Abstract  Much confusion exists in the English-language literature on plant invasions concerning the terms ‘naturalized’ and ‘invasive’ and their associated concepts. Several authors have used these terms in proposing schemes for conceptualizing the sequence of events from introduction to invasion, but often imprecisely, erroneously or in contradictory ways. This greatly complicates the formulation of robust generalizations in invasion ecology. Based on an extensive and critical survey of the literature we defined a minimum set of key terms related to a graphic scheme which conceptualizes the naturalization/invasion process. Introduction means that the plant (or its propagule) has been transported by humans across a major geographical barrier. Naturalization starts when abiotic and biotic barriers to survival are surmounted and when various barriers to regular reproduction are overcome. Invasion further requires that introduced plants produce reproductive offspring in areas distant from sites of introduction (approximate scales: > 100 m over < 50 years for taxa spreading by seeds and other propagules; > 6 m/3 years for taxa spreading by roots, rhizomes, stolons or creeping stems). Taxa that can cope with the abiotic environment and biota in the general area may invade disturbed, seminatural communities. Invasion of successionally mature, undisturbed communities usually requires that the alien taxon overcomes a different category of barriers. We propose that the term ‘invasive’ should be used without any inference to environmental or economic impact. Terms like ‘pests’ and ‘weeds’ are suitable labels for the 50–80% of invaders that have harmful effects. About 10% of invasive plants that change the character, condition, form, or nature of ecosystems over substantial areas may be termed ‘transformers’.

Abstract  Recent comprehensive data provided through the DAISIE project (www.europe-aliens.org) have facilitated the development of the first pan-European assessment of the impacts of alien plants, vertebrates, and invertebrates in terrestrial, freshwater, and marine environments on ecosystem services. There are 1094 species with documented ecological impacts and 1347 with economic impacts. The two taxonomic groups with the most species causing impacts are terrestrial invertebrates and terrestrial plants. The North Sea is the maritime region that suffers the most impacts. Across taxa and regions, ecological and economic impacts are highly correlated. Terrestrial invertebrates create greater economic impacts than ecological impacts, while the reverse is true for terrestrial plants. Alien species from all taxonomic groups affect "supporting", "provisioning", "regulating", and "cultural" services and interfere with human well-being. Terrestrial vertebrates are responsible for the greatest range of impacts, and these are widely distributed across Europe. Here, we present a review of the financial costs, as the first step toward calculating an estimate of the economic consequences of alien species in Europe.

Abstract  [Biofuel crops, particularly certain species of grasses and woody plants, have the potential to become invasive and must be carefully evaluated.]

Abstract  The emerging interest in cellulosic biofuel production has led the call for alternative cropping systems that maximize production along with the accompanying regulating, supporting, and cultural ecosystem services. We evaluate the potential for biomass harvested from invaded wetlands to achieve these goals. The ecosystem service trade-offs associated with a wetland invader harvest are evaluated followed by a case study estimating the energy production and nutrient removal of harvesting Phalaris arundinacea from invaded wetlands in Wisconsin, United States. Estimates for energy production from this single species harvest dwarf current renewable energy sources for the state of Wisconsin and offer the potential to recapture approximately 50-200% of the excess nitrogen and phosphorus annually applied as fertilizer. This restoration technique would not only generate income from biomass sales to subsidize the cost of restoration, but also has the potential to shift the system toward more desirable environmental conditions by removing nutrients annually, reducing downstream eutrophication, and enhancing the ability of more desirable vegetation to establish by removing the litter layer created by the invasive species.

Abstract  With the growing body of literature assessing the impact of invasive alien plants on resident species and ecosystems, a comprehensive assessment of the relationship between invasive species traits and environmental settings of invasion on the characteristics of impacts is needed. Based on 287 publications with 1551 individual cases that addressed the impact of 167 invasive plant species belonging to 49 families, we present the first global overview of frequencies of significant and non-significant ecological impacts and their directions on 15 outcomes related to the responses of resident populations, species, communities and ecosystems. Species and community outcomes tend to decline following invasions, especially those for plants, but the abundance and richness of the soil biota, as well as concentrations of soil nutrients and water, more often increase than decrease following invasion. Data mining tools revealed that invasive plants exert consistent significant impacts on some outcomes (survival of resident biota, activity of resident animals, resident community productivity, mineral and nutrient content in plant tissues, and fire frequency and intensity), whereas for outcomes at the community level, such as species richness, diversity and soil resources, the significance of impacts is determined by interactions between species traits and the biome invaded. The latter outcomes are most likely to be impacted by annual grasses, and by wind pollinated trees invading mediterranean or tropical biomes. One of the clearest signals in this analysis is that invasive plants are far more likely to cause significant impacts on resident plant and animal richness on islands rather than mainland. This study shows that there is no universal measure of impact and the pattern observed depends on the ecological measure examined. Although impact is strongly context dependent, some species traits, especially life form, stature and pollination syndrome, may provide a means to predict impact, regardless of the particular habitat and geographical region invaded.

