Agriculture Reference
In-Depth Information
while allowing naturally ignited
veld
fires to burn to their full extent (Seydack
et al.
2007
). Over the past 30 yrs under this program, the area burned by anthropogenic
fires has declined as well as the frequency of fires. A similar program was initiated
in the 1970s in remote wilderness areas of Sequoia National Park in California
(Kilgore & Briggs
1972
). In these largely conifer-dominated forests this program
over the past 50 yrs has successfully allowed a return of fire where the fire
suppression policy had largely excluded it during most of the twentieth century
(Colllins & Stephens
2007
).
Highly fire-prone MTV spans much of the southern edge of Australia, with
strong MTC in the western half and gradually shifting to aseasonal rainfall
conditions in the southeast. As a consequence, fire regimes vary widely accord-
ing to local climate (Bradstock
2010
). Impacts of European land use on MTV
fire regimes are multiple. Vast areas of shrubland and woodland have been
cleared for cereal cropping or utilized for rangeland grazing in drier regions
and this has resulted in a decline in fire, among other changes to ecosystem
functions (Hobbs
2002
). Large areas of intact dry shrublands remain in
sparsely inhabited coastal regions of southwestern Western Australia and
South Australia (
Table 13.1
), where lightning ignites occasional large bushfires
(McCaw & Hanstrum
2003
). Suppression capacity and other management activi-
ties in these areas are often minimal.
Australian mosaics of open forests, woodlands and shrub-dominated commu-
nities are often juxtaposed with densely populated urban centers and intensive
rural industries, and substantial resources go toward fire suppression efforts and
prefire fuel treatments. This is particularly true for the southeast that includes the
weakly-MTC Victoria and aseasonal climate region of New South Wales. Consid-
erable areas of eucalypt forest are managed for timber production or as conser-
vation reserves and these resources are vulnerable to frequent anthropogenic and
lightning-ignited fires necessitating aggressive fire suppression (Bradstock & Gill
2001
; McCaw
et al.
2003
).
One common pattern observed across all MTC landscapes is the role of humans
in increasing fire frequency and the non-linear relationship between population
density and fires (Syphard
et al.
2007
,
2009
). As people move into wildland areas,
fire frequency increases with increasing population density. However, there is a
population threshold where further population increases result in decreased fire
frequency, due to reduction in patches of fire-prone vegetation as well as increased
infrastructure leading to rapid suppression of fire starts.
Fire Impacts on Human Populations
MTC regions differ in community vulnerability to catastrophic wildfires. These
landscapes have been prone to such events for tens of millions of years (see
Chapter 10
), and historical records show that massive, high-intensity fires were a
common feature in Australia and California at the time of European colonization
(Edgell
1973
; Bradstock
2008
; Keeley & Zedler
2009
). However, during the
