As part of the provincial Timber Supply Review, the B.C. Forest Service has examined the availability of timber in the Bulkley Timber Supply Area (TSA). The analysis assesses how current forest management practices affect the supply of wood available for harvesting over the next 200 years. It also examines the potential changes in timber supply over a range of uncertainty about forest growth and management actions. It is important to note that the various harvest forecasts included in the report only indicate the timber supply implications of current practices and uncertainty. As such, the forecasts should be used for discussion purposes only; they are not intended to imply any particular allowable annual cut (AAC) recommendations.
The Bulkley TSA covers a total area of
736 000 hectares, of which about 278 000 hectares are considered available for timber harvesting under current management practices. The area is dominated by balsam forest, with significant areas of spruce and lodgepole pine. The current allowable annual cut for the TSA is 895 000 cubic metres per year.
Modeling current management involved the exclusion of sensitive and protected areas, and assignment of forest cover requirements to the entire remaining timber harvesting area. While much of the area is managed for integrated resource activity, one quarter of the land base is assigned special cover requirements to account for wildlife habitat and travel corridors, water conservation, aesthetics and recreation values.
Given current management assumptions, the analysis shows the current AAC can be maintained for another 20 years without causing a sharp drop in future harvest levels below the long-term level. Beginning 20 years from now, harvests must decrease 9% per decade until the long-term harvest level of 424 000 cubic metres per year is reached 90 years from now.
Although the present AAC is sustainable for another 20 years, the log size and species profile presently harvested is not sustainable in the short term. To maintain the present harvest level, approximately half the present rate of spruce harvest must be replaced with harvests from pine and hemlock stands. Also, at least one third of the total timber harvest must be redirected from sawlog stands to marginal sawlog and pulplog quality stands, as defined in Appendix A.
Given current management assumptions, harvest rates will decrease in the future. If present harvest rates were immediately lowered to the long-term harvest level the initial harvest rate would be 424 000 cubic metres per year. The harvest forecast at this rate maintained significantly higher growing stock volumes, and older forest, than the forecast that starts with a harvest of 895 000 cubic metres per year.
Many of the data and assumptions used in the
analysis are subject to varying degrees of uncertainty. Bulkley
Forest District staff feel that the volumes used in the analysis
are good estimates of existing stand volumes, but that the regenerated
yields used in this analysis are too low and as a result the long-term
harvest level may be under-estimated. Sensitivity analysis was
used to examine how these and other data and assumptions impact
the results of the timber supply analysis. Short-term timber
supply is mainly sensitive to volume estimates for existing stands.
Tighter forest cover constraints may also impact short-term timber
supply. Higher yield estimates for existing stands and relaxed
forest cover requirements permit the present AAC to be maintained
for up to four decades. Changes in regenerated yields have no
impact on short-term harvest rates although the long-term harvest
level is significantly affected.