A traditional approach to limit impacts of forestry on biodiversity is to set aside forests of conservation value. Many set-asides are relatively untouched, but some have a history of disturbances; wildfires, forest grazing, coppicing or small-scale felling. Such areas may gradually lose their value for biodiversity conservation unless the disturbances are re-introduced or managed otherwise. On the other hand, many currently protected forests have a history of commercial management, and may lack important characteristics of natural forests. Some of these lost features, can be brought back by active management faster than they would recover naturally. Recently, interest in active management of forest set-asides has increased, but opinions differ among conservationists on how such management should be balanced against non-intervention .
In many protected forests remaining biodiversity values are legacies of past disturbance regimes that are nowadays suppressed. This is common e.g. in the boreal pine forest, which in its natural state is shaped by recurring fires creating dead wood and keeping the stands relatively sparse and with a significant broadleaf component. In northern Europe, forest fires are now rare, and pine forests have therefore become denser, with an increasing dominance of spruce; calling for reintroduction of fire.
In other forest set-asides, conservation values is a result of earlier forest grazing, coppicing, small-scale felling or similar human influences. Since these activities were often discontinued several decades ago, the forest has become denser and more shaded, negatively influencing associated species. Such reserves may need active management to conserve the characteristics that were the reason for setting them aside.
Finally, active management designed to achieve a favorable conservation status can be particularly relevant in regions where forests have been extensively degraded by human land-use. In such areas, the creation of a network of forest reserves with high-quality habitats may require some level of stand-scale restoration.
Until quite recently, few well-designed experiments have been conducted to investigate how forest set-asides are affected by various kinds of interventions. Management have mainly been based on historical data or palaeoecological land-use studies, natural disturbance regimes and past environmental qualities. We have performed a set of Systematic Reviews of primary field studies of how active management affect biodiversity in boreal or temperate forests.
The studies are from both protected areas as well as studies of interventions in commercially managed forests. These studies provide a starting point for evidence-based management of protected forest areas. However, the reviews also highlight significant knowledge gaps for further experimental research.
 Halme, P. et al. 2013. Challenges of ecological restoration: Lessons from forests in northern Europe. Biol. Conserv. 167:248-256