Wilding pines are increasingly smothering the scenic landscapes and farms of Aotearoa, shading out native species, and creating fuel for wildfires.
Speakers at the Wilding Pines Conference in Twizel next week (14-16 Oct) will focus on innovative ways to slow their rapid spread, a year after funding for control efforts was significantly reduced.
The SMC asked experts for background on the problem, what is at stake and potential solutions.
Dr Thomas Carlin, Invasion Ecologist, Bioeconomy Science Institute, comments:
What’s the current state of wilding pine management in NZ?
“The extent of the wilding conifer problem remains huge and there is a risk of increasing expansion. Although some areas are relatively contained where wildings have been removed for now, they are still spreading in other places. Control measures in some areas have been put on hold due to limited funds.
“The National Wilding Conifer Control Programme is making progress and is envied by other countries as a rare and valuable example of a national weed control programme. However, further investment is needed to maintain this progress. Our latest research shows some conifer species in New Zealand have evolved to become more invasive than anywhere else in the world. Every day they’re left to spread will cost us significantly more in the long run.”
What’s at stake if things continue as they are?
“Wilding conifers can spread across many kilometres as seed is carried on the wind. They can therefore invade a variety of habitats and threaten many of our already vulnerable and unique ecosystems. High-country and hill-country farmland can become unusable over time when conifers are left to establish. These trees alter sites in ways that can make them vulnerable to re-invasion, even after the initial conifers are removed.
“Wilding conifers out-compete low-stature native vegetation such as our iconic tussock grasslands, as they grow faster and taller. They can also establish at higher altitudes where indigenous tree species struggle and provide refuge for mammalian pests (e.g. rats and possums). Wilding conifers can increase the severity of wildfires and spoil the unique aesthetic landscapes that underpin New Zealand’s tourism industry.”
What are the standard methods used to manage wilding pines? Are there any new technologies on the horizon?
“Control methods can be ground- or aerial-based. Common ground-based methods include pulling seedlings or cutting the tree and applying herbicide to the stump. Common aerial methods are herbicide-based. They can be targeted at individual trees with minimal impacts on the surrounding vegetation or spread across larger areas over dense infestations.
“There are exciting technologies on the horizon including novel and automated drone spray systems, potential biocontrol (fungi, mistletoe), remote sensing for better conifer detection and controlled burns.”
What will you be presenting at the conference?
“I’m giving two talks at the conference. The first discusses the results of a survey of wilding conifer perceptions from multiple stakeholder groups (academics, farmers, foresters, government etc.), particularly relating to participants’ levels of concern between wilding conifers and other invasive species. The second talk covers a recent herbicide trial I led – looking into how long seeds continue developing after herbicide is applied, to determine optimum control windows and avoid seed spread.”
No conflicts of interest.
Dr Justin Nairn, Team leader, Plant Protection Chemistry and Physics, Bioeconomy Science Institute, comments:
What’s the current state of wilding pine management in NZ? Are we holding the line?
“I don’t think we are holding the line. The scale, remoteness and ruggedness of New Zealand’s landscape mean control and long-term management are difficult and expensive. Long-term investment is needed to ensure our landscape is resilient to future invasions.
“Significant investment was made to reduce the wilding pine-affected area in New Zealand. Ensuring we don’t lose these gains becomes harder as government investment has declined. This means we need to prioritise management and, in some areas, the line will be broken.”
What’s at stake if things continue as they are?
“If things continue as they are, pines will continue to invade degraded native ecosystems, driving further ecosystem changes and causing a loss of productive land and iconic landscapes for tourism, and a decline of environmental services such as water quantity.”
What are the standard methods used to manage wilding pines? Are there any new technologies on the horizon?
“The standard methods used to manage wilding pine include manual and mechanical cutting or application of herbicides, and aerial (helicopter) application.
“Uncrewed aerial spray systems (UASS) coupled with remote sensing technology could provide a more efficient way to manage scattered and remote infestations. These are currently one of the most difficult infestation typologies to manage. Swarms of UASS operating in a seek-and-destroy fashion or with targets identified from pre-identified aerial imagery could work, but their effectiveness and cost have yet to be proven.
“Remote sensing detection of pine trees is getting better and UASS hardware and software are improving rapidly, with the latter already being used in small pockets. Wider use could soon be a reality, with investment in UASS research and development.”
What will you be presenting at the conference?
“At the conference I will talk about reducing herbicide rates for aerial applications: Refining the currently used herbicide mix (TDPA to TD) to also reduce costs of boom spraying (lower costs per hectare means more area can be covered).”
Conflict of interest statement: “I am engaged in UASS research, so, while qualified to comment, I could also gain from investment in UASS research.”
Dr Duane Peltzer, Portfolio Leader, Managing Invasive Species at NZ Institute for Bioeconomy Science, comments:
“Wilding pine management is a long-term and strategic undertaking that seeks to ‘stop or contain wilding pine invasion nationally’ through co-ordinated efforts. There has been amazing progress in both management methods themselves and the scale of operations completed over the past decade. However, declines in base funding by nearly two-thirds mean that ‘holding the line’ is likely only in some places. The open question is which places, and for how long.
“Both research and management of wilding pines are at a crucial stage or ‘tipping point’ because of base funding changes to management, and major changes to the science system. Wilding pine management nationally will require long-term effort and co-ordination across science and practice for the foreseeable future despite these short-term challenges.”
What’s currently at stake with the way things are?
“We’ve included some research in three investment cases to support wilding conifer management; these were roughly about protecting primary industry and water resources; biodiversity and valued ecosystems; and most recently, regional employment. Ongoing wilding, invasion or reinvasion in previously managed areas, could erode the benefits sought by these investments at landscape scales.
What are the standard ways wilding pines are managed? What are new technologies on the horizon?
“There are many ways that wilding pines are managed in practice. This reflects different stages of invasion, the tree species involved, and area being managed. Management thus ranges from broad ground-based weeding, backpack spraying, drill and fill of trees, or helicopter spraying. These methods are well detailed and reviewed, but no one method can achieve 100% removal of wilding pines, or work across the different densities encountered. Most operators use mixed methods within a site, so there are huge practical skills and knowledge involved doing wilding pine management.
“There are multiple technologies either well-developed or in train including high resolution mapping of invasions to plan operations or do reporting or using UAVs. Translating these new technologies into practice is an ongoing need. Aside from new technologies themselves, there are other methods being considered ranging from biocontrol of lodgepole pine for intractable invasions to reinstating grazing as a control tool in some sites to slow reinvasion. A next step is how we integrate the various methods currently being used with new approaches.”
What will you be presenting at the conference?
“I’ve worked on many aspects of the causes and consequences of wilding conference invasions, but for this year’s conference, I’ve been asked to present on grazing as a potential tool for wilding pine management. Many areas where wilding pines have been managed previously are now being reinvaded. These reinvasions can be sparse, but rapid. The question we’ve been asked is whether grazing could be used in some sites to slow reinvasion. There are layers of both ecological nuance and political consideration here. For example, does reinstating grazing to a level that might control wilding pine reinvasion also have unacceptable effects on biodiversity or animal welfare? Many sites where grazing could be considered include post tenure review land which require major social or political considerations. We need better evidence to understand the impacts of grazing on wilding pine reinvasion, and if this approach has a niche alongside the suite of other management methods already available.”
Conflict of interest: None declared.