Fire Management of Mediterranean Landscapes - Fire in Mediterranean Ecosystems - page 359

critical factor is population density, which determines the potential number of
people at risk and varies by more than an order of magnitude between MTC
regions ( Table 13.1 ). However, other inherent factors that vary between MTC
regions include: (1) vegetation type, which affects fuel loads (see Table 2.1 ) : (2)
terrain, which affects fire behavior; (3) climate, which controls fuel production
and fuel moisture, and (4) fire weather, in particular severe winds that can

generate “firestorms” (see Box 1.3 ).
One of the more extreme comparisons would be the impact of fires on the
communities in southern California vs. Western Australia. Since the late 1800s
southern California has experienced major chaparral fires encroaching on the
urban environment and destroying homes and lives; and in the last 60 yrs these
have occurred about every decade (Keeley & Zedler 2009 ). The frequency of such
events has accelerated since 2000, with major events in 2003 (Keeley et al. 2004 )
and a repeat in 2007 (Keeley et al. 2009b ). In contrast, Western Australia has not
had such catastrophic fires ( Table 13.1 ), although the region commonly experi-
ences large bushfires (McCaw & Hanstrum 2003 ). On the surface it might
seem as though fire management practices play a role since, as discussed below,
fuel treatments using prescription burning are more widely applied in Western
Australia than in southern California. However, fuel load is not a major determin-
ant of whether or not a fire becomes catastrophic in southern California (Keeley
et al. 1999a ; Moritz et al. 2004 ).
More important factors include vast differences in population density, which
result in many times more people at risk in southern California ( Table 13.1 ). In
addition, fuels differ radically between these two regions as chaparral stands
inherently have substantially higher fuel loads than Western Australian heath-
lands and Banksia woodlands (see Table 2.1 ), which typically border urban areas.
When fires ignite in southern California, control is always compromised by rugged
terrain, which accelerates fire spread and reduces accessibility, and many homes
are placed in these dangerous watersheds. In contrast, much of Western Australia
is an ancient flat landscape with a few isolated mountain ranges. The worst fires in
southern California are driven by extreme offshore winds known as Santa Anas
that occur 15-30 days per year, but in Western Australia, severe winds are less
predictable and in southwestern forest areas there is on average only one extreme
fire weather day a year (McCaw & Hanstrum 2003 ). In short, much more cata-
strophic fires in southern Californian than in Western Australia are the result of
differences in human demography and fire regime. Central Chile also seems not to
have the same problem with catastrophic fires as southern California. The inten-
sive land use that surrounds most metropolitan areas may be a factor in keeping
fuel loads low, although this situation may be changing as rural populations are
declining with increased migration to the major cities.
Historically wildfires have not been a major threat to urban environments in the
Western Cape of South Africa. Some of this is because not only do the native
fynbos shrublands have relatively low fuel volumes (see Table 2.1 ) , but they are
maintained at a low level by a fire frequency of roughly every 15 yrs. In contrast,