|Forest biodiversity. Illustration: Lisa Larsson
More than half of Sweden is covered with forests, and these have been severely affected by forestry during the last 100-150 years, in particular during the last 60 years when systematic clear-cutting and replanting started. The change to young managed production forests and conifer plantations threatens many forest species (see item 2 below). This is important since loss of biodiversity threatens human survival as much as climate change. The problems are also linked: ecosystems with high biodiversity are more resilient to change, that is, they respond better to stress such as a warming climate. For instance, a mixed forest is less susceptible to insect outbreak than a monoculture, and the large variety of mycorrhiza fungi ensures that natural forests store more carbon than plantations. It is important to conserve rare species for ecosystems to thrive in the long run.
In a natural forest ecosystem, trees go through their whole life-cycle: they germinate, grow, become old, die and fall over. The dead trunks decay slowly and provide a home to many organisms. Forests consist of different tree-species at different stages of their life-cycles, yielding many ecological niches. In a plantation, all trees are of the same species and age and the trees are felled relatively young, yielding a completely different ecosystem. Some older natural forests have formal protection in Sweden, and forestry operations do take some environmental considerations during harvest, but not enough for all threatened species to survive in the long run. In mountainous regions it can be difficult to prevent changes due to climate warming.
Some debaters in Sweden deny that there is a serious threat to biodiversity, but ecological researchers and government agencies both agree the threat is real. For instance:
- About 2000 forest species are red-listed in Sweden according to the Swedish Species Information Centre. They state: "Three out of four red-listed forest species are declining because of conversion of natural forest with a long continuity to plantations. Swedish forestry methods, in particular clear-cutting, therefore have a strong negative impact on forest species."
- Much research has been done on extinction due to habitat fragmentation, for instance Berglund and co-workers 2005, 2008 och 2009, as well as a Ph.D. thesis from Finland. Important conclusions from these papers are that it is worth protecting even forests without red-listed species because they can be re-colonized, and that woodland key habitats often are too small. Large intact forest areas are needed to preserve biodiversity. Hanski mentions that it is easy to underestimate the risk of extinction. In the future even genetic conservation status needs to be considered.
- According to the latest official reporting to the EU on the Birds and Habitat Directives, 14 out of 15 important forest habitat types do not have favorable conservation status.
- The Swedish Forest Agency reported in 2010 about conservation research on how much productive forest needs to be taken out of production to preserve biodiversity. For 17 umbrella species an average of 19% of productive forests would be needed. Umbrella species have specific demands on their environment, and the reasoning is that if these species can survive many others will too. Presently about 4% of productive forests have formal protection and outside the mountainous regions the amount is just 2%. On top of that, 5% of forests is set aside for conservation on a voluntary basis, however the long-term fate of these areas as well as their suitability for conservation purposes is unknown.
- The Swedish Species Information Centre states: "Since 1950 about 60% of Sweden's productive forest has been clear-cut and converted to production forests - in many cases plantations. Even before 1950 there have been clear-cuts. Within 20 years all forests outside formally protected areas will be clear-cut as well. At current rates 5% of the productive forest area will be protected and 95% production forests. This large change in land-use implies that biodiversity will be reduced severely, even though new forest reserves are created, and despite voluntary conservation and certifications."
Despite the available knowledge on what needs to be done to protect biodiversity and despite laws (partly based on the EU Birds and Habitat Directives) and a number of international agreements, harmful forestry practices and the felling of forests with high conservation values continues.