Analysis · October 2026
The bulge
Nearly a quarter of New Zealand's planted forest went into the ground in a single decade. Those trees are now old enough to harvest. In some regions, most of them are still standing.
Where it comes from
One decade of planting
In the 1990s New Zealand planted new forest faster than at any other time on record.
Between 1992 and 1998 about 483,000 hectares of new land went into plantation forest, peaking at 98,000 hectares in 1994. Most of it was radiata pine, much of it on steep hill country that came out of pastoral farming after subsidies ended.
Radiata is typically harvested at 26 to 32 years. Those 1990s plantings crossed that line between 2020 and 2026. The chart shows today's forest by the year it was planted. The tall block in the middle is the bulge.
The outline shows the same forest in 2018. Where the bars have shrunk, trees were harvested. Nationally, about 30% of the 1992–98 planting came down between 2018 and 2025. In some regions far less did.
What it tells us
Trees that are ageing, not being cut
When a region harvests its forest on time, the age profile stays roughly level: what comes down gets replanted, and the young classes refill. When harvest stalls, the mature cohort simply moves to the right between surveys, and the young classes behind it thin out.
That is what the explorer below shows for much of the lower North Island and Canterbury. A few reasons are visible in the data:
- Harvest barely pays. Real log prices are near their lowest in more than 30 years, while logging and cartage costs keep rising. On steep ground far from a port, the net return to the owner can be close to nothing.
- Carbon changes the sums. Most forests planted after 1989 are in the Emissions Trading Scheme. Harvesting one means handing back carbon units, so at recent carbon prices many owners are better off leaving the trees standing.
- Crews, trucks and mills are finite. A region cannot suddenly double its harvest.
Why it matters
- A wall of wood that has to go somewhere. Ageing stands do not wait forever. Windthrow, disease and storm damage rise with age, and much of this forest is on erosion-prone land where clear-fell slash has already done serious damage downstream.
- A cliff behind the wall. Thin young age classes mean that once the bulge is harvested, local wood supply falls sharply in the 2030s. MPI's own forecast for the western lower North Island drops by about three-quarters. That matters to every crew, haulier and mill in the region.
- A window for transition. An ageing pine canopy is exactly where a move to permanent native forest can begin. Natives establish in the shelter of the pines, so the land does not have to be clear-felled and left bare. The bulge is the largest pool of land facing that choice at once.
The bulge does not tell anyone what to do with their forest. It shows how much land is arriving at the same decision at the same time, and where.
Explore
The bulge in your district
Pick an area and the survey years to compare. Ages are at 1 April of each survey year. Hatched sections are estimates where MPI keeps the figure confidential.
Compare
Where the bulge is biggest
The bulge index divides the area aged 26–40 by the area aged 1–15. Both span 15 years, so an evenly aged forest scores about 1. A score of 3 means three times as much mature forest as young. Click a row to see it above.
How we measured it
Method and data
Source. The Ministry for Primary Industries' National Exotic Forest Description (NEFD), which records planted forest area by age class for every district each year. We use the 2012, 2014, 2016 and 2018–2025 surveys.
Confidential cells. MPI hides some district figures to protect individual owners. Treating those as empty badly distorts small districts, so we estimate them. Every hidden cell sits under figures MPI does publish: the district's total area and the region's area in that age class (and, for regions, the national figure). We fill the gap so those published totals are met exactly, using iterative proportional fitting, starting from the same forest's area in the previous survey aged forward. When we tested this by hiding figures we already knew, using real patterns of suppression, the estimated bulge index was within 10% of the true value 89% of the time. Treating hidden cells as empty managed that only 39% of the time. Areas that rely heavily on estimates are marked in the table.
Still standing compares the area aged 31–35 in 2025 with the area aged 26–30 in 2020: the same trees, five years on. A value near 100% means almost none were harvested.
Limits. Age records for small woodlots can lag behind harvesting, so in some districts the backlog may be smaller than shown. Regions here follow district boundaries; wood supply regions are MPI's own groupings and are fully published.
Data: bulge-data.json (age classes and index for every area). Analysis by Transition Forestry, October 2026, from MPI NEFD data.
Working through it
Own forest in the bulge?
If you manage ageing pine and are weighing harvest, holding or a move to native forest, we would like to compare notes. We are working through the same decision at Rangitatau.