Consequences of mountain pine beetle outbreak on forest ecosystem services in western Canada

Abstract

After affecting millions of hectares of pine forests in western Canada, the mountain pine beetle (MPB; Dendroctonous ponderosae Hopkins) is spreading out of its native range and into Canada’s boreal forest. Impacts of outbreaks can be environmental, economic, and social, and an ecosystem services (ES) viewpoint provides a useful perspective for an integrated approach to assessing these impacts and may help to identify how possible management strategies could minimize these impacts. In this regards, a comprehensive overview of the ecosystem functions and socioeconomic factors that have been impacted by the current outbreaks in western Canada was carried out to facilitate a more general ES assessment. In addition to timber production, current MPB outbreaks have negative effects on provisioning services (water supply and food production) and aesthetic cultural services, while effects on regulating services (carbon and forest fire) are still in debate. Among the supporting services, nutrient cycling and aquatic habitat showed short- and long-term negative effects, while terrestrial habitat showed a mostly positive response. The overall impact on ES may be more severe if salvage logging is practiced as a post-MPB forest management strategy. The outcomes of this study may help to identify areas of greatest socioecological vulnerability to MPB and identify knowledge gaps and avenues for research to advance the ES framework for MPB outbreak management.

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

“…However, forest management practices before (e.g., fire suppression) and after (e.g., salvage logging) beetle attack may also play a vital role in the composition and size structure of understory and overstory species [33]. It is well established that structure and compositional development of salvage-logged (equivalent to clear cut) stands are significantly different from those of unsalvaged stands [32,44] as artificial regeneration with planting of nursery-grown tree seedlings is the basis of reforestation activity. In BC, nursery-grown tree seedlings such as lodgepole pine or hybrid spruce (Picea glauca Moench VossP icea engelmannii Parry) or subalpine fir (Abies lasiocarpa Hook.…”

“…In unsalvaged stands, residual stand structure and composition play a vital role in development of the future forest [23,32,44]. Although the forests of central BC appear to have been devastated by the mountain pine beetle, studies of residual stand structure in many locations revealed that this was not the case for unsalvaged stands, as abundant residual green trees, regenerating saplings and seedlings of currently acceptable commercial tree species remain in the stands [51][52][53][54][55].…”

“…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].…”

“…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]. This relatively homogenous landscape, in conjunction with warming climates (warmer summer, mild winter), allowed the beetle population to spread exponentially.…”

“…The mid-term timber supply (portion of the timber that would be available for harvest within the middle of the normal management cycle which is generally 30-70 years in interior BC) [24] has been especially affected, as well as different ecosystem services (water supply, non-timber forest, products, habitat suitability, scenic beauty, carbon storage, nutrient cycling etc.) provided by the forest [25].…”