Biosecurity Bonanza 2025

The Forgotten Costs of Rabbits — and the Economic Power of Research

Presenter: Mandy Barron

Rabbits are a serious economic and environmental pest in dryland ecosystems across Aotearoa-New Zealand. Their numbers and impacts are expected to grow under climate change and with increasing immunity to Rabbit Haemorrhagic Disease Virus (RHDV).  Despite these substantial current and future costs, we lack a coordinated and effective approach to rabbit management resulting in piecemeal rabbit control and the use of inappropriate methods that potentially jeopardise future control efforts e.g. through induction of bait shyness. We argue that cost-effective rabbit management requires sustained investment in collaborative research to scope the problem and identify and trial new solutions. We will also talk about changing rabbit population – disease dynamics and some new work to monitor which RHDV strains are circulating in the landscape.

Removing the last 1% of a mainland predator population: evaluating a novel approach

Presenter: Graham Hickling

Predator eradication programmes fail, in part, because bait-shy and trap-shy individuals evade traditional control measures. Our previous research has shown, however, that these shy individuals are still willing to cautiously sample novel baits and lures - although their caution leads to sublethal dosing and failure to trigger traps. Recently, we tested the hypothesis that pre-feed baits containing a central nervous system (CNS) stimulant can trigger reward-seeking behaviours that overcome shyness. For the approach to be practical, several criteria need to be met: the stimulant needs to be stable in a cereal or paste matrix; the pre-feed is palatable; and a short series of exposures to pre-feed will increase the target species’ behavioural drive. This presentation summarizes tests of three potent CNS stimulants on the responses of ship rats and brushtail possums to control devices.

Cats protecting birds: Non-lethal tools for urban cat management

Presenters: Patrick Garvey and Sarah Edwards

Cats are a major driver of biodiversity decline, yet lethal management is often neither feasible nor desirable in urban environments. Our MBIE project developed a non-lethal tool based on the “ecology of fear” that showed predator auditory cues - especially cat vocalisations - can significantly alter urban cat movements. We conducted surveys in Auckland, Wellington, and Christchurch that documented cat incursions into reserves and their impacts on nesting birds. Through a series of captive and field experiments, we discovered that auditory playbacks could manipulate cat behaviour for conservation, as we reduced cat detections across all reserves by 30% and foraging time by up to 80%. Alongside our ecological studies, we carried out social research with Zealandia’s ‘halo’ community to explore the complexities of managing cats and identified practical strategies to encourage responsible ownership. Building on this research, we are now focusing on the Ashley Rakahuri braided river, where we will integrate ecological studies with social perspectives to manage risks to native birds. Our programme highlights how non-lethal approaches, such as auditory playbacks and cat containment, can provide practical, humane solutions to mitigate the impacts of urban cats.

Reactive or Adaptive? Cost-efficient invasive species management

Presenter: Dean Anderson

Environmental management strategies are widely expected to be guided by robust scientific research. Adaptive management, first articulated in the late 1970s and 1980s, provides a framework for embedding research within management implementation and experimentation. In principle, this iterative cycle can improve understanding of ecological systems while delivering more cost-efficient outcomes. Despite its enduring appeal, real-world examples of adaptive management remain rare. In this talk, I review cases from New Zealand where adaptive approaches have been applied to invasive species management, and highlight opportunities where reactive or short-term responses prevailed instead. I evaluate the costs, risks, and benefits of adaptive approaches, and examine the institutional and professional constraints that continue to impede their adoption. I argue that stronger management-science partnerships are essential if adaptive management is to move beyond rhetoric. Environmental managers have an obligation to funders to maximise the use of science, while applied scientists have a parallel responsibility to frame and pursue research questions that feed back into more effective and efficient invasive species management.

Browsing impacts of tahr on native alpine vegetation

Presenters: Amy Whitehead & Laureline Rossignaud

Introduced browsing mammals are considered both a valued resource and a management challenge in Aotearoa New Zealand’s alpine environments. Himalayan tahr, in particular, support recreational hunting but also affect the condition and composition of native vegetation. Three decades of monitoring provide a rare opportunity to understand these long-term impacts and assess whether current management thresholds are sufficient to maintain ecosystem integrity. Using tahr as an example, we show the value of long-term monitoring for guiding adaptive wildlife management and balancing conservation outcomes with stakeholder expectations in New Zealand’s alpine environments.

