Research into the control and eradication of New Zealand’s introduced predator species is making great in-roads and there are a multitude of new publications available.
Glen et al 2017; Landholder Participation in regional-scale control of invasive predators.
Control of invasive predators is necessary for the conservation of many endemic species. Invasive predator management tends to focus on priority sites, which often comprise only a small fraction of the impacted area. Landscape-scale ecological recovery requires threatening processes to be managed not only in these priority areas, but also in the matrix between them. However, wide-scale control of invasive species can be logistically, economically and socially challenging. We developed a spatially explicit model to estimate the effects of varying levels of landholder participation in landscape-scale programs to control invasive predators.
Byron et al, 2016; A review of biodiversity outcomes from possum focused pest control in New Zealand
Worldwide, introduced vertebrate pests impact primary production, native biodiversity, and human health. In New Zealand, extensive pest control (~10 million ha) is undertaken to protect native biota and to prevent losses to the primary sector from wildlife vectors of bovine tuberculosis (TB), primarily possums (Trichosurus vulpecula). Control is conducted by TBfree New Zealand and by conservation agencies. Remote, forested terrain is treated using the toxin 1080 via aerial delivery in bait with a return time of ~5 years. Ground-based control is conducted annually using traps and/or poison bait. Possums are controlled to very low abundance by these operations. Aerial 1080 is effective against another forestdwelling vertebrate pest, the ship rat (Rattus rattus). Possum control has reduced TB rates, but collateral benefits for native biodiversity have not been quantified, making it difficult to demonstrate a return on investment.Wereview information from 47 accounts of responses of native biota to possum control. Of these, 60% quantified responses to aerial 1080; the remainder were ground-based. Possum control benefited vegetation by increasing foliage and fruit production, and by reducing tree mortality. Controlling ship rats and possums together improved bird populations, but rats recovered rapidly and long-term outcomes for rat-vulnerable birds are unknown. Large-bodied invertebrates also benefited from extensive pest control. We conducted a meta-analysis of 84 response measures from 35 of these 47 studies in order to provide a quantitative assessment of these findings. The analysis demonstrated that both ground and aerial control of this invasive pest in New Zealand has provided substantial collateral benefits for native biota. Few studies have taken advantage of decades of extensive pest control in New Zealand to monitor ecosystem-level outcomes, which have received only short-term attention thus far. Nontreatment experimental controls and replicate sites that enable validated assessments of outcomes for native biota are vital. Future studies would benefit from a standardised set of biodiversity indicators from a range of taxonomic and functional groupings, and from standardising experimental designs so individual studies can contribute to future meta-analyses, to strengthen the evidence base for the impacts of invasive pests on native biota in New Zealand and worldwide
Parkes et al, 2016, Past, present and two potential futures for managing New Zealand’s mammalian pests.
In 2003, a review of how introduced mammals were managed as pests in New Zealand was published. Since then trends for the control of these mammals include moves from pest-by-pest prioritisation towards site-based and multiple-pest management, extension of large-scale aerial control of predators to include beech forests, increasing intensive management of sites by private and non-government agencies, and increasing effort by regional councils and managers of vectors of bovine tuberculosis. We discuss how this deployment might evolve as a network of smaller core areas aiming to achieve zero or low densities of all or more pests, with surrounding halos with lesser control effort against fewer species, enough to allow for at least ‘safe passage’ of native animals between the cores. For sustained control options, research is needed to inform the frequency and intensity of control, and thus the best control tools.The ability to detect target pests at low densities and management of re-invasion are essential for achieving zero or low pest density goals.
Holland et al, 2016 Species and site-specific impacts of an invasive herbivore on tree survival in mixed forests
Invasive herbivores are often managed to limit their negative impact on plant populations, but herbivore density – plant damage relationships are notoriously spatially and temporally variable. Using the invasive brush tail possum, Trichosurus vulpecula, in New Zealand as a case study, we parameterized a generic model to predict annual probability of browsed-induced mortality of five tree species at 12 sites. Model results indicated it is likely that possum browse was the primary cause of all tree mortality at nine of the 12 species-site combinations.
Peters et al, 2015; Action on the ground: A review of community environmental groups’ restoration objectives, activities and Partnerships in NZ
More than 600 community environmental groups across New Zealand are engaged in restoring degraded sites and improving and protecting habitat for native species. In the face of ongoing biodiversity declines, resource management agencies are increasing their reliance on these groups to enhance conservation outcomes nationally. Our aim was to develop a profile of community groups and their projects through examining group and project characteristics, objectives, activities and the support provided by project partners.
Farnworth et al, 2014; Understanding Attitudes Towards the Control of Nonnative Wild and Feral Mammals
Lethal control is used extensively in New Zealand to control nonnative nonhuman mammals. respondents were surveyed about 8 mammal groups considered pests and their attitudes towards their control and pest status. They also identified the most appropriate method of control for the 8 different mammals. Information was gathered from 3 groups of respondents: nonhuman animal protectionists, conservationists, and the general public.