As part of the provincial Timber Supply Review, the British Columbia Forest Service has examined the availability of timber in the southern portion of the Kalum Timber Supply Area (TSA) and the Kitimat Municipality (Kalum South). The analysis assesses how current forest management practices affect the supply of wood available for harvesting over the both the short (next 20 years) and long (next 250 years) term. 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.
Kalum South consists of a total of about 550 000 hectares of land within the Skeena, Kitimat, Kitsumkalum, and Nass River drainages. About 104 000 hectares of the area are considered available for timber harvesting and production under current management practices. The area is heavily dominated by hemlock forests, with minor amounts of balsam, lodgepole pine, spruce, and cottonwood.
The results of this timber supply analysis suggest that a small reduction from the current harvest level in Kalum South (480 000 cubic metres per year) would be required in the short term to avoid either substantial harvest level reductions in the near future, or large timber shortages further into the future. Using current inventory and timber growth information, and assuming continuation of current forest management practices, a harvest of 464 000 cubic metres per year - 16 000 cubic metres per year or 3.3% below the current harvest - could be maintained for 10 years, followed by a 10% decline to 418 000 cubic metres per year for the next 10 years, and finally to a long-term level of 400 000 cubic metres per year 20 years from now. The current harvest of 480 000 cubic metres per year could be maintained only by dropping the harvest level by 80 000 cubic metres per year (16.7%) to the long-term level immediately after the next 10 years.
A harvest level between the current level and 464 000 cubic metres per year could be achieved by declining by more than 10% after the next 10 years. Under any of these regimes, most timber harvesting would occur in second growth by about 70 to 80 years from now.
The above results reflect current knowledge and information on forest inventory and growth. However, it is important to recognize that uncertainty exists about several of the factors that define timber supply. A series of sensitivity analyses indicate that these uncertainties can affect timber supply to varying degrees.
Two important uncertainties which may affect future harvest levels are estimates of timber volumes in existing stands, and second-growth site productivity. Recent timber cruise figures suggest that timber volumes used for existing stands in the harvest forecast described above may overestimate actual volumes. If this is the case, an immediate drop in the harvest would be required to avoid significant future timber shortages.
While existing stands may have lower volumes, field observations suggest that second growth stands may have higher productivity than is being estimated from the existing inventory. Higher productivity second-growth stands would grow faster, produce higher volumes, and require less time to reach merchantable size than lower productivity stands. If second growth can be harvested at younger ages than currently assumed, the current harvest rate in existing old-growth forests could potentially be maintained. In the longer term - perhaps 80 to 90 years from now - harvests might be able to rise above the current level.
Sensitivity analysis shows that higher productivity from second growth may offset lower existing stand volumes. The degree to which second-growth volume production would have to increase above current estimates to offset a decreased estimate of existing timber volumes depends on: 1) how much lower existing stand volumes are than current inventory-based estimates; and 2) the time needed for second growth to reach merchantable conditions.
Timber supply over the next few years is also sensitive to uncertainty in the size of the timber harvesting land base. Currently, a significant portion of Kalum South is classified as operable only for harvesting systems not conventionally used in the area, such as long-line skyline systems. If harvesting activities do not move into these areas, both short- and long-term timber supply would be significantly smaller than indicated in the base case results summarized above. Conversely, future economic factors may expand the land base available for harvesting, for example, if currently non-merchantable species become marketable, or if wood prices rise significantly. Whether or not the harvesting land base will expand in the future is unknown; however, it is clear that short-term harvests depend significantly on the use of timber in areas operable for non-conventional harvesting systems.
The uncertainties associated with existing timber volumes, site productivity and the land base have the greatest potential impact on future timber supply. However, several other factors can also affect the timber supply in the short or long term.
Uncertainty about minimum harvestable ages has a large effect on timber supply. Lower harvest ages would increase potential harvests, while higher ages would require either immediate harvest reductions, or reductions to well below the productive capacity of the land for several decades beginning about 20 years from now. There would be little long-term effect from harvesting at the range of ages tested.
Second-growth harvest ages are highly uncertain, since they depend on future markets and technology, and are affected by uncertain estimates of second-growth productivity. Until there is clear evidence that second-growth productivity differs significantly from estimates used in this analysis only increase in short-term timber supply stemming from optimistic estimates of productivity and harvestable ages should be approached with caution. A belief that minimum harvestable ages will be longer than assumed for this analysis would indicate a conservative, or cautious, viewpoint but would also be based on conjecture.
Uncertainty about both forest cover guidelines to protect visual quality, and the ages at which harvested areas reach green-up conditions, particularly in visual quality management areas, have moderate effects on timber supply in the short term, and only small impacts over the long term. If visual quality could be maintained while placing fewer limitations on harvesting than assumed in this analysis, the timber supply would increase sufficiently to maintain current harvest levels for up to 20 years. Conversely, if maintaining visual quality required more restrictive guidelines, harvests would have to be reduced somewhat. Similarly, if green-up periods are 5 years less than assumed for the base case, the current harvest level for Kalum South could be maintained for another 10 years without causing future timber supply shortages. If the ages are 5 years longer, harvests would have to decline immediately to avoid future shortages.
Timber supply is affected only slightly by uncertainty in forest cover guidelines for old growth, the estimated age at which stands reach oldgrowth conditions, and the amount of commercial thinning.
In conclusion, this analysis based on current
inventory and growth and yield information indicates that timber
harvests in Kalum South will have to decline to the long-term
growth potential of the land base over the next 10 to 20 years.
Several uncertainties important to timber supply deserve attention
both in discussions about shortterm harvest levels, and
in inventory and research over the next few years. First, indications
from recent inventory work that existing merchantable timber volumes
may be overestimated should be investigated. Second, field observations
suggesting that second-growth productivity may exceed estimates
based on the existing inventory require corroboration. Third,
to maintain the timber supply indicated in this analysis, harvesting
operations must move into areas operable for non-conventional
harvesting systems. Finally, although the above three factors
appear most important in defining the Kalum South timber supply,
visual quality objectives also have moderate effects. It will
be important to examine the visual quality management classification,
forest cover guidelines, and desired green-up conditions and ages
to ensure they accurately reflect demands and meet objectives.