Rapid rise in wildfires in large parts of Canada are
predicted as ecologists show for the first time threshold values
for natural wildfires
GLOBE-Net, January 4, 2012 -
Large forest regions in Canada are about to experience increased
risks of wildfires due to climate change according to new models
that show there are threshold values for wildfires just as there
are for epidemics.
Large areas of Canada are apparently approaching this threshold
value and in the near future may exceed it due to climate change.
As a result both the area burnt down annually and the average size
of the fires would increase, according to researchers of the
Helmholtz Centre for Environmental Research (UFZ) and the
University of Michigan.
Writing in the December 2011 issue of the journal The American
Naturalist, the study authors suggest strategies for
combating wildfires in large parts of Canada should be
reconsidered.
Citing media reports about forest and scrubland fires in British
Columbia the authors questioned whether such events were the result
of climate change, a question that is being hotly debated by
ecologists all over the world.
In July a group of US researchers led by Anthony Westerling of
the University of California forecasted that climate change
might result in a dramatic increase in the threat of wildfires in
Yellowstone National Park and that forests in those areas might
disappear in the 21st century.
Fires are an important factor in many terrestrial ecosystems.
They are a result of the interaction of the weather, vegetation and
land use, which makes them very sensitive to global change.
"Changes in the wildfire regime have a significant impact
on a local and global scale and therefore on the climate as well.
It is therefore important to understand how the mechanisms which
shape these wildfires work in order to be able to make
predictions on what will change in future," explains PD Dr. Volker
Grimm of the UFZ.
Left: Dead trees destroyed by forest fire in British
Columbia. Photo: © Scott Latham, Fotolia.com Zoom (473.6 KB)
For their model, the scientists evaluated data from the Canadian
Forest Service, which had recorded fires greater than 200 hectares
between 1959 and 1999, and sorted these by ecozone.
This showed that three of these ecozones in Canada are
close to a turning point: the Hudson Plains south of the Hudson
Bay, the Boreale Plains in the Mid-West the Boreale Shield, which
stretches from the Mid-West to the East coast and is
therefore the largest ecozone in Canada.
The closest to a turning point is apparently the Boreale Shield.
In order to check their model and the theory of a threshold value
for wildfires, the scientists looked at the fires in this
region more closely.
Around 1980 the average size of the fires in this part of the
provinces of Alberta, Saskatchewan and Manitoba tripled rapidly.
"In our opinion this is a sign that there are also threshold
values for forests above which the wildfire regime drastically
changes," reports Volker Grimm.
"It is likely that the Boreale Plains have in recent decades,
particularly around 1980, experienced a change to a system
characterised by wildfires. This has fundamental repercussions for
the environment and the combating of wildfires. Small changes in
the fire propagation parameters have a great impact on the size of
the fires."
Gradual changes, such as those which can
be expected due to climate change, can therefore result in an
abrupt and sharp increase in the size of the
fires.
The scientists were also interested in the parallels with
disease propagation. Prevention strategies, which reduce
combustible material, are in a way similar to the vaccinations
which are used against the spread of diseases such as the
measles.
Here too there is a threshold value above which a disease
spreads and below which it falls. Other modellers from the UFZ were
therefore able to turn this theoretical threshold value into a
practical value.
Citation: Richard D. Zinck, Mercedes Pascual and Volker
Grimm (2011)
Understanding Shifts in Wildfire Regimes as Emergent Threshold
Phenomena. The American Naturalist. Vol. 178, No. 6, December
2011