Building a synthesis of economic costs of biological invasions in New Zealand

Biological invasions are a major component of anthropogenic environmental change, incurring substantial economic costs across all sectors of society and ecosystems. However, the economic costs of invasions have been disparately reported, lacking synthesis across taxonomic and sectorial scales. Using the newly compiled InvaCost database, we analyse reported economic damage and management costs incurred by biological invasions in New Zealand — a country renowned for its approaches to invasive species management — from 1968 to 2020. In total, US$69 billion (NZ$97 billion) is currently reported over this ~50 year period, with approximately US$9 billion of this considered highly reliable, observed (c.f. projected) costs. Most (82%) of these observed economic costs are associated with damage, with comparatively little invested in management (18%). Reported costs are increasing over time, with damage averaging US$120 million per year and exceeding management expenditure in all decades. Where specified, most reported costs are from terrestrial plants and animals, with damages most often borne by primary industries such as agriculture and forestry. Management costs are associated more with interventions by authorities and stakeholders. However, some known ecologically (c.f. economically) impactful invasive species are notably absent from estimated damage costs, and management costs are not reported for a number of game animals and agricultural pathogens. Given these gaps for known and potentially damaging invaders, we urge improved cost reporting at the national scale, including improving public accessibility through increased access and digitisation of records, particularly in overlooked socioeconomic sectors and habitats. This also further highlights the importance of investment in management to curtail future damages across all sectors.

Science for Social Licence to Arrest an Ecosystem-Transforming Invasion

The primary role for science in addressing complex environmental problems, such as biological invasions, is generally assumed to be as a guide for management decisions. However, science often plays a minor role in decision-making, with practitioners instead relying on professional experience and local knowledge. We explore alternative pathways by which science could help reduce the spread and impacts of invasive species. Our study centred on attempts to understand the science needs of three local governance bodies responsible for the management of invasive (wilding) conifer species in the southern South Island of New Zealand. We used a combination of workshop discussions, questionnaire responses and visits to field sites to elicit feedback from study participants. We applied a mixed inductive-deductive thematic analysis approach to derive themes from the feedback received. The three main themes identified were: 1) Impacts of wilding conifers and goals for wilding conifer control; 2) barriers to achieving medium- and long-term goals; and 3) science needed to support wilding conifer control.Participants identified both instrumental (e.g. reduced water availability for agriculture) and intrinsic (e.g. loss of biodiversity and landscape values) impacts of wilding conifer invasions, with long-term goals focussed on avoiding or reversing these impacts. Barriers to achieving goals were overwhelmingly social, relating either to unwillingness of landowners to participate or poorly designed regulatory frameworks. Consequently, science needs related primarily to gaining social licence to remove wilding conifers from private land and for more appropriate regulations. Participants did not perceive any need for additional scientific information to guide management decisions, relying instead on professional experience and local knowledge. International experience suggests that invasive species control programmes often face significant external social barriers. Thus, for many biological invasions the primary role for science might be to achieve social licence and regulatory support for the long-term goals of invasive species control programmes and the management interventions required to achieve those goals.

To ban or not to ban, is it the only option to regulate biological invasions?

Las invasiones biológicas son una de las mayores causas de pérdida de biodiversidad. Para paliar los impactos de las especies exóticas invasoras (EEIs) que suponen una amenaza grave, se creó el Catálogo Español de Especies Exóticas Invasoras, una herramienta dinámica en su creación, pero rígida en su aplicación. Aunque sujeto a continuas modificaciones, la inclusión de una EEI en el Catálogo supone generalmente la prohibición genérica de su posesión, transporte, tráfico y comercio. Sin embargo, esa rigidez genera a menudo conflictos socio-económicos cuando las EEIs son recursos explotables económicamente. En esta revisión, ejemplificamos las dificultades de implementar prohibiciones genéricas y proponemos que, para ser eficaz, la legislación sobre EEIs debería ampliar el abanico de herramientas disponibles (i.e. flexible), más allá del dilema de prohibirlo o permitirlo todo. Para ello proponemos la creación de categorías de EEIs que impliquen diferentes niveles de restricción y de estrategias de gestión. En el caso de EEIs ampliamente distribuidas sin posibilidades técnicas de control poblacional a gran escala ni de prevención de su expansión, planteamos la permisividad de su explotación comercial bajo ciertas restricciones, y señalamos las dificultades asociadas a prohibir dicha explotación cuando ésta ya se realiza. Aunque las soluciones simples (i.e. prohibir o no prohibir) pueden ser más fáciles de entender e implementar, no son siempre las más eficaces. Por tanto, animamos a que la legislación introduzca flexibilidad, que, pese a introducir una mayor complejidad, facilitaría la toma de decisiones en la gestión de las EEIs, mejoraría la eficiencia en el uso de recursos y reduciría los conflictos sociales asociados a esa gestión.

