If you take the nearly 1000-kilometre-long train trip from Helsinki, the capital of Finland on the northern shore of the Gulf of Finland in the Baltic Sea, all the way to Kolari, the northernmost train station still in use, and look out the window at almost any point of the journey, it is likely that the scenery flashing by the window alternates between seedlings of planted trees, middle aged trees in neat rows and clear-cut openings. As the train voyages northwards through the southern, middle and finally to the northern boreal zone, and the landscape gets more rugged, the decreasing productivity of vegetation is mirrored by the tree compositional changes from mixed spruce dominated forests towards more abundant pine forests in the landscape.

Finland, and Fennoscandia in general, lies almost completely in the boreal biome, which is generally considered as one of the most intact biomes in the world. However, in this area, forests have long been intensively managed and deployed for wood extraction. Forestry is the main driver affecting boreal species in Northern Europe, and many of them have become red-listed or declined due to habitat degradation. As almost all forests outside the protected area (PA) network are under management, these species are forced to live in an increasingly fragmented landscape.

The patchwork of different management stages alternating in the landscape, observed from the train window, becomes even more evident when viewed from above. Aerial images and space-borne remote sensing effectively reveal the extent of habitat transformation. In our study, we opted to use this point of view to investigate how intensively the surrounding forests have been managed around biologically important protected areas during the past couple of decades. This is an important question in the light of national and international conservation targets and agreements, that call for not only the expansion of protected spaces but also representativeness and connectedness of these additions to the current PA network.

We gathered a dataset, including 864 red-listed forest species that primarily inhabit mature or old-growth forests, to see how many of these species' occurrences were recorded in PAs. For each PA, we calculated a species importance index that reflected its’ conservation value. Our index reflected the rarity of each species’ observations in relation to the full set of all species observations, i.e., how many observations a given species had in the data. Next, using CORINE landcover data as a baseline and Global Forest Change (GFC) as land-cover change data, we identified the areas where a forest that is close to the end of the rotation cycle, or existing old-growth and mature forest, was clear cut during the years 2001-2019 around the PAs with valuable forest species occurrences. These analyses were done for 100m, 1km and 10km buffers around the PAs.

Our results showed that the largest proportion of clear cuts, ca. 20%, occurred in the landscape and regional scales around PAs in the southern and middle boreal zones. At this rate, nearly all forests outside PAs might be clear-cut during a 70–100-year rotation cycle, leaving many species in trouble as climate change forces them to search for new areas of sufficiently suitable living conditions. We compared the PAs with the top 5% scores of species importance to other PAs with red-list species and noticed that the change in forest cover was lower around the biologically most important sites – this suggests that there may still be potentially useful forest stands available next to present PAs for the enlarging of the PA network. Improving structural connectivity is especially urgent in the southern boreal zone, where PAs are small and rotation cycles are short. An effective strategy to improve the permeability of the managed forest matrix for species requiring structural elements of old-growth forests and humid microclimates would be to increase such elements, e.g., the amount of dead wood and large retention trees all through the forest management cycle.

This piece of research is part of a project that aims to assess boreal forest biodiversity in the PA network in Finland and promote informed climate-wise conservation planning. We are currently working on a follow-up paper, where we include climate change velocity estimates in biologically valuable PAs and discuss climate-wise planning strategies that could help forest species survive under the joined pressures of land use and climate change. While there might not even be a final station on the pursuit of enhancing the state of biodiversity in the intensively managed boreal forests, and the track is undoubtedly not straight forward, it is crucial that everyone gets onboard.

References:

Määttänen, AM., Virkkala, R., Leikola, N., Heikkinen RK. (2022) Increasing loss of mature boreal forests around protected areas with red-listed forest species. Ecol Process 11, 17. https://doi.org/10.1186/s13717-022-00361-5d

Tikkanen OP, Martikainen P, Hyvärinen E, Junninen K, Kouki J (2006) Red-listed boreal forest species of Finland: associations with forest structure, tree species, and decaying wood. Ann Zool Fenn 43:373–383

Virkkala R, Lehikoinen A, Rajasärkkä A (2020) Can protected areas buffer short-term population changes of resident bird species in a period of intensified forest harvesting? Biol Conserv 244:108526. https://doi.org/10.1016/j.biocon.2020.108526

Funding:

This work was supported by funding provided by the Finnish Ministry of the Environment (Evaluating the protected area network in the changing climate, SUMI, and the Finnish Ecosystem Observatory, FEO), and the Strategic Research Council (SRC) at the Academy of Finland (Decision No 312559).

Poster image: ©Riku Lumiaro