Oral Submission Presentation by Blake Foster - New Zealand ...

Oral Submission Presentation
by Blake Foster
1. Thanks for the opportunity to give a presentation to the honorable members
of the select committee.
2. My name is Blake Foster; I am the manager of Pukaki Downs Station near
Twizel and a director of Pukaki Forestry Ltd.
3. I am here to share with you how the ETS had given us hope to deal with a
huge environmental problem of wilding contorta pines. But with the crash of
the carbon market this is a fading memory.
4. The present wilding problem on Pukaki Downs was inherited. It is huge and
costs a tremendous amount of money to eradicate and control with no
return on the money spent –a black hole.
5. When we heard of the ETS, we knew that the funds from the ETS carbon
credits would give the capital to finance the clearing of the trees and to fund
re‐engineering the core forest with a non‐spreading hybrid.
6. We initially commissioned a study by Nick ledgard of Scion to identify where
the spread was coming from, where it was going, identify areas of low spread
risk for carbon storage and develop an overall management plan. We then
set about following this plan. (a copy of the plan is attached)
7. A core area of wildings was registered in the ETS and the funds from the sale
of these credits were used to clear the outlier wildings‐approximately 750
hectares outside the core area in the last few years.
8. Last year, Rural Delivery TV show, heard of our innovative way to deal with
the wilding spread by using the ETS funds from Carbon Credits in one area to
control the spread in another. They came and did a segment. Here is the link
to that video segment http://tvnz.co.nz/rural‐delivery/s2011‐e28‐video‐

4454527 Here is a link to the written press release by Rural Delivery about
this video segment
http://www.ruraldelivery.net.nz/2011/10/wilding‐pine‐control/
9. The 15 yr plan is to change or re‐engineer the core wilding spread by clearing
it and replanting with a non‐spreading species. We were going to be clearing
80 hectares a year.
10. Our attempt to clear the contorta wildings is coming to a standstill due
to the Carbon legislation in NZ ETS not supporting the local forestry and
carbon industry by allowing the emitters to buy cheap units from overseas
and not having a regulation like Australia does with 50% cap of buying local.
11. Buying local credits would not only help our current account deficit by
stopping money going overseas to buy cheap credits but bring in tax revenue
locally when local credits are purchased.
12. We were employing up to 50‐60 people directly or indirectly‐clearing
gangs, planters and nurseryman transport operators. This has now virtually
stopped. Planting programs are long term commitments of at least two years
13. Some may say this is just market correction and that the goverment
shouldn’t get involved. The government has already intervened by giving the
emitters a two for one deal. The emitters have been given 90% of the units
and now only have to pay 5% of the 10 they were to buy. The emitters can
buy the cheapest credits possible. We are asking that the NZ Carbon forest
industry needs to be stabilized. This can be done very simply by aligning
ourselves with the Australian system.
14. I request the committee to seriously look at aligning the NZETS with
the Australian system by having a 50% cap on international units and 12.5%
CERs.
15. If wildings are entered into the ETS with a proper management plan
this should be seen as positive.

16. The responsibility the NZ carbon market is in your hands. If there is not
a change soon there won’t be a carbon market in NZ.

CLIENT REPORT (Confidential)
Wilding conifer spread on Pukaki Downs station:
origin, future spread risks and management options
Contorta pine wildings invading terrace country on Pukaki Downs station, with Lake Pukaki behind – taken in 2008.

REPORT TITLE
AUTHORS
CLIENT
CLIENT CONTRACT
NO:
FRST CONTRACT
NO:
SIDNEY OUTPUT
NUMBER
SIGNED OFF BY
DATE
CONFIDENTIALITY
REQUIREMENT
INTELLECTUAL
PROPERTY
REPORT INFORMATION SHEET
WILDING PINE MANAGEMENT ON PUKAKI DOWNS
NICK LEDGARD, SCION
PUKAKI TOURISM HOLDINGS LTD
QUIKTRAK NUMBER QT-1372
NONE
MAY 18, 2010
CONFIDENTIAL (FOR CLIENT USE ONLY)
MICHAEL WATT, PROJECT LEADER, WEEDS
© NEW ZEALAND FOREST RESEARCH INSTITUTE LIMITED
ALL RIGHTS RESERVED. UNLESS PERMITTED BY CONTRACT OR LAW,
NO PART OF THIS WORK MAY BE REPRODUCED, STORED OR COPIED
IN ANY FORM OR BY ANY MEANS WITHOUT THE EXPRESS PERMISSION
OF THE NEW ZEALAND FOREST RESEARCH INSTITUTE
LIMITED (TRADING AS SCION).
Disclaimer
The information and opinions provided in the Report have been prepared for the Client and its specified
purposes. Accordingly, any person other than the Client uses the information and opinions in this report
entirely at its own risk. The Report has been provided in good faith and on the basis that reasonable
endeavours have been made to be accurate and not misleading and to exercise reasonable care, skill
and judgment in providing such information and opinions.
Neither Scion, nor any of its employees, officers, contractors, agents or other persons acting on its behalf
or under its control accepts any responsibility or liability in respect of any information or opinions provided
in this Report.

EXECUTIVE SUMMARY
The problem
Wilding conifers have been invading Pukaki Downs station since the early 1960s . Initially, invasion was
restricted to a short section of the lakeshore by the Homestead, but more extensive invasion started to
take hold in the late 1980s / early 1990s. The main spreading species is Lodgepole or contorta pine
(Pinus contorta), the country’s most vigorous spreading conifer. At the present time, wildings are
approaching canopy closure over approximately 30-40% of the station, with much of the remaining area
affected by widely scattered outlier trees (often accompanied by patches of fringe spread). If left
unmanaged, wildings would dominate the majority of Pukaki Downs. Hence, the owners are attempting
to manage the spread by containment within the areas least likely to spread further, and removal of
wildings from areas with higher risk of distant spread.
Client Initiative
In April, 2010, Nick Ledgard (NL) of Scion in Christchurch was asked by Blake Foster of Pukaki Tourism
Holdings Ltd to carry out a field inspection and write a report on the wilding conifer situation and
management options on Pukaki Downs station. NL visited the station from May 30 – June 2, 2010, after
which he wrote this report.
The project
The major objectives of this report are to describe:
a) the history of conifer spread, its origin and present location
b) the likely future spread risk and pattern if left unmanaged
c) priority control areas for minimising spread risk beyond present locations (particularly off-station)
d) options for containing conifers within the managed areas.
e) areas with least spread risk which could be managed for carbon storage.
Key Findings
o The wilding conifer problem along the south-western shores of Lake Pukaki is well
known, situated alongside a major tourist route (SH80). Unfortunately, it involves
the most spread-prone conifer species, contorta pine.
o Wildings have been spreading since the 1960s, but the area obviously affected
has only increased significantly in the last 15 years. This has been largely
triggered by spread from the lake-shore plantings carried out after the lake was
raised in the early 1970s, although most of the contorta forests in the southeastern
portion of Pukaki Downs originate from trees present before that time.
o The pattern of spread likely in the future is well indicated by the pattern of spread
over the last few decades. These show that spread is mainly to the south, driven
by the prevailing strong northerly winds, but that occasionally a more northeasterly
wind can pick up and carry seed high into the air and more to the west.
o Such an event in the early 1990s gave rise to outlier wildings in the upper Twizel
river catchment, which were allowed to mature and cone before they were
removed in the mid 2000s, giving rise to the islands of fringe spread so obvious
today.
o The ‘one-off’ nature of this spread event indicates that once the Twizel river flats
are cleared, they should not be re-invaded often and hence should not be too
difficult to keep clear in the future – as long as any wilding trees which do establish
are removed before age 5-6, when they begin coning.
o This ‘stitch-in-time-saves-nine’ maxim must always be kept foremost in any
management plan.
o Within the wilding cleared zones, a containment area of trees will remain.
o Removal sweeps outside the containment area will be needed at least every 4
years for as long as seeding contorta pine trees remain in the locality.
o The incidence of re-invasion, and need for timely removal, should be diminished by
the control and containment management options recommended below.
(i)

