Performance Audit Report

Transcription

1 Performance Audit Report Yield Forecasts Eden Regional Forest Agreement Issue The Auditor General s Performance Audit Sustaining Native Forest Operations: Forests NSW of April 2009 included an action item (Recommendation 3), requiring Forests NSW to Undertake and publicly report the results of a review of yield estimates for native forests in Southern Region including Eden, South Coast & Tumut This report addresses the review of yield estimates for Eden Regional Forest Agreement (RFA), in the form of a review of timber supply from the Eden sub region of the Forests NSW Southern Region. Background In 2008 Forests NSW commenced an internal review of 1998 wood supply modelling for Eden RFA area. This review was extended in and forms the basis of this report. Aspects of the 2008 study included: Logging history and stand structure updated to end No additional inventory was included. Regrowth was modelled using the REDEN model, which was a local growth and yield simulator incorporating 9,000+ inventory plots, unique local biometrics (growth models, stem volume equations, species and site specific height functions) and thinning schedules. Yields for multi age forest were based on standing volume only (no growth). Net harvest area was recalculated but no modifiers were applied. Yield scheduling undertaken using Remsoft Woodstock planning system. Species modelling based on forest typing. Future sawlog/pulp volume proportions from current regrowth incorporate scaling factors. It should be noted that that REDEN is not consistent with FRAMES (the Forests NSW Forest Resource And Management Evaluation System). The location specific biometrics and underlying inventory program are no longer supported. Timber harvesting in the Eden management area is in transition with harvesting changing from remaining multi age forest (harvested with alternate coupe silviculture) to older fire regrowth (which is 90% thinned) to younger harvesting regrowth. Yield Forecasts Eden Regional Forest Agreement Page 1 of 10 20/3/12

2 Timber supply from the Eden area is covered by a number of agreements Agreement Length Dates (yr) Eden Regional Forest Agreement 20 August Eden Forest Agreement 20 5/3/1999 5/3/2019 Eden Integrated Forestry Operations Approval (IFOA) 19 1/1/ /12/2018 Wood Supply Agreement (WSA) with Blue Ridge Hardwoods ~ 20 7 /3/1999 1/1/2019 Project Design The modelling undertaken as part of this review provides more detail on future sawlog and pulpwood volumes for the remainder of the Wood Supply Agreement (WSA) which extends to the end of Changes included in the review were restricted to: Updating area statements, incorporating: o Reanalysis of the remaining mature age forest (MAF) resource including identifying areas not harvested in previous operations. Approximately 20% of this area was field verified; the remainder was updated using aerial photography interpretation (API) and GIS analysis. o Areas of older fire regrowth and harvesting regrowth forest were updated to incorporate harvesting to 30 June o Allowing for operational factors, such as excluding small areas theoretically available for harvesting where these are below a threshold size. Incorporating Net Harvest Area Modifiers (NHAM) calculated as part of the 2011 NHAM review (reported separately). The NHAM factors were applied to the updated area statements. Reviewing the thinning strategy including extension of the thinning window the age range where thinning is permitted in the model and providing more flexibility with the way thinning is scheduled by the model. Revising and simplifying yield tables by: o Removing scaling factors used in the previous model. o Scaling raw yield data to match previous yield table volumes, but in a simpler format. o Cross checking scaled yields with recent harvest volumes to confirm that the yield tables were providing comparable results. Updating recovery information for regrowth stands based on actual harvest data realised sawlog volume changed to 50% of yield table volume (up from 30%); realised pulp volume changed to 60% of yield table volume (up from 50%). Investigating impacts of changes to minimum harvest age. Investigating the effect of reducing sawlog small end diameter (sed) from 30 cm to 25 cm. Yield Forecasts Eden Regional Forest Agreement Page 2 of 10 20/3/12

3 Current resource The area base for this forecast covers the which is included in the Eden sub region of Forests NSW Southern Region (see Figure 1). The forest resource can be categorised into areas of high, medium and low site quality and by growth stage. Figure 2 shows the extent of these site quality areas across the Eden RFA region. Figure 3 shows the location of multi age forest, pre 1970 regrowth and post 1970 regrowth stands. Figure 1: Extent of study area for Eden region yield estimates. State Forests 2011 Berridale Cobargo Bermagui Nimmitabel Bemboka Candelo Bega Tathra Bombala Merimbula Pambula Delegate Eden Native Forests Planted Forests Yield Forecasts Eden Regional Forest Agreement Page 3 of 10 20/3/12

