Forest Investment Account (FIA) - Forest Science Program
FIA Project Y071061

    Climatic Influence on the Economic Impacts of Spruce Bark Beetle
Project lead: Swain, Harry
Contributing Authors: Murdock, Trevor Q.; Pacific Climate Impacts Consortium
Imprint: Victoria, BC : University of British Columbia, 2007
Subject: Forest Investment Account (FIA), Dendroctonus Rufipennis, British Columbia
Series: Forest Investment Account (FIA) - Forest Science Program
This project will estimate stand level losses due to the spruce bark beetle (SBB) across British Columbia (BC). Mapping estimates will be created for all areas with current stands and potential future stands across BC. Results will be incorporated into decision support tools. The spruce beetle, Dendroctonus rufipennis (Kirby) occurs throughout the range of spruce, Picea spp., in North America. In the west, Picea Engelmannii, P. glauca and P. sitchensis are principal hosts (Furniss and Carolin 1977). Under endemic conditions this beetle is present in small numbers, attacking weakened trees or trees that are downed by wind, or in slash. However, sporadically, major outbreaks occur which kill thousands of trees in western North America, including BC and Alaska. Normally this insect has a two year cycle, but at higher elevations or latitudes a 3 year cycle is common. New adults emerge during August to October, from killed trees after spending 2 or 3 years under the bark and move to attack the lower bole and root collar of new host trees. Recent outbreaks in Alaska’s Kenai Peninsula have been linked to above-normal temperature years, particularly in the summer (Berg 2000). This massive outbreak killed nearly every mature spruce tree on the Kenai. Most of the attacked trees were more than 100 years old. The mechanism triggering outbreaks is not clearly understood but it is believed that warmer climate accelerates the insect life cycle to less than 2 years. In addition, warmer and drier climates may induce stress on trees, which are less likely to successfully defend against this beetle. Spruce trees defend themselves against beetle attack by producing copious resin which drowns eggs and young larvae. Spruce bark beetle (SBB) is a more difficult organism to model than mountain pine beetle (MPB) due to complexities and variability in its life cycle. We do not know enough at this point about SBB entomology and spread dynamics to construct a population spread model for SBB, although new techniques are evolving (e.g., Landes et al., 2003). From what we do know about SBB, how it has spread over recent decades (Zhang et. al., 1999), and about the relationship between MPB and climate, it is reasonable to postulate that there is a significant relationship between SBB and climate (Woods et. al, 2004). Like its relative, the mountain pine beetle, the spruce beetle is also killed by temperatures below -35 or -40 degrees C. A technique that may be utilized to take the first step towards understanding the potential effects of climate change on SBB stand-level losses is physical envelope modeling, an empirical method recently used by Hamann and Wang (2005, 2006) and Wang et al. (2006) to study BC forest impacts under future climates. The stand-level loss estimates, then, may be used to consider adjustment of management practices through bio-economic modeling (Eisenworth and van Kooten, 2002). The project will start by compiling empirical data about the potential impact of SBB in reducing recoverable timber across BC. Specifically, the climatic conditions such as variations of 30-year averages of monthly minimum and maximum temperatures and precipitation for both occurrence of SBB and outbreaks of SBB will be defined by analysis of geographic SBB occurrence data and climate data (Wang et al. 2006). It is in this step that SBB entymological expertise of Alfaro and Taylor will be incorporated. Because of the nature of such 'climatic suitability’ mapping, a first-order relationship between climate and white spruce, as well as climate and SBB will be appropriate. Once climate-SBB relationships are determined, then tools such as ClimateBC (Wang et al. 2006) will be used to create future projections of climate and stand-level SBB impacts for the next century. Subsequently, climate variables from all available climate models and experiments will be extracted. A set of projections representing the 10th, median and 90th percentile values will be compiled and used to generate future climatic conditions based as has been completed (by the Canadian Institute for Climate Studies) for several species distributions in the Royal BC Museum Climate Change exhibit. In addition to defining climate envelopes for SBB and its outbreaks, the climate envelope for white spruce itself will also be established. To summarize, an estimate of the degree of climate stress on spruce will be developed using forest inventory and growth and yield data. By combining future tree health and distributions with SBB outbreak conditions, potential future SBB outbreak impacts will be projected under future climatic conditions (for the time periods of the 2020s, 2050s and 2080s) resulting in a series of high resolution maps. The next task will be to understand what those impacts may mean for resource management decisions. SBB may affect forest landscape values (scenic amenities, carbon flux, wildlife habitat, recreational opportunities), fire regimes, and available options for managing forests on a large scale for decades to come. In order to understand how a landscape should be managed during a period of projected stand-level losses, it is necessary to have some knowledge of its total economic value (TEV) and how that value changes as a result of management and other natural threats. Knowledge of TEV spatially and over time is crucial in order for informed decisions to be made. The future spatial projections of SBB-impacts generated in the beginning of the project will be used, through bio-economic modeling, in order to attempt to address such research questions as: Should healthy timber in the SBB-infected region be logged for its commercial benefits and contribution to community stability, or should it be left standing? If left standing, when is it optimal to harvest the timber, particularly given the risks posed by fire and climate-induced invasions by (other) insect pests or disease? Synthesis of results from each phase of the project, with an application to decision support tools, means that results may be incorporated into resource management options and planning, both in terms of responding to projected losses and possibly even to mitigate stand level losses themselves or at least the economic impact of them on communities. In climate science jargon, the results of this project will directly enable extension agents to facilitate the development of adaptation strategies (during and after project completion). This project will be closely coordinated with FS-FIA project Y07-1173 'Spruce beetle risk modeling in a changing climate', led by S. Taylor, of the Pacific Forestry Centre. This one year project aims at clarifying the voltinism of the spruce beetle under different climate regimes and based on this, to develop risk models. Our project will use results from this project to model stand and landscape losses. Mr. S. Taylor has kindly accepted to be a Project Partner. In addition, close coordination will be maintained with T. Shore, also of the Pacific Forestry Centre, who is gathering information on the losses by spruce beetle in the Yukon Territory. The project will make extensive use of the Climate BC software package developed with support from MoFR and the Forest Science Program (project Y062149). Finally, the project will also be closely coordinated with projects at the Pacific Climate Impacts Consortium, funded by BC Hydro and BC Ministry of Environment, which will also develop additional climate envelope modeling projections. Links to these ongoing projects will ensure that the methods used to project future SBB impacts, while only implicitly dependent on detailed weather event data and SBB biology, make the appropriate assumptions and parameterizations regarding these factors. Furthermore, these links will ensure immediate use of SBB impact projection results for further progress towards development of an integrated forecast model which depends explicitly on these factors, and to which future climate changes may also be applied.
Related projects:  FSP_Y082061
Contact: Murdock, Trevor, (250) 472-4681,


Executive summary (21Kb)

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Updated August 16, 2010 

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