Two decades of variable retention in British Columbia: a review of its implementation and effectiveness for biodiversity conservation

Abstract

Stand-level retention is an important component of sustainable forest management which aims to balance ecological, social and economic objectives. Long-term retention of mature forest structures at the time of harvesting (variable retention) is intended to produce future forest stands that more closely resemble conditions that develop after natural disturbances, thereby maintaining greater diversity of habitats for a variety of organisms. Structure includes features such as live and dead trees representing multiple canopy layers, undisturbed understory vegetation and coarse woody debris. Over the past two decades, variable retention has become common on forest lands in the temperate rainforests of coastal British Columbia (BC) and has been applied to a lesser extent in inland forest types. Our review of studies in BC and in similar forest types in our region indicates that both aggregated and dispersed retention can contribute to biodiversity conservation by providing short-term 'life-boating' habitat for some species and by enhancing the structural characteristics of future stands. For example, greater abundance of species present in the pre-harvest forest have been documented for vegetation, birds, carabid beetles, gastropods, ectomycorrhizal fungi and soil fauna in retention cutblocks compared to clearcuts. There are, however, some negative consequences for timber production such as wind damage to retained trees and reduced growth rates of tree regeneration compared to clearcuts. The authors suggest an adaptive management approach for balancing competing objectives when faced with uncertainty. This includes monitoring the implementation and effectiveness of various strategies for achieving goals. Over two decades of experience applying variable retention harvesting to industrial-scale management of forest lands in BC suggests that it is possible to balance production of wood with biodiversity conservation.

Variable retention harvesting in the Douglas-fir region

“…Hence, the Clayoquot Sound Science Panel contributed significantly to the concept as well as the name "variable retention." The panel's recommendations also helped set the stage for MacMillan-Bloedel Corporation's decision to replace clear-cutting with variable retention a few years later (Beese et al 2019).…”

Combining problem‐based learning and team‐based learning in a sustainable soil management course

“…Dispersed treatments more evenly maintain soil microbial communities across the harvested area, likely due to overlap in root systems, but are more prone to windthrow (Beese, Deal, Dunsworth, Mitchell, & Philpott, 2019). The clearcut system manages successive, even-aged stands by cutting the entire stand of trees at planned intervals.…”

Research on retention forestry in Northern Europe

“…Retention forestry (variable retention, variable retention forestry, retention silvicultural system, retention system, see Beese et al 2019) is a relatively new forestry management concept in which measures to promote biodiversity are integrated into harvest operations (Gustafsson et al 2012). It has expanded globally during the last decades and is today practiced on several continents (Lindenmayer et al 2019;Palik and D'Amato 2019;Martínez Pastur et al 2019;Shorohova et al 2019), most commonly at clearcutting operations but the approach is equally justified at selective harvest (Gustafsson et al 2019).…”