Elizabete Marchante

Recovery Potential of Dune Ecosystems Invaded by an Exotic Acacia Species (Acacia longifolia)1

Abstract The effect of mechanical clearing and litter removal on control of Sydney golden wattle was studied in areas of Portugal that had been invaded for either long or short periods. The plant species that emerged and soil parameters were monitored to assess the recovery potential and the soil status of these areas after Sydney golden wattle control. More plant species emerged in the plots where mechanical control in combination with litter removal was applied than in nontreated plots or in plots where mechanical control alone was used. More plant species emerged in the recently invaded areas than in those that had been invaded for a long time. More Sydney golden wattle seedlings were found in the long-invaded area than in the recently invaded one. Total litter, nitrogen and carbon content, and β-glucosaminidase activity were higher in the soil of the long-invaded compared with the recently invaded areas. Regarding the efficacy of the methods used to remove Sydney golden wattle, sprouting was not observed 10 mo after cutting the trees in both areas, although this was not the case in other parallel studies. Nomenclature: Sydney golden wattle, Acacia longifolia (Andrews) Willd. Additional index words: Invasive plants, mechanical control, native species recovery, soil properties. Abbreviations: A, with Acacia longifolia; AR, Acacia longifolia removed; ALR, Acacia longifolia and litter removed; NAG, N-acetyl-β-d-glucosaminidase (NAGase EC 3.2.1.30); NRSJD, Natural Reserve of São Jacinto Dunes.

Temporal changes in the impacts on plant communities of an invasive alien tree, Acacia longifolia

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.

Using a WebMapping Platform to Engage Volunteers to Collect Data on Invasive Plants Distribution

WebMapping and citizen science are increasing their importance as tools both in science communication and in gathering abundant data. Nevertheless, gathering good and plentiful data from citizens when the scientific theme is unknown to them is a demanding challenge. Invasoras.pt is a science communication endeavor that targets the general public and one of its core elements is a WebMapping platform that intends to engage volunteers to geolocate invasive plants in Portugal. Besides gathering data for scientific research and to support management, the platform raises awareness about invasive plants. The platform has been available since March 2013 and receives data from a smartphone application and a Web application. Validated sightings are shown on an online map. All data is available through a Google Fusion Table and GBIF database (open data logic). Several strategies (interactive contents, printed materials, workshops and social media) were used to overcome the challenges of engaging contributors and making them better skilled to contribute with good data. After two years of steady growth in members (ca. 600) and sightings (>5400) the results are better than expected particularly amongst a population not familiarized with either citizen science or invasive plants. The outcomes of the platform and the efficacy of each strategy are analyzed and the accuracy and usefulness of the data are discussed.

Public perception of invasive plant species: assessing the impact of workshop activities to promote young students awareness

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.

Explaining people's perceptions of invasive alien species: A conceptual framework

Human perceptions of nature and the environment are increasingly being recognised as important for environmental management and conservation. Understanding peoples perceptions is crucial for understanding behaviour and developing effective management strategies to maintain, preserve and improve biodiversity, ecosystem services and human well-being. As an interdisciplinary team, we produced a synthesis of the key factors that influence peoples perceptions of invasive alien species, and ordered them in a conceptual framework. In a context of considerable complexity and variation across time and space, we identified six broad-scale dimensions: (1) attributes of the individual perceiving the invasive alien species; (2) characteristics of the invasive alien species itself; (3) effects of the invasion (including negative and positive impacts, i.e. benefits and costs); (4) socio-cultural context; (5) landscape context; and (6) institutional and policy context. A number of underlying and facilitating aspects for each of these six overarching dimensions are also identified and discussed. Synthesising and understanding the main factors that influence peoples perceptions is useful to guide future research, to facilitate dialogue and negotiation between actors, and to aid management and policy formulation and governance of invasive alien species. This can help to circumvent and mitigate conflicts, support prioritisation plans, improve stakeholder engagement platforms, and implement control measures.

Stakeholder engagement in the study and management of invasive alien species

Invasive alien species are a major driver of global environmental change and a range of management interventions are needed to manage their effects on biodiversity, ecosystem services, human well-being and local livelihoods. Stakeholder engagement is widely advocated to integrate diverse knowledge and perspectives in the management of invasive species and to deal with potential conflicts of interest. We reviewed the literature in the ISI Web of Science on stakeholder engagement (the process of involving stakeholders (actors) in decision making, management actions and knowledge creation) in invasion science to assess and understand what has been done (looking at approaches and methodologies used, stakeholders involved, and outcomes from engagement) and to make recommendations for future work. Research on stakeholder engagement in invasion science has increased over the last decade, helping to improve scientific knowledge and contributing towards policy formulation and co-implementation of management. However, many challenges remain and engagement could be made more effective. For example, most studies engage only one stakeholder group passively using questionnaires, primarily for assessing local knowledge and perceptions. Although useful for management and policy planning, these stakeholders are not active participants and there is no two-way flow of knowledge. To make stakeholder involvement more useful, we encourage more integrative and collaborative engagement to (1) improve co-design, co-creation and co-implementation of research and management actions; (2) promote social learning and provide feedback to stakeholders; (3) enhance collaboration and partnerships beyond the natural sciences and academia (interdisciplinary and transdisciplinary collaboration); and (4) discuss some practical and policy suggestions for improving stakeholder engagement in invasion science research and management. This will help facilitate different stakeholders to work better together, allowing problems associated with biological invasions to be tackled more holistically and successfully.

