Otago and Southland Wood Availability Forecasts for the Period 2007–2040
Scenarios for radiata pine
Five wood availability scenarios have been modelled for radiata pine. These scenarios show the range of potential ways the forests in the region could be harvested in the future.
To ensure the scenarios presented here are reasonable, they were developed in consultation with the NEFD Steering Committee and feedback was received from major forest owners and consultants in the Otago and Southland Wood Supply Region.
Scenario 1: Harvest all areas at age 30
All owners are assumed to harvest their trees at age 30. This scenario shows the potential future harvest in any given year, based on the area of radiata forest that reaches 30 years of age in that year.
Scenario 2: Large-scale owners harvest at stated intentions, small-scale owners harvest at age 30
Large-scale owners’ wood availability is assumed to be at stated harvest intentions for 2005 to 2015. After 2015, the large-scale owners’ wood availability is assumed not to decrease. Small-scale owners are assumed to harvest their forest holdings at age 30.
Scenario 3: Non-declining yield (NDY) – 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 modelled to be non-declining in perpetuity.
Scenario 4: Split NDY – 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, an annual reduction of up to 10 percent was allowed before the yield was required to be non-declining for the next rotation (from 2037 on).
Scenario 5: Target rotation age variations
This is similar to Scenario 4 except target rotation ages of 28 and 32 years are also modelled.
Discussion on scenarios for radiata pine
With the exception of Scenario 1, the small-scale forest owners have been modelled separately from the large-scale owners. Future harvesting by small-scale owners is generally less certain than by large-scale owners.
Figure 1 uses the wood availability forecasts for the Otago region to show how wood availability varies under each scenario (radiata pine in Southland and the combined regions is not shown).
In Scenarios 1 and 2 (Figures 1a and 1b respectively), forests owned by small-scale owners are assumed to be harvested at age 30. In Scenario 1, all forests (large and small-scale) are harvested at 30 years. Both 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 Otago and Southland regions. For practical reasons, already described, it is unlikely that the future harvesting would occur this way. The 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, the future harvesting model 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 logistical and market constraints into account, to some extent.
Scenarios 3 to 5 avoid the large year-to-year fluctuations seen in Scenario 1. A fundamental property of the forests in Otago and Southland (like many regions in New Zealand) is the large area of forests established during the 1990s. Scenarios 4 and 5 illustrate 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 has been harvested, the model lets the volume decline again.
The main limitations of Scenarios 3 to 5 are that log prices and other market factors significantly determine harvesting in any given year. When log prices go up, harvesting will generally increase. When log prices fall, the level of harvesting will generally decrease. It is beyond the scope of this analysis to predict future timber prices.
Figure 1: The sequence of wood availability scenarios presented in this report for radiata pine
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
(Scenario 5 is the same concept except it shows wood availability profiles at varying harvesting ages)
Contact for Enquiries
Parnell Trost
Policy Analyst
MAF Policy
Natural Resources Group
PO Box 5648
Dunedin
Ph: 03 951 4705
Fax: 03 951 4711
Cell: 029 951 4705
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