Low-level retention forestry, certification, and biodiversity: case Finland

Abstract

In managed forests, leaving retention trees during final harvesting has globally become a common approach to reconciling the often conflicting goals of timber production and safeguarding biodiversity and delivery of several ecosystem services. In Finland, the dominant certification scheme requires leaving low levels of retention that can benefit some specific species. However, species responses are dependent on the level of retention and the current low amounts of retention clearly do not provide the habitat quality and continuity needed for declining and redlisted forest species which are dependent on old living trees and coarse woody debris. Several factors contribute to this situation. First, the ecological benefits of the current low retention levels are further diminished by monotonous standwise use of retention, resulting in low variability of retention habitat at the landscape scale. Second, the prevailing timber-oriented management thinking may regard retention trees as an external cost to be minimized, rather than as part of an integrated approach to managing the ecosystem for specific goals. Third, the main obstacles of development may still be institutional and policy-related. The development of retention practices in Finland indicates that the aim has not been to use ecological understanding to attain specific ecological sustainability goals, but rather to define the lowest level of retention that still allows access to the market. We conclude that prevailing retention practices in Finland currently lack ecological credibility in safeguarding biodiversity and they should urgently be developed based on current scientific knowledge to meet ecological sustainability goals.

The challenge of combining variable retention and prescribed burning in Finland

“…Even though prescribed burnings do not fully mimic wildfires, as they are intentionally set at a chosen time in selected locations and circumstances, they can create similar structural elements such as charred and decaying wood, and dead wood in general, that are important for biodiversity (Esseen et al 1997, Granström 2001. However, the current true retention levels in Finland can be significantly lower than those suggested by research as we discuss below (see also Kuuluvainen et al 2019). The overall assessment of research on variable retention forestry in Fennoscandia is described by Gustafsson et al (2020).…”

“…Lately, silvicultural burnings have been modified to also safeguard biodiversity through leaving and burning retention trees to create fire-affected wood and habitat for firedependent species, following the recommendations from ecological research. According to research evidence, the amount of retention should be clearly higher than the current Finnish practice of leaving less than 2% of the stand volume as living retention trees in clear-cut areas of private forests (Kuuluvainen et al 2019). Retention levels of 10-20% of stand volume (Heikkala et al 2014, Heikkala 2016) have been recommended with minimum levels of at least 10 m 3 /ha (Hyvärinen et al 2006, Heikkala 2016).…”

Experimental evidence on biodiversity impacts of variable retention forestry, prescribed burning, and deadwood manipulation in Fennoscandia

“…This finding suggests that the overall biodiversity does not fully recover until the structures and microclimate return to near-pristine conditions. The size, species, and quality of retained trees are important in this respect (Kuuluvainen et al 2019).…”

“…Effects of VRF on biodiversity have been studied in several experiments, first in North America (e.g., Beese et al 2019), but later on also in Fennoscandia (Kuuluvainen and Grenfell 2012;Koivula et al 2014). Although conventional clear felling is increasingly often replaced with alternative felling methods in Fennoscandia, it is still the prevailing regeneration felling method, usually combined with up to 3% of retention (proportion of the volume of living trees), i.e., about ten retention trees per ha (Kuuluvainen et al 2019). It is notable that Fedrowitz et al (2014) consider such low-level retention (< 2%) as clear felling and not VRF.…”

Research on retention forestry in Northern Europe

“…Data on current state suitable for comparisons between North European countries are lacking, but an average of 11% of the area of harvested stands plus about 10 trees with special habitat value were recently reported from Sweden (Skogsstyrelsen 2019;Sveriges Officiella Statistik 2019). In Finland up to about 2% of the total volume of the growing stock is retained in final felling operations (Kuuluvainen et al 2019). An indication of large differences between countries is a compilation of prescriptions on buffer zone widths along lakes and watercourses on forestland in the Nordic-Baltic region (Ring et al 2017), revealing a very large between-country variation.…”