Systematic review Hotspots in cold climate: Conservation value of woodland key habitats in boreal forests Jonna Timonen a,⇑ , Lena Gustafsson b , Janne S. Kotiaho c,d , Mikko Mönkkönen a a Department of Biological and Environmental Sciences, PO Box 35, University of Jyväskylä, FI-40014 Jyväskylä, Finland b Department of Ecology, Swedish University of Agricultural Sciences, PO Box 7044, SE-750 07 Uppsala, Sweden c Centre of Excellence in Evolutionary Research, Department of Biological and Environmental Sciences, PO Box 35, University of Jyväskylä, FI-40014 Jyväskylä, Finland d Natural History Museum, PO Box 35, University of Jyväskylä, FI-40014 Jyväskylä, Finland article info Article history: Received 15 October 2010 Received in revised form 7 February 2011 Accepted 13 February 2011 Available online 26 May 2011 Keywords: Biodiversity Conservation Evidence-based Meta-analysis Production forests WKH abstract The concept of Woodland Key Habitats (WKH, small-scaled presumed hotspots of biodiversity) has become an essential component of biodiversity conservation in Fennoscandian and Baltic forests. There have been debates over the importance of WKHs in relation to the conservation of biodiversity in produc- tion forests. We applied a systematic review protocol and meta-analysis to summarize knowledge on comparisons of biodiversity qualities, such as dead wood and species richness, between WKHs and pro- duction forests in relevant countries. We also summarized the knowledge on the impact of edge effects by comparing WKHs surrounded by production forests to WKHs surrounded by clear cuts. Studies had been conducted in Finland, Norway and Sweden. Based on our meta-analysis, WKHs seem to be relative hotspots for dead wood volume, diversity of dead wood, number of species and number of red-listed spe- cies. There were some differences also between countries in these biodiversity qualities. Only two studies compared WKHs surrounded by production forests and clear cuts, respectively. Hence, the capability of WKHs to maintain their original species composition and support species persistence over time remains to be addressed, as well as their role in relation to other conservation tools. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Globally, habitat depletion and fragmentation have contributed to the current rampant loss of biodiversity. In the boreal forest zone, the total forest area is not decreasing but habitat availability has rapidly diminished due to habitat degradation as a conse- quence of effective logging and intensified silvicultural practices. Before industrialization the forests were utilized in a less intensive manner by burnbeating, tar and potash production, and thinning (Esseen et al., 1997). From the beginning of 20th century, forest harvesting methods in Fennoscandia shifted from selection felling towards clear cutting. Intensive forest management altered the species composition and the structure of the forests from old- growth to young, even-sized, single-aged forest stands (Östlund et al., 1997; Löfman and Kouki, 2001). Forestry also reduces natural disturbances and decreases the volume of dead wood (Esseen et al., 1997). Natural forests are primary habitats for a substantial num- ber of threatened species and forestry is the main cause of species endangerment (Rassi et al., 2001), especially due to the reduction of dead wood (Siitonen, 2001), and large living deciduous trees (e.g. Berg et al., 1994). In Finland, 20–25% of all the forest-dwelling species are dependent on dead wood, and many of them are very specific in their substrate requirements making dead wood and dead wood diversity important biodiversity qualities (Siitonen, 2001). Although not always related to human impact, and thus claimed to have limitations as a measure of biodiversity (e.g. McGill et al., 2007), species richness is often applied as a measure of biodiversity since it gives a common currency for the compari- sons of communities. Forest conservation has traditionally concentrated on establish- ing large forest reserves. Such reserves are vital due to their ability to maintain many taxa and ecological processes but establishing them also has its constraints. One of the main constraints is the limited area available for conservation (Lindenmayer and Franklin, 2002); large continuous areas of intact forests simply do not exist anymore in Fennoscandia, particularly in the southern boreal zone. Many areas of high priority for nature conservation are located on unprotected, productive private lands (Knight, 1999). However, protecting privately owned land for biodiversity involves many challenges. For example, traditional obligatory approaches, such as acquisition of land by government have resulted in an intense resistance by land owners (e.g. Hansson, 2001; Wätzold and 0006-3207/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biocon.2011.02.016 ⇑ Corresponding author. Tel.: +358 14 2602286. E-mail address: jonna.e.timonen@jyu.fi (J. Timonen). Biological Conservation 144 (2011) 2061–2067 Contents lists available at ScienceDirect Biological Conservation journal homepage: www.elsevier.com/locate/biocon