Written by Sian Reynolds, Boffa Miskell

Aotearoa New Zealand – our little island vista – is constantly under threat from invasive weeds and animals. Biosecurity threats within New Zealand are ever-pressing, ever-spreading, and the number of pests banging at our doorstep are constantly on the rise.

Government funding has always played a pivotal role in protecting this country from the myriad of pests that now call New Zealand home. No ecosystem is untouched, we have hundreds of weeds, both terrestrial and aquatic, an array of mammalian predators and browsing animals that wreak havoc, as well as marine pests that threaten the livelihood of some of our communities.

*Wilding conifer spread at Rangitahi | Molesworth Station. It's a prime time to be controlling this pest while it is still relatively medium density, and not like a brick wall. Source: Boffa Miskell.*

I’ve spent over a decade working on landscape-scale predator, ungulate, weed, and wilding conifer control. The Boffa Miskell biosecurity team has led the wilding conifer control programme at Mid Dome in Southland since 2014, and we’ve managed the same pest at Rangitahi | Molesworth Station since 2020. These are both vast, ecologically significant areas and the impact of wilding conifers is no longer benign. It is visible, tangible, and deeply concerning.

The fact is, wilding conifers are a pest we can win against. Seeds rot in the ground after approximately five years and, for the worst wilding conifer species, seedlings do not cone until at least five years of age.

Therefore:

Complete the initial round of control to remove the coning tree;
Return in three years’ time to control the seedlings;
Repeat this process three years later, and
Voilà – odds are, you have almost eliminated the problem.

Why, then, are we not on top of the wilding conifer situation?

Because our ability to achieve suppression, elimination, or even eradication of a pest within New Zealand is positively correlated with consistent levels of adequate funding.

Unfortunately, ebbs and flows of committed biosecurity funding has the most significant influence on our ability to persistently apply pressure to key pest species.

Why are we so reliant on government funding?

Because approximately one third of all New Zealand is public land, not to mention the expansive marine space that surrounds the entirety of the country. Additionally, the New Zealand Acclimatisation Societies, established in New Zealand by European colonists from the 1860s, operated with government support and legal authority and are responsible for the introduction of many plants and animals that we call ‘pests’ today.

Possums, rabbits, deer, ferrets, stoats, gorse, broom, willow, hornwort and sweet briar are just a handful of the species that were introduced to this country. Little did they know at the time that the desire to naturalise all kinds of exotic species would have such lasting economic impacts. With responsibility over such an expanse of land, now home to the pests that were introduced to New Zealand with governmental support, it’s no wonder that many believe that the current government needs to take accountability for the problems it created in the past.

Wilding pines aren't the only plants that negatively impact the environment and economy. New Zealand's freshwater and marine environments are threatened by lagarosiphon, caulerpa, and other aquatic weeds.

It needs to be noted that, in many cases, private landowners contribute to control efforts through council rates, or through their own appreciation of the importance of pest control – whether from an economic, amenity or biodiversity perspective.

Wilding conifers were initially brought to New Zealand in the 1880s. Their proliferation stems largely from well-intentioned government efforts during the mid-20th century to stabilise erosion-prone land. Between the 1940s and 1970s, extensive plantings of exotic conifers, particularly contorta pine, Douglas fir, Scots pine, larch and Corsican pine, were established across scree slopes, tussocklands, and high-country areas. Over time, these species have spread well beyond their intended boundaries. In other cases, wilding conifers have emerged from shelterbelts, homestead plantings, and ill-sited forestry plantations.

The economic consequences are significant. The spread of wilding conifers can lead to the loss of productive farmland, reducing agricultural output and economic returns. Wilding conifers soak up an immense amount of water from the environment, leading to reduced water availability (sometimes up to 40% in a catchment) for irrigation and hydropower generation. Additionally, conifers are highly flammable, and their spread increases the risk of wildfires – which are expensive to fight and devastating to affected communities and farming infrastructure.

Constant changes in government leadership, policies, and intention are worrying for the biosecurity industry, and the uncertainty in funding that comes with these changes means that wins made against pests with one government can be quickly unravelled by another.

A major funding injection in 2020 allowed for significant progress against wilding conifers. Over the last four years, the programme received $140 million from government and a further $20 million from partner organisations. This approximately $40 million per year allowed us to reduce wilding conifer pressure in many high-risk areas like Rangitahi | Molesworth Station, Mid Dome and throughout the Canterbury high-country.

Wilding conifer spread at Rangitahi | Molesworth Station. It's a prime time to be controlling this pest while it is still relatively medium density, and not like a brick wall.

But we know that effective pest control requires consistency and a long-term commitment to outcomes. These weeds were not established overnight and the outcome of eradication, or at least containment, will not be achieved with this expectation either.

We are now at a tipping point in the fight against wildings.

Funding has returned to a national baseline of only $10 million per year – just a quarter of what was previously being spent and what is needed to maintain positive progress.

Of the 79 Management Units throughout the country, only 31 are currently funded. Forty-two others receive nothing, despite known and spreading infestations not slowing down within them. Without immediate and consistent funding at levels beyond $40 million per annum, all the significant progress made since 2020 will be rapidly reversed. At Rangitahi | Molesworth, for example, control budgets have dropped from $3.5 million to just $900,000 per annum. That reduction has forced difficult decisions, including the deferral of control in areas like the Tarndale and Sedgemere lakes, which are of national ecological significance.

The economics of wilding conifer control are clear. A 2022 report by independent research consultancy Sapere [PDF link] showed a cost-benefit ratio of 1-to-34 for controlling wildings. That means that every $1 invested in wilding conifer control delivers $34 in avoided losses and costs. But the earlier we act, the better. Wilding conifers grow and multiply over time, and so does the price of dealing with them. The most invasive wilding conifer species, such as contorta, can be eliminated but only if we act before they reach seeding age; and only if we act consistently.

What we lack is not capability to do the job but consistency in our ability to do it properly. Without stable, long-term funding, we are doomed to repeat a cycle of progress and regression, boom and bust. Every dollar withheld today is not just a missed opportunity, it’s a future cost magnified.

Over the past four years, the wilding conifer programme has proven that with adequate investment, we can turn the tide. But with inadequate investment, we risk undoing years of gains, allowing these pests to reclaim ground we’ve already fought to protect.

If we are serious about safeguarding Aotearoa New Zealand’s unique biodiversity — our beautiful landscapes, fisheries, and high-country pastoral areas — as well as our economic interests and the livelihood of many our communities, then we must treat biosecurity funding not as a nice-to-have discretionary expense, but as a long-term national priority.

Because in the fight against invasive pests, the greatest threat isn’t the pest — it’s the pause in the fight against them.

Editor’s note

This article first appeared in Boffa Miskell’s ‘Be Bold’ series in May 2025 and has been reproduced with permission. See also Fire and wilding conifers (2021) and Lessons learned for our work with wilding conifers (2020)

Staying on the topic of trees LAA readers who have mixed opinions about Willows may be interested in a highly readable, in-depth feature story published in New Zealand Geographic’s July/August edition this year under the title ‘Our deeply toxic relationship with willows’.

Pests in the shape of trees: Wilding pines

Editor’s note