4 Figure 2: Site Quality. Site Quality Berridale Cobargo Bermagui Nimmitabel Bemboka Candelo Bega Tathra Bombala Merimbula Pambula Delegate Eden Site Quality High Medium Low Yield Forecasts Eden Regional Forest Agreement Page 4 of 10 20/3/12

5 Figure 3: Forest Structure. Forest Structure Berridale Cobargo Bermagui Nimmitabel Bemboka Bega Tathra Candelo Merimbula Bombala Pambula Delegate Eden Forest Structure Multi-age Forest Pre 1970 Regrowth Post 1970 Regrowth Yield Forecasts Eden Regional Forest Agreement Page 5 of 10 20/3/12

6 The Eden management area has a gross area of just over 164,200 ha. The net area used in the 2008 modelling was 95,945 ha. The revised net harvestable area (NHA), incorporating Net Harvest Area Modifier (NHAM) factors and additional area statement adjustments discussed above, is 88,018 ha. This is a reduction of 7,927 ha (8%) from the 2008 area. Table 1 below summarises the NHA by age class and thinning category. Table 1: Net harvestable area by age class and thinning category Resource Category Unthinned Thinned Total NHA NHA (ha) NHA (ha) (ha) Multi age forest (MAF) 13,616 13,616 Pre 1970 Fire Regrowth 748 1,826 2,574 Post 1970 Regrowth 63,706 8,122 71,828 Total 78,070 9,948 88,018 Estimates of standing volume associated with multi age forest (MAF) in the 2008 model were generally sourced from older field estimates. The process to update MAF area for this model also included yield verification of standing volume using field inventory or links to harvested yields from adjacent areas. Approximately 1,100 ha of the 13,616 ha of MAF did not have any form of yield verification. Estimates of standing volume for this area were made using the more conservative 2008 yield tables. Table 2 below summarises the standing volume by site quality remaining on multi age forest. Note that there is no growth associated with this forest type. Table 2: Standing volume in multi age forest (MAF), Eden management area Site NHA HQ vol Tot HQ vol Quality (ha) (m 3 /ha) (m 3 ) High 3, ,200 Medium 4, ,900 Low 4, ,600 Total 13, ,700 Scenarios Two wood supply scenarios were modelled using Woodstock and updated net harvestable area. Non Declining Sawlog Yield scenario The objective of this scenario was to balance the supply of high quality sawlog (Large Graded Log and Small Graded Log) to ensure future yields are always the same or higher than for the previous period. The model was run over a 100 year planning horizon. Yield Forecasts Eden Regional Forest Agreement Page 6 of 10 20/3/12

7 Wood Supply Agreement (WSA) scenario The objective of this scenario was to meet current ( ) WSA volumes, while continuing to maximise long term sustainable supply levels of high quality sawlog. Results Non Declining Sawlog Yield scenario Table 3 and Figure 4 summarise the results of the even flow scenario, showing volume (m 3 /year) of high quality sawlog and pulp available summarised by 4 year periods (commencing 2011) over a 48 year planning horizon. Four year periods have been used to align the model outputs with the end of the Wood Supply Agreement. Table 3: Available volume (m 3 /year) over 48 year horizon for all products. Product Class 4 year period HQ Large Sawlog 16,100 16,000 12,800 7,300 5,900 14,000 21,200 35,400 34,500 34,500 36,300 36,700 HQ Small Sawlog ,400 8,900 10,200 13,000 21,900 37,900 38,800 38,800 37,000 36,600 Total HQ Sawlog 16,100 16,100 16,100 16,100 16,100 27,000 43,100 73,300 73,300 73,300 73,300 73,300 Pulp 285, , , , , , , , , , , ,500 Figure 4: Non Declining Sawlog Yield scenario available volume (m 3 /year) over 48 year horizon for high and low quality product grades. 80,000 70,000 60,000 (m3/yr) Volume 50,000 40,000 30,000 20,000 10, Year Periods HQ Large Sawlog HQ Small Sawlog Total HQ Sawlog Yield Forecasts Eden Regional Forest Agreement Page 7 of 10 20/3/12

