Rapid rise in wildfires in large parts of Canada?

Dec 16, 2011 by Tilo Arnhold
This shows a forest fire in Canada. Large areas of Canada are apparently approaching this threshold value and may in future exceed it due to climate change. As a result both the area burnt down annually and the average size of the fires would increase, write the researchers of the Helmholtz Centre for Environmental Research (UFZ) and the University of Michigan in the December issue of the journal the American Naturalist. Credit: Photo: skylight/Fotolia

Large forest regions in Canada are apparently about to experience rapid change. Based on models, scientists can now show that there are threshold values for wildfires just like there are for epidemics. Large areas of Canada are apparently approaching this threshold value and may in future exceed it due to climate change. As a result both the area burnt down annually and the average size of the fires would increase, write the researchers of the Helmholtz Centre for Environmental Research (UFZ) and the University of Michigan in the December issue of the journal the American Naturalist. The strategies for combating wildfires in large parts of Canada should therefore be reconsidered.

According to media reports, after weeks of drought around 1,000 hectares of forest and scrubland were burnt down in the West Canadian province British Columbia in the summer of 2009 alone. 11,000 people had to be evacuated. Are such events on the rise as a result of climate change? This question 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 similar changes in the journal PNAS. They believe that climate change might result in a dramatic increase in the threat of in and that the forests might disappear here in the 21st century.

Fires are an important factor in many . They are a result of the interaction of the weather, vegetation and land use, which makes them very sensitive to . "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.

The strategies for combating wildfires in large parts of Canada should be reconsidered, say German and US researchers in the journal the American Naturalist. Credit: Photo: Scott Latham/Fotolia

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 , 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. With foxes it was shown that only 60 per cent had to be vaccinated against rabies in order to successfully combat the disease. The scientists therefore hope to find out more in future studies which cover both disciplines.

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More information: 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 www.jstor.org/pss/10.1086/662675

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jrsm
5 / 5 (1) Dec 16, 2011
Fires are a natural component of forest ecology. Given that there have been extensive efforts since the 1920's to suppress wildfires, how valid is this data? The extensive fires we have seen in BC are often the results of previous fire suppression activities allowing the accumulation of fireload in the forest. There are many natural ecosystems that rely on natural periodic fires and these have been suppressed as well. Not only have these ecosystems been threatened, but now the fire load in these areas will destroy the soil when the fire does occur.
Nanobanano
5 / 5 (1) Dec 16, 2011
Not only have these ecosystems been threatened, but now the fire load in these areas will destroy the soil when the fire does occur.


That's why the U.S. national parks and fire fighters just let small fires burn, unless they are threatening homes or businesses.

As long as you keep it under control, it helps both ways. If you burn the fuel up regularly, you prevent most of the big fires, or at least give them less room to spread when they do form.
JimB135
5 / 5 (2) Dec 16, 2011
And with fire suppression over time tree density goes way up. When fires then occur, they turn into these huge crown fires that wipe everything out instead of just clearing the forest floor as periodic fires do.