Recommendations
On Pukaki Downs it is recommended that:
• All wildings be removed in the near future from the upper Twizel river catchment
(blocks 25-29), except in the most densely forested areas in the eastern margin of
that area (blocks 9-13 plus 19).
• All wildings should also be removed from block 29, although planting it with a less
spread-prone species is an option.
• All wildings be removed from the steep slopes of the Rhoboro Range in the most
north-western part of the station (block 30).
• All wildings be removed in a 20m strip along the northern boundary with Ferintosh
station and in a similar strip alongside SH80.
• If finances allow (last priority) all wildings be removed from the steeper eastern
scarp slopes (northern portion) of the Little Rhoboro Hills (block 20 and steeper part
of 14).
• Improved pasture and associated grazing (and/or arable cropping) be maintained
where it is currently stopping wilding establishment - blocks 31 and 32 (both sides of
SH80) and further to the west in parts of block 25). The north-eastern margin of
block 31 would run out from the northern margin of DOC’s Dusky Reserve in order
to maintain a treeless pasture margin.
• Replacement plantings of less spread-prone species, such as radiata pine, its
hybrid with Knobcone pine (P.radiata x P. attenuata) or ponderosa pine, be carried
out along the eastern margins of the cleared areas in the upper Twizel river valley,
either as 4-row marginal plantings along the western edges of blocks 9, 12, 13 and
19 (if retained in contorta pine), or as whole block replacement.
• Replacement plantings of less spread-prone species, such as radiata pine, its
hybrid with Knobcone pine (P.radiata x P. attenuata) or ponderosa pine (minimum
of 4 rows), could also be carried out along the western margins of the lakeshore
contorta pine forests in the south-eastern part of block 32. This will not be
necessary where ponderosa or Corsican pine make up the current margin, or where
adjacent pasture cover and grazing pressure is sufficient to stop significant
establishment of wildings.
• Replacement plantings or fertilising be carried out in the 20m marginal strips along
the Ferintosh boundary (top of blocks 16 and 24) and alongside SH80.
• Marginal strips (4 rows wide) be planted along the fenced north and western
margins of the tree-less pasture-dominated block 31.
• Blocks 9-24 (the pink and pink-striped areas on the map), including the corridor
north of the Dusky Reserve between blocks 21 / 16 and 17 / 22 – 23, will become
the containment area and could be managed for carbon storage. Initially, the
dominant species would be contorta pine, but over time the aim should be to
replace these with less spread-prone species.
• Wilding removal sweeps be carried out before coning age (no more than 4 years
apart) on all cleared or otherwise tree-less areas.
• Long-term planning be initiated to ensure that the above to be implemented.
ii

Table of Contents
Wilding spread on Pukaki Downs station:
Origin, future spread risks and management options
Nick Ledgard
Scion
PO Box 29237, Fendalton, Christchurch 8540
June, 2010
EXECUTIVE SUMMARY -----------------------------------------------------------------------------------i
Project and client ------------------------------------------------------------------------------------------1
Introduction --------------------------------------------------------------------------------------------------1
Objectives ----------------------------------------------------------------------------------------------------1
Methods -------------------------------------------------------------------------------------------------------2
Main findings ------------------------------------------------------------------------------------------------2
Spreading species----------------------------------------------------------------------------------------2
History of wilding spread--------------------------------------------------------------------------------3
Likely future spread with no further management------------------------------------------------6
Priority control areas for minimising spread risk beyond present locations (particularly
off-station) --------------------------------------------------------------------------------------------------7
Options for containing conifers within managed areas --------------------------------------- 10
Assisting containment on Pukaki Downs. -------------------------------------------------------- 11
Areas for C storage management------------------------------------------------------------------ 12
Discussion ------------------------------------------------------------------------------------------------- 12
Recommendations -------------------------------------------------------------------------------------- 13
Acknowledgement--------------------------------------------------------------------------------------- 14

Project and client
In April, 2010, Nick Ledgard (NL) of Scion in Christchurch was asked by Blake Foster of
Pukaki Tourism Holdings Ltd to carry out a field inspection and write a report on the
wilding conifer situation and management options on Pukaki Downs station. NL visited
the station from May 30 – June 2, 2010, after which he wrote this report.
Introduction
Wilding conifers have been invading Pukaki Downs station since the early 1960s .
Initially, invasion was restricted to a short section of the lakeshore by the Homestead, but
more extensive invasion started to take hold in the late 1980s / early 1990s. The main
spreading species is Lodgepole or contorta pine (Pinus contorta), the country’s most
vigorous spreading conifer. At the present time, wildings are approaching canopy closure
over approximately 30-40% of the station, with much of the remaining area affected by
widely scattered outlier trees (often accompanied by patches of fringe spread). If left
unmanaged, wildings would dominate the majority of Pukaki Downs. Hence, the owners
are attempting to manage the spread by containment within the areas least likely to
spread further, and removal of wildings from areas with higher risk of distant spread.
Authors credentials
• Nick Ledgard obtained a BSc (Botany) from Auckland, and an MSc
(Forestry) from Bangor College of the University of Wales.
• He has been employed as a scientist with Scion since 1971. His specialist
research area is in production and protection forestry in the South Island hill
and high country.
• Since the early 1980s, he has carried out a number of research projects on
conifer natural regeneration or wilding spread. Refereed papers on this
topic have been published both locally and overseas. From 2006 to the
present day he has managed a wilding project for the South Island (now the
New Zealand) Wilding Conifer Management group.
• He has given numerous presentations, and organised many workshops and
field-days on wilding spread issues, and written twenty contract reports on
the topic. Most of these have dealt with local histories of wilding spread, the
current situation and future management options.
• He privately manages 380 ha of wilding Corsican pines (near L. Coleridge)
for environmental (including spread control) and production objectives.
Objectives
The major objectives of the report are to describe:
1. The history of conifer spread, its origin and present location.
2. The likely future spread risk and pattern if left unmanaged.
3. Priority control areas for minimising spread risk beyond present locations
(particularly off-station).
4. Options for containing conifers within the managed areas.
5. Areas with least spread risk which could be managed for carbon storage.
1

Methods
A total of 2.5 days were spent on Pukaki Downs station and in the surrounding area (May 31 –
June 2, 2010). Most of this time was spent in the company of Blake Foster of Pukaki Downs
station. A short time was also spent talking to Gill Seymour of Ferintosh station, and Peter
Willemse and Neil Bolton of the Department of Conservation, Twizel. In addition, NL has been
familiar with the wilding situation on Pukaki Downs and within the Mackenzie Basin since the
1970s, and has studied and written reports on the topic.
Useful documents and other material consulted were:
• Department of Lands and Survey, 1985: Trees planted in association with
power development in the mid and upper Waitaki 1958-1984. Technical
Report Series No 1, Department of Lands and Survey, Dunedin. Copy held
by Alexander Turnbull Library, Wellington.
• Maps and aerial photos supplied by Pukaki Downs station and Carbon Farm
Ltd.
• Photos supplied by Pukaki Downs station and from NL’s collection.
• Ledgard, N.J.; Baker, G.C 1997: Management options for introduced trees
on Ruataniwha Farm, around lakes Tekapo, Pukaki and Ruataniwha and
within the Tekapo, Pukaki and Ohau rivers. Contract report for Bob Lysaght,
Crown Property Services, Land Information NZ, Christchurch
• Ledgard, N.J. 2004: Wilding conifers – New Zealand history and research
background. In Hill, R.l.; Zydenbos, S.M.; Bezar, C.M. (Eds) “Managing
wilding conifers in New Zealand – present and future”. Proceedings of a
workshop held in conjunction with the annual general meeting of the NZ Plant
Protection Society in Christchurch on August 11, 2003. ISBN 0-478-10842-7
Published by NZPPS: 1-25
Main findings
Spreading species
The major conifer species spreading on Pukaki Downs are given in Table 1. By far the most
dominant species is contorta pine. Unfortunately, this is the most spread-prone conifer in New
Zealand, with the lightest seed – which can be disseminated the greatest distances.
Table 1. Major spreading species on Pukaki Downs
Common
name
Latin Name Wilding seed source Comments
Lodgepole or Pinus contorta 1. Trees ‘mistakenly’ planted The most spread-prone species in NZ,
contorta pine
on the shores of L. Pukaki in and by far the major spreading species
the 1970s. 2. Spread from (99%) on Pukaki Downs. Usually first
farm homestead plantings
now under the lake
coning around age 5-6
European larch Larix decidua 1970s lake-shore trees – plus Mostly associated with widely
the earliest arrivals possibly scattered outlier wildings, a number of
by seed from old stand near which now have fringe spread.
mouth of Whale Stream Spreading from age 15
Douglas-fir Pseudotsuga Mostly from lake-shore trees Most wildings under age 12 and still
menziesii
planted in the 1970s – plus close to lakeside seed source. Likely
some from earlier farm to become much more frequent in the
plantings
future. Coning from age 8-10.
Corsican pine Pinus nigra Lake-shore trees associated Surprisingly few wildings west of
with early homestead
SH80 (oldest seen aged 20). A shy
plantings
coner before age 20.
Scots pine Pinus sylvestris Short shelterbelt by yards – Only localised spread, mainly to south.
planted in 1970s
Coning from age 10+
Ponderosa pine Pinus ponderosa Shelterbelt by yards, plus A little localised spread. Coning from
homestead trees – planted in
1970s
age 12+. Not a major threat.
Radiata pine Pinus radiata Homestead plantings, plus a Very few wildings seen. Coning from
few old trees by Dusky site age 10+. Not a major threat.
2

