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. With foxes
|Contact: Tilo Arnhold|
Helmholtz Association of German Research Centres