Professor Hubert Hasenauer: ’A wooden house makes a better carbon storage than the forest’

On a visit to Finland, the Austrian professor praised the tradition of sustainable forest management in Finland and Europe. He considers that in forest matters, Europe should not be compared to the tropics.

Visiting Helsinki in April Hubert Hasenauer, Professor for Forest Ecosystem Management at the University of Natural Resources and Life Sciences (BOKU) in Vienna, Austria, praised the sustainable forest management in Europe and called for the use of wood in construction.

’Our challenge now is to combine forest management with combating climate change, but even so, in connection to this Finland and Europe should not be compared to tropical countries. Our forest management is definitely sustainable. Our tradition goes back to more than a century,’ Hasenauer said in his lecture at a seminar arranged by the Finnish Forest Industries Federation (FFIF).

Hasenauer pointed out that on average since 2010, the forest cover in Europe has increased by 44,000 hectares each year, and that Europe is the only continent to see any increase in the forest area at all. As regards the use of wood as construction material and a source of renewable energy, it is much higher in Europe than the global average.

In Finland, for example, the increase in the volume of timber in the forests exceeds that of the volume felled. Since the 1970s, the volume of timber in Finnish forests has increased by 67 percent.

Reducing the volume of fellings has been suggested as a remedy against global warming. With more trees, the forests would bind more atmospheric carbon. According to Hasenauer, however, reducing fellings would not be a sustainable solution.

’The key thing is to understand the difference between a carbon storage and carbon sequestering. As forests grow older, the carbon storage does continue to increase slowly, but the sequestering of carbon decreases. In an older forest, less of the carbon bound by the trees is used for growth, and more is used in cell respiration.’

With the trees growing older and stouter, the risks also increase. Tall old trees are more easily felled by winds. Fallen trees attract the bark beetle, which leads to more insect damage. Hasenauer also says that the probability of wildfires increases with more fuel available in the forest.

For all these reasons Hasenauer speaks for moving the focus of climate work more towards the carbon storage in wood products.

’A forest carbon storage does not have to be in a forest. It can just as well be located in sustainable wood products, such as wooden buildings. In fact, they are superior to the forest in the sense that when wood is stored as buildings, the forest it came from can be rejuvenated and bind carbon more effectively than an old forest would.’

Hasenauer stressed that not every part of a felled tree is used as construction material: the share would be 50–60 percent, depending on the species. The rest consists of branches, canopy and bark, which form sidestreams that are used for other products and energy.

’Using wood to replace concrete gives an obvious climate benefit, because the carbon emissions of concrete are very high. In fact, the greatest climate benefits of wood can be achieved with wood construction.’

Active forest management can combine fellings and carbon sinks

In Finland, with the widest forests in Europe, there is lively debate on the most sensible actions to take in Finnish commercial forests to curb the climate change: should the rotation period of forests be prolonged or the fellings reduced, or should the fellings be continued at the current rate?

To have a more solid foundation for the debate, the Finnish Forest Industries Federation commissioned a study on the matter from Natural Resources Institute Finland (Luke). The study examined the growth, carbon sink and nature values of Finnish commercial forests by means of two forest management scenarios spanning the years 2026–2055. The results were presented in the FFIF seminar by Research Professor Jari Hynynen.

In both scenarios, the FFIF set the same annual cutting yields: 79.8 million cubic metres up to and including 2029, and 87.2 cubic metres from 2030. This means that any differences are due to different management practices.

In the basic scenario, the management of Finnish commercial forests would continue as before, complying with the current recommendations for forest management and the forest certification systems PEFC and FSC.

In the second scenario, based on adaptation to climate change, forest management would be intensified in several ways. More fertilization would be used and young stands would be tended more frequently. Regeneration would always be made by using improved seedlings and seeds. For a better adaptation to the climate change, conifer-dominated forests would be diversified by ensuring that one fifth of the trees on appropriate sites are broad-leaved. Continuous-cover silviculture would be increased, especially for spruce stands on peatlands.

The Luke study shows that intensifying the management operations would bring a clear benefit. In the basic scenario, the annual increment (i.e., total forest growth) would remain at slightly above 100 million cubic metes throughout the period studied. In the climate scenario, the increment would increase for every decade studied. At the end of the period, in 2046–2055, it would come close to 120 million cubic metres.

Without the intensification measures, the planned annual felling volumes would begin to cause a decrease in the forest carbon sink after 2030. With the intensification, the carbon sink would continue to increase. In addition, it would improve forest biodiversity values, such as the share of broadleaves and the volume of deadwood, which is vital for thousands of species.

’To achieve this, the intensification measures described in the climate adaptation scenario must be implemented in full, and they must be targeted appropriately. Fertilization, for example, must be used on sites where it gives the best result,’ Hynynen pointed out.

Karoliina Niemi, Forest Director at the FFIF, also stressed that it is precisely active forest management that makes it possible to increase forest growth while also improving carbon sinks and climate sustainability.

’Active forest management does not mean that forests are tended every once in a while, but that we know our forests and manage them throughout the rotation period,’ Niemi emphasized.