Invasive non-native plants (INNP) cause severe impacts on nature and human well-being, and these are predicted to increase. While management tools have been developed to control early-stage invasions ...or to clean particular sites from INNP, they are only rarely available to halt and reduce large-scale invasions. Importation biological weed control (IBWC; also termed classical biological weed control) offers a potentially effective tool, especially when combined with other land management interventions. Here, we aim to bridge the gap between IBWC advocates and critics by providing a state of the art of IBWC and exploring untapped opportunities and new ideas to further increase efficacy and safety of this tool. We first present a decision tree to identify the circumstances under which IBWC should be considered, either alone or as part of an integrated weed management approach. We then address concerns raised against IBWC by contrasting historical approaches with recently suggested improvements and outline a path forward. With two case studies, we emphasize that successful reduction of weed densities using IBWC will specifically also contribute to environmental health and human well-being by restoring ecosystem services without pesticide input and reaching areas with otherwise no INNP management options. We hope that our compilation helps to reconcile advocates and critics of IBWC and lead to a more constructive discourse and hopefully closer collaboration between the two groups. A joint effort is needed to further improve IBWC and to consider it more often, as the increasing threats imposed by INNP are urgently awaiting sustainable and affordable solutions.
•Management tools to reduce large-scale plant invasions are often not available.•Importation (classical) biological weed control (IBWC) can be an effective tool.•We analyze benefits of IBWC, list untapped opportunities and outline a path forward.•We advocate to use IBWC more often, but also more rigorously.
1. Invasive non-native plants (INNPs) can have serious and widespread negative ecological and socio-economic impacts. It is therefore important they are managed appropriately. Within domestic gardens ...management decisions, which will tend to be made by individual members of the public, are likely to vary depending on (a) understanding of problems caused by INNP, and (b) knowledge of best practice. 2. Using content analysis, an approach seldom employed in an ecological context, this study analysed variation in internet-based information sources regarding INNP to determine how this collective discourse might influence risk perceptions and management decisions for domestic garden owners/managers. We used Japanese knotweed Fallopia japonica in the UK, as a case study, as it is one of the most ecologically and economically damaging INNP in the region. Our analysis categorized the types of author disseminating information about Japanese knotweed, the relative frequency of documents between author categories, and variation in content and style between and within author categories. 3. We identified five author categories: environmental NGOs, control companies, government, media and the property market. There was extensive variation in document structure, topics discussed, references and links to other sources, and language style; sometimes this variation was between author categories and sometimes within author categories. The most significant variation in topics discussed between author categories was indirect socio-economic problems, with control companies discussing these most. The number of pieces of legislation referenced and the proportion of militaristic words used were also highly significantly different between author categories. Some documents used neutral terminology and were more circumspect, whilst others were more forceful in expressing opinions and sensational. 4. The author category returning the highest number of documents was the subcategory local government, the shortest of which contained neither links to other information nor referenced any organizations. Further analysis of local government documents revealed conflicting advice regarding the disposal of Japanese knotweed waste material; confusion about this topic could result in decisions being made that spread Japanese knotweed further and are potentially unlawful. 5. The potential implications of our findings for the management of INNP in domestic gardens and societal perceptions of risks posed by INNP are discussed. 6. Synthesis and applications. To help prevent inappropriate management of invasive nonnative plants (INNPs), for example Japanese knotweed Fallopia japonica in domestic gardens, we recommend that local and national authorities collaborate and work towards disseminating more consistent messages about (a) the potential socio-economic and ecological problems caused by INNP, whilst avoiding hyperbole, and (b) the most appropriate management techniques.
Abstract Target 10 of the Global Strategy for Plant Conservation establishes that "Effective management plans are in place to prevent new biological invasions and to manage important areas for plant ...diversity that are invaded" by 2020. The rationale for the target is that invasive alien species are a major threat to native plants, and thus should be excluded from areas reserved for the conservation of plant species, especially when endemic and/or threatened. In Brazil, although most management plans report the presence of invasive alien species and the need for management in federal protected areas, there are only a very limited number of management plans implemented. The national strategy on invasive alien species, published as CONABIO Resolution 05/2009, has not been implemented, so progress on policies and legislation focused on invasive alien species at the federal level has been slow. In order to reach an effective development of public policies in Brazil, federal environmental agencies must function as focal points and be in charge of coordinating actions aimed at (1) identifying priority areas for preventing and managing biological invasions, and (2) managing invasive alien species and reduce their impacts.
