Southern North Island wood availability forecasts for the period 2008–2040
Introduction
These forecasts show the range of harvest volumes potentially available from the planted production forests in the Southern North Island (SNI) region for the period 2008–2040.
The wood availability forecasts are based on each region’s forest resource and the forecasting assumptions described later in this report. The forecasts have been developed incorporating the harvesting intentions of the region’s large-scale forest owners (those with 1000 hectares of forest or more):
- Ernslaw One
- Juken New Zealand
- Wellington Regional Council
- Matariki Forests
- Global Forest Partners
- West Coast Development Company
- Wanganui District Council
- Crown Forestry
- Palmerston North City Council
- Anglican Schools
- Department of Conservation
The last three owners listed above, while not defined as large-scale owners, all had harvest operations underway at the time of the survey.
The investment syndicates managed by Forest Enterprises have been included in the small-scale ownership category because the ownership systems and age structure of these forests is similar to the small-scale owners.
The forecasts incorporate the views of the region’s forest managers and consultants. This feedback was critical for ensuring that the forecasts represent a realistic range of future wood availability.
Five scenarios have been modelled to indicate the potential range of wood availability. A key issue is the timing of harvesting by the small-scale forest owners, which will be driven by a range of factors including individual forest owners’ objectives, forest age, log prices, demand by local wood processing plants, and perceptions about future log prices and future wood supply. Experience has shown that predicting future harvesting patterns from these owners is difficult.
The scenarios indicate there are many different ways for the forest estate in the region to be harvested. The forests are managed to maximise the benefits to the enterprise that owns them. Each enterprise has its own harvest strategy based on the owners’ objectives, market conditions and the forest estate that it owns or manages. Any change in harvesting strategies by forest owners affects the age-structure and maturity of the forests they own. This in turn feeds back directly into future wood availability.
Different levels of uncertainty are associated with the wood availability from each ownership segment of the estate. The volumes forecast from the large-scale owners’ forests are subject to change because of changes in harvest intentions or changes in the resource description (areas and yields). Yet, they have greater certainty than those forecast from the small-scale owner’s estate. Not only are harvest intentions less clear for small-scale owners, the resource description is likely to be less accurate also.
Scenarios for radiata pine
Five wood availability scenarios have been modelled for radiata pine in this analysis. These scenarios show the range of potential ways for harvesting the forests in the region in the future.
To ensure the scenarios used in this analysis are reasonable, the methodology used was developed in consultation with the National Exotic Forest Description (NEFD) Steering Committee. In addition input and feedback on the forecasts was sought from major forest owners and consultants in the region.
Years are assumed to be to 31 December. For example 2008 indicates the year to 31 December 2008.
Scenario 1: Harvest all areas at age 30
All owners are assumed to harvest their forests at age 30. This scenario shows the potential future harvest in any given year based on the area of radiata pine forest that reaches 30 years old in that year.
Scenario 2: Large-scale owners harvest at stated intentions, small-scale owners at age 30
Large-scale owners’ wood availability is assumed to be at stated harvest intentions for 2006 to 2015. After 2015, the large-scale owners’ wood availability is not allowed to decrease and can increase by no more than 10 percent per year. Small-scale owners are assumed to harvest trees at age 30.
Scenario 3: Non-declining yield – target rotation 30 years
Large-scale owners’ wood availability is assumed to be at stated harvest intentions (as for Scenario 2). The total wood availability of radiata pine from the region is constrained to be non-declining in perpetuity and to increase by no more than 10 percent per year.
Scenario 4: Split non-declining yield – target rotation 30 years
This is the same as Scenario 3 except that the total wood availability of radiata pine from the region is allowed to step down from 2034 (at the end of the current rotation). Thereafter, a reduction is modelled.
Scenario 5: Target rotation age variations
This is similar to Scenario 4 except target rotation ages of 28 and 32 years are also evaluated.
Discussion on scenarios
With the exception of scenario 1, the small-scale forest owners have been modelled separately from the large-scale owners. Future harvesting from the small-scale owners is generally less certain than for the latter.
In scenarios 1 and 2 (Figures 1A and 1B respectively), forests owned by small-scale owners are assumed to be harvested at age 30 years. In the case of scenario 1 all forests (large and small-scale) are harvested at 30 years. These two scenarios show the “potential” availability of mature forest in any given year. These scenarios directly reflect the area of forest in each age class in the Southern North Island region. For practical reasons already described it is unlikely that the future harvesting would occur like this. These two scenarios simply show the potential magnitude of harvesting under favourable market conditions in any given year.
Scenarios 3 to 5 (Figures 1C and 1D respectively) are based on yield regulation. Under these scenarios, future harvesting is generally constrained to be non-declining, that is, each year the volume must either be the same or higher than in the previous year. Yield regulation provides a more orderly harvesting volume profile that takes into account, to some extent, logistical and market constraints.
These scenarios avoid the large year-to-year fluctuations seen in scenario 1. A fundamental property of the forests in the Southern North Island (like many regions in New Zealand) is the large area of forests established during the 1990s. Scenarios 4 and 5 allow for the harvesting of these forests by applying a non-declining yield constraint for the period 2006 to 2034. Then once the “bulge” of forests planted during the 1990s have been harvested, the model allows the volume to decline again.
The main limitation of scenarios 3 to 5 is that log prices and other market factors are a significant determinant of harvesting in any given year. When log prices increase harvesting will generally increase. When log prices fall the level of harvesting will generally fall. It is beyond the scope of this analysis to predict future timber prices.
Figure 1 shows the sequence of models (scenarios) that are presented throughout the rest of this report.
Figure 1: The sequence of wood availability scenarios presented in this report for radiata pine for combined SNI
1A – Scenario 1 example: harvest all areas at age 30
1B – Scenario 2 example: large-scale owners harvest at stated intentions, small-scale owners harvest at age 30
1C – Scenario 3 example: non-declining yield with target rotation 30 years
1D – Scenario 4 example: split non-declining yield with target rotation 30 years
Note
Scenario 5 is the same concept as scenario 4 except it shows wood availability profiles of varying harvesting ages.
Scenarios for Douglas-fir
One scenario is presented for Douglas-fir (all owners). It is based on the harvest intentions of large-scale owners for 2006 to 2015 with harvest area regulated in subsequent years at a rotation age of 45 to 55 years.
Wood availability from other species has not been modelled.
Contact for Enquiries
Policy Adviser
Pastoral House
MAF Policy
PO Box 2526
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NEW ZEALAND
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