Abstract  Perennial grasses are promising candidates for bioenergy crops, but species that can escape cultivation and establish self-sustaining naturalized populations (feral) may have the potential to become invasive. Fertile Miscanthus × giganteus, known as "PowerCane," is a new potential biofuel crop. Its parent species are ornamental, non-native Miscanthus species that establish feral populations and are sometimes invasive in the USA. As a first step toward assessing the potential for "PowerCane" to become invasive, we documented its growth and fecundity relative to one of its parent species (Miscanthus sinensis) in competition with native and invasive grasses in common garden experiments located in Columbus, Ohio and Ames, Iowa, within the targeted range of biofuel cultivation. We conducted a 2-year experiment to compare growth and reproduction among three Miscanthus biotypes-"PowerCane," ornamental M. sinensis, and feral M. sinensis-at two locations. Single Miscanthus plants were subjected to competition with a native grass (Panicum virgatum), a weedy grass (Bromus inermis), or no competition. Response variables were aboveground biomass, number of shoots, basal area, and seed set. In Iowa, all Miscanthus plants died after the first winter, which was unusually cold, so no further results are reported from the Iowa site. In Ohio, we found significant differences among biotypes in growth and fecundity, as well as significant effects of competition. Interactions between these treatments were not significant. "PowerCane" performed as well or better than ornamental or feral M. sinensis in vegetative traits, but had much lower seed production, perhaps due to pollen limitation. In general, ornamental M. sinensis performed somewhat better than feral M. sinensis. Our findings suggest that feral populations of "PowerCane" could become established adjacent to biofuel production areas. Fertile Miscanthus × giganteus should be studied further to assess its potential to spread via seed production in large, sexually compatible populations.

Abstract  Lignocellulosic biomass has become an emerging feedstock for second-generation bioethanol production. Sugarcane (Saccharum spp. hybrids), a very efficient perennial C4 plant with a high polyploid level and complex genome, is considered a top-notch candidate for biomass production due to its salient features viz. fast growth rate and abilities for high tillering, ratooning, and photosynthesis. Energy cane, an ideal type of sugarcane, has been bred specifically as a biomass crop. In this review, we described (1) biomass potentials of sugarcane and its underlying genetics, (2) challenges associated with biomass improvement such as large and complex genome, narrow gene pool in existing commercial cultivars, long breeding cycle, and non-synchronous flowering, (3) available genetic resources such as germplasm resources, and genomic and cell wall-related databases that facilitate biomass improvement, and (4) mining candidate genes controlling biomass in genomic databases. We extensively reviewed databases for biomass-related genes and their usefulness in biofuel generation. This review provides valuable resources for sugarcane breeders, geneticists, and broad scientific communities involved in bioenergy production.

Abstract  The efficacy of any pesticide is an exhaustible resource that can be depleted over time. For decades, the dominant paradigm - that weed mobility is low relative to insect pests and pathogens, that there is an ample stream of new weed control technologies in the commercial pipeline, and that technology suppliers have sufficient economic incentives and market power to delay resistance - supported a laissez faire approach to herbicide resistance management. Earlier market data bolstered the belief that private incentives and voluntary actions were sufficient to manage resistance. Yet, there has been a steady growth in resistant weeds, while no new commercial herbicide modes of action (MOAs) have been discovered in 30 years. Industry has introduced new herbicide tolerant crops to increase the applicability of older MOAs. Yet, many weed species are already resistant to these compounds. Recent trends suggest a paradigm shift whereby herbicide resistance may impose greater costs to farmers, the environment, and taxpayers than earlier believed. In developed countries, herbicides have been the dominant method of weed control for half a century. Over the next half-century, will widespread resistance to multiple MOAs render herbicides obsolete for many major cropping systems? We suggest it would be prudent to consider the implications of such a low-probability, but high-cost development. © 2017 Society of Chemical Industry.

Abstract  Invasive alien species (IAS) are one of the most important drivers of species loss. A series of recent (inter)national policies and guidelines however did not prevent new introductions and further spread of non-indigenous species. But instead of considering invasive plant species as a burden, the biomass production of IAS can be considered and used as an ecosystem service. To assess the possibilities for bioenergy production of four invasive alien plant species in Europe, Fallopia japonica, Heracleum mantegazzianum, Impatiens glandulifera and Solidago gigantea, we determined their biomass production, gross calorific value and biogas yield. The viability of the propagules after digestion was also tested to assess the dispersal risk related to the bioenergy chain. Fallopia japonica and S. gigantea achieved a high annual biomass yield of 8.6 ton DM per hectare. Impatiens glandulifera and H. mantegazzianum had a lower biomass production (5.8 and 6.0 ton DM ha(-1)). Without extra inputs or agronomic optimization of the crops, the anaerobic digestion of the studied invasive plant species achieved comparable energy outputs per hectare (28-88 GJ ha(-1)) as some of the current bioenergy systems. All propagules lost their viability after digestion. The risk of further invasion is thus minimized during the digestion process. However, caution during harvest and transport is required to prevent the spread of new propagules. The energetic valorization of the biomass of IAS can create an economic incentive for habitat restoration of invaded sites and offers the opportunity to reconcile the restoration of the invaded habitats with renewable energy goals.