History of wilding spread
Pre 1970s. Very few trees were present on Pukaki Downs station before the 1970s.
From photos taken prior to that time and talks with local people, it appears that small
areas of trees (nearly all introduced conifers) were present around the early lake-side
station homesteads at Dusky, Mackenzie Peaks, and Pukaki Downs. Most of these trees
were submerged when L. Pukaki was raised in the early 1970s. On the area presently
occupied by Pukaki Downs station, Lodgepole or contorta pine (Pinus contorta) and
Corsican pine (P. nigra) must have been growing somewhere at or between Mackenzie
Peaks and Pukaki Downs stations, as both species were present as wildings alongside
the shores of the lake after it was raised. A plot established by NL in the contorta pine in
1983 contained trees aged 22. Five kilometres to the west on the Twizel River flats, the
only current evidence of ‘early’ introduced trees are three felled contorta pine by the
musterer’s hut at the junction of Gladstone Stream and the Twizel river. One tree was
aged at 50 years old when felled in the early 2000s.
To the north, on the present Ferintosh station, there were radiata pine (P. radiata),
European larch (Larix decidua) and Douglas fir (Pseudotsuga menziesii) present when the
lake was raised. All three species were probably planted, but larch was moving down the
lake shore (G. Seymour, pers comm.), most likely establishing from seed from trees
planted possibly over 100 years ago, just north of the Ferintosh homestead by the mouth
of Whale Stream.
To the south on Rhoborough Downs, a plantation of Douglas-fir was present
alongside the lake just north of the current dam site. The upper-most parts of this
remained above the lake (aged at 27 years in 1983 – NL plots), from which spread has
occurred since. Also on Rhoborough Downs and close to the Pukaki Downs boundary
was a stand of Corsican and ponderosa pine and European larch planted by a water
reservoir around the 1960s. These have also spread to the south since (but not nearly as
vigorously as the contorta pine), and no evidence was seen that they have spread north
onto Pukaki Downs (lack of Corsican pine wildings near boundary).
1970s. With the raising of the lake, began a period of lakeshore tree establishment
by the Ministry of Works and Development (MOWD). The trees were planted to slow
erosion of the newly formed lakeshore banks and also for ‘amenity’ purposes. The first
recording of ‘Pukaki’ planting was in 1970, with the first mention of Pukaki Downs in 1972.
The 1985 Dept of Lands and Survey report on the MOWD plantings records that 10,500
‘Pinus species (mixed)’ were planted on Pukaki Downs in 1977. This planting went on
into the early 1980s (completed in 1983). Virtually all these trees were established
between the highway (SH80) and the lakeshore, from Jack Steel Stream to just north of
Boundary Stream, on land which is now administered by Land Information New Zealand
(LINZ). One exception was some shelterbelt trees planted further south on the western
side of the road, close to the current Pukaki Downs yards. The main species present
there are Corsican, ponderosa, Scots (Pinus sylvestris) and Big Cone pine (P. coulteri),
but mixed in with these is a small component of contorta pine.
The MOWD plantings on LINZ land involved a wide range of species, often planted
as individuals or small groups, but also including larger plantations (a few hectares) of
larch, Douglas-fir and Big Cone pine, established in the early 1980s. About this time,
there were additional amenity tree plantings of widely spaced deciduous trees, such as
oak (Quercus spp), ash (Fraxinus spp) and rowan Sorbus spp).
In the MOWD report, the last mention of contorta pine was in 1965. This was at the
time when there was some publicity about the spreading tendency of this species,
especially in the Central Plateau area of the North Island. Consequently, it was resolved
that there should be no more planting of this species in the upper Waitaki catchment.
However, there is strong circumstantial evidence that there was a ‘contaminant’ of
contorta pine in the mixed conifer species which were supplied for planting in the 1970s.
These probably explain the 35-year-old contorta trees which are still growing between the
highway and the lake - seen by NL between Big Rock Stream and the old Dusky
3

homestead trees (but they were also present further north on the lake shore – removed
some years ago – G. Seymour, pers comm).
It is very likely that most of the contorta wildings currently on Ferintosh and the
northern half of Pukaki Downs originated from the ‘mistake’ plantings established on
‘LINZ’ land by the lake shore in the mid 1970s . The contorta wildings on the southern
half of Pukaki Downs most probably established from seed blown from the older and
much denser lake-side stands of contorta pine growing closer to the homestead – along
the eastern lakeshore margins of block 32.
1980s. Apart from fringe spread alongside the wilding forests by the eastern
lakeshore margins of block 32 (in the south-eastern part of Pukaki Downs), wilding trees
in the 1980s would not have been very apparent to those not deliberately looking for them.
One has to look fairly hard at 1986 aerial photographs to see evidence of wildings.
Although the older lake-side forests close to the homestead are obvious, 10-year old
plantations on LINZ land north of the northern boundary can only just be seen. Just a
kilometre or so further north again, a closer inspection of the photo reveals scattered trees
(most likely contorta pine) along the lakeshore south of Big Rock Stream, plus a few
outlier trees with small downwind (S side) areas of fringe spread at the top of blocks 16
and 24. Even closer inspection can just detect the odd lone tree in the northern parts of
the middle terrace flats, the most obvious of the larger ones looking like larch – both on
the flats and the steep scarp slope running up onto the Little Rhoboro Hills.
1990s. During this decade, the major battles with wilding spread were waged in the
south eastern part of the property (block 32) along the western margins of the lakeshore
wilding forests – although higher sheep numbers meant that there was not much new
recruitment of wildings at that time. Plantings of less spread-prone ponderosa and
Douglas-fir were carried out along these forest margins, probably in order to restrict this
fringe spread. It appears that during the 1980s and 90s some seed from these contorta
stands blew over SH80 in a south-westerly direction to give rise to the denser wilding
stands in blocks 9 and 10, west of the airstrip, not far above the Rhoboro Downs
boundary.
Elsewhere on the station, wilding trees were still not obvious - an NL slide (from the
air) of the Big Rock Creek stream area (top of blocks 16 and 24) taken in 1990, shows
very few conifers – although two have discernable fringe spread. However, it was in this
decade that the foundations were laid for the later major advance of wildings elsewhere
on the property. Many of the older scattered trees which were seen (and found felled) all
over Pukaki Downs, particularly in the north and western parts (and out onto neighbouring
DOC land) can be aged back to an arrival date around 15-20 years ago – indicating that
they arrived in the early 1990s. Even though they would have been present as small
seedlings, there is no sign of these trees in an NL slide taken in the Twizel catchment in
1993, when the present owner was showing the area to forest company representatives
looking for afforestation opportunities. As stated above, all the evidence points to these
outlier wildings having established from seed disseminated from the MOWD lakeside
contorta ‘mistake’ plantings established in the early/mid 1970s. The fact that they are
widely scattered out to a distance of 10kms indicates that the seed was lifted high before
dropping in a widely scattered ‘salt and pepper-like’ distribution. The wind carrying the
seed must have had more of a north-easterly flow than usual, as some were carried right
‘around the corner’ of the Rhoboro Hills (over the Little Rhoboro Hills ridge) and up into
the junction area of the Duncan and Mackenzie Streams (the topmost tributaries of the
Twizel River). Such a wind-flow pattern is different from the normal prevailing nor-west
winds (see ‘2000s on’ below). It is these trees which have given arise to the very obvious
‘islands’ of fringe spread (often between 500 – 1000 m 2 in size), currently aged around 5-6
years old (and just starting to cone). The majority of the scattered outlier parent wilding
trees were removed between 2004-2008, but not before they had produced viable seed
and initiated the present islands of 5-6 year olds. In the upper Twizel river area there is
one major exception to the wilding origin being the Lake Pukaki shoreline plantings. This
4

