Summary
• Storm Gudrun struck southern Sweden in 2005 and Per two years later.
• A total of 33 million m³ of Södra’s timber was felled.
• The timber was stored and kept moist, in some cases for five years.
• The last of the stormwood was sawn at the end of 2009.
When the winter storm Gudrun hit southern Sweden in January 2005, it was the worst seen in the country since 1969, claiming seven lives in Sweden alone, gusting winds at close to 150 miles per hour, and affecting almost all of the countries around the Baltic Sea. Then, just two years later, another huge storm, Per, pounded southern Sweden once again.
The devastation caused to southern Sweden’s forests was immense. For the country’s largest timber and pulp producer, Södra, it presented the unenviable task of collecting, storing and processing stormwood on a scale the company had never seen before. Gudrun left 25 million m³ fub (under bark) of Södra members’ wood on the forest floor and Per another 8 million m³ fub.
Södra is a co-operative of around 50,000 members of private forest owners in southern Sweden – many of them smallholdings and small private landowners. Clearings in the areas hardest-hit by the storms represented 15-20% of the forest area. Worst affected were the Ljungby and Alvesta-Växjö forestry districts where close to 20% of the forest area was cleared in the 2004–2008 period. This is equivalent to 20 years of normal final harvesting.
Other figures were even more extreme. Södra estimated the total area of clearings between mid-2004 and mid-2008 with the assistance of the National Board of Forestry. The calculations show that 164,000ha of land belonging to Södra members was cleared, with the figure for the entire Götaland region being 320,000ha. The normal annual clearance area in Götaland is 40,000-50,000 ha; the area cleared by storms in 2004–2008 was 80% more than normal and represented an area equivalent to seven years’ harvesting. Consisting mainly of forest damaged in the Gudrun and Per storms, the estimated clearing area also includes harvesting of bark beetle infested areas and forest remnants, as well as normal harvesting during the period.
When the last of the stormwood was finally sawn at Södra Timber’s Värö mill at the end of last year, ready to ship to the UK as construction timber, it had been stored for almost five years at the Värö terminal.
“We’ve learned a lot from this experience,” said Lars Woxneryd, environmental manager for Södra Timber. “We had never dealt with wood processing on this scale before, nor had we stored wood for five years – the longest average storage time at our sawmills is five to six months.
“The timber remained a very high quality, better than we expected. We had initially intended to store it for a maximum of three years after Gudrun hit us, but then Per followed and we filled up again for another two years. The Gudrun timber held up well right up until mid-2009 when we started to see extensive storage decay on the lateral area of the saw logs. The Per wood has generally been lower quality due to bark beetle damage which in turn caused storage decay in some areas. Saw yield has been 1-2% lower than normal but, overall, it has been as expected.”
Storage space
Södra’s immediate challenge was finding suitable places to store the wood, close to a water supply and to major road networks to minimise transportation costs. These were secured through its members and existing operations. Next was the challenge of preserving the wood’s quality and commercial value for an unprecedented length of time.
“The critical thing here was keeping the wood moist enough to avoid fungal decay, but not too wet,” said Mr Woxneryd. “We used our experience of storing wood from our sawmills during the summer months, using a calculation of 50mm of water per day per square metre of wood. It was a risk – we weren’t sure it would be the right percentage over a much longer term – but it worked. We also had to calculate how high we could build the piles for that length of time – the highest were 7m.”
“We spent quite some time on educating everyone involved on the huge value of the timber in our hands and the importance of looking after it during its entire stored life,” he added. “That paid off. Even if the wood appeared very black on the outside, it has largely been good quality.”
Södra had a total of more than 10 million m³ of stormwood simultaneously stored at terminals, mills and vehicle roads during the post-storm period, while its annual delivery of plants during 2007-2009 rose to 40-45 million m³, compared with a normal annual level of 25 million m³.
With the last of the wood now cleared, Södra is looking ahead. Close to 90% of the storm clearings have now been replanted, natural regeneration has occurred on a further 7% and the balance will be fully replanted this spring.
“We are counting on the planting rate being just as high in 2010,” said Mr Woxneryd. “The high demand for plants has coincided with excellent harvests in Södra nurseries.”
The chances of two severe storms hitting the same area and causing the same amount of damage are remote, but in the unlikely event of it happening again, Mr Woxneryd said Södra is equipped to deal with it.
“We will be better prepared next time in the sense that we now have several suitable storage locations secured. Contacting our members to find the ideal storage sites is at least one step we wouldn’t have to take next time.”
