The Ministry for Primary Industries has led the development of a non-regulatory strategy that
proposes actions to improve the efficiency and effectiveness of wilding control (MPI, 2014a). In the
right place, exotic conifers can provide economic, environmental, social and cultural benefits. In the
wrong place, unwanted exotic conifers (wilding conifers) can impact on a range of ecosystem
Scion was contracted by MPI to understand and quantify, where possible, the current
and future economic impacts of wilding conifers on New Zealand over the next 20 years as no
recent, national-level, cost-benefit analysis for wilding management has been carried out. The
analysis does not represent a comprehensive assessment of all impacts and benefits of wilding
conifers in New Zealand. For many of the direct and indirect impacts of wilding conifers identified
no data exist that would allow the quantification and monetisation of their value losses or gains. All
identified but not quantified impacts are shown provided in the results and reasons given for their
exclusion in this report.
Wilding conifers could affect over 5 million hectares or 20% of New Zealand’s land area by 2035 if
the current levels of management do not change. The amount of land affected is likely to treble
from 1.82 M ha (2015) to 5.43 M ha by 2035. The land affected by scattered wilding conifer trees
(0.01 to 400 trees per hectare) will increase from 1.71 M ha to 5.1 M ha. Dense wilding conifer
stands will increase from 0.11 M ha to 0.33 M ha in 2035.
The ongoing infestation1 of land with wilding conifers could result in approximate average annual
losses of $141 million or $ 1.2 billion net present value between 2015 and 2035. The increasing
infestation will affect productive dry stock land, water supply/availability, biodiversity, nature-based
international tourism, forest fire propensities, carbon stocks and sequestration, and sedimentation.
The current annual management cost of wilding conifers is $5.8 million. Assuming that annual
expenditures do not change over the next 20 years the total discounted expenditures would be
approximately $55 million. Current management control would not prevent the losses described in
This report establishes the assumptions used; the limitations of these assumptions; describes the
impact variables and their assessment methods; and provides the results, conclusions and
recommendations of the analysis.