STOCKHOLM, 27. AUG, 09:17
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The EU Commission recently published its new controversial forest strategy. The strategy, if it comes into force, will have negative implications for Nordic forestry.
Among many aspects of forestry discussed in the strategy is the matter of how to best harvest the wood.
The Commission seems to advocate continuity forestry, without regeneration felling (which is when the greater part of a forest is felled where most of the trees are fully grown) and by doing so ignoring the complex biology of the Nordic forests.
Recent experience of such an approach to forestry, as advocated by the Commission, has had clear negative consequences, however.
Forestry without regeneration felling, or continuity forestry, means that the largest trees in a forest are successively harvested. New trees are expected to regenerate among the remaining trees.
This model was applied on a large scale in Sweden from around 1920 to 1950. The labour cost was low and the large trees were more valuable.
The high cost of creating new forests was avoided. Many of the forestry administration’s leading representatives also advocated this type of forestry.
But the result was catastrophic. The remaining trees were unable to form new productive forest areas, and instead enormous areas arose that were sparsely grown with mainly spruce and birch.
It was the often-brutal dismantling of these residual forests in the Northern parts of Sweden that created the giant clear-cut areas that in turn sparked the debate about the regeneration felling and Swedish forestry.
Why did the continuity forest management – or close-to-nature forestry – work so badly? There were several reasons.
The level of felling was excessive. The remaining stock of trees were not enough to act as a base for new forests. The genetic quality was impoverished by consistently removing the best trees.
There was harvesting in cold areas with poor fertility where leftover tree remains did not decay, but were instead left behind in an increasingly thick layer where new forest plants could not establish themselves.
The necessary nutrient circulation that occurs, for example, after a fire or a regeneration felling did not get started and the ground was depleted. Light-loving tree species, mainly pine, could not be regenerated among the remaining trees.
Today we know more. It is possible to run clear-cut-free continuity forestry but only locally. You have to stick to tree species that can grow up in shade, primarily spruce and beech.
The forest that is left must be able to sustain production. The soil should be so fertile that the necessary nutrient circulation can take place without the soil being laid bare or burned.
Historically, we have always had bare forest land in Sweden. Before human influence, it was fires, storms, and insect infestations that created these bare areas, which in turn allowed pine and birch to establish themselves.
Later, forests were felled for mining, shipbuilding and housing, while more and more land was used for cultivation and grazing.
In today’s sustainable Nordic forestry, the active establishment of new forest and consequently regeneration felling is an important component.
The foundation for our modern forestry was already laid around the year 1800.
At the time, Heinrich Cotta of the Academy of Forestry in Tharandt, Germany showed that an analysis of the effects of forestry must encompass the entire forest, i.e. bare-forest areas, newly planted forests, young forest, middle-aged forest, and older forests at the same time.
If you only look at a bare clearing, no forest grows and the clearing leaks carbon dioxide by leaving parts of the felled trees to rot. But if you look at the forest as a whole, rejuvenation is absolutely necessary to revitalise the forest and keep the growth rate up.
And it is the effect of forest management on the entire forest that is crucial for growth and carbon sequestration.
Over time, you theoretically achieve the highest growth, and thus the highest carbon bound in an entire forest, by harvesting each stand when its average growth rate (total volume produced divided by age) starts to decline.
This normally occurs a few decades after a typical harvesting age today.
The fact that harvesting takes place earlier is partly due to the fact that the risk of damage – storm, rot and insects – rises with increasing age, and partly because in many cases it is possible to increase growth by replacing the existing stock of trees with new ones that grow better.
For example, replacing spruce on weak, dry soils with pine. In the current situation of climate change, it is also important to be able to build new forests with a plant material that is better suited to the conditions than that which is locally available.
Continuity forestry means that you harvest less trees but more frequently, maybe 10-20 percent of the volume every 10 years.
During a normal Swedish cycle time – 80-90 years – you harvest a given forest area about 8-9 times, while in today’s forestry thinning is done 1-3 times before a regeneration felling.
Today’s cost-effective harvesting technology is also not suitable for continuity forestry. It damages soil and roots and requires large volumes from each felling.
Instead, small, lightweight machines have to be brought in, which in turn results in greatly increased felling costs.
In order to make such forestry work on a large scale, the price of timber and thus forest products must be greatly increased which will in turn lower the competitiveness of the sector in a global market.
It is simply not possible to operate continuity forestry on a large scale on commercial terms in the Nordic region.
The method may be justified where there are strong drivers other than the economy, for example in recreational areas, or where there are rare and disturbance-sensitive species.
However, in order for the method not to eventually lead to more and more spruce forest, open spaces must also be created in these areas where pine and/or birch forest is preferred.
Dr. Björn Hägglund is professor Emeritus Swedish University of Agricultural Sciences and former Director General of the Swedish Forest Agency.