Appendix G is a summary of the assumptions used in the timber supply analysis of the FPC.
The harvest forecast for the Strathcona TSA with FPC requirements for riparian management areas and biodiversity is illustrated in Figure A-1. For comparison, the harvest forecast from the Strathcona TSR is represented by the dotted line. The thin solid line shows a harvest forecast using a harvest flow policy similar to the TSR base case. The initial rate of harvest using this flow policy is about 18% below the initial rate of harvest in the TSR base case, or about 30% below the current AAC.
An alternative harvest flow policy that allows a much faster rate of decline in decades two and three (up to 23% per decade) is represented by the thick solid line. The initial rate of harvest with this harvest flow policy is only 11% below the initial rate of harvest in the TSR base case, or about 23% below the current AAC.
For the purpose of the provincial impact analysis, the Working Group chose the "11% below the initial rate of harvest of the TSR" option (thick solid line).
The reduced timber supply forecast due to implementing riparian and biodiversity FPC requirements is a result of a reduced timber harvesting land base and decreased timber yields from each hectare of forest land harvested. The reduced size of the timber harvesting land base is due to an increase in riparian reserves. The decrease in timber yields is due to unharvested timber volume left in riparian management zones along streams and lake shores, unharvested timber retained in wildlife tree patches, and the proportion of the forest that must always be maintained in older age stands. This is expected to significantly reduce timber yields over both the short and long term.
Figure A-1. Harvest forecast showing the impact of FPC requirements for riparian management areas and biodiversity on the timber supply of the Strathcona TSA.
A 1994 report by Wild Stone Resources provides average figures for stream length by stream class per cutblock, based on a statistically significant sample of coastal cutblocks. These stream length figures were used together with the reserve widths prescribed for each stream class in the FPC to arrive at an average area per cutblock expected to be excluded for riparian reserves. The required reserves for each stream class are as follows:
The above requirements for riparian reserves result in the exclusion of almost 11 000 hectares or about 4.8% of the timber harvesting land base.
All streams that require forested reserves along their length (S1, S2 and S3) are also assumed to have an additional 20-metre management zone on each side. An average of 50% of the timber volume is assumed to be available for harvest from these management zones.
All streams that do not require forested reserves (S4, S5 and S6 streams) will require a 20-metre (S6 only) or 30-metre management zone. An average of 75% of the volume is assumed to be available for harvest from management zones along S4 and S5 streams, and 95% of the volume is assumed to be available from management zones along S6 streams.
(There were no lakes in the data base for the Strathcona TSA.)
In total, approximately 15% of the timber harvesting land base is assumed to fall within riparian management zones, most of which is alongside S6 streams (due to the frequency of these small streams). The reduction factor applied to the volume-over-age curves in the timber supply model to account for the timber volume left unharvested in riparian management zones is 4.2%.
Based on inventory summaries of area by biogeoclimatic classification, the Kyuquot supply block is assumed to be natural disturbance type 1 (NDT1) (rare stand initiating events) and the Sayward and Loughborough are assumed to be 40% NDT1 and 60% NDT2 (infrequent stand initiating events). Only the "old forest" cover requirements are applied in the impact analysis. The forest cover requirements for early and mature seral stages are assumed to have considerable flexibility in application and are adequately addressed by existing forest cover requirements for cutblock adjacency and management of visually sensitive areas. The old forest cover requirements used to model landscape biodiversity in the impact analysis are calculated as shown in Table A-1. Table A-1 only shows the calculation done for natural disturbance type 1 (NDT1) forests. The same method of calculation was used to calculate the forest cover requirements over time for other NDTs.
Since the impact that the biodiversity guidebook recommendations have on the timber supply forecast is sensitive to the amount of area that is designated to each biodiversity emphasis class, two different breakdowns of area by biodiversity emphasis class were modelled. Table A-1 assumes a 20%, 70%, 10% breakdown between low, intermediate and high emphasis, respectively. An additional model run was completed that assumes a 50%, 40%, 10% breakdown between the three emphasis categories, respectively. Increasing the amount of area in the low emphasis category reduces the percentage of older forest required in the short term, but does not change the percentage of old growth required in the long term.
The proportion of the required area of old growth that is already present in excluded areas is not fully accounted for in Table A-1. Inventory summaries indicate that the amount of each forest type excluded from the timber harvesting land base for reasons such as inoperability, timber quality, sensitive soils or riparian reserves already exceeds the total amount of old growth that is required by the biodiversity guidebook recommendations. However, the assumption that only half of the required old growth is provided by excluded areas is based on the premise that the excluded areas are not likely to be geographically distributed in such a way that a forest ecosystem network (FEN) could be created without including some of the remaining timber harvesting land base.
Table A-1. Calculated landscape-level biodiversity requirements for old forest over time, for natural disturbance type 1 (NDT1)
Note: The analysis on the Sunshine Coast TSA is based on the FPC requirements for riparian management areas and on the November 1994 draft FPC requirements for biodiversity. The analysis was not redone using the February 1995 revised requirements, as was done for the Strathcona and Quesnel TSAs. Using the revised biodiversity requirements, the impact on the harvest forecast is likely to be similar to that shown for the Strathcona TSA.
The harvest forecast for the Sunshine Coast TSA with FPC requirements for riparian management areas and the November 1994 draft FPC requirements for biodiversity is represented by the solid line in Figure B-1. For comparison, the harvest forecast from the Sunshine Coast TSR is represented by the dotted line. The initial rate of harvest is about 20% below the initial rate of harvest (equal to the current AAC) in the TSR base case. From this reduced initial rate, the harvest level declines by about 10% per decade to a long-term level that is about 14% below the long-term level shown in the TSR base case.