is by the musterer’s hut at the mouth of Gladstone Stream (block 26), where a few
contorta trees were planted over 50 years ago. They were felled in the early 2000s (the
oldest at age 50), but by then they had parented an area of fairly dense wildings over
some hectares to the south. Many of these had been allowed to reach coning age before
they were felled.
2000s. The most obvious increase in wilding numbers on Pukaki Downs has taken
place since 2000. This is largely due to progeny of the outliers which arrived in the early
1990s becoming very obvious – mostly as fringe spread ‘islands’ but also in the form of
same-aged outliers beyond the ‘island’ borders. An NL slide of the Little Rhoboro Hills
east-facing scarp slopes (block 14) taken in 2003 shows the first of the larger fringespread
‘islands’ starting to become very obvious. The direction of spread of the fringe
wildings out from their parent trees strongly indicates a wind-flow pattern from the north.
On Pukaki Downs, there are two origins of this northerly wind – one from down the lake
and the other, on the western side of the Rhoboro Hills, from the Twizel river headwaters.
Spread in the upper Twizel river catchment is generally north to south, but on the western
side and on top of the Little Rhoboro Hills ridge it has more of a south-easterly flow as the
taller Rhoboro Range mountains to the north drop sufficiently to allow an eddy of wind to
the east. Along the ridge of the Little Rhoboro Hills, the Twizel River and lake wind flows
meet and move together to the south.
Age classes of wilding conifers. A feature of wilding spread on Pukaki Downs
and Ferintosh is the uniformity of wilding ages. The commonest age is 5-6 years – trees
which are progeny of the outliers which arrived in the early 1990s. The uniformity of tree
age is particularly striking where relatively closely-spaced parent trees were felled, often
when they were 10-12 years old. This ‘flush’ of new wildings which appears to occur after
parent-tree felling, has been observed on Pukaki Downs (and elsewhere) for some time.
The reason for this ‘flush’ is not clear. As contorta can first start to cone at age 5-6 years
of age, and there are many of this age-class present, there is obviously a great risk of a
new wave of wildings appearing in the near future – although the viability of seed
produced before age 10 is thought to be lower than when the trees are more mature.
Coning age. A summary of age of significant coning per species is given in Table
1. A small minority of trees will always start coning earlier. However, there is strong
suspicion that the earliest produced seed does not have as high viability as seed
produced later. Work is underway to confirm this. It is also known that the first obvious
appearance of wildings often occurs quite a few years after the first seed is produced. For
instance, on Pukaki Downs it seems that significant numbers of wilding contorta do not
appear much before age 10, even though cones are often produced from age 5-6.
Prevailing wind flows. As explained above, the direction of wilding appearance
out from a parent tree indicates the direction of the most common seed dispersing winds.
On Pukaki Downs these winds blow from the north. They are also the warmest, which is
important for wilding spread, as the cones open in warm conditions. As the Rhoboro Hills
are oriented north-south, the wind blows down both sides of the range, with the Twizel
river flow diverting more to the east before joining the lakeside flow over the Little Rhoboro
Hills and heading on south. Even though there is strong evidence for this wind flow
pattern, there is also evidence that the occasional strong winds can blow more from the
north east. Such a wind was responsible for the major spread event in the early 1990s,
which disseminated seed from the lakeshore parents to establish widely separated lone
wildings in and around the upper Twizel river flats
Frequency of spread events. The age of wilding trees enables any observer to
obtain a good estimate of when the seed arrived. However, in addition to the winds
needed to disseminate seed to a suitable site, successful seed germination and seedling
establishment requires a growing season without extremes of moisture stress and
5

temperature or unseasonal frosts, as well as light grazing/browsing pressure (from both
domestic and wild animals). The evidence from many wilding spread areas throughout
New Zealand is that this set of circumstances do not happen nearly as frequently as many
people think - as wildings often appear in uniform age classes separated by many years.
This is the case at Pukaki Downs. Even though the major seed source beside the lake
has been producing contorta pine seed since the early 1980s, there appears to have been
just one event (in the early 1990s) which allowed wildings to become established out to 10
km to the west (on the Twizel river flats). There is no certainty when such events will
occur, but time and again this author has seen them happening between 15-20 years
apart, sometimes earlier if contorta pine is involved.
Susceptibility of land to wilding establishment. Wilding conifers establish most
readily on lightly vegetated and lightly grazed land. They are least likely to establish
where the vegetation cover is thick (herbaceous and woody) and/or where animal grazing
is medium to heavy. Rabbit numbers can have a major negative effect on wilding
establishment, and in the high country the arrival of rabbit haemorrhagic disease in 1997
heralded a significant rise in seedling numbers. However, sheep have been the main
grazing influence on Pukaki Downs. Even a low stocking pressure of around 0.5 stock
units per hectare will significantly decrease wilding establishment, but only while the seed
rain is light and infrequent. Once the seed rain becomes heavy, higher animal stocking
rates are required to prevent seedling establishment – they are especially difficult to
remove with grazing once they become woody (usually at 2 years of age).
Herbaceous growth following conifer felling. In the high country it is well known
that after the felling of conifers, the growth of herbaceous species (particularly grasses)
within the ‘carcass’ of the felled tree can be vigorous - as long as the slash is not too thick,
preventing light from reaching the ground surface. This increase in vigour is due to a
‘flush’ of nutrients released from decaying needles and bark, combined with the sheltered
microclimate created by the slash. The resulting vigorous grass growth can prevent the
establishment of a new crop of wildings (or any woody species for that matter) for a
number of years. And as conifer seed does not remain viable in the ground for more than
a few years, the opportunity for wilding reinvasion can be lost – as long as there is no new
outside seed source available when the grass vigour declines.
Likely future spread with no further management
Understandably, the incidence of wilding spread on Pukaki Downs would increase
significantly if no further control was exercised.
Relative to this three points deserve further mentioned:
• Role of more intensive land use. Wildings will always have trouble
establishing in the presence of improved pasture and/or higher stock
grazing pressures. Although Pukaki Downs does not lend itself to
large-scale pasture improvement, such areas do exist, the main one
being in the southern mid and eastern zones (blocks 31 and 32), with
a smaller area of thicker pasture swards on flat land to the west on the
Twizel river flats (southern end of block 25). Parts of these areas are
being worked up for an arable crop. These wilding-free areas can only
be maintained if the more intensive management is continued, even if
it may not be as cost-effective today to maintain the higher grazing
levels of the past. It should also be noted that as seed rains get
heavier (from higher seed production of adjacent trees) the likelihood
of wilding invasion of less susceptible land increases.
• Most susceptible land. The most susceptible land for further invasion
is the western half of the property - that draining into the upper Twizel
river catchment (blocks 25 to 29). This is the largest area with the
6

