Executive Summary

As part of the provincial Timber Supply Review, the British Columbia Forest Service has examined the availability of timber in the Boundary 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 stemming from uncertainties about forest growth and management actions. It is important to note that the various harvest forecasts included in the report indicate only the timber supply implications of current practices and uncertainty. As such, the forecasts should be used for discussion purposes only; they are not allowable annual cut (AAC) recommendations.

The Boundary TSA covers a total area of 580 000 hectares, of which about 311 000 hectares are considered available for timber harvesting under current management practices. The area is dominated by lodgepole pine forests, with significant areas occupied by stands of Douglas­fir, larch, spruce and balsam. The current AAC for the Boundary TSA is 900 000 cubic metres per year. The present AAC is comprised of the base AAC of 700 000 cubic metres plus a temporary AAC uplift of 200 000 cubic metres to allow prompt salvage of Mountain Pine Beetle infested stands. The temporary AAC uplift is scheduled to expire December 31, 1995. However, the current harvest level has declined to about 700 000 cubic metres as the salvage program nears completion.

There are several management emphases in the Boundary TSA. Much of the area that is considered available for timber harvesting in the TSA is managed for integrated resource activity. Approximately one­quarter of the land base is assigned special forest cover requirements to account for wildlife habitat and travel corridors, protection of water quality, aesthetics and recreation values. Non­clearcutting silvicultural systems are used on a further one­fifth of the land base in order to accommodate non­timber values.

Given current management assumptions, the analysis shows that the harvest level of 700 000 cubic metres per year could be maintained for another 80 years without causing a drop in future harvest levels below the long­term harvest level. Beginning 80 years from now, harvests would have to decline by 10% per decade until the long­term harvest level of 560 000 cubic metres is reached 100 years from now.

Although the analysis indicates that the current harvest level could be maintained for another 80 years, it cannot be maintained if harvesting continues to be conducted predominately in lodgepole pine stands. To maintain the current harvest level, some of the harvest from pine stands would have to be replaced with harvests from Douglas­fir, larch, spruce and balsam stands. Also, an increased percentage of the pine harvest would have to be taken from dense pine stands containing small diameter timber.

The results of this analysis indicate that under current management assumptions, an even­flow harvest level can be achieved; however, the initial harvest level would have to be lowered immediately to the long­term harvest level of 560 000 cubic metres per year. The analysis results also show that a higher initial harvest rate could be supported given current management. The initial harvest level could be increased to 900 000 cubic metres per year; however, the decline to the long­term harvest level would occur sooner and would be more severe.

Many of the data and assumptions used in the analysis are subject to varying degrees of uncertainty. Sensitivity analysis is used to examine how uncertainty about data and assumptions impact the results of the timber supply analysis. Short­term timber supply is mainly sensitive to tighter forest cover constraints. Volume estimates and large changes in green­up periods may also impact short­term timber supply. Changes in regenerated stand volume estimates have no impact on the short­term harvest level, although the long­term harvest level is significantly affected. Removal of 50% of dense lodgepole pine stands from the timber harvesting land base decreases by one­half the amount of time that the current harvest level can be maintained. All factors evaluated in the sensitivity analyses affect the length of time that the current harvest level can be maintained, and some factors also impact the initial harvest level.