The spring of 1992 in southern Sweden did not suggest anything else than yet another wet and rainy summer. In April the highest precipitation for more than 100 years was recorded at several stations. Low pressures kept coming in with some rain every other day. Then suddenly the trend was broken around 14 May as a high pressure system established over Scandinavia. The high pressure proved to be unusually stable for this part of the world, and soon farmers were starting to complain about the drought. People were also becoming increasingly aware of the rising fire danger, but surprisingly few fires were reported.
Then within a couple of days in the second week of July, two fires got out of hand and for several days forest fire fighting got a tremendous coverage in the national media. By international standards, however, these fires were rather modest. The worst in terms of fire behaviour and property lost was a fire burning in pine forest on the eastern side of the Baltic island of Gotland. It was first observed at two o’clock in the morning, was attacked within an hour and was declared dead by noon when less than two hectares had been burnt. The wind was, however, picking up speed, and as the fire fighters started to leave the area they observed smoke further out in the forest. For three hours the fire spread over relatively flat terrain and homogeneous vegetation. The head of the fire travelled at a mean speed of around 22 m/min, mainly as a surface fire, but crowning whenever there was sufficient undergrowth of juniper and spruce among the pines. Spotting distances of up to 400 meters were documented. The wind was 12-15 m/sec during the run, and we have calculated the Fire Weather Index of the Canadian fire danger rating system to have been 56. The fire was not contained until the third day, but winds were only around 5 m/sec during the second and third days, and the burning was no longer aggressive. On the second day another fire started in Southern Småland, burning mainly over a dwarf-shrub covered mire complex.
The Gotland fire eventually covered 1100 ha and the Småland fire 2000 ha. This makes these fires the two largest for several decades in Sweden. The drought in 1992 affected also the Baltic states, where several fires were burning in early July. The total burnt area in Sweden up to mid August 1992 was 5800 ha, the highest figure since 1959, when 9000 ha burnt. The worst fire year this century was in 1933, with approximately 30,000 ha burnt. But as late as the mid 19th century much of the forest in Northern Sweden still had a fire cycle of around 100 years, corresponding to more than 100,000 ha burnt per year on average. In the southern half of the country, fire may have been even more prevalent.
The main reason behind the relatively small burnt area in Sweden in recent years is the well developed network of forest roads, allowing very fast access to fires with pumps and hoses. It is very rare that fires burn for more than a few hours. The result is that fire fighters today usually have little experience with forest fires, and particularly big ones. They rely exclusively on water, delivered from hoses or from helicopters, which may present problems once a fire grows big.
At the Gotland fire, the only effort to burn out fuel ahead of the advancing front was done by an old, retired firefighter on his own initiative, and this helped save a small farm, lying in the direction of the head of the fire. A few months after these fires of 1992, it is evident that they have activated an intense discussion on forest fire fighting and also of the role of fire in our ecosystems.
Fire Ecology Course in Sweden
In contrast to many other countries within the boreal and subboreal region, Sweden today has very small problems with forest fires, despite the unusual size of the fires of 1992. In fact, fire protection has been successful to such a degree that the lack of fire creates problems for nature conservation. In former times fire was the main disturbing agent and many plants and animals were adapted to fire.
To meet a growing demand for basic knowledge about fire ecology and the use of fire, a two day course was held at the Swedish University of Agricultural Sciences in Umeå, Northern Sweden. For several years there has been more and more talk about the need to start using fire as a management tool in nature reserves that had been structured earlier by repeated fires, but nothing has been done so far on the ground. Forest managers on the other hand are eager today to adjust forestry practices to the former patterns of natural disturbance. The use of prescribed fire is one of the ways to achieve this. Until the late 1960s prescribed fire was extensively used for site preparation, but today most of the experienced people have gone.
Thirty people from Sweden and Finland attended the course. They were a mix of company foresters, nature conservation officials and officials from the forest extension service. Lectures were given on forest history, cultural aspects of fire, fire behaviour, the effects of fire on plants, fire dependent insects, and legislation. At an evening workshop people had to solve one of two tasks: a plan for prescribed burning in Björnlandet National Park or a plan to use fire for integrated nature conservation and site preparation on commercial forest land. One day was dedicated to field exercises. Fire behaviour in various fuels was demonstrated on small plots, and waterbombing with a helicopter was shown. Thanks to suitable weather a larger burning operation could also be undertaken. A pine-dominated piece of forest, surrounded by good fire breaks on three sides, was burnt over. The course will be given again in early summer of 1993, this time with particular emphasis on the situation in the southern half of Sweden.
From:Anders Granström ‘Address: Department of Forest Ecology Swedish University of Agricultural Sciences S-901 83 Umeå