most depleted existing cover and it has very low grazing pressure
(mostly none) – plus there is good scattering of young wildings just
approaching the age of serious coning.
• Phases of spread. Even though wilding numbers will increase in an
unmanaged situation, there is likely to be a ‘lull’ in the invasion rate
during the next few years. This is due to many of the coning outlier
trees (which arrived in the early 1990s and gave rise to the present
islands of fringe spread) having been removed, and their progeny still
having a few years to reach the age of significant coning. In addition,
the occurrence of ‘outlier’ invasions (from distant seed sources) is not
frequent, so it may well be some years before there are new wildings
appearing from that source.
The dominant spreading species will remain contorta pine, but there is likely to be an
increase in the numbers of Douglas-fir. The spreading vigour of this species has
increased significantly over the last couple of decades, probably due to the more
widespread occurrence of the symbiotic mycorrhizas which are so important for early
seedling survival and growth. In addition, it has a light seed which is borne in cones which
hang from the ends of branches, well displayed for the dispersal of seed by passing
winds. At present there are many mature Douglas-fir trees between SH80 and the lake,
and those already on Pukaki Downs are into their early years of seed production.
Priority control areas for minimising spread risk beyond present
locations (particularly off-station)
Boundary risks
Looking at the north, east, south and western boundaries of Pukaki Downs, the risk of
spread off-station varies from virtually zero to high.
• Northern boundary. This boundary is a long and irregular one,
stretching over 8 kilometers and bounding with Ferintosh station to the
east and DOC to the west. With the strongest prevailing winds coming
from the north down either side of the Rhoboro Range, the risk of seed
dissemination in that direction is generally low. This is supported by
fringe spread around older trees in the area all being to the south.
Having stated as much, the boundary does run from north-east to
south-west, and the spread event of the early 1990s (see above) has
shown that seed can be disseminated to the west – although
infrequently. In addition, there are coning contorta pine high up (to
900m asl) on the Rhoboro Range slopes in the northern most corner
of Pukaki Downs (block 30) which could quite easily throw seed to the
south-east over the Range onto DOC land in the upper Twizel river
catchment - where the low vegetation cover and zero grazing pressure
allows for ready wilding establishment. The middle third of this
northern boundary (top of block 29) has a few young wildings on the
Pukaki side, while the western third (top of blocks 25 and 28) has even
fewer, so as long as they are removed in the near future before
serious coning begins, the risk of spread will remain low.
A higher risk is present in the eastern third of the boundary (with
Ferintosh – top of blocks 16, 23 and 24), as it has spread-prone
species (contorta and Douglas-fir) right up to the fenced margin, and
there is evidence elsewhere on the station of some small movements
of seed to the north. For example, near the southern Pukaki Downs
boundary by the yards (southern end of block 31) Scots and
ponderosa pine wildings can be found out to a few hundred meters (at
7

most) to the north of a shelterbelt of those species. Therefore, some
seed may well fall to the north of the eastern section of the northern
boundary, but while seeding trees are growing nearby on Ferintosh
station (and presently there are many), they remain the most likely
origin of any new wildings which may appear.
• Eastern boundary. Apart from spread onto the road margin, which is
regularly controlled by contract spraying from the highway (SH80), the
risk of future spread here is very low. This is due to the presence of
the lake and the fact that much of the ‘LINZ’ land between the highway
and the lake is already well covered with forests. Even if these forests
are removed, the likelihood of reinvasion will not be high (due to heavy
branch slash and/or vigorous grass invasion) – unless there is
significant ground disturbance exposing large tracts of mineral soil.
• Southern boundary. Even though the prevailing wind flow is from
north to south, and there are mature seeding conifers just inside the
Pukaki Downs boundary, the risk of spread along the eastern section
of this boundary with Rhoboro Downs station (south ends of blocks 9
and 31) is low. This is because there is already closed-canopy forest
immediately over the boundary on Rhoboro Downs. However, it is
quite a different story along the western section of this boundary
(south end of blocks 25 and 26), where there are virtually no trees on
either side of the fenceline, and both the vegetation cover and grazing
pressure over on Rhoboro Downs is light. In the middle section of this
stretch, there is a high risk of spread to the south-west, from mature
coning contorta pine in block 9. Further to the west, along the
remainder of the southern fenceline (south end of blocks 25 and 26),
although the land is very susceptible to wilding invasion, there is a low
current risk, as no wildings are present close to the boundary and
seed spread from more distant sources to the north are infrequent.
However, the risk situation will change if conifers are allowed to seed
close to the boundary.
• Western boundary. Virtually all of this (blocks 26 to 28) bounds onto
DOC land. The vegetation cover is light and the grazing level zero, so
although the prevailing winds are more north-south than east-west,
there is a risk of spread in this direction. However, this risk of spread
from Pukaki Downs will remain low as long as the present scattering of
contorta (mostly present as fringe-spread ‘islands’) is removed soon
ie., not allowed to mature to significant coning age.
Priority control (wilding removal) areas
Based on the boundary risks outlined above, the major areas for control within Pukaki
Downs in order of priority removal (see map) would be:
• The upper Twizel river catchment - blocks 25-29. As explained
above, this area is not subjected to regular arrivals of conifer seed
from elsewhere. In addition, currently there are no mature trees
present. However, many of the ‘islands’ of spread have trees just
starting to cone, and unless these are removed in the very near
future, there is a high likelihood of much wider invasion.
Means of removal. Local DOC staff (based in Twizel) are very
experienced in wilding removal options and should be consulted
on this score. They are intending to use herbicides for much of the
removal of the same type of wildings on their land. If herbicides
are not favoured on Pukaki Downs, then the most obvious options
are mechanical or physical removal. Burning is not recommended,
due to the small size of the spread ‘islands’ and risk of the fire
spreading elsewhere. Mechanical mulching has been used
8

successfully on small trees close to the Musterer’s hut, but this
would be difficult to repeat successfully on boggy and/or uneven
ground. In addition, in order to remove all green branches at
ground level, mulching must be deep, and this can expose mineral
soil, which invites the reinvasion of conifers from residual seed
(although a tracked digger working a mulcher head would cause
less soil disturbance). Of the physical options, that using scrubbars
would probably be the most cost-effective, although
chainsaws would be more suitable for the isolated trees,
particularly those in thick tussock.
• The NW corner – eastern slopes of Rhoboro Range (block 30). As
explained above, many of the trees in this area are coning and located
on high altitude exposed sites. Hence, there is a high risk of seed
being blown west and south onto DOC land.
Means of removal. If aerial herbicides are not to be used, the only
option is physical removal. The land is too steep for machines.
Local DOC should be consulted on the most cost-effective
technique and operators for physical removal.
• A strip along the Ferintosh boundary (top of blocks 16, 17 & 24).
Although the risk of seed dissemination north (from Pukaki Downs
onto Ferintosh) is not high and unlikely to go far, the clearance of a
20m wide strip is recommended – as much for ‘good neighbour’
reasons as anything else. Where trees are dense, the resulting thick
branch slash and vigorous grass regrowth after felling should mean
that new invasion of wildings will be light for a number of years. There
are the options of promoting this herbaceous grass growth by
oversowing seed and adding fertilisers, or of preventing wilding
reinvasion by planting a less spread-prone tree species (see
containment options below).
Means of removal. If aerial herbicides are not to be used, the only
option is physical removal. Much of the land is too steep and
uneven for machines, plus many of the trees are large – although
a tracked digger working a mulcher head, could do a good job.
Local DOC should be consulted on the most cost-effective
technique and operators for physical removal.
• Blocks 13 and northern half of 19. These are low priority, as they
are close to the thicker and more mature contorta wildings in block 11
and the southern half of block 19 ( and hence more susceptible to the
arrival of new seed). However, with the prevailing strong winds from
the north, the risks of re-invasion from outside seed sources are lower
than further to the south and east. Although there are considerable
numbers of wildings currently present, most are small and only just
starting to cone. If the area was to be cleared of wildings, their
replacement with a less-spread-prone woody cover is recommended –
due to the higher risk of reinvasion by seed from the adjacent contorta
stands to the east.
Means of removal. If aerial herbicides are not to be used, the main
other option is physical removal. Much of the land is probably too
uneven for machines, although a tracked digger working a mulcher
head, could do a good job on the patches of dense trees. Local
DOC should be consulted on the most cost-effective technique and
operators for physical removal.
• Eastern scarp slopes of Little Rhoboro Hills (block 20 and the
steeper parts of block 14). This area is the last priority for control.
As explained above, even though they are relatively exposed and can
be subject to strong winds, the evidence is that most seed is blown
9

