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Invasion by alien plants results in serious adverse impacts on biodiversity, ecosystem services, economy and social welfare, and is an ever-increasing challenge for nature conservation. Control of established invasive species is frequently very difficult and costly. Therefore, predicting which species have risk of becoming invasive is crucial both to prevent introduction of new invaders and to target high risk species already present in order to avoid their spread, particularly to areas with high conservation value. In Portugal more than 600 alien plant species are present as casuals or naturalized, and decision support tools are needed to discriminate which of these have higher probability of becoming invasive. We aimed to assess the effectiveness of the Australian Weed Risk Assessment, adapted to the Portuguese conditions (P-WRA), by evaluating 172 plant species: 49 considered as invasive; and, 123 as non-invasive species. The results showed that the P-WRA correctly identified all invasive species. As for non-invasive species, 17% were accepted, 78% rejected and 5% required further evaluation. Receiver Operating Characteristic (ROC) curve reflected high accuracy of predictions despite lower than that found in other regions. The best cutoff level for P-WRA score, maximizing the ability for classification of the protocol, was 13 resulting in more non-invasive species accepted (46%). In the end, this assessment informed that in addition to the 49 species already invasive, a high number (66) of alien plant species have invasive risk. Amongst these, a list of 20 species is proposed for targeted priority management aiming to prevent their spread. Comparison of the scores obtained with A-WRA for other regions with Mediterranean climate revealed that 17% of the species compared (78) reached different outcomes, signaling the need to be careful when extrapolating the use of previous scores. The P-WRA can be a promising screening system post-border for predicting invasive species already present in Portugal and contribute to the targeting of species for priority intervention, particularly in natural areas with high conservation value. [ABSTRACT FROM AUTHOR]

Background: Attention has recently been drawn to the issue of transboundary invasions, where species introduced and naturalized in one country cross international borders and become problematic in neighbouring countries. Robust modelling frameworks, able to identify the environmental drivers of invasion and forecast the current and future potential distribution of invasive species, are needed to study and manage invasions. Limitations due to the lack of species distribution and environmental data, or assumptions of modelling tools, often constrain the reliability of model predictions. Methods: We present a multiscale spatial modelling framework for transboundary invasions, incorporating robust modelling frameworks (Multimodel Inference and Ensemble Modelling) to overcome some of the limitations. The framework is illustrated using Hakea sericea Schrad. (Proteaceae), a shrub or small tree native to Australia and invasive in several regions of the world, including the Iberian Peninsula. Two study scales were considered: regional scale (western Iberia, including mainland Portugal and Galicia) and local scale (northwest Portugal). At the regional scale, the relative importance of environmental predictors sets was evaluated and ranked to determine the main general drivers for the species distribution, while the importance of each environmental predictor was assessed at the local scale. The potential distribution of H. sericea was spatially projected for both scale areas. Results: Model projections for western Iberia suggest that a large area is environmentally suitable in both Portugal and Spain. Climate and landscape composition sets were the most important determinants of this regional distribution of the species. Conversely, a geological predictor (schist lithology) was more important in explaining its local-scale distribution. Conclusions: After being introduced to Portugal, H. sericea has become a transboundary invader by expanding in parts of Galicia (Spain). The fact that a larger area is predicted as environmentally suitable in Spain raises concerns regarding its potential continued expansion. This highlights the importance of transboundary cooperation in the early management of invasions. By reliably identifying drivers and providing spatial projections of invasion at multiple scales, this framework provides insights for the study and management of biological invasions, including the assessment of transboundary invasion risk. [ABSTRACT FROM AUTHOR]

Studies on the impacts of invasive plants are common but most are short term and fail to consider the temporal context of invasion. The present work investigated particular invasions on two different time scales and asked: (1) Do the impacts of an invasive tree on plant communities change after decades of invasion? (2) Are patterns of impacts dynamic over a period of five years? (3) Can multiple parameters reveal impacts that are unnoticed when single-value parameters are measured alone? Contrasting plant communities (long invaded, recently invaded and non-invaded) of a Portuguese coastal dune were compared during a 5-year period to assess the impacts of the invasive Acacia longifolia. Plant diversity, richness, cover, plant traits, indicator species analysis, similarity between areas and species turnover were analysed to reveal spatial and temporal patterns of change. Native species richness declined in both invaded areas. As invasion time increased, species shared with natural habitats decreased along with native plant cover, diversity and species turnover. Many species typical of dunes were replaced by generalists and exotics species, and richness of species with some level of nitrophily increased, particularly in recently invaded areas. Life form spectrum was radically transformed in invaded areas with several small-sized life forms being replaced by one single microphanerophyte. Germination of A. longifolia was greatest in long invaded areas. Findings show that modification of plant communities intensifies with invasion time and that invasion promotes a diversity of structural and functional changes which are dynamic over a few years (medium-term scale) but which tend to stabilize after several decades (long-term scale). An analysis of parameters in combination revealed changes that were not apparent when the same parameters were considered separately. [ABSTRACT FROM AUTHOR]

