Agriculture Reference
In-Depth Information
California chaparral inherently has higher fuel loads and fire return intervals of
15 yrs are at the lower threshold of tolerance; historically fire return intervals
were double or triple that interval. Other factors are likely at work as well. The
population density in the Western Cape is relatively high, although it doesn't
approach the level of southern California. However, the urban growth pattern of
the Western Cape appears to have avoided the extensive wildland-urban interface
problem of southern California with developments and consequently has suffered
less damage from wildfires. The closest the Cape has come to destructive fires are
two that occurred in January 2000 on the urban fringe, burning a total of 8000 ha.
Homeowners were evacuated and there was general panic, but there were very few
structures lost and no one died (
Table 13.1
).
Similar to the situation in southern California is the major bushfire threat in the
Australian state of Victoria, and adjacent states of South Australia and New
South Wales. In contrast to Western Australia, fire losses have historically been
very high, including lives, structures and livestock (
Table 13.1
). The reasons are
similar to those in California: higher population density and substantially higher
of immense interest to our focus on MTC ecosystems because Victoria has a weak
MTC, yet its neighbor South Australia to the west, with a stronger MTC, and its
neighbor New South Wales to the east, with an aseasonal rainfall regime, both
have equally severe bushfire problems (see
Chapter 8
).
For similar reasons (i.e. high population density and high fuel loads) the
Mediterranean Basin has a history of catastrophic wildfires, from westernmost
Portugal to the eastern end of the basin in Greece (
Table 13.1
). Commonly these
fires have had extreme impacts on rural populations, and under severe wind
conditions such as the Mistral or the Meltemia winds (see Box 1.3) there are often
extensive losses in rural areas of lives, structures and agricultural crops.
Climate Impacts on Major Fire Events
Although annual summer droughts contribute to large fire events in all MTC
regions, there are regionally unique factors. For example, the intensity of annual
summer drought is greater in California than in some other MTC regions (see
Box 1.1
), which can affect summer fuel moisture. Also, timing of winter rains is
different: for example, there is high probability of rains beginning in the autumn in
the Mediterranean Basin, whereas this is rare in California. Very different synop-
tic weather conditions lead to major fires in different regions. For example, in
Western Australia they are associated with the eastward passage of strong anti-
cyclones, whereas in southeastern Australia dangerous fire weather is associated
with warm, dry air masses generated by southern ocean cold fronts and/or tropical
depressions (Luke & McArthur
1978
; McCaw & Hanstrum
2003
; Hennessy
et al.
2006
; Hasson
et al.
2009
).
Two factors closely associated with major fire events are extreme winds and
anomalously long droughts. High-intensity wind storms associated with large fires