8 Wood Supply Agreement scenario Table 4 and Figure 5 summarise the results of the scenario to meet existing wood supply agreement commitments. Results are given for high quality sawlog and pulp per year for each 4 year period. Periods 1 and 2 cover the remaining WSA years 2011 to Table 4: Available volume (m 3 /year) over 48 year period for high quality products WSA scenario. Product Class 4 year period HQ Large Sawlog 23,000 19,800 10,800 8,800 6,900 8,000 8,900 31,700 34,300 35,300 35,000 33,500 HQ Small Sawlog 0 3,200 7,800 10,200 12,300 11,200 10,300 36,400 37,100 36,200 36,500 38,000 Total HQ Sawlog 23,000 23,000 18,600 19,000 19,200 19,200 19,200 68,100 71,500 71,500 71,500 71,500 Pulp 279, , , , , , , , , , , ,800 Figure 5: Wood supply agreement scenario available volume (m 3 /year) over 48 year horizon for high and low quality product grades. Volume (m3/yr) 80,000 70,000 60,000 50,000 40,000 30,000 20,000 10, Year Periods HQ Large Sawlog HQ Small Sawlog Total HQ Sawlog Yield Forecasts Eden Regional Forest Agreement Page 8 of 10 20/3/12

9 Comparison Table 5 compares the results of the two scenarios. These results show a significant decline in the volume of high quality sawlog follow the end of the Wood Supply Agreement, relative to the non declining sawlog yield scenario. Table 5: Comparison of high quality sawlog volume (m 3 /year) available from Non declining Sawlog Yield and Wood Supply Agreement scenarios. Period Even Flow scenario Wood Supply Difference Agreement scenario 1 16,100 23,000 6, ,100 23,000 6, ,100 18,600 2, ,100 19,000 2, ,100 19,200 3, ,000 19,200 7, ,100 19,200 23, ,300 68,100 5, ,300 71,500 1, ,300 71,500 1, ,300 71,500 1, ,300 71,500 1,800 Yield Forecasts Eden Regional Forest Agreement Page 9 of 10 20/3/12

10 Conclusion This review demonstrates that Wood Supply Agreement (WSA) volumes can be met for the duration of the WSA timeframe. High quality (large graded and small graded) sawlog will predominantly be sourced from multi age forest and older fire regrowth. Following the end of the Wood Supply Agreement in 2018, the model shows the rapid transition to log supply from the regrowth resource. A drop in the sawlog supply during this transition is mitigated by minor adjustments to the silvicultural strategy for approximately 10 years. During this period the minimum harvest age for regrowth stands is allowed to drop to 50 years. After this period the minimum harvest age is reset to 60 years. A further adjustment was applied to the sawlog yield data to bring it in line with sawlog specifications applied more generally in NSW coastal forests. The current minimum sawlog small end diameter (sed) specification of 30 cm was reduced to 25 cm sed. This results in a 10% increase of sawlog volume. The minimum sawlog diameter adjustment is applied to the regrowth resource only. There will be several challenges associated with supplying the modelled volume including: managing the local reduction in high quality log volume post WSA in the context of broader regional log supply; managing the transition from multi age forest to older fire regrowth and younger harvesting regrowth; addressing the incomplete inventory of fire regrowth and harvesting regrowth stands; and managing changes in the supply of pulp from multi age forest to thinning of harvesting regrowth stands. A number of issues identified by this review will require further work to support the transition from multi age forest and older fire regrowth to younger regrowth. These include: Review of log product definitions, particularly smaller sawlog. Ongoing verification of recovery and actual log volumes and dimensions harvested (ie are assumptions about 25 cm sed sawlog being achieved). Comprehensive forest structure mapping using remote sensing to provide a more accurate picture of the regrowth resource. Developing a spatial version of the resource database including: o Forest structure o Age Class of regrowth o Thinning status o Site Quality. Incorporating REDEN growth and yield models in the FRAMES Growth and Yield simulator. This would allow tree level quality and product data to be included in modelling. Developing new growth models in FRAMES using plot data updated with thinning status and age class. Collection of additional data to enable review and refinement of product proportion information for regrowth thinning and harvesting. Further refinement of the Net Harvest Area Modifier to reflect harvesting practices in regrowth forest areas. Yield Forecasts Eden Regional Forest Agreement Page 10 of 10 20/3/12