Note: The analysis on the Okanagan 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 in the Strathcona and Quesnel TSAs.
The harvest forecast for the Okanagan 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 D-1. For comparison, the harvest forecast from the Okanagan TSR is represented by the dotted line. The initial rate of harvest is about 5.5% below the initial rate of harvest in the TSR base case. From this reduced initial rate, the harvest level declines by about 11% per decade to a long-term level that is about 10% below the long-term level shown in the TSR base case.
The timber supply forecast for the Okanagan TSA is affected only slightly by the FPC requirements for riparian reserves and landscape-level biodiversity. The area excluded for riparian reserves is expected to be far less than is removed in wetter areas of the province, and the Okanagan TSA Timber Supply Review already includes requirements for maintenance of old-growth forest that are considered comparable to the FPC requirements for landscape-level biodiversity. Of greater significance are the requirements for stand-level biodiversity (wildlife tree patches) and the partial retention of timber volume when harvesting in riparian management zones. These two factors reduce the expected timber yield from each hectare of forest land harvested by about 4%.
Figure D-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 Okanagan TSA.
Approximately 70% of the productive forest area in the Okanagan TSA is available for harvest (from Table 1 in the Okanagan TSR). If about 20% (overall) of the area has already been harvested without regard for WTP recommendations (which appears reasonable given the age class distribution on page 16 of the Okanagan 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 recommendations, the percent area that will have to be left as WTPs 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 quarter of the percent area that must be maintained in WTPs. The reasoning behind this assumption is that three quarters 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.
Note: The analysis on the Lakes 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 in the Strathcona and Quesnel TSAs.
The harvest forecast for the Lakes 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 E-1. For comparison, the harvest forecast from the Lakes TSR is represented by the dotted line. The initial rate of harvest is unchanged from the TSR base case; however, it can only be maintained for three decades before declining to a steady long-term level of about 1.22 million m3/year. Although the short-term harvest level is unchanged, the area between the solid and dotted lines from year 30 to the end of the 250-year period represents a significant reduction in the projected medium- and long-term timber supplies.
The timber supply forecast for the Lakes TSA is affected by the riparian and biodiversity FPC requirements for the same reasons stated for the Strathcona and Sunshine Coast TSAs; both the timber harvesting land base and the expected timber yield from each hectare of forest land harvested are reduced.
Figure E-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 Lakes TSA.
The Cranbrook TSR harvest forecast reflects the extensive history of fires in the Cranbrook TSA which has led to a short supply of mature timber. This shortage in mature timber has resulted in harvesting being allowed at younger ages and lower volumes than would normally be permitted. As a result, the long-term timber supply projection of the TSR is lower than the theoretical maximum sustainable level.
Note: FPC requirements for riparian management areas were not included in the Cranbrook analysis.
The harvest forecasts for the Cranbrook TSA with FPC requirements for biodiversity only are represented by the solid lines in Figure F-1. For comparison, the harvest forecast from the Cranbrook TSR is represented by the dotted line. The initial rate of harvest either starts at a level 14% below (thin solid line) or 8% below (thick solid line) the initial rate of harvest in the TSR base case. The only difference between the lines is the timing of harvests (harvest flow). As per the Biodiversity Guidebook, 60% of the TSA was treated as low biodiversity emphasis, 30% moderate and 10% high.
For the purpose of the provincial impact analysis, the Working Group chose the "8% below the initial rate of harvest of the TSR" option (thick solid line).
Biodiversity requirements specify that a certain proportion of the landscape must be retained in mature and older forest cover. Over time, these retained areas will produce much older trees with higher volumes. As other areas over the landscape mature and grow older, the biodiversity cover requirements can be shifted to these areas, freeing previously retained areas to be harvested. The older harvest ages in the previously retained areas will, for the most part, come closer to the culmination point (as compared to the TSR long-term forecast), and will therefore yield higher volumes per hectare. As a result, the long-term harvest level is about 20% higher than that of the TSR base case beginning in decade 13. This level approaches the theoretical maximum sustainable level of 832 000 m3/year, which is based on maximum mean annual increment.
It is assumed that both the short- and long-term timber supply will be further impacted with the inclusion of other FPC requirements.
Figure F-1. Harvest forecast showing the impact of FPC requirements for biodiversity (riparian management areas not included) on the timber supply of the Cranbrook TSA.
Other resource values were not analyzed, and as such, the impacts shown overestimate the effect of applying the biodiversity guidebook recommendations on a managed forest. For example, riparian areas, visual quality, identified wildlife and watershed assessments all have certain forest cover requirements that can account for meeting seral stage requirements for maintenance of biodiversity. The results, however, do portray estimated harvest levels given the minimum requirements for biodiversity with the following breakdown; 60% low, 30% intermediate and 10% high emphasis.
Seral stage requirements for mature and old forest were essentially the only parameters modelled. The forest cover requirements for early seral stage were included; however, they were unconstraining. The mature and old forest cover requirements for landscape biodiversity were modelled by first determining how much of each biogeoclimatic type (natural disturbance type) is already excluded by other netdowns (e.g., inoperable areas, environmentally sensitive areas). The area already excluded was subtracted from the amount of area that must be maintained at older ages in the timber harvesting land base.