Abstract  The perennial grass genus Miscanthus has great promise as biomass feedstock, but there are concerns about potential invasion outside production fields. While the sterile hybrid Miscanthus x giganteus is currently one of the leading feedstock options due to its low invasive potential, fertile varieties are being developed to reduce establishment costs, and their invasive risks need to be further assessed. We performed seed addition experiments in Ohio and Iowa, USA to examine the establishment, flowering, persistence, and shoot biomass per plot of a fertile M. x giganteus biotype (PowerCane) and two Miscanthus sinensis biotypes, one feral, and one ornamental. Seeds were added to small, replicated plots in each of the 2 years under two seeding densities and two competition treatments, and plots were monitored for 2-3 years. The PowerCane biotype established better, survived better, and produced greater amounts of biomass per plot than both M. sinensis biotypes. All three biotypes flowered by the second or third year after establishment, with inflorescences more numerous in PowerCane and the Ornamental M. sinensis biotypes. Effects of seeding density and competition on these patterns were minor in most cases. Our research suggests that PowerCane exhibits many traits shared by both biomass crops and invasive species: multi-year persistence, high biomass potential, and fertility. We suggest that the benefits of a seeded M. x giganteus should be carefully weighed against its increased invasive risk prior to deployment across the landscape.

Abstract  Genetically engineered (GE) herbicide-resistant crops have been widely adopted by farmers in the United States and other countries around the world, and these crops have caused significant changes in herbicide use patterns. GE crops have been blamed for increased problems with herbicide-resistant weeds (colloquially called by the misnomer "superweeds"); however, there has been no rigorous analysis of herbicide use or herbicide-resistant weed evolution to quantify the impact of GE crops on herbicide resistance. Here, I analyze data from the International Survey of Herbicide Resistant Weeds and the USDA and demonstrate that adoption of GE corn varieties did not reduce herbicide diversity, and therefore likely did not increase selection pressure for herbicide-resistant weeds in that crop. Adoption of GE herbicide-resistant varieties substantially reduced herbicide diversity in cotton and soybean. Increased glyphosate use in cotton and soybean largely displaced herbicides that are more likely to select for herbicide-resistant weeds, which at least partially mitigated the impact of reduced herbicide diversity. The overall rate of newly confirmed herbicide-resistant weed species to all herbicide sites of action (SOAs) has slowed in the United States since 2005. Although the number of glyphosate-resistant weeds has increased since 1998, the evolution of new glyphosate-resistant weed species as a function of area sprayed has remained relatively low compared with several other commonly used herbicide SOAs.

Abstract  Biofuels are being embraced worldwide as sustainable alternatives to fossil fuels, because of their potential to promote energy security and reduce greenhouse gas emissions, while providing opportunities for job creation and economic diversification. However, biofuel production also raises a number of environmental concerns. One of these is the risk of biological invasion, which is a key issue with second generation biofuel crops derived from fast-growing perennial grasses and woody plant species. Many of the most popular second generation crops proposed for cultivation in the U.S. and Canada are not native to North America, and some are known to be invasive. The development of a large-scale biofuel industry on the continent could lead to the widespread introduction, establishment, and spread of invasive plant species if invasive risks are not properly considered as part of biofuel policy. In this paper, we evaluate the risk of biological invasion posed by the emerging second generation biofuel industry in the U.S. and Canada by examining the invasive risk of candidate biofuel plant species, and reviewing existing biofuel policies to determine how well they address the issue of invasive species. We find that numerous potentially invasive plant species are being considered for biofuel production in the U.S. and Canada, yet invasive risk receives little to no attention in these countries biofuel policies. We identify several barriers to integrating invasive species and biofuel policy, relating to policy analytical capacity, governance, and conflicting policy objectives. We recommend that governments act now, while the second generation biofuel industry is in its infancy, to develop robust and proactive policy addressing invasive risk. Policy options to minimize biological invasions include banning the use of known invasive plant species, ongoing monitoring of approved species, and use of buffer zones around cultivated areas. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  Some ecologists and environmentalists have asked whether existing plant invaders could be used as sources of lignocellulosic ethanol, as an alternative to the introduction of potentially invasive non-native energy crops. Although the idea is tempting and could theoretically motivate the control or eradication of large invasive populations, we recognize that a number of major economic, logistic, and legal barriers currently prevent adoption of this plan. Here, we enumerate these barriers in detail, but conclude with an idealistic vision for the role of invasive biomass in the bioenergy industry.

