The state of Brandenburg is the region in Germany that is most strongly exposed to forest fires. From 1991 to 1995, there were on average 6 fires per 10,000 ha (average in Germany: 1.8 fires per 10,000 ha). Since the occurrence of forest fires is strongly influenced by climate, the question arises how the risk of forest fires will develop under changing climate conditions.
Fig.1. Number of forest fires in the state of Brandenburg 1975 – 1995
The future climate development is estimated by means of regional scenario models that consider large-scale climate tendencies as well as locally observed meteorological values. The development of climate and forest fires are connected by an index that is based on climate parameters. The calculation of this forest fire index (FFI) is based on temperature and precipitation conditions during the vegetation period:
sd= 1 if the daily maximum of air temperature > 25.0°C0 in all other casesp= daily sum of precipitationvb= beginning of vegetation period (April 1st)ve= end of vegetation period (September 30th)
Calculation of the average number of forest fires in nine almost equally sized regions of Brandenburg as of 2050 with an assumed temperature increase by 1.5(C. The moderate temperate increase is connected with a decrease of the annual sum of precipitation by 50-100 mm (Fig.2a and b). As a consequence, an increase of the average number of annual forest fires in the whole state from 512 to 605 forest fires is to be expected. This increase varies between 5 and 30 in the different regions (Fig.2c and d).
Fig.2a. Mean annual sum of precipitation 19511990
Fig.2b. Mean annual sum of precipitation as of 2050 based on scenario calculations
Fig.2c. Mean regional number of forest fires 1975 1995
Fig.2d. Mean regional increase of annual forest fires as of 2050 based on scenario calculations
Climate changes can lead to a distinct increasing risk of forest fires in the state of Brandenburg. With the climate scenario model used, climate changes will be calculated for different regions. Based on this, climate impacts can now be better estimated than before. The results are valuable as a basis for decision-making in forest management. For example, adaptive forest management strategies aiming at a modified species composition could help to reduce the susceptibility of forest stands to forest fires.
F.-W. Gerstengarbe, P.C. Werner, M. Lindner, G. Bruschek Potsdam Institute for Climate Impact Research Telegrafenberg C4 14473 Potsdam Germany