Interactive Regulations of Dynamic Methylation and Transcriptional Responses to Recurring Environmental Stresses During Biological Invasions

Deoxyribonucleic acid methylation and gene transcription have been proved as two underlying mechanisms involved in rapid plastic response to environmental stresses. However, it remains elusive on how DNA methylation regulates gene transcription under acute and recurring environmental challenges to form the stress memory, further contributing to invasion success during range expansions. Using a model invasive species Ciona robusta, we investigated the regulatory roles of DNA methylation on gene transcription and their contribution to the formation of stress memory at 30 genes under acute and recurring osmotic challenges simulated during the invasion process. We found the bimodal distribution of methylation level for the 68 mCpGs identified across all the genes after challenges, but only five sites were significantly correlated with the expression of their corresponding genes. These genes participated in the biological processes of Ca2+ transport and metabolism of lipid and proline. At the DNA methylation level, we found two early-responding and four tardy-responding sites of stress memory and these sites were functionally related to genes involved in the biosynthesis of proline, metabolism of lipid, and transport of taurine and Ca2+. At the transcriptional level, three tardy-responding and five early-responding memory genes were involved in the transport of ions, regulation of water channels, biosynthesis of taurine, and metabolism of lipid. Altogether, the findings here suggest that DNA methylation and gene transcription should work in concert to facilitate the formation of stress memory, thus further improving the performance of invaders under recurring environmental challenges during biological invasions.

The interface between invasive species science and legal regulation, using Hymenopteran species and their pathogens as a model system

<p>Biological invasions are one of the major causes of biodiversity decline on the planet. The key driver of the global movement of invasive species is international trade. As a response to trade driven invasive species risk, international and domestic regulations have been promulgated with the goal of managing the spread and impact of non-native species. My aims in this thesis were twofold. First, my goal was to review a subset of international and domestic regulations with a view to commenting on their fitness for purpose and suggesting potential improvements. Second, I used the example of non-native and invasive Hymenoptera, as well as their pathogens, to illustrate the risks posed by invasive species and gaps in their management. In order to assess international and domestic regulations, I reviewed the World Trade Organization’s (WTO) Agreement on Sanitary and Phytosanitary Measures, as well as associated disputes. I argue that the WTO’s regulatory system does, for the most part, allow domestic regulators to manage invasive species risk as they see fit. Subsequently, the focus of the thesis narrows to investigate New Zealand’s pre- and post-border regime managing invasive species. I argue that New Zealand’s pre-border approach represents international best practice, but the post-border management of species is fragmented. The power to manage invasive species has been delegated to sub-national and regional bodies, which typically approach invasive species management in different ways. This variation has led to regulatory inconsistencies in pests managed and funding allocated. There appears to be a substantial lack of planning in some spaces, such as the risk of aquatic invasions. I make recommendations to ameliorate these inconsistencies. My second aim involved the study of non-native and invasive Hymenoptera in New Zealand, as well as the pathogens they carry, in order to illustrate the risks posed by invasive species and gaps in their management. I show that the globally widespread invasive Argentine ant (Linepithema humile) may play a role in the pathogen dynamics and mortality of honey bee hives where the species occur sympatrically. Hives in the presence of Argentine ants suffered significantly higher mortality rates relative to hives without ants and always had higher levels of a honey bee pathogen Deformed wing virus. I demonstrate that honey bee pathogens are found in a range of invasive Hymenoptera in New Zealand. I amplify entire genomes of the honey bee virus Kashmir bee virus (KBV) from three species of non-native or invasive Hymenoptera (Argentine ants, common wasps and honey bees). I show that there is KBV strain variability within and between regions, but more between regions. Further, I demonstrate the result that as sampled KBV sequence length increases, so too does sampled diversity. These results highlight how ‘an’ invasive species is typically not alone: they carry a range of diseases that are almost always not considered in international and regional management plans. Patterns of non-native Hymenoptera carrying honey bee diseases were not restricted to New Zealand. I used mitochondrial DNA to find the likely origin of invasive populations of the globally distributed invasive German wasp. I demonstrate that German wasps show reduced genetic diversity in the invaded range compared to the native range. Populations in the introduced range are likely to have arrived from different source populations. In some regions there were likely multiple introductions. Other regions are genetically homogenous and represent potential areas for use of gene drive technologies. All four different honey bee pathogens assayed for were found in German wasp populations worldwide. These results highlight how the introduction of one exotic species likely brings a range of pathogens. This example of pathogens in Hymenoptera is likely to be true for nearly all non-native introductions. Many of the impacts of biological invasions, such as predation and competition, are relatively obvious and are frequently studied. However some, such as the impact of pathogens, are unseen and poorly understood. Legal regulation is often a post-hoc response implemented once a problem has already arisen. At a global level regulatory regimes operate relatively effectively. As the focus becomes more granular, such as the case of pathogens of Hymenoptera, fewer controls exists. This thesis helps to reduce uncertainty in this area as well as makes recommendations as to how these risks may be managed.</p>