Invasive species are one of the main threats to biodiversity worldwide. Even though they are identified and recognized as such by the Portuguese law, the majority of the population is not yet aware of this problem. Aiming to increase awareness about biological invasions among young students, a workshop on Invasive Plant Species was organized at the Botanical Museum of the University of Coimbra. A total of 170 teenager students from five schools participated in the workshop. Three activities were prepared, focusing on: (1) identification of invasive plants, (2) competition between native and invasive plants and (3) control of invasive plants. One year later, questionnaires were sent to the participants, aiming to appraise workshop effectiveness, and this questionnaire revealed that these students know more about invasive plant species than a comparable group of students that did not participate in the workshop. The results clearly showed that practical informal education activities may be effective in raising public awareness. Questionnaires were essential to evaluate the knowledge acquired and retained by the students during the workshop. [ABSTRACT FROM PUBLISHER]

Aim Many Australian Acacia species have been planted around the world, some are highly valued, some are invasive, and some are both highly valued and invasive. We review global efforts to minimize the risk and limit the impact of invasions in this widely used plant group. Location Global. Methods Using information from literature sources, knowledge and experience of the authors, and the responses from a questionnaire sent to experts around the world, we reviewed: (1) a generalized life cycle of Australian acacias and how to control each life stage, (2) different management approaches and (3) what is required to help limit or prevent invasions. Results Relatively few Australian acacias have been introduced in large numbers, but all species with a long and extensive history of planting have become invasive somewhere. Australian acacias, as a group, have a high risk of becoming invasive and causing significant impacts as determined by existing assessment schemes. Moreover, in most situations, long-lived seed banks mean it is very difficult to control established infestations. Control has focused almost exclusively on widespread invaders, and eradication has rarely been attempted. Classical biological control is being used in South Africa with increasing success. Main conclusions A greater emphasis on pro-active rather than reactive management is required given the difficulties managing established invasions of Australian acacias. Adverse effects of proposed new introductions can be minimized by conducting detailed risk assessments in advance, planning for on-going monitoring and management, and ensuring resources are in place for long-term mitigation. Benign alternatives (e.g. sterile hybrids) could be developed to replace existing utilized taxa. Eradication should be set as a management goal more often to reduce the invasion debt. Introducing classical biological control agents that have a successful track-record in South Africa to other regions and identifying new agents (notably vegetative feeders) can help mitigate existing widespread invasions. Trans-boundary sharing of information will assist efforts to limit future invasions, in particular, management strategies need to be better evaluated, monitored, published and publicised so that global best-practice procedures can be developed. [ABSTRACT FROM AUTHOR]

• Both native and invasive species grew better on the invaded foredune soil. • Adding litter did not influence the growth of native and invasive plants in foredunes. • Results suggest no need for measures to restore invaded soils in foredunes. Despite growing evidence that many invasive plants have impacts at soil level, it is less clear how these changes affect the recovery of invaded systems after their removal. Acacia longifolia is an invasive species in coastal areas around the world; it modifies soil properties and forms a thick layer of litter that can hinder the recovery of native dune communities and facilitate its own invasion. Ammophila arenaria is a key native species in the Portuguese foredunes but its habitat is gradually invaded by A. longifolia. Aiming to assess the influence of the soil altered by A. longifolia invasion on the germination and early growth of A. arenaria and A. longifolia , seeds of both species were sown under controlled conditions in native and invaded soils, and in the presence or absence of A. longifolia litter. Considering our main goal (to assess the development of each species in different conditions), and because study species have different growth forms, species were treated separately. Both species germinated better in the native soil, but after 12 weeks A. arenaria and A. longifolia had better performance in the invaded soil, exhibiting longer shoots, and higher biomass, leaf area, and relative growth rate. The root mass fraction was higher in the native soil. The added litter had no significant effect on germination or growth of either species. These results suggest that after the removal of A. longifolia no special measures are necessary to restore foredunes soil when promoting A. arenaria populations, although such measures could delay the growth of A. longifolia. Our results emphasize the importance of managing biological invasions at early stages as restoration is easier and prevent positive feedbacks that further promote the invasive species. However, more studies are needed to understand when management measures at soil level are required in ecological restoration projects. [ABSTRACT FROM AUTHOR]