Editorial: Emerging and neglected pests
Across the history of colonisation, humankind brought 32 terrestrial mammal species to Aotearoa, alien to this land, that managed to establish self-sustaining populations. In addition, many birds, amphibians and reptiles have similarly been introduced and established, as well as countless invertebrate pests and weeds. We are all aware of how devastating these introductions have been for our native biodiversity, through depredation, herbivory, resource competition and disease impacts. What is astounding, however, is that the breadth and depth of these impacts are such that we are still discovering new ones today.
In this issue of Kararehe Kino we highlight ongoing studies into what are generally considered some of the more ‘minor’ pest species and impacts that we are contending with in New Zealand. While major new initiatives such as Predator Free 2050 are rightly focussing on the biggest threats, and driving the goals and timescales essential for building the national and international momentum needed to address them, we cannot lose sight of the other pest issues that are not ‘minor’ by any definition of the word. Some are neglected. Perhaps of greater concern is that some are emerging to become bigger threats in the future.
Continuing to inform on the impacts of invasive species, Grant Norbury and Chris Jones present data showing that the seemingly innocuous hedgehog sometimes poses the greatest predation risk to some native species, with up to 51% of native shorebird nests in the Mackenzie Basin being lost to them. Dave Latham and Graham Nugent highlight how many of the more ‘minor’ ungulate species in New Zealand can very likely cause large amounts of damage to native vegetation. And Peter Sweetapple and Mandy Barron show the complexities of achieving biodiversity outcomes through pest management, illustrating how the competitive release of rats caused by possum control can deleteriously impact arboreal invertebrates.
Furthering the insight into complexity, John Innes argues that not all rats are equal, and that there are likely to be benefits for tree-nesting birds from the control of ship rats alone. Mandy Barron and colleagues present work investigating why some islands in the Hauraki Gulf that have undergone mammal eradication programmes had subsequently become free of German and common wasps, wondering whether there is a mechanism at play that can be turned to their management.
In terms of emerging vertebrate pests in New Zealand, perhaps of greatest concern are wallabies. And we’re not talking rugby. Bruce Warburton and colleagues present model predictions that indicate, if not managed, populations of Bennett’s and dama wallabies could eventually occupy most of the South and North Islands respectively. But it’s not as though we can’t eradicate invasive vertebrates if we put our mind to it. James Reardon illustrates the exceptional progress being made in the eradication of the alpine newt, likely introduced to the Central North Island around the turn of the current century. In other cases, eradication may not be essential or even desirable for controlling impacts. For example, Grant Morriss advises that for the management of feral pigeons in New Zealand, the use of non-lethal methods that leave some resident pigeons to satisfy the demands of individuals who value them may be the best compromise in current New Zealand society.
Finally, Pablo Garcia-Dias suggests that we may be facing more and different pest problems in the future due to the ongoing threat of new emergent exotic species in New Zealand posed by the pet trade. While not arguing for a blanket ban, he contends that we need a more nuanced and up-to-date knowledge of the biosecurity risk currently posed by this trade.
Agencies such as the Department of Conservation and Regional Councils, and the many sanctuaries and community groups around the country, do exceptional jobs of protecting our native biodiversity against invasive species. It is the job of the New Zealand science system to support them to the best of our ability through the provision of new and increasingly improved management tools and strategies, and the necessary prioritisation of resources to do this well.
Dan Tompkins, Portfolio Leader Managing Invasives, Manaaki Whenua Landcare Research