The management of invasive non-native species is a frequent cause of conflict in the field of biodiversity conservation because perceptions of their costs and benefits differ among stakeholder groups. A lack of cohesion between scientific researchers, the commercial sector and policy makers lies at the root of a widespread failure to develop and implement sustainable management practices for invasive species. The crisis of this situation is intensified by drivers stemming from international conventions and directives to address invasive species issues. There are further direct conflicts between legislative instruments promoting biodiversity conservation on the one hand while liberalizing trade at the national, European and global level on the other. The island of Ireland provides graphic illustration of the importance of cross-jurisdictional approaches to biological invasions. Using primarily Irish examples in this review, we emphasize the importance of approaching risk assessment, risk reduction and control or eradication policies from a cost-efficient, highly flexible perspective, incorporating linkages between environmental, economic and social objectives. The need for consolidated policies between Northern Ireland and the Republic of Ireland is particularly acute, though few model cross-border mechanisms for such consolidation are available. The importance of engaging affected stakeholders through positive interactions is discussed with regard to reducing the currently fragmented nature of invasive species management between the two jurisdictions.

Climate change is likely to affect plants in multiple ways, but predicting the consequences for habitat suitability requires a process-based understanding of the interactions. This is at odds with existing approaches that are mostly phenomenological and largely restricted to predicting the effects of changing temperature and rainfall on species distributions at a coarse spatial scale. We examine the multiple effects of climate change, including predicting the effects of altered flood regimes and land-use change, on the potential distribution of the invasive riparian species lippia (Phyla canescens) across a 26 000 km 2 catchment in eastern Australia. We determined habitat suitability for lippia by combining process-understanding of experts and an eco-physiological bioclimatic model within a Bayesian belief network. The bioclimatic model predicted substantial changes in habitat suitability by 2070 under both a wetter (Echam Mark 3) and drier (Hadley Centre Mark 2) climate change scenario, but only the more likely drier scenario reduced suitability in our test region. The area suitable for lippia was predicted to increase at least threefold with increased flooding under a wet climate scenario, although this would be partially negated by land-use change to cultivation. The region would become unsuitable to lippia with reduced flooding under a drier scenario irrespective of land-use changes, although existing populations would persist if grazing persisted. Independent field validation verified model structure and parameterization, and therefore the opinion of experts, but identified site-scale deficiencies in the available environmental data layers. Model predictions suggest that adaptation options for managing lippia will be greatly reduced under a drying scenario, but identify potential restoration opportunities under either scenario. This work highlights the value of predictive models that incorporate process-understanding at sufficiently fine spatial resolution to capture the important processes underpinning habitat suitability.

The role of mutualisms in contributing to species invasions is rarely considered, inhibiting effective risk analysis and management options. Potential ecological consequences of invasion of non-native pollinators include increased pollination and seed set of invasive plants, with subsequent impacts on population growth rates and rates of spread. We outline a quantitative approach for evaluating the impact of a proposed introduction of an invasive pollinator on existing weed population dynamics and demonstrate the use of this approach on a relatively data-rich case study: the impacts on Cytisus scoparius (Scotch broom) from proposed introduction of Bombus terrestris . Three models have been used to assess population growth (matrix model), spread speed (integrodifference equation), and equilibrium occupancy (lattice model) for C. scoparius . We use available demographic data for an Australian population to parameterize two of these models. Increased seed set due to more efficient pollination resulted in a higher population growth rate in the densityindependent matrix model, whereas simulations of enhanced pollination scenarios had a negligible effect on equilibrium weed occupancy in the lattice model. This is attributed to strong microsite limitation of recruitment in invasive C. scoparius populations observed in Australia and incorporated in the lattice model. A lack of information regarding secondary ant dispersal of C. scoparius prevents us from parameterizing the integrodifference equation model for Australia, but studies of invasive populations in California suggest that spread speed will also increase with higher seed set. For microsite-limited C. scoparius populations, increased seed set has minimal effects on equilibrium site occupancy. However, for density-independent rapidly invading populations, increased seed set is likely to lead to higher growth rates and spread speeds. The impacts of introduced pollinators on native flora and fauna and the potential for promoting range expansion in pollinator-limited 'sleeper weeds' also remain substantial risks.