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Notes

This study evaluated the climate change impacts on the productivity, health, and value of a forest for a specific region in California—the Sierran mixed conifer timberbelt. The research team adapted an industry standard planning tool to forecast 30-year tree growth and timber yields for forest stands in El Dorado County under a changing climate. The model projections were constrained by structural and demographic data from the Blodgett Forest Research Station in El Dorado County in order to represent a realistic range of legal management regimes employed on private and governmental forests in the region.
Conifer tree growth was reduced under all downscaled climate change scenarios. For the most extreme case (GFDL A2), productivity in mature stands (a status representative of approximately 20% of the federal forest in the region) was reduced by 18% by the end of the century. The reductions in yield were more severe (31%) for pine plantations—a management regime common among industrial landowners in the region.
Based on the relationship between mortality risk and growth, the reductions in growth projected under the climate change scenarios explored here generally led to moderate increases in the vulnerability of the tested species (white fir, Abies concolor) to non-catastrophic (i.e., not fire) causes of mortality. The most severe decrease in survival probability occurred under the GFDL A2 scenario. By the end of the century, median survival probability had decreased from the baseline rate of 0.997 per year to 0.982 per year.
The complexity of disease and insect interactions in forest ecosystems will limit the accuracy of predictions regarding the responses of specific pathogen and pests to climate change. However, a current concern in El Dorado County is the recent range expansion of pitch canker disease to the Sierran forests. Pitch canker is believed to be limited primarily by environmental conditions; these conditions may be changing in its favor in the Sierra Nevada, a region where several important timber species are susceptible to this devastating non-native pathogen.
Given the results of the climate-adjusted growth scenarios presented in this report, the economic impacts are likely to be negative, in the form of reduced harvest revenues to landowners, reduced employment and income in timber harvesting and processing, reduced indirectly generated income and employment in rural counties, and reduced Timber Yield Tax revenues distributed to counties.