south to remain within Pukaki Downs. Movement to the west is
restricted by winds coming down the Twizel valley and eddying east
around the end of the Rhoboro Range. In addition, most of these
scarp slopes now have a dense cover of wildings, which would be
both expensive to remove and to retain free of trees.
Means of removal. If aerial herbicides are not to be used, the only
other option is physical removal. Much of the land is too steep and
uneven for machines, although a roller-crusher (as used to clear
scrub in the past by the NZ Forest Service) could be operated from
the top ridge. This could be followed-up by burning, as the slopes
lend themselves to easier fire containment - but the resource
consent proceedure required to carry out a burn could well be
onerous. Local DOC should be consulted on the most costeffective
technique and operators for physical removal.
Containment area. This area, within which trees would remain, ties in very closely with
the pink-coloured blocks on the map, with two exceptions:
• The striped-pink corridor north of DOC’s Dusky Reserve (running
between blocks 21/16 and blocks 17 / 22-24) should be included in the
containment area, as it is surrounded by wilding contorta pine forests,
and keeping it wilding-free would be a large and on-going
commitment. Even if it is improved for heavier grazing (which would
require fencing as well), the seed rain would be high and wilding
control will become increasingly difficult to maintain.
• As indicated elsewhere, the current wilding cover in western parts of
blocks 12, 13 and 19 is relatively light, and where this is the case,
could be removed. With the major seed disseminating winds coming
from the north, wilding reinvasion would not be frequent, despite the
proximity of these areas to contorta forests to the east.
Options for containing conifers within managed areas
The areas recommended above for the clearing of wildings were chosen to reduce the risk
of wilding spread outside Pukaki Downs, and also because they had a relatively low
wilding presence, which would not be too costly to remove. Other areas could also be
cleared (continuing the strategy of control from the north), but clearing them and keeping
them clear would be very expensive. Once the trees outside the containment area have
been cleared, there are management options for minimising the risk of reinvasion. These
are establishing a vegetation cover which is too dense for wilding establishment,
developing and maintaining pasture for more intensive grazing, and planting a
surrounding ‘shelter-belt’ of a less spread-prone tree species.
• Establishment of a dense vegetation cover.
This could be another woody crop (usually forest) or it might be a vigorous herbaceous
cover.
~ Woody crop – usually forest. Most of the invasive conifers are too light
demanding to be able to establish from seed under a closed canopy woody cover,
especially if it is tall, such as a forest. Hence, one wilding prevention option for Pukaki
Downs is to establish susceptible land in a new forest cover. If the area to be planted is
one from which seed could be disseminated elsewhere, then a non or less spread-prone
species should be chosen. This might be ponderosa or radiata pine, or a radiata x
Knobcone pine (P. attenuata) hybrid on the harsher sites, or perhaps a cypress
(Cupressus species, such as Leyland or Lawsons cypress) on the more benign sites,
depending on the objective of the planting (timber production or carbon storage). Where
the risk of spread off-site is less, then a more valuable species such as Douglas-fir could
be planted.
10

~ Herbaceous cover. Wildings have difficulty establishing within a vigorous
herbaceous cover. This has been demonstrated over on Mt Cook station, where no
wildings can be found in the dense grass / clover cover which established quickly after a
fire destroyed a large area of a wilding Corsican pine forest. Where trees are felled, and
the resulting slash is not so thick as to prevent any light reaching the ground surface,
herbaceous growth, particularly of grasses, can be sufficiently vigorous to prevent wilding
re-establishment from seed for a number of years (see above). Evidence of this can be
seen at a number of sites on Pukaki Downs.
• Maintaining improved pasture and intensive grazing.
Pasture which is improved by seeding and fertilising will not be invaded by wildings. This
is well shown on the Canterbury plains, despite the presence of a wide range of spreadprone
conifers. There is also good evidence on Pukaki Downs, where the hay paddocks in
block 31 and parts of block 25 are free of wildings despite the fact that there are forests of
contorta pine adjacent. Although improved pasture will prevent wilding invasion, it is
acknowledged that much of Pukaki Downs does not lend itself to this form of wilding
prevention. Also, it must be remembered that a) this improvement and the grazing which
it can support must be maintained, and b) if the seed rain from immediately adjacent trees
is high, then even a relatively small easing of grazing and/or fertiliser regimes can result in
wildings getting established. In addition to improved pasture, the cropping of land for
arable purposes will deliver the same wilding prevention outcome.
• Planting a margin of less spread-prone trees.
The theory here is that in a forest, most cones are produced on edge trees which have
green crowns extending to ground level - as opposed to the smaller and higher canopies
of internal trees. In addition, edge trees are more likely to disseminate seed onto
unplanted adjacent land. Therefore, if the margin of a forest is planted with a zero or less
spread-prone species, the risk of wilding spread is reduced. If the marginal species is
faster growing than the forest species, then it can also create a greater physical barrier to
the spread of seed. However, this marginal planting can only be most effective on flat
land. Where the forest is on rolling or hilly land, especially if this faces into the prevailing
wind, then there are greater opportunities for seed to be picked up from the internal tree
canopy and the effectiveness of marginal planting is diminished.
Assisting containment on Pukaki Downs.
Taking the above points in mind, the best containment management options appear to be
the:
~ Establishment of forests of less spread-prone species, such as the radiata x
attenuata hybrid, on areas immediately to the west of the contorta forests most likely to
remain intact – such as on blocks 12, 13, 19 and the western parts of block 9. In a
continuation of this western edge planting to the north of the property, further
establishment could be made on the eastern slopes under the Little Rhoboro Hills (blocks
20 and 14) - and also along the northern boundary with Ferintosh, down to SH80. Over
time, the 20m strip of less spread-prone species could be extended down the northeastern
margin alongside SH80, thereby minimising the spread of wildings onto the
highway margin. Such a strip could be established wherever spread-prone trees are likely
to grow alongside SH80. As they would be on the western side of the road, there should
be no risk of promoting highway icing during the winter.
To the east of SH80 in block 32, improved pastures and grazing are restricting fringe
spread westwards from the lakeside forests of contorta pine – and also from smaller
planted areas of Corsican pine and Douglas-fir. Additional forests, or a 4-row strip, of less
spread-prone species could be established along the western margin of these more
spread-prone species, in order to further reduce the risk of unwanted spread.
~ Maintenance of improved pasture and associated grazing (or arable cropping)
where it is currently restricting wilding establishment. This is in blocks 31 (especially
around the Dusky Reserve) and 32 and further to the west in the southern half of block 25,
just beyond the forested blocks 9 and 12. The hilly topography, limited moisture
11