The interface between invasive species science and legal regulation, using Hymenopteran species and their pathogens as a model system

<p>Biological invasions are one of the major causes of biodiversity decline on the planet. The key driver of the global movement of invasive species is international trade. As a response to trade driven invasive species risk, international and domestic regulations have been promulgated with the goal of managing the spread and impact of non-native species. My aims in this thesis were twofold. First, my goal was to review a subset of international and domestic regulations with a view to commenting on their fitness for purpose and suggesting potential improvements. Second, I used the example of non-native and invasive Hymenoptera, as well as their pathogens, to illustrate the risks posed by invasive species and gaps in their management. In order to assess international and domestic regulations, I reviewed the World Trade Organization’s (WTO) Agreement on Sanitary and Phytosanitary Measures, as well as associated disputes. I argue that the WTO’s regulatory system does, for the most part, allow domestic regulators to manage invasive species risk as they see fit. Subsequently, the focus of the thesis narrows to investigate New Zealand’s pre- and post-border regime managing invasive species. I argue that New Zealand’s pre-border approach represents international best practice, but the post-border management of species is fragmented. The power to manage invasive species has been delegated to sub-national and regional bodies, which typically approach invasive species management in different ways. This variation has led to regulatory inconsistencies in pests managed and funding allocated. There appears to be a substantial lack of planning in some spaces, such as the risk of aquatic invasions. I make recommendations to ameliorate these inconsistencies. My second aim involved the study of non-native and invasive Hymenoptera in New Zealand, as well as the pathogens they carry, in order to illustrate the risks posed by invasive species and gaps in their management. I show that the globally widespread invasive Argentine ant (Linepithema humile) may play a role in the pathogen dynamics and mortality of honey bee hives where the species occur sympatrically. Hives in the presence of Argentine ants suffered significantly higher mortality rates relative to hives without ants and always had higher levels of a honey bee pathogen Deformed wing virus. I demonstrate that honey bee pathogens are found in a range of invasive Hymenoptera in New Zealand. I amplify entire genomes of the honey bee virus Kashmir bee virus (KBV) from three species of non-native or invasive Hymenoptera (Argentine ants, common wasps and honey bees). I show that there is KBV strain variability within and between regions, but more between regions. Further, I demonstrate the result that as sampled KBV sequence length increases, so too does sampled diversity. These results highlight how ‘an’ invasive species is typically not alone: they carry a range of diseases that are almost always not considered in international and regional management plans. Patterns of non-native Hymenoptera carrying honey bee diseases were not restricted to New Zealand. I used mitochondrial DNA to find the likely origin of invasive populations of the globally distributed invasive German wasp. I demonstrate that German wasps show reduced genetic diversity in the invaded range compared to the native range. Populations in the introduced range are likely to have arrived from different source populations. In some regions there were likely multiple introductions. Other regions are genetically homogenous and represent potential areas for use of gene drive technologies. All four different honey bee pathogens assayed for were found in German wasp populations worldwide. These results highlight how the introduction of one exotic species likely brings a range of pathogens. This example of pathogens in Hymenoptera is likely to be true for nearly all non-native introductions. Many of the impacts of biological invasions, such as predation and competition, are relatively obvious and are frequently studied. However some, such as the impact of pathogens, are unseen and poorly understood. Legal regulation is often a post-hoc response implemented once a problem has already arisen. At a global level regulatory regimes operate relatively effectively. As the focus becomes more granular, such as the case of pathogens of Hymenoptera, fewer controls exists. This thesis helps to reduce uncertainty in this area as well as makes recommendations as to how these risks may be managed.</p>