Fraser TSA
Timber Supply Analysis

B.C. Ministry of Forests
1450 Government Street
Victoria, B.C.
V8W 3E7

October 1994

Executive Summary

As part of the provincial Timber Supply Review, the B.C. Forest Service has examined the availability of timber in the Fraser Timber Supply Area (TSA). The analysis assesses how current forest management practices affect the supply of timber available for harvesting over the next 250 years. It also examines the potential changes in timber supply stemming from uncertainties about forest growth and management actions.

The Fraser TSA covers approximately 1.17 million hectares, of which about 275 000 hectares are considered available for timber harvesting under current management practices. The area is dominated by hemlock/balsam and Douglas-fir stands.

The current allowable annual cut for the Fraser TSA is 1.76 million cubic metres per year. Using current management assumptions, the analysis results indicate that the current harvest level must be reduced immediately by about 12% to about 1.55 million cubic metres per year in order to avoid a more severe decline in the timber supply and harvest levels in the future. From this reduced initial harvest level, the harvest forecast declines by about 10% per decade over the next 3 decades to a steady long-term harvest level of about 1.2 million cubic metres per year. The most important factors contributing to the projected decline in timber supply are:

1) The area considered to be available for timber harvesting has been reduced by about 25% since the last timber supply analysis completed for the Fraser TSA. This change is due primarily to new mapping of the area available for timber harvesting, known as operability mapping. Operability is determined using the terrain characteristics of the area as well as the quality and quantity of timber on the area.

2) Approximately 25% of the area that is available for timber harvesting is also being managed for scenic values. Forest cover requirements used to limit the visual impact of timber harvesting significantly limit the rate at which timber may be harvested from these scenic areas. Forest cover requirements for other forest resources such as wildlife habitat and recreation have less significant effects on the short-term harvest forecast.

Uncertainty in the data and assumptions used in the analysis may affect results. The short­term harvest forecast (next 30 years) is most strongly affected by changes in the estimated volume of timber in existing mature stands and in the forest cover requirements used to manage for scenic values. The short-term harvest forecast is also significantly affected by large changes (plus or minus 20 years) to the minimum harvest ages used in the analysis.

Changes to the estimated growth rate of regenerated stands have a strong effect on the long­term harvest forecast, but have no effect in the short­term harvest forecast.

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