The timber supply forecast for the Sunshine Coast TSA is affected by riparian and biodiversity FPC requirements for the same reasons stated for the Strathcona TSA; both the timber harvesting land base and the expected timber yield from each hectare of forest land harvested are reduced.
Figure B-1. Harvest forecast showing the impact of FPC requirements for riparian management areas and the November 1994 draft FPC requirements for biodiversity on the timber supply of the Sunshine Coast TSA.
The harvest forecast for the Quesnel TSA with FPC requirements for riparian management areas and biodiversity is illustrated in Figure C-1. For comparison, the harvest forecast from the Quesnel TSR is represented by the dotted line. The thin solid line shows the harvest forecast if almost all the old and mature forest required by the Biodiversity Guidebook can be found in areas already excluded from the timber harvesting land base as inoperable, poor quality timber or environmental concerns. Given this assumption, the only effect that the FPC requirements have on the timber supply forecast is a slightly reduced long-term harvest level.
The thick solid line shows the harvest forecast if the proportion of mature and older forest required by the Biodiversity Guidebook must come out of the existing timber harvesting land base. This assumption is reasonable if the timber harvesting land base is generally made up of large contiguous areas that are not well dispersed with excluded areas. Using this assumption, the initial rate of harvest is still unchanged from the TSR base case, but can only be maintained for five decades before declining by 10% per decade to a long-term level 4% below the long-term harvest level in the TSR base case.
The riparian and biodiversity FPC requirements do not have an effect on the short-term timber supply forecast since the existing inventory of mature timber in the Quesnel TSA is very large. Even with the increased exclusions for riparian reserves and reduced timber availability due to biodiversity requirements, there are enough alternative areas available for harvesting to sustain the current rate of harvest over the short term. However, the initial rate of harvest cannot be maintained as long as in the TSR base case.
Figure C-1. Harvest forecast showing the impact of FPC requirements for riparian management areas and biodiversity on the timber supply of the Quesnel TSA.
A total of 3241 kilometres of streams and 500 kilometres of lake shore were measured on 22 sample map sheets. Streams and lake shores are assumed to occur equally in all areas of the TSA. Therefore, the average percent area of each map sheet that falls under riparian reserves is excluded from the timber harvesting land base. The proportion of stream length assumed to fall into each of the "S" designations and the required reserve widths on each side of the stream/lake are as follows:
All streams that require forested reserves along their length (S1, S2 and S3) will also have an additional 20-metre management zone on each side. An average of 50% of the timber volume is assumed to be available for harvest from these areas.
All streams that do not require forested reserves (S4 and S5 streams) will require a 30-metre management zone in which only 75% of the timber volume will be removed during harvesting.
All lakes with reserves will require an additional 40-metre management zone outside of the forested reserve. An average of 50% of the timber volume in the management zone will be available for harvest.
The percent area excluded for streams and the volume-over-age curve adjustments made to account for the area of ripararian management zones that will be only partially harvested are shown in Table C-1.
Table C-1. Riparian reserve netdown and volume-over-age curve adjustment to account for riparian management zones
Only the mature and old forest cover requirements are applied in the impact analysis. The forest cover requirements for the early seral stage are assumed to be non-constraining and are adequately addressed by existing forest cover requirements for cutblock adjacency and management of visually sensitive areas. The mature and old forest cover requirements for landscape biodiversity in the impact analysis are modelled by first determining how much of each forest type is already excluded by other netdowns (e.g., riparian buffers, sensitive soils, inoperability). The area already excluded is subtracted from the area that must be maintained at the older ages in the timber harvesting land base (i.e., if 13% old growth is required and 9% is already in excluded areas, then only another 4% of old growth is required to be maintained on the timber harvesting land base). Sufficient forest area is already excluded in the Quesnel TSA, such that, assuming the excluded area is well distributed between landscape units, the minimal forest cover requirements for mature forest shown in Table C-2 are all that is required on the timber harvesting land base.
Table C-2. Forest cover requirements for biodiversity if all excluded forest area is well distributed and contributes to landscape-level biodiversity
A second model run was set up using the assumption that the inoperable areas are not well distributed among operable areas, and that the required proportion of mature and old-growth forest would have to be maintained entirely from operable areas. The forest cover requirements for mature forest are calculated for this run as shown in Table C-3.
Table C-3. Mature forest cover requirements over time, if the requirements must be met exclusively from the timber harvesting land base
Approximately 70% of the forest area in the Quesnel TSA is available for harvest (from Table 1 in the Quesnel TSR). If about 20% (overall) of the area has already been harvested without regard for WTP guidelines (which appears reasonable given the age class distribution on page 17 of the Quesnel TSR), Table 21 in the February 1995 draft Biodiversity Guidebook indicates that 9% of the area of cutblocks to be harvested in the near future will have to be left in WTPs. In the future, as more areas have been harvested using WTP guidelines, the percent area that will have to be left as a WTP in each block will be reduced to 8% (also from Table 21 in the February 1995 draft Biodiversity Guidebook). The percent reductions in timber yields applied to model the effect of WTPs are assumed to be one half of the percent area that must be maintained in WTPs. The reasoning behind this assumption is that at least half of the area required for WTPs will be contributed by inoperable stands, unmerchantable stands and areas excluded for riparian reserves.
Recommendations regarding retention of coarse woody debris are assumed to have no impact on the timber supply forecast and are not included in this analysis. The revised biodiversity guidebook recommendations state that no timber meeting utilization standards will be required to be left on site for biodiversity purposes.