Resumo Na meta 10 da Estratégia Global para a Conservação de Plantas está estabelecido que, até 2020, planos de manejo efetivos serão implementados para impedir novas invasões biológicas e para manejar áreas importantes para a diversidade de plantas e que estejam invadidas. A justificativa para a meta é que espécies exóticas invasoras usualmente são uma grande ameaça de extinção a plantas nativas, e assim devem ser excluídas de áreas que são destinadas à conservação de espécies vegetais, especialmente aquelas que são endêmicas e/ou estejam ameaçadas de extinção. No Brasil, apesar da maior parte dos planos de manejo de unidades de conservação federais reportarem a presença de espécies exóticas invasoras nessas áreas, um número bem limitado de planos já foi implementado. A Resolução CONABIO 05/2009, que estabelece uma estratégia nacional sobre espécies exóticas invasoras, não foi colocada em prática, sendo lentos os avanços em políticas e legislação focadas em espécies exóticas invasoras em nível federal. Para que políticas efetivas sejam desenvolvidas no Brasil, órgãos federais da área ambiental devem funcionar como pontos focais e coordenar ações para (1) identificar áreas prioritárias para a prevenção e o manejo de invasões biológicas, e (2) para manejar espécies exóticas invasoras, reduzindo impactos pelas mesmas provocados.
Astragalus tricarinatus A.Gray is a federally-listed short lived perennial herb endemic to southern California. Its primary habitat is along the ecotone of the Mojave and Colorado Deserts in the San ...Bernardino and Little San Bernardino Mountains between 390 and 1525 m. Discovery of this species' upland habitat has prompted research into the ecology of populations across its range, as the life history and threats may be different from those of the previously-known wash populations. Our study sought to further document A. tricarinatus distribution and abundance within its range, as well as quantify impacts to its growth and reproductive efforts associated with co-occurring native and invasive plant species. We mapped all known localities in our study area on aerial imagery then used this to visually recognize its typical edaphic habitat and identify new potential sites. Where A. tricarinatus was found, we established plots in which plant size, the number of reproductive structures, and microhabitat characteristics were recorded. Two new occurrences (defined here as >1 km away from known localities) were recorded within its existing range as well as a previously undocumented locality between two known occurrences containing an estimated 2600 plants. Most plants were found on south and east aspects, and on slopes ranging from 30–45°. We found that increases in invasive cover correlated with a decrease in production of reproductive structures. As a federally-listed species occurring in steep, remote habitats with few threats, these findings suggesting an association between invasive species presence and reduced reproductive structures should be further investigated experimentally, as they affect population dynamics and conservation of this species.
The spread of neophytes (non-native plant species) challenges the conservation status and ecological integrity of forests, especially in lowland areas. Long-term resurvey studies are needed to ...evaluate the temporal dynamics of neophytes in forests; however, such data are scarce. In 2023, we resampled a set of 45 permanent vegetation plots (established in 1992/93) in two forest vegetation types: oak-hornbeam forests dominated by
and colline oak-beech forests dominated by
. Over the last 30 years, oak forests have experienced extensive oak tree mortality, with the degree of habitat degradation being greater in
forests. In the early 1990s, only three neophytes with low abundance were recorded across all plots. In the 2023 resurvey, the total number of neophytes increased to 22 species (15 herbaceous and 7 woody species), comprising 6.9% of the total species pool in the understory layer. The increase in the plot-level number and cover of neophytes was significant in plots dominated by
but not in those with
. The most frequent neophytes were
(present in 31% of plots),
(27%),
(16%) and
(16%). The richness and cover of neophytes were significantly affected by the tree layer cover (negative correlation) and the degree of soil disturbance (positive correlation). All neophytes established in disturbed patches, whereas the occurrence of
was exceptional as it was able to colonize less degraded, shaded understory environments. Habitat degradation (the mortality-induced loss of stand-forming oak trees resulting in extensive tree layer cover decrease) emerged as a key driver promoting neophyte proliferation, coupled with the impact of management-induced disturbances affecting overstory and soil conditions. The spread is expected to continue or even intensify in the future because novel light regimes and disturbances make forest habitats less resistant to neophyte proliferation.
Although plant invasions are often associated with disturbance, localized disturbances can promote invasion either by: (i) creating sites where individuals establish; or (ii) enabling an invader to ...colonize the entire stand. The former is expected when both establishment and survival to reproductive age require disturbed conditions, whereas the latter should occur in systems when either establishment or survival are limited to disturbed sites. We investigated the role of localized disturbance, specifically treefalls, in the invasion of the Asian Rubus phoenicolasius in a deciduous forest in Maryland, USA. We investigated the density and demography of R. phoenicolasius in treefall gaps of various sizes, but identical age to non‐gap areas, using Classification and Regression Tree (CART) analyses to identify the most important predictors. To explore how the demography of established individuals responds to disturbed versus undisturbed conditions, we carried out a garden experiment with three different levels of shade (5, 12 and 22% full sun). We found vegetative and sexual reproduction, and seedling establishment, to be limited to large gaps in an old stand, but not in a stand in an earlier age of succession. However, in the garden experiment, established plants were able to survive and grow under all shade treatments. These findings indicate that R. phoenicolasius requires disturbances such as treefalls to establish in forests, but established plants will survive canopy closure, leading to stand‐wide invasion. Managers should be able to prevent invasion, however, by inspecting large gaps for new recruits every 3 years.
