We are officially in the UN Decade on Ecosystem Restoration (2021 – 2030), which is global movement to prevent, halt and reverse the degradation of ecosystems. Whichever way you look at ecosystem restoration, chances are that you will eventually encounter trees, and by extension forests. Here in Sweden, forests have been in the national discourse since the EU’s new forest strategy for 2030 came out in July 2021. The strategy says that clear-cutting, which is the felling of forests to the stumps, should be “approached with caution” and “used only in duly justified cases”. Forests cover around 70% of Sweden and the country is the world’s fifth-largest exporter of pulp, paper and sawn timber, according to Swedish Forest Industries. Because of the economic importance of forests in Sweden, the EU’s new strategy caused quite a bit of political commotion in the country. In light of these events, I think it forests are an appropriate topic as a blog post.

Forests are ingrained in the human psyche for being beneficial. The benefits of forests can take different forms that may or may not be representative of a healthy ecosystem. For example, a corporation sees economic benefits in plantation forests; a community may see recreational and cultural benefits in local forests; a farmer may see ecological benefits of forest patches; a logger sees livelihood benefits in clear-cutting forests; a scientist may see climate and biodiversity benefits of forests, and so on. Even the term “forest” means different things to different people. In scientific literature, for example, a forest may be “any land with tree canopy cover of more than 10% and area of more than 0.5 hectares” or “any land that is 0.05 hectares in size and has a minimum tree canopy cover of 10% to 30%”. In everyday discourse, and depending on where in the world one lives, a forest may be any piece of land that has a certain number of trees on it, regardless of canopy cover.

We’ve known the importance of forest for hundreds of years. In 1217, King Henry III signed the Charter of the Forest that established for the people of Britain the right to access and use the forests. The Charter was formerly part of the famous Magna Carta and was issued at the time. In Europe, primary forests, which are those with either no known significant human intervention or the last significant human intervention was so long ago that the natural ecosystem re-established itself, only cover 0.7% of the existing forest area. So, much of the 70% to 80% forest cover in Europe comprises managed and semi-natural forests.

Monocultures, which are managed plantation forests dominated by a single species, are the preferred type of production forest. There are economic reasons for this preference. These selected species are usually fast growing and economically valuable, but monocultures provide little in terms of biodiversity and overall forest health. Recently, there has been a growing interest in mixed-species forests as a way to increase biodiversity and enhance the functioning of the ecosystem. A classic benefit of mixed forests is resistance to pests. So, if a particular pest such as European spruce bark beetles, which specialize in the Norway spruce, were to infest a spruce monoculture forest, there’s a pretty good chance that they will spread quickly through the forest. However, if the beetles were to infest a forest with five or so different tree species, then the damage can be contained because the pests will not be able spread as quickly. Additional benefits of mixed forests include resistance to droughts, higher forest productivity, and several other ecosystem services.

An accurate account of tree species diversity and extent is important from the perspective of conservation and natural resource management as well as for monitoring biodiversity and sustainable forestry. There are a significant hurdles in conducting field inventories of forests over large areas, in particular that it takes a lot of time and effort. Earth observation technology offers a practical and economical method to map tree species distribution at very large scales. Studies from Germany, Sweden, Poland and other countries indicate that the European Commission’s recently-launched Sentinel-2 satellites have the necessary capabilities to distinguish between different tree species. Research in tree species mapping will likely gain momentum in the coming years as Sentinel-2’s twin satellites gather more data over European forests.

Note: This is a reproduction of my guest blog post at Tidningen Curie.