Weed sessions

Remote sensing for invasive weed management

Presenter: Paul Peterson

In this talk, we present a remote sensing mapping method to assess impacts of a weed control programme on invasive, ecosystem-altering, legumes on the Central Plateau, North Island. To help counter this threat, the Desert Road Invasive Legume Control Group (DRILCG) was formed in 2012 and includes an unusually diverse range of stakeholders: Department of Conservation, NZ Defence Force, Ngā Waihua o Paerangi, Transpower, Genesis Energy, Horizons Regional Council, Waikato Regional Council, and the Lake Rotoaira Forest Trust. The DRILCG funded high-resolution aeroplane imagery during the flowering of invasive gorse (Ulex europaeus), broom (Cytisus scoparius) and tree lupin (Lupinus arboreus) over a 23,000 ha area. Resulting imagery was cut into 200 x 200 m grids and the target weeds manually scored as zero, low, medium or high density. Change maps, produced from repeat imagery, helped assess the impacts of herbicide operations, enabling recommendations for more targeted and sustainable landscape-scale management strategies such as focussing on outlying populations. This study demonstrates how a remote sensing method using RGB (visible light) imagery can produce cost-effective weed mapping solutions for informing management decisions.

The Nationally Significant Collections & Databases supporting biosecurity

Presenter: Bevan Weir

The Manaaki Whenua group of the Bioeconomy Science Institute has several ‘nationally significant’ collections of plants, invertebrates, fungi, and microbes. These collections provide a critical role in supporting biosecurity research and operational activities in New Zealand. In this talk, various case studies will be presented showing the utility of these comprehensive, well-curated, data-rich collections with specimens dating from early European exploration of the country.

Wilding conifers reinvade despite control efforts, while native plants fail to thrive

Presenter: Elise Arnst

Wilding conifers are some of most widespread and abundant invasive plants of conservation land in Aotearoa New Zealand. Pinus contorta has been controlled for decades, but pine reinvasion has not been measured. We measured reinvasion and native plant communities in sites controlled for pines across a range of habitats and climates. After dense invasions, conifers reinvaded quickly and native plant cover was low, even after a decade since control, and did not improve over time. Other wilding conifers, particularly Douglas fir, were commonly observed, raising concerns about the future of these plant communities and highlighting the need for adaptive, repeated management of invasive conifers.

Anticipating Aotearoa’s weedy future to best support changing needs for management

Presenter: Angela Brandt

Aotearoa New Zealand is already struggling under the weight of weeds, and the problem is only likely to worsen in future. We expect new weeds to emerge, and that environmental and social change will exacerbate weed invasion. With a range of collaborators, we have identified research priorities and management needs that are likely to arise under four possible future scenarios: 1) increased Māori land tenure, 2) widespread native afforestation, 3) the success of Predator Free 2050, and 4) increasing extreme weather events. We found that unique research is needed to address each scenario, but also that emergent research priorities and needed management tools would provide benefit in any weedy future.

Advancing weed biocontrol for ecosystem resilience in the Pacific: efforts to manage African tulip tree and prickly solanum

Presenters: Indigo Michael & Zane McGrath

Invasive weeds continue to pose serious threats to biodiversity, agriculture, and ecosystem resilience across the Pacific. We discuss two ongoing biocontrol programmes under the Natural Enemies – Natural Solutions programme targeting African tulip tree (Spathodea campanulata) and prickly solanum (Solanum torvum). African tulip tree is considered among the world’s 30 worst terrestrial invaders and is a major problem in most non-atoll countries across the Pacific, including Tonga, Cook Islands, Samoa, Fiji, and Vanuatu. Prickly solanum is a serious agricultural weed with major impacts in countries such as Vanuatu, where cattle farming is a vital livelihood. Its spread has been directly linked to reduced pasture quality and a documented decline in cattle numbers. Huge efforts have been made in the last decade to develop, release, and monitor biocontrol agents to manage these invasive weeds. Together, these programmes represent a critical step toward protecting Pacific livelihoods, restoring ecosystems, and building long-term resilience against invasive species.