Frequency and density of four invasive non-native plants (Lonicera japonica .L. Thunb., Ampelopsis brevipedunculata Maxim. Trautv., Celastrus orbiculatus Thunb. and Rosa multiflora L. Thunb.) were ...measured in the Pennypack Wilderness, a 324 ha natural preserve located in a southeastern Pennsylvania suburban landscape. Stem frequency and density of each species were measured during 1988 and 1989 in 163 plots of 20 m2each located randomly and distributed proportionally among the 10 successional plant communities comprising the preserve. Lonicera japonica was the most frequently encountered and densely growing plant; frequency and density of the other three species appeared to be related to autecological characteristics of the species. Analysis of colonization and density patterns revealed that mature forest generally supported the fewest and least dense colonies, a result of complete shading and limited colonization sites. Frequency and density were also lower in successional plant communities comprising a Mixed Oak forest sere than they were in communities comprising a Mixed Mesophytic forest sere, probably a result of edaphic characteristics or vagaries of the location of introduction.
The restoration of areas invaded by non‐native plants is challenging as invasive plants may affect both biotic and abiotic components of ecosystems, leading to impacts that constrain recolonization ...by native species after invaders are eliminated. In such a scenario, restoration techniques as topsoil transposition might accelerate colonization by native species in forests. Hedychium coronarium J. Koenig (Zingiberaceae) is a Himalayan herbaceous rhizomatous plant recognized as invasive in several countries. This study aimed to experimentally evaluate the response of plant assemblages to topsoil transposition on a site invaded by H. coronarium after chemical control. Four treatments were applied: chemical control integrated with topsoil transposition, chemical control of H. coronarium alone, topsoil transposition alone, and no intervention (control). Plots were evaluated prior to the application of treatments and then monthly for 11 months after treatments. Parameters were measured for H. coronarium (number of ramets, ramet height, and cover) and other species (species richness, abundance, and cover). Plots treated with chemical control (regardless of topsoil transposition) were similar in terms of all parameters measured and species composition, with dominance of herbs and shrubs. Plots managed solely with topsoil transposition had lower species richness, abundance, and cover, but more diverse life‐forms, being equally rich in climbers, trees, and herbs. Chemical control was effective to control invasion by H. coronarium and increase species richness and abundance on the managed site. Topsoil transposition promoted colonization by species that might accelerate restoration.
The success of invasion by non-native species can be influenced by positive interactions established in the area of introduction. For instance, seed dispersal by birds can increase seed rain, seed ...germination, and, as a consequence, the probability of establishment of new invasion
foci
.
Schefflera arboricola,
an ornamental shrub with fruits largely consumed by birds, is invasive in several countries. To our knowledge, this is the first research project on mechanisms that might explain the success of
S. arboricola
in areas where it is invasive. The main aim of this study was to assess the invasiveness of
S. arboricola
associated with seed dispersal by birds. Fruit availability and frugivory interactions with local birds were registered and the germination percentage of seeds not consumed by birds was compared to the germination of seeds collected from bird feces. Our results show that frugivory and seed dispersal by native birds increase the establishment of
S. arboricola.
In addition, intrinsic species traits such as extended flowering and fruiting, high percentage of seed germination, early germination due to frugivory, and ability to establish in different microhabitats facilitate invasion by
S. arboricola
. Given the intensive horticultural use of
S. arboricola
and seed dispersal interactions with generalist birds, there is an imminent risk of invasion in forest remnants close to wherever
S. arboricola
is cultivated. We recommend that adult plants of
S. arboricola
are eliminated from gardens and semi-natural areas close to protected areas as a prevention measure to avoid invasions and impacts on natural habitats.
To test the effects of invasion by strawberry guava trees (Psidium cattleianum) on the forest soil ecosystem, we compared soil properties between pairs of adjacent native and P. cattleianum stands. ...We set up six study sites that had developed under different mean annual precipitation levels in the Ko'olau Mountains on the island of O'ahu, Hawai'i. Accumulated litter mass and soil pH decreased with precipitation in the native stands. Invasion by P. cattleianum increased the amount of litter and reduced the differences in soil water content and pH among the sites. We compared the decomposition process using the Tea Bag Index, which is determined by the difference in dry mass of commercially available green and rooibos teas in nylon mesh bags before and after 90 days of burial. Psidium cattleianum increased the initial litter decomposition rate irrespective of precipitation and other soil properties. On the other hand, P. cattleianum increased the long-term litter stabilization factor of the Tea Bag Index in wetter sites. The accumulation of litter was likely caused by indirect effects of P. cattleianum through the alteration of soil moisture properties. In summary, this study shows that invasion by P. cattleianum could alter the soil properties in both wet and mesic sites, suggesting the possibility of change in composition and/or function of decomposers.
PDF
