According to an article recently published in the esteemed science journal Nature, the annual harvested forest area in Europe has increased by 49 per cent from the comparison years of 2011–2015 to the years 2016–2018. The article claims that the amount of harvested biomass has increased by as much as 69 per cent during the same time period. According to the article, fellings have increased, in particular, on the Iberian Peninsula and in the Baltic and Nordic countries.
In Finland, the felling volumes have indeed increased during the periods under review due to global economic trends and the resulting growth in the demand of wood. However, according to statistics from the Natural Resources Institute Finland (Luke), the increase in felling volumes in both Finland and Europe is considerably less than what is stated in the article.
According to Luke’s statistics (stat.luke.fi), the removals amounted to an average of 64 million cubic metres of stem wood with bark in 2011–2015, and 74 million cubic metres in 2016–2018. There was an increase of 10 million cubic metres, or 15 per cent. In 2019, the felling volumes began to clearly decrease. Statistics from the Food and Agriculture Organization (FAO) of the United Nations show that in Europe (during the period under review in 28 EU member states), the harvested amounts were 463 and 488 million cubic metres of stem wood without bark during the corresponding time periods. The increase in the EU countries was thus 25 million cubic metres, or 5 per cent. In Sweden, felling volumes even decreased slightly during the period under review.
Why is the Nature article overestimating the amount of harvesting to such an extent?
The researchers who wrote the article published in Nature used Hansen’s global forest cover maps, which are based on an interpretation of satellite imagery, in their estimate. The maps have not been made in an attempt to interpret felling, but the changes in canopy cover that have taken place in picture elements 30 m × 30 m in size.
In the past couple of decades, significant development has taken place in the Landsat satellite imagery material used, and the authors of the maps warn that maps depicting change should only be compared with each other with caution. The authors of the Nature article have not followed this instruction. In addition, it is clear that if the goal is to detect harvesting in the satellite imagery, this should be carried out as direct change detection, taking into account the changes in the satellite imagery material and the coverage of cloud-free images.
Nor does the article make it clear how forest damage has been detected and taken into account in the research. The article only states that an attempt has been made to distinguish forest fires from harvesting with the help of forest fire maps. All other damage, such as insect and storm damage in Central Europe, is presumably considered as harvesting in the research.
Why is the Nature article causing concern?
The authors of the article are researchers from the Joint Research Centre (JRC), operating under the European Commission. The researchers present as their conclusion that the increase in harvesting is unsustainable in terms of climate change mitigation and maintaining biodiversity. The researchers have used, among other things, statistics from EUROSTAT, the statistical office of the European Union, when attempting to convert the estimated harvested areas into biomass – but have forgotten the statistics when critically evaluating the results of their research. The statistics are not fully free of errors either but, for instance, in Finland, Sweden and the Baltic countries, the harvested volumes are also estimated in National Forest Inventories (NFIs), and their results are consistent with the statistics at least in Finland and Sweden.
The published article and the methods used is raising international criticism, for example https://www.skogsstyrelsen.se/en/news/incorrect-figures-on-harvested-forests-in-nature-article/. International research teams are preparing responses that will draw attention to the defects in the article published in Nature and the sources of error in the conclusions drawn based on the research. This is an important part of the functioning of the scientific community and of the process of producing and assessing scientific information.