Geoscience Reference
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responseā€ to the overall warming trend in the 20th century. The treeline is
perceived as most sensitive to climate change, with the upslope migration
being a typical response to warming at higher elevations. However, an
investigation at three sites near the Columbia Icefi eld, Luckman and
Kavanagh (1998) showed that the nature of treeline response to climate
change depends on local environmental conditions and 'the strategies
adopted by individual species', as well as to the genetic diversity of the
species in their ability to adapt to rapid environmental change and to be
able to achieve wide dispersion of seeds. For example, the treeline of Abies
lasiocarpa on the north-facing slope has not moved for the last 400 years. On
the other hand, the treeline of Picea engelmannii on the south-facing slope
has migrated upslope by seedling establishment. They have noted that other
factors, such as soil and groundwater level, are important in infl uencing
changes in plant species distribution over time. In addition, intensity and
extent of forest fi res due to frequent drought and high temperatures (as well
as due to diebacks caused by insect infestation) can also alter the ecological
succession of plant species. Referring to Ebata (2004), Hamann and Wang
(2006) mentioned that the pine beetle infestation in British Columbia has
become an epidemic, with over 4 x 10 6 ha destroyed. This is partially caused
by increasingly warmer winter minimum temperatures in the Rockies.
Ordinarily, colder winter temperatures would kill much of the insect larvae
residing inside the tree barks. Harvell et al. (2002) showed that the warming
of winter temperatures will cause increased probability in the wintertime
survival of various pathogens, as well as causing increased severity in forest
disease outbreaks. Henderson et al. (2002) suggested two possible ways in
which a forest can change in response to climate change, one by slow and
cumulative decline or by catastrophic change, such as a major forest fi re.
Hamann and Wang (2006) also found that: (1) Tree species at the northern
range limits have migrated northward at a rate of 100 km per decade, (2)
Hardwood species are generally not affected by climate change, and (3)
many of the important conifer species will eventually disappear as their
suitable habitat shrinks under climate change. These changes will have a
profound impact on the forest industry in British Columbia.
Every year the Rocky Mountains experience a number of forest
fi res, endangering human lives and socio-economic activities of urban
communities (such as Kelowna, British Columbia) located within
mountainous regions. As stated earlier in the chapter, IPCC-AR4 (2007) has
projected prolonged periods of summer drought with climate warming.
It is reasonable to assume therefore, that such a change will cause an
enhancement in forest fi re frequency and intensity, producing increased risk
to major population centres. A combination of summer dryness and insect
infestation (such as the pine beetle) would produce increasingly favourable
conditions for major forest fi res.
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