Striving for Sustainability and Resilience in the Face of Unprecedented Change: The Case of the Mountain Pine Beetle Outbreak in British Columbia

Abstract

A massive insect outbreak in the public forests of central British Columbia (Canada) poses a serious challenge for sustainable forest management planning. Tree mortality caused by natural disturbances has always been a part of wild and managed forests, but climate change is accentuating the uncertainty around such losses. Policy responses to accelerate overall timber harvesting levels to prevent further tree mortality and to aggressively salvage value from dead wood before it deteriorates can be disruptive and even counter-productive in the long run. Current alternatives are to strategically redirect existing timber harvesting quotas to the most vulnerable areas, minimize overall uplifts in cutting activity, prolong the period over which harvested timber can be processed, avoid the harvesting of mixed species stands or those with good advance regeneration, employ more partial cutting or “selective logging” techniques, and relax standards for acceptable species and inter-tree spacing during post-disturbance stand recovery. At the same time, careful attention to species composition and evolving landscape risk profiles may facilitate adaptation to anticipated climate change and reduce vulnerability to future disturbances. Harvest levels must be set conservatively over the full planning horizon if it is important to assure continuity of the timber supply with few disruptions to regional socio-economics and less stress to ecosystems. Broader lessons in sustainability include the option to emphasize persistence, continuity and flexibility over the long term, though at the expense of maximized production and full resource utilization in the short term

Aftermath of Mountain Pine Beetle Outbreak in British Columbia: Stand Dynamics, Management Response and Ecosystem Resilience

“…In addition, MPB-impacted, unsalvaged stands are likely to be more complex and heterogeneous in structure and, therefore, more ecologically resilient than stands developed following salvage logging. It is also critical that abundant numbers of live and dead standing trees be retained for wildlife habitat, and that forest understories are protected to allow rapid recovery and readjustment of the ecosystem [105]. Moreover, this new dimension of forest structure opens up the opportunity to design forests that are more diverse and more resilient to climate change, pest outbreaks and other unforeseen challenges that are sure to follow [123].…”

“…The current climatic change projections suggest that many BC tree species' (i.e., Larix occidentalis Nutt., natural hybrids of Picea englemannii and Picea gluca; Abies lasiocarpa (Hooker) Nuttall, Tsuga heterophylla (Raf.) Sarg., Thuja plicata Donn ex D.Don) distributions are predicted to shift their geographic ranges and some of these species are already found in the understory of MPB-impacted pine dominant forests [104,105]. MPB outbreaks may facilitate the shift of geographic distribution for those species by opening gaps in the forest canopy and breaking the "biological inertia" [106] of the mature pine trees that have been in holding for a long time.…”

“…This will influence species' geographic ranges, with species shifting northward and to higher elevations as well as impacting primary ecosystem processes like succession and disturbance [105]. The current climatic change projections suggest that many BC tree species' (i.e., Larix occidentalis Nutt., natural hybrids of Picea englemannii and Picea gluca; Abies lasiocarpa (Hooker) Nuttall, Tsuga heterophylla (Raf.)…”

“…Too much salvage logging can lead to a system of greatly decreased resilience (Figure 2, pathway A) and thus increased susceptibility to future disturbances. Many authors have argued that this is one of the main reasons why the current MPB outbreak is in an epidemic stage in Canada [105]. Due to previous forest management policies, most of the MPB impacted Canadian pine forests were even-aged and homogenous in structure [22,43,44,152,153].…”

“…If beetle-impacted stands are managed by salvage logging then a significant alteration occurs in the backloop of the ecosystem reorganization phase (α) of the adaptive cycle, potentially shifting the system to a less resilient state (pathway A in Figure 2). A combination of MPB attack and salvage logging diminishes the capacity for re-establishment of pre-disturbance communities, affects biogeochemical and hydrological processes, and develops a homogeneous landscape structure and composition [23,32,44,105]. In addition, salvage logging after MPB attack also negatively affects water quality, aquatic habitats and soil erosion [23,117,[125][126][127].…”