn when live fuel moisture is at its lowest and this does not
change with extended drought. Thus, it has been hypothesized that the association
between major droughts and major fires is due to the short-term increase in dead
fuels, which increases fire spread directly, and indirectly through enhanced spot-
ting behavior (Keeley & Zedler
2009
). Fire danger indices fail to capture these
short-term changes in dead fuels and this may explain the limited explanatory
value of such indices in southern California (Schoenberg
et al.
2007
). It is
unknown to what extent recent severe droughts are tied to anthropogenically
induced climate change. However, temperatures have been steadily increasing
and do exacerbate drought impacts, and climate changes can lead to more extreme
conditions in general (e.g. Hasson
et al.
2009
; Bradstock
2010
).
Fire Management Strategies
Contemporary fire management goals are focused on minimizing impacts of fire
hazard to human population centers and sustaining natural ecosystems. Regions
and jurisdictions within regions vary greatly in the importance of these two goals.
For environments where both human vulnerability and ecosystem sustainability
are important, balancing these two goals is a challenge. Meredith (
1996
) put it
rather succinctly; “The placing of houses in flammable bushland increases the risk
factor associated with fire to such an extent that the need for trade-offs between
fire protection and ecological management is greatly increased.” Thus, an issue of
potential conflict is how to find the appropriate balance between fire hazard
reduction and resource protection.
Perhaps the biggest conflict between resource management and fire hazard
management lies in the application of prefire fuel treatments such as prescription
burning. A common management philosophy is that hazard-reduction burning