Engaging Society to Fight Invasive Alien Plants in Portugal—One of the Main Threats to Biodiversity

Invasive alien species (IAS) are a major threat to biodiversity all over the world and Portugal is no exception. The problem is so serious that such species are recognized by the Portuguese legislation since 1999 which includes 32 species of invasive animal and plants. Nevertheless, a large proportion of the population is still unaware of the problem. Considering that citizens represent a vector of introduction and spread of IAS and, on the other hand, can play a major role in helping to prevent and control IAS, this lack of awareness can be largely detrimental. In an attempt to reduce this gap, and aiming to contribute for a more sustainable environment and society, researchers from CFE/UC and from ESAC/IPC have been raising public awareness and engaging the public with the IAS problem, namely with invasive plants. Since 2003, several strategies have been used, including the website invasoras.pt which aims to aggregate several elements of these strategies. The most recent version of the website is online since 2013 and includes as core element a citizen science platform that aims to engage the public countrywide, voluntarily, to report sightings of invasive plants. Publications about invasive plants in Portugal, including a field guide and other printed materials, workshops and social media have been used to engage the public with the WebMapping platform. Additionally, field-work projects for university students and training courses for professionals dealing with alien plants and for school teachers have been organized. In this chapter, the different strategies implemented and the results of an effort to evaluate the effectiveness and outreach of these various approaches are presented. Overall, awareness about IAS is increasing amongst the Portuguese population, with citizens more educated about the problem and contributing more to the prevention and control of IAS, but much more work is needed. The challenge to reach publics other than the peers or professionals related to the topic is still daunting.

Using Landsat Time Series to Understand How Management and Disturbances Influence the Expansion of an Invasive Tree

Invasive plant management is both challenging and expensive and as such strategic and well-informed decisions may contribute for a more effective management. Remote sensing time series can inform decision-making, improving management strategies. Acacia longifolia is one of the most widespread invasive plants in Portuguese coastal areas. We used this species to test a new approach to assess how different management practices and disturbances may influence invasive plants’ distribution. The Mann–Kendall statistical test was applied to a 15-year time series (2000–2015) of Landsat TM/ETM+ derived normalized difference vegetation index to detect statistically significant vegetation trends. These maps were interpreted together with a land-cover map derived from a combined rule-based and supervised classification of a Landsat OLI image from November 27th 2013; this interpretation was then complemented with information about management practices and disturbances allowing to identify the processes influencing the current distribution of A. longifolia. The overall accuracy of the classification was 0.785 (Kappa 0.753) and A. longifolia was detected in 9% (8691 ha) of the study area. Of the nine processes of land cover change identified, “vegetation cover intensification” and “vegetation recovery after removal” were the main drivers of expansion. Pine forests were vulnerable to invasion but offered resistance to conversion into A. longifolia monospecific stands, while herbaceous and shrub habitats seemed less resistant to invasion. Some interventions aiming to control A. longifolia were shown to aggravate the invasion. This approach facilitates monitoring the invasion and allows managers to allocate resources to areas where management may be most effective.

A multi-scale modelling framework to guide management of plant invasions in a transboundary context

BackgroundAttention 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.MethodsWe 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.ResultsModel 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.ConclusionsAfter 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.

Mapping the Flowering of an Invasive Plant Using Unmanned Aerial Vehicles: Is There Potential for Biocontrol Monitoring?

Invasion by alien species is a worldwide phenomenon with negative consequences at both natural and production areas. Acacia longifolia is an invasive shrub/small tree well known for its negative ecological impacts in several places around the world. The recent introduction of a biocontrol agent (Trichilogaster acaciaelongifoliae), an Australian bud-galling wasp which decreases flowering of A. longifolia, in Portugal, demands the development of a cost-efficient method to monitor its establishment. We tested how unmanned aerial vehicles (UAV) can be used to map A. longifolia flowering. Our core assumption is as the population of the biocontrol agent increases, its impacts on the reduction of A. longifolia flowering will be increasingly visible. Additionally, we tested if there is a simple linear correlation between the number of flowers of A. longifolia counted in field and the area covered by flowers in the UAV imagery. UAV imagery was acquired over seven coastal areas including frontal dunes, interior sand dunes and pine forests considering two phenological stages: peak and off-peak flowering season. The number of flowers of A. longifolia was counted, in a minimum of 60 1 m2 quadrats per study area. For each study area, flower presence/absence maps were obtained using supervised Random Forest. The correlation between the number of flowers and the area covered by flowering plants could then be tested. The flowering of A. longifolia was mapped using UAV mounted with RGB and CIR Cannon IXUS/ELPH cameras (Overall Accuracy > 0.96; Cohen’s Kappa > 0.85) varying according to habitat type and flowering season. The correlation between the number of flowers counted and the area covered by flowering was weak (r2 between 0.0134 and 0.156). This is probably explained, at least partially, by the high variability of A. longifolia in what regards flowering morphology and distribution. The very high accuracy of our approach to map A. longifolia flowering proved to be cost efficient and replicable, showing great potential for detecting the future decrease in flowering promoted by the biocontrol agent. The attempt to provide a low-cost method to estimate A. longifolia flower productivity using UAV failed, but it provided valuable insights on the future steps.