Auckland wood availability forecasts for the period 2008–2040
Wood availability forecasts for the Auckland region
Assumptions
The wood availability forecasts for the Auckland region are based on the following assumptions:
- Replanting – All area is replanted (with a regeneration lag of 1 year).
- The area awaiting replanting as at 31 March 2007 is included as area at age 0, that is, area to be replanted in the 2007 planting season.
- Species/Regime – Area is replanted into the same regime except that only 20 percent of old (planted in 1989 and earlier) pruned area is replanted into the pruned croptype following harvest.
Table 1: Volumes harvested in 2007 and 2008 for radiata pine
| Harvest year | Large-scale owners (m3) | Small-scale owners (m3) | Total (m3) |
|---|---|---|---|
| 2007 | 657 000 | 252 000 | 909 000 |
| 2008 | 643 000 | 197 000 | 840 000 |
These harvest figures differ from roundwood removal estimates by region as reported in MAF’s statistics (http://www.maf.govt.nz). The difference is attributed to the fact that the roundwood removal estimates are derived from regional mill outputs and log export volumes; the difference indicates a net flow of logs out of the region for processing or export.
- Overmature stands – Area that was age 61 years or older (26 hectares total) was removed on the assumption that these trees will not be harvested.
Scenario 1 – Harvest all forest at age 30
This scenario with all forest harvested at age 30 indicates the “pure” (that is, unconstrained) availability of wood from the Auckland region. It is essentially a translation of the age-class distribution into volume. Figure 2 shows the age-class distribution of radiata pine in the Auckland region, while Figure 3 shows the wood availability. The low point at 2021 in Figure 3 occurs because of the small area (698 hectares) at age 16 (planted in 1991) in Figure 2. Conversely, the high point at 2024 in Figure 3 occurs because of the large area (3177 hectares) at age 13 (planted in 1994) in Figure 2.
Figure 2: Age-class distribution of radiata pine in the Auckland region – combined estate as at 1 April 2007
Figure 3: Radiata pine availability in the Auckland region under scenario 1
Scenario 2 – Large-scale owners harvest at intentions, small-scale owners harvest at age 30
In this scenario, large-scale owners harvest in line with their stated intentions until 2013 and small-scale owners harvest trees at age 30.
Large-scale owners
The age-class distribution of the large-scale owners’ estate (Figure 4) indicates that there is a large variation in the area in age-classes. There is relatively little area in age-classes 14 to 17 years because of limited planting in 1990 to 1993.
The area at age 0 is the area awaiting replanting as at 31 March 2007; that is area to be replanted in the 2007 planting season.
Figure 4: Age-class distribution of the radiata pine estate in the Auckland region – large-scale owners as at 1 April 2007
For this scenario the availability of wood from large-scale owners is based on stated harvest intentions for 2005 to 2013, with the volumes for 2014 to 2018 capped at the 2013 level. From 2018 on the availability is constrained to be non-declining with a target rotation age of 30 years. The wood availability of large-scale owners (Figure 5) is forecast to be at a lower level from 2018 to 2026. This is partially a consequence of the relatively small areas planted from 1990 to 1993. However, a more important factor is that a number of large-scale owners will be harvesting less volume from their Auckland region forests during this period and more volume from their forests in the Central North Island region. The reality is that companies manage their total estate without consideration of whether they are in the Auckland or Central North Island regions.
The potentially available volume from the large-scale owners’ estate increases to over 700 000 cubic metres per year from 2029.
Figure 5: Radiata pine availability in the Auckland region under scenario 2 – large-scale owners
Small-scale owners’ estate
The age-class distribution of the small-scale owners’ estate (Figure 6) is very irregular with over 1200 hectares in each of the ages 11 to 15 years (planted in 1992 to 1996) and much less area in all other age-classes. The key issue is how to forecast the availability from this estate. In particular whether the large area in ages 11 to 15 will be harvested:
- at a fixed rotation age (scenario 2);
- spread over many years (scenario 3);
- spread over an intermediate number of years (scenario 4).