availability and poor soil quality on much of the rest of Pukaki Downs limits the use of
improved pasture and arable cropping - unless irrigation is introduced. Fertilising would
enhance any grass regrowth amongst felled trees (even though no grazing would be
associated) and further diminish opportunities for wilding invasion.
~ Planting of a margin of less spread-prone trees. In effect, this is what is being
implemented by the containment forest planting recommended immediately above. It is
recommended that the felled strips by the northern boundary with Ferintosh and in the
forested areas alongside SH80 be made ‘wilding-proof’ by either fertilising to promote
vigorous herbaceous growth or planting of less spread-prone species. Even though the
main spread of conifer seed is from north to south, a marginal strip of trees along the
southern fence-line with Rhoboro Downs station is less important, due to there either
being dense forest on both sides of the boundary (the eastern half) or no trees present at
all (the western half). Apart from the outer boundaries, all the fenced margins between
remaining contorta pine forests and the tree-less pasture areas within the station could be
planted in four rows of radiata, its hybrids or ponderosa pine – around the northern and
western margins of block 31 and around the western margins of blocks 9, 12, 13 and 19.
If this were to be carried out, the latter four blocks would be the priority as, although the
topography on the forested side of the fence is more varied (greater risk of seed being
blown from the forest canopy), the grazing pressure is generally lighter (and hence the
spread risk higher) on that side of the property. Prior to any marginal strip planting, any
existing contorta pine trees would have to be removed from along the fencelines. The
need for this marginal 4-row planting would, of course, be negated if the contorta forests
were replaced with a less spread-prone species.
Areas for C storage management
Described above are the areas recommended for wilding removal, those where less
spread-prone species could be planted and those where the maintenance of current
pasture and arable management will restrict wilding establishment. The remainder of
Pukaki Downs could be managed for carbon storage. This ties in closely with the pink
and pink-striped portions shown on the map (see ‘containment area’ above). Initially, the
dominant species would be contorta pine, but over time it may be possible to replace
these with the less spread-prone species.
Discussion
As there is a major tourist road (SH80) running through the property, the wilding
conifer problem along the south-western shores of Lake Pukaki is well known.
Unfortunately, it involves the most spread-prone conifer species, contorta pine. Although
other species such as Douglas-fir, Corsican pine and larch are also involved, if contorta
pine was not present, then there would be no need for this report. Wildings have been
spreading since the 1960s, but the area obviously affected has only increased significantly
in the last 15 years. This has been largely triggered by spread from the lake-shore
plantings carried out after the lake was raised in the early 1970s - although most of the
contorta forests in the south-eastern portion of Pukaki Downs originate from trees present
before that time. The patterns of spread likely in the future are well indicated by the
pattern of spread over the last few decades. These show that spread is mainly to the
south, driven by the prevailing strong northerly winds, but that occasionally a more
easterly wind can pick up and carry seed high into the air and far to the south-east. This
is what appears to have happened back in the early 1990s, resulting in a scattering of
wide-spread outlier trees in the upper Twizel river valley. Unfortunately, these outliers
were allowed to mature and cone well before they were removed in the mid 2000s, giving
rise to the islands of fringe spread so obvious today. The ‘one-off’ nature of this spread
12

event indicates that once the Twizel river flats are cleared, they should not be re-invaded
often and hence should not be too difficult to keep clear in the future – as long as any
wilding trees which do establish are removed before age 5-6, when they begin coning.
This ‘stitch-in-time-saves-nine’ maxim must always be kept foremost in any management
planning. Importantly, the incidence of re-invasion and need for timely removal should be
diminished by the control and containment management options outlined above.
Apart from removing wildings, particularly outlier trees, before they cone, the other
major aspect of wilding control which should never be forgotten is the need for long-term
commitment. Even if a first removal sweep can be carried out in good time, there will be
some delayed germination of seed in the soil (although little takes places after 4 years)
plus small seedlings will be missed. A second sweep is therefore needed within 4 years
of the first removal (for contorta pine), and there is usually a need for a third sweep 4
years later to remove the last wildings. This sequence is needed if there is no other local
seed source, which unfortunately there will be at Pukaki Downs due to the present
strategy involving containment, not eradication. Therefore, if wildings are not to affect
more land in and around Pukaki Downs, removal sweeps outside the containment area
will be needed at least every 4 years for as long as seeding contorta pine trees remain in
the locality.
Within the containment area, the conifer forests could be managed, although
contorta pine is not a favoured production species in New Zealand, and there is currently
no ready market for timber or fibre. Such prospects are not improved by the forests being
‘wild’ and having had no previous management – leading to considerable stand variation
within the forest. The other obvious management option is to target carbon credits via the
Emissions Trading Scheme (ETS). Although this author is not in favour of wilding-risk
species (such as contorta) being managed for carbon gain, especially in high spread-risk
environments, the financial gains from such management on the areas with lower spreadrisk
could be used for control of wildings on the higher risk areas. If forest management is
a long-term aim (as opposed to conifer eradication), then even better would be the
gradual replacement of contorta pine in the containment area with a less spread-prone
species. Such replacement would eventually suppress the resident contorta pine, but
significant inputs would be required to ensure that the replacement species prevailed over
the naturally regenerating and vigorous contorta pine wildings.
Local community wilding control group. Recently, led by occupants of Pukaki
Downs, local land owners affected by wilding spread have got together to form the Lake
Pukaki Wilding Tree Management Trust. There are six other similar groups operating
within New Zealand, and they have shown how collaborative action can make a huge
difference to fund-raising opportunities and the mounting of large-scale and cost-effective
wilding removal operations. Unfortunately, not all affected landowners around Lake
Pukaki are members of the present Trust and this will affect the success of their
management, as wildings have no respect for property boundaries. In addition, the L.
Pukaki Trust is the only group to be proposing containment as an integral part of their
management – all the others have targeted elimination of both wildings and the seed
source trees. All the same, the formation of the Trust does give formal recognition to the
seriousness of the wilding spread in the area, and sets the foundation for a worthwhile
long-term control programme.
This author wishes them all the very best in their endeavours.
Recommendations
On Pukaki Downs it is recommended that:
• All wildings be removed in the near future from the upper Twizel river
catchment (blocks 25-29), except in the most densely forested areas
in the eastern margin of that area (blocks 9-13 plus 19).
13

• All wildings should also be removed from block 29, although planting it
with a less spread-prone species is an option.
• All wildings be removed from the steep slopes of the Rhoboro Range
in the most north-western part of the station (block 30).
• All wildings be removed in a 20m strip along the northern boundary
with Ferintosh station and in a similar strip alongside SH80.
• If finances allow (last priority) all wildings be removed from the steeper
eastern scarp slopes (northern portion) of the Little Rhoboro Hills
(block 20 and steeper part of 14).
• Improved pasture and associated grazing (and/or arable cropping) be
maintained where it is currently stopping wilding establishment -
blocks 31 and 32 (both sides of SH80) and further to the west in parts
of block 25). The north-eastern margin of block 31 would run out from
the northern margin of DOC’s Dusky Reserve in order to maintain a
treeless pasture margin.
• Replacement plantings of less spread-prone species, such as radiata
pine, its hybrid with Knobcone pine (P.radiata x P. attenuata) or
ponderosa pine, be carried out along the eastern margins of the
cleared areas in the upper Twizel river valley, either as 4-row marginal
plantings along the western edges of blocks 9, 12, 13 and 19 (if
retained in contorta pine), or as whole block replacement.
• Replacement plantings of less spread-prone species, such as radiata
pine, its hybrid with Knobcone pine (P.radiata x P. attenuata) or
ponderosa pine (minimum of 4 rows), could also be carried out along
the western margins of the lakeshore contorta pine forests in the
south-eastern part of block 32. This will not be necessary where
ponderosa or Corsican pine make up the current margin, or where
adjacent pasture cover and grazing pressure is sufficient to stop
significant establishment of wildings.
• Replacement plantings or fertilising be carried out in the 20m marginal
strips along the Ferintosh boundary (top of blocks 16 and 24) and
alongside SH80.
• Marginal strips (4 rows wide) be planted along the fenced north and
western margins of the tree-less pasture-dominated block 31.
• Blocks 9-24 (the pink and pink-striped areas on the map), including
the corridor north of the Dusky Reserve between blocks 21 / 16 and
17 / 22 – 23, will become the containment area and could be managed
for carbon storage. Initially, the dominant species would be contorta
pine, but over time the aim should be to replace these with less
spread-prone species.
• Wilding removal sweeps be carried out before coning age (no more
than 4 years apart) on all cleared or otherwise tree-less areas.
• Long-term planning be initiated to ensure that the above to be
implemented.
Acknowledgement
The author is most grateful to the residents of Pukaki Downs, especially Blake Foster, for
their support during the field-work and the writing of this report.
14

Above. The clear corridor (pink-striped on map) in the north-eastern part of Pukaki
Downs, between blocks 21 / 16 and 17/ 22-23). This will be very hard to maintain free
of wildings, so unless the contorta forest alongside is replaced with a less spread-prone
species, it should become part of the forested containment area.
Below. Felled 50+ year old contorta trees by the musterer’s hut in block 26. These
would have given rise to much of the dense wilding cover immediately to the south.
15

