ABSTRACT
Natural ecosystems are inherently complex, resilient and adaptive (Levin 1998). Millions and thousands of years of evolution of life on earth have led to flourishing ecosystems of amazing diversity and complexity. This also applies to forest ecosystems (Filotas et al. 2014). Endurance and ability to adapt to changing environmental conditions, and to recover even from catastrophic events, are convincing evidence of the resilience of forest ecosystems. However, human activities are changing ecological systems at local, regional and global scales at unprecedented rates (Rockström et al. 2009; Steffen et al. 2011a, 2011b). For example, it has been estimated that on a global scale the rate of species extinction, mostly driven by habitat destruction, is from 100 to 1000 times faster than it would be naturally. Although habitat destruction and species extinction rates are fastest in the tropical forests, habitat destruction, decline of biodiversity and local species extinctions are prevalent phenomena also in the boreal forest (Hanski 2000; Bradshaw et al. 2009). These are mostly driven by direct human impact due to resource extraction, notably timber harvesting, but increasingly so because of the rapid warming of climate at high latitudes (Scheffer et al. 2012). This risks the health of boreal forest ecosystems and leads to a growing plea for forest restoration and ecosystem-based management (Halme et al. 2013; Moen et al. 2014).