Figure 6: Age-class distribution of the radiata pine estate in the Auckland region – small-scale owners only
Combined estate
The wood availability from all owners is presented in Figure 7, with that of large-scale owners being the same as in Figure 5. In this scenario 2, forest in the small-scale owners’ estate is assumed to be harvested at age 30. The fluctuations in the total volume harvested reflect the variation in the age-class distribution of the small-scale owners’ estate.
The large increase in volume from 2022 (Figure 7) occurs when the large areas from the small-scale owners’ estate in young age-classes (11–15) is harvested. For example, the increase in 2022 results from the 1223 hectares planted by small-scale owners in 1992 (age 15 in Figure 6) being harvested at age 30.
Following the 2007 and 2008 harvests, there is limited area of age 30 or older in the small-scale owners’ estate available for harvest in 2009 to 2012.
Figure 7: Radiata pine availability in the Auckland region under scenario 2 – combined estate
Fluctuations in harvest volumes of the magnitude shown in Figure 7 would be impractical because of marketing and logistics realities (immediate availability of logging crews, transport capacity, and wood processing capacity).
Scenario 3 – Non-declining yield (target rotation 30 years)
The third scenario assumes a non-declining yield, with a target rotation age of 30 years. Figure 8 indicates that, when the small-scale owners’ estate is harvested to complement the large-scale owners’ estate, the potential total volume is almost 800 000 cubic metres per year from 2011 and increases to 950 000 cubic metres per year from 2021. An extra constraint was added so the total volume was not allowed to increase by more than 10 percent annually.
This scenario is similar to the base case scenario adopted in the 2000 wood supply forecasts. However it results in the small-scale owners’ estate being harvested at rotation ages that differ markedly from 30 years (Figure 9).
Figure 8: Radiata pine availability in the Auckland region under scenario 3
Figure 9: Average radiata pine clearfell age by ownership category under scenario 3
Scenario 4 – Split non-declining yield (target rotation 30 years)
The fourth scenario (Figure 10) is based on a split non-declining yield with a rotation age of 30 years. This scenario gives a forecast wood availability that is similar to scenario 3 through to 2021. Wood availability increases to 1.07 million cubic metres per year from 2022 before reducing to 0.8 million cubic metres per year from 2037.
The main difference from scenario 3 is that the large area of young stands in the small-scale owners’ estate is assumed to be harvested over a shorter period of time. The total volume was modelled to be non-declining from 2009 to 2034; that is, for 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). As a consequence, the average clearfell age for small-scale owners stays closer to the target of 30 years (Figure 11) than was the case in scenario 3.
Figure 10: Radiata pine availability in the Auckland region under scenario 4
Figure 11: Average radiata pine clearfell age by ownership category under scenario 4
The total volume forecast for scenario 4 is broken down by log grade in figure 12.
Figure 12: Radiata pine availability in the Auckland region under scenario 4, by log product
Scenario 5 – Target rotation age variations
Different wood availability profiles are generated if target rotation age is changed from 30 years to either 28 or 32 years (Figure 13). Because of the limitations imposed by the current age-class distribution and large-scale owners’ stated harvest intentions, it takes some time to achieve separation of average clearfell age (Figure 14).
Figure 13 shows wood availability to be broadly in the range 700 000 to 800 000 cubic metres per year until 2016 with the potential for a subsequent increase to over 1 million cubic metres per year. There is a range of possibilities for timing the increase.
Figure 13: Radiata pine availability in the Auckland region under scenario 5
Figure 14: Average radiata pine clearfell age for each target rotation age under scenario 5
Contact for Enquiries
Policy Adviser
Pastoral House
MAF Policy
PO Box 2526
Wellington 6140
NEW ZEALAND
Fax: +64 4 894 0741
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