Graduate Thesis Or Dissertation
 

A Multi-Spatial Scale Economic Analysis of the Impacts of Bear Damage to Douglas-fir on Private Timberlands in the Pacific Northwest

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  • Black bears (Ursus americanus) in western Oregon and Washington peel bark from conifers in early spring to forage on the sugar-rich phloem and cambial tissues. This provides important energy at a time when similarly attractive forage is scarce. Bears often damage Douglas-fir (Pseudotsuga menziesii) trees in stands that are intensively managed for timber production, as management activities including thinning and fertilization increase productivity. Fully girdled trees result in a complete economic loss while partial girdling reduces survival rates as well as merchantable volume. Previous studies on economic impacts have assessed only those losses to fully girdled trees, but not additional impacts from wounded trees. We surveyed four severely damaged stands to assess economic impacts at the stand-level, and surveyed 122 randomly selected vulnerable stands to assess economic impacts at the landscape-level. Two damage scenarios were considered. Scenario one accounted for the additional mortality and volume losses from partially girdled trees, whereas scenario two assumed that all bear-peeled trees resulted in a complete loss. Stand volumes were estimated using the Forest Vegetation Simulator growth and yield model. Economic losses were estimated using the Fuel Reduction Cost Simulator and present value models. At the stand-level, economic losses to severe bear damage in scenario one ranged from $6,100 to $24,500. Economic losses in scenario two ranged from $19,500 to $74,700. Undamaged stands were valued from $43K-$250K. At the landscape level, economic losses to vulnerable stands in scenario one ranged from $44,500 to $726,000. Economic losses in scenario two ranged from $169,000 to $2.8M. Undamaged stands were valued from $48M-$780.5M. Root disease was a more prevalent damage agent than black bear damage. The majority of bear damage observed (92%) was older (>2 yrs) and existed at a low frequency (1.5 bear damaged trees/ha) and severity across the landscape. Our results suggest that bear damage management over the last two decades may have reached a level of efficiency at reducing damage, and if continued, bear damage may remain at low levels across the landscape. On-the-ground monitoring of the status of bear damage frequency and severity across western Oregon and Washington at both the stand and landscape levels will provide an understanding of these changes over time as a result of management decisions.
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