Abstract  The Australian weed risk assessment has been promoted as a simple and effective screening tool that can help prevent the entry of weeds and invasive plants into new areas. On average, the Australian model identifies major-invaders more accurately than it does non-invaders (90% vs. 70% accuracy). While this difference in performance emphasizes protection, the overall accuracy of the model will be determined by its performance with non-invaders because the frequency of invasive species among new plant introductions is relatively low. In this study, we develop a new weed risk assessment model for the entire United States that increases non-invader accuracy. The new screening tool uses two elements of risk, establishment/spread potential and impact potential, in a logistic regression model to evaluate the invasive/weedy potential of a species. We selected 204 non-invaders, minor-invaders, and major-invaders to develop and validate the new model, and compare its performance to the Australian model using the same set of species. Performing better than the Australian model, our new model accurately identified 94.1% of major-invaders and 97.1% of non-invaders, without committing any false positives or false negatives. The new secondary screening tool we developed reduced the number of species requiring secondary evaluation from 22 to 12%. We expect that the new weed risk assessment model should significantly enhance the United State's timeliness and accuracy in regulating potential weeds.

Abstract  Biofuels are being pursued for their potential greenhouse gas (GHG) emissions benefits, among other reasons. In order to maximize productivity, avoid food-fuel conflicts, and minimize GHG emissions, many advanced biofuel feedstock crops, such as those desired by the aviation community, are under consideration based on traits, such as high biomass and/or seed production, tolerance of marginal cultivation conditions, and short generation times, that may also be predictors of potential invasiveness risk. Biofuel-related invasion risks can be mitigated through careful feedstock crop selection and cultivation techniques developed from the invasion science literature. Existing voluntary best practices and some state and federal regulatory requirements in the United States recommend and/or require the use of such risk mitigation strategies. However, other policies and programs allow or provide incentives for biofuel production without conditions requiring the use of these strategies. We have synthesized information on the scientific knowledge of invasive species predictors and their use (or absence) in voluntary codes and U.S. regulatory frameworks and incentive programs. We highlight the existing tools and approaches for assessing invasion risk and avoiding the introduction and spread of invasive species as a result of biofuel feedstock cultivation. A well-coordinated combination of species restrictions, biosecurity requirements, and incentives for selection of less risky biofuel crops may effectively balance the desire for increased biofuel production while minimizing invasion risk.

Abstract  This paper considers the possible impacts of oil development on wildlife in the grasslands ecosystem, particularly in the province of Saskatchewan. The Bakken formation, a major North American shale play, overlaps with one of the largest areas for grassland birds in Canada the US. Access to the oil is made possible through fracking and horizontal drilling, which are controversial techniques that have been regulated and banned in other parts of North America and the world. Drawing on analysis of recovery documents for listed species at risk, this paper illustrates that oil development is impacting species through habitat destruction, oil and noise pollution, invasive species, and road infrastructure. Current wildlife policy in Saskatchewan is inadequate to protect species at risk in the Bakken formation.

Abstract  Herbicide resistant (HR) weeds are of major concern in modern agriculture. This situation is exacerbated by the massive adoption of herbicide-based technologies along with the overuse of a few active ingredients to control weeds over vast areas year after year. Also, many other anthropological, biological, and environmental factors have defined a higher rate of herbicide resistance evolution in numerous weed species around the world. This review focuses on two central points: 1) how these factors have affected the resistance evolution process; and 2) which cultural practices and new approaches would help to achieve an effective integrated weed management. We claim that global climate change is an unnoticed factor that may be acting on the selection of HR weeds, especially those evolving into non-target-site resistance mechanisms. And we present several new tools -such as Gene Drive and RNAi technologies- that may be adopted to cope with herbicide resistance spread, as well as discuss their potential application at field level. This is the first review that integrates agronomic and molecular knowledge of herbicide resistance. It covers not only the genetic basis of the most relevant resistance mechanisms but also the strengths and weaknesses of traditional and forthcoming agricultural practices.

Abstract  Human-mediated species invasions are a significant component of current global environmental change. There is every indication that the rate at which locations are accumulating non-native species is accelerating as free trade and globalization advance. Thus, the need to incorporate predictive models in the assessment of invasion risk has become acute. However, finding elements of the invasion process that provide consistent explanatory power has proved elusive. Here, we propose propagule pressure as a key element to understanding why some introduced populations fail to establish whereas others succeed. In the process, we illustrate how the study of propagule pressure can provide an opportunity to tie together disparate research agendas within invasion ecology.