Above (2008) and below (2010) - outlier wildings in the upper Twizel river catchment. Their uniform age indicates
that they arrived at the same time in the early 1990s, and that such a distant spread event does not happen often.
Unfortunately, they were allowed to cone before removal, resulting in islands of fringe spread (obvious in bottom photo).
All fringe spread has been to the south of parent trees, indicating the prevailing north wind (right to left in photos). If
removed before coning, it should not be onerous to keep this site free of wildings – as invasion is infrequent.
Left – Twizel river flats (2010). An ‘island’ of
young wildings, parented by a lone outlier wilding
parent tree, which was felled a few years
previously (being held up in photo). If this tree had
been felled before age 5, no wildings would be
present. Its progeny are now aged 5-6 and just
starting to cone. If left intact and allowed to
disseminate seed, wilding removal costs will be
increased significantly. Hence the wilding control
motto of “Stitch in time saves nine”
Left (2009). Looking
south from Little
Rhoboro Hills ridge.
Contorta pine is rapidly
becoming dominant,
except in middle distant
left where improved
pasture is preventing
invasion. Containment
(and possibly forest
management) is the
cheapest option for this
area, where seed sources
may remain upwind.
16

Developments from Rural Delivery website for program on wilding control at Pukaki Downs
Wilding Pine Control
October 8, 2011
Pukaki Downs are using the carbon credits from a core area of wilding pines now in the
Emissions Trading Scheme to fund wilding control over the rest of their property.
After Lake Pukaki was raised for the second time – by 37m in the 1970’s – there were areas of
wilding conifers along the lake front shore, indicating this spread had come from plantings
around the now submerged early homesteads.
Over 10,000 mixed pine species, including Pinus contorta, were planted on the lake front of Lake
Pukaki in the 1970’s for erosion control by the Ministry of Works.
It’s a very good climate for growing trees. This species is most prone to spreading, and they
have, and they are very costly to control. And until now there’s been no money floating around
to help landowners with pine control.
The rest of the farm is used for grazing sheep and cattle, organic grain cropping and organic
lavender production. Eco-tourism and other forestry ventures are being developed.
Blake is also treasurer of the Lake Pukaki Wilding Tree and Management Trust that has been
formed by a number of station holders in the area to try and get funding for wilding control.
Pukaki Downs has a huge problem with wilding pines on its property but the problem has only
increased in the last 15 years.
By the middle of last year, wilding Pinus contorta had spread so much that it covered 30 or 40%
of the property and had turned into a forest.
Much of the remaining area has widely scattered outlier trees and if left unmanaged, wildings
would dominate the majority of the property.
It’s a very visual weed in an area with high landscape values, and the major tourist route of Mt
Cook Road runs through the property for about 8km.
The spread is mainly from the lakeshore plantings, and the seed has been blown by strong
northerly winds.
When the owners were looking at ways they could self-fund wilding conifer control, the ETS
was coming into play.

We talked with MAF people in Wellington who said the wilding pines fitted the definition of a
forest under the ETS, and could be entered into the scheme.
The ETS seemed to be a self-funding way to deal with the situation, and provide an income
stream for us to contain it, including planting a tree buffer zone and chip away at the forest area
over a number of years, replacing it with a different species.
The whole idea is to get rid of the wildings, so we drew a line in the sand surrounding a core area
of trees, and put that area into the ETS.
We use the funds from the sale of carbon credits to clear all the outliers around it.
We are planting 40,000 non-spreading trees around the core area to act as a buffer. These trees
will gradually form an effective natural barrier to prevent the airborne spread of wild conifer
seed.
Gradually we also plan to replace the core wilding area with a hybrid species, a cross between
Pinus radiata and P. attenuata, (knobcone pine) which is less prone to spreading. That’s because
the knobcone pine’s cones only open as a result of fire, and radiata pine is a low-spread risk for
us.
Our core ETS area is 1100ha, which is approximately a quarter of the property. The remainder of
the property has wildings spread across it.
Last year we made huge inroads, clearing 500ha. You have to get them while they are young and
haven’t produced cones, which is after about five years.
After receiving our first round of carbon credits and selling some of them, we then knew we had
the funds to be proactive with the problem.
We were fortunate to be able to obtain help from Nick Ledgard of Scion to do a detailed report
which identified where the spread was coming from, where we should start control from and
what the high and low risk areas were.
That’s how we came to put the low spread risk area into the carbon sink.
We have followed his recommendations.
This way we have a self-funding project, and last year we employed a gang of nine for five
weeks who used scrub bars. We had another crew of four. And we have purchased a mechanical
slasher at a cost of $150,000 to slash small trees.
The control work costs us $15,000 a week, and it is going well. It’s pretty hard work for the
team.
We also clear the road frontage back to the forest edge in areas that are clear of trees.

We have sold the carbon credits through a broker/consultant. For each of the commitment
periods you get an allotment of carbon credits. You don’t have to sell them; you can keep them.
But for us selling them pays for the control work on the rest of the area.
The core area doesn’t have a lot of commercial value, and it has never had any silviculture. It’s
quite a long way from the market unless there is a major market change.
We have been looking at making wood pellets and firewood out of them; we’re just investigating
that at the moment.
We are trying to use the funds responsibly, not just put the wildings in the ETS, take the money
and run.
While we are using the funds to eradicate the trees, we feared others might not use the funds
from the sale of carbon credits for eradicating wildings.
Our central aim is to get rid of the contorta species.
We’ve had huge success in the last year and the ETS has provided a way for it to happen.
I would say we are looking at control for another 15 years at least.
Wilding forests are called Tree Weed Forests under the ETS.
Blake has lobbied MAF and ECAN to give an alternative view on how to get funding from the
ETS to deal with the problem of wilding trees. This view of using the ETS funds to deal with
clearing wildings can be seen as partnering with ECAN. And the submission was received
favourably with ECAN amending one of its rules. The theme of the submissions were to:
• use a certain percentage of the income derived from ETS Carbon Credits to be put back into
controlling the spread ;
• set the area of the tree weed forest to be the area placed in the ETS and not allow it to expand
beyond this area ;
• use income from ETS, plant buffer zones of non spreading species to contain seed spread ;
• replant the existing forest into a non spreading species over time and enter this new forest of
non spreading trees into the ETS to further fund the programme ;
• use the money from ETS to fund the long term eradication of wildings outside the containment
area;

• use income from ETS to pay for mulching machines and scrub bar gangs to make buffer zones
and to eradicate juvenile wilding conifers as they grow among the planting of non spreading
species.
Blake’s conclusion to his MAF submission stated:
“New, non-traditional approaches to containment and eradication of pest species should be
allowed.
For example with wilding pines, changing from a standard policy of informal
forest management with a focus on eradication, to a new policy of structured forest monitoring
and replacement of existing wilding species with non-wilding ones.”
He wanted a move from a short-term focus on eradication of wilding conifers to a longer-term,
progressive series of steps that include initial containment, managed harvesting and replacement
of wilding species by non-wilding ones over decades.
“If this process is extended over a longer timeline there may be better chance of long-term
success plus the project might become self-funding if revenue from environmental services such
as carbon sequestration or commercial timber production was integrated into the management
plan.
The management at Pukaki Downs has spent considerable, time, energy, money and resources
over the years in consultation with other landowners, foresters, scientists, DoC consultants,
practical working people and independent business people who specialise in tree and forestry
management.
Through this process we have arrived at the conclusion that eradication of all wilding trees is an
unreal goal. We have seen first hand that in the face of this unattainable outcome many people
with a wilding pest problem simply stop trying to beat the odds and give up.
The biggest obstacle to wilding pine containment is an economic one. The enormity of the
problem,(which in most cases in the Twizel area was an inherited one, either from original
plantings from Lands and Surveys operations or from wind blown seed scattering), has reduced
landowners to despondency.
Millions of dollars are required to create change and landowners are well aware of their lack of
ability to effect such change. We have reached the conclusion of creating buffer zones around
existing wilding forests with fast growing, non-spreading tree species, while maintaining and
managing any new growth.”