Abstract  To avoid major negative impacts of the widespread adoption of biofuel species, whether the), are exotic species, natives, or novel constructs, we need a system for screening their weed potential. Australia is all important global center of biodiversity and also has major cropping industries to protect. prevention of the entry of further weeds is therefore a major national priority. The Weed Risk Assessment (WRA) system was developed and implemented for importation decisions in 1997; it has since been introduced into other countries and is probably as good as any system currently in operation. However, we need to be aware of the limitations of any system, to address these, and to work toward improved or alternative systems. WRA is a very simple spreadsheet requiring answers to questions about a species' life-history traits, dispersal, habitat suitability, impacts oil other species, and history overseas, which are then added together and compared with numerical decision criteria. Its predictive powers are limited by this simplicity and by the complexity of human attitudes toward risk and Impact. Alternative risk-management methods are available but, even so, the capacity for improvement is limited. It is quite possible, therefore, that in using any, trait-based system to assess the negative risks of importation or interstate translocation of biofuel species, we will wrongly reject a Valuable species or approve a species chat turns Our to be a major weed. It is suggested that, rather than attempting to improve a single-tiered decision-support system (the quarantine "sieve"), a multitiered system (nested sieves) Would lead to a more effective System and greater cost-effectiveness. The key to this would be a postentry screening process for those species that have Successfully passed through the WRA system.

Abstract  The characters of the ideal bioenergy crop are shared by many of our worst invasive plants, and we are in need of methods to identify their invasive potential prior to large-scale introduction. Unfortunately, predicting which species will be invasive and in what location is often viewed as a near impossible task to most ecologists. Despite the underlying complexity of invasions, and the predictability challenge, weed risk assessments (WRA) have emerged as promising biosecurity tools designed to prevent the introduction of new invaders. WRAs are simple questionnaires on the species traits, introduction history, impact, and management that yield high or low risk scores, generally employed prior to the introduction of new species. WRAs have been used widely across the globe and boast >90% accuracy in predicting invasive species. We examined Australian and US WRA tools, and compared the WRA outcomes of several bioenergy crops against invasive species introduced for agronomic purposes and several traditional row crops. Candidate bioenergy crops were found to vary tremendously in their WRA scores, while current invaders all received high risk scores. Interestingly, several row crops received high risk scores, which we attribute to feral populations or weedy variants. We also examined how the WRAs would respond to infraspecific variation for several crops. Overall, the WRAs were not capable of distinguishing cultivar-level information, nor did they do well for species with little available information. Thus, the outcomes of WRAs should be viewed carefully and within the context of how much we know about that taxon. WRAs are useful biosecurity tools, but we do not recommend they be used exclusively; rather they should be a component of an integrated system that includes field studies to best understand the invasion risk posed by bioenergy crops.

Abstract  The United States is charging toward the largest expansion of agriculture in 10,000 years with vast acreages of primarily exotic perennial grasses planted for bioenergy that possess many traits that may confer invasiveness. Cautious integration of these crops into the bioeconomy must be accompanied by development of best management practices and regulation to mitigate the risk of invasion posed by this emerging industry. Here I review the current status of United States policy drivers for bioenergy, the status of federal and state regulation related to invasion mitigation, and survey the scant quantitative literature attempting to quantify the invasive potential of bioenergy crops. A wealth of weed risk assessments are available on exotic bioenergy crops, and generally show a high risk of invasion, but should only be a first-step in quantifying the risk of invasion. The most information exists for sterile giant miscanthus, with preliminary empirical studies and demographic models suggesting a relatively low risk of invasion. However, most important bioenergy crops are poorly studied in the context of invasion risk, which is not simply confined to the production field; but also occurs in crop selection, harvest and transport, and feedstock storage. Thus, I propose a nested-feedback risk assessment (NFRA) that considers the entire bioenergy supply chain and includes the broad components of weed risk assessment, species distribution models, and quantitative empirical studies. New information from the NFRA is continuously fed back into other components to further refine the risk assessment; for example, empirical dispersal kernels are utilized in landscape-level species distribution models, which inform habitat invasibility studies. Importantly, the NFRA results in a relative invasion risk to known species (e.g., is giant reed a higher or lower invasion risk than johnsongrass). This information is used to design robust mitigation plans that include record keeping, regular scouting and reporting, prudent harvest and transport practices that consider species biology, and eradication protocols as an ultimate precaution. Finally, a socio-political balance must be struck (i.e., a cost-benefit analysis) among our energy choices that consider the broader implications, which includes the risk of future invasions.

Abstract  Twelve taxa under exploration as bioenergy crops in Florida and the U.S. were evaluated for potential invasiveness using the Australian Weed Risk Assessment system (WRA) modified for separate assessment at the state and national scales. When tested across a range of geographies, this system correctly identifies invaders 90%, and non-invaders 70% of the time, on average. Predictions for Florida were the same as for the U.S. Arundo donax, Eucalyptus camaldulensis, Eucalyptus grandis, Jatropha curcas, Leucaena leucocephala, Pennisetum purpureum, and Ricinus communis were found to have a high probability of becoming invasive, while Miscanthus x giganteus, Saccharum arundinaceum, Saccharum officinarum, and the sweet variety of Sorghum bicolor have a low probability of becoming invasive. Eucalyptus amplifolia requires further evaluation before a prediction is possible. These results are consistent with reports on other tests of these taxa. Given the economic and ecological impacts of invasive species, including the carbon expended for mechanical and chemical control efforts, cultivation of taxa likely to become invasive should be avoided. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract  1. Many alien weeds pose significant environmental and/or economic threats across the globe, and methods to assess the potential risk of species introductions are key components in the management of plant invasions. Three broad approaches have been adopted in weed risk assessment: quantitative statistical models, semi-quantitative scoring and qualitative expert assessment. Yet, the effectiveness of these different approaches is rarely evaluated. By bringing together perspectives drawn from statistics, complexity theory, bioeconomics and cognitive psychology, this review presents the first interdisciplinary appraisal of whether weed risk assessment is a valuable tool in the management of plant invasions. 2. Problems in obtaining an objective measure of the hazards posed by weeds, challenges of predicting complex hierarchical and nonlinear systems, difficulties in quantifying uncertainty and variability, as well as cognitive biases in expert judgement, all limit the utility of current risk assessment approaches. The accuracy of weed risk assessment protocols is usually insufficient, given inherent low base-rates even when the costs and benefits of decisions are taken into account, and implies that the predictive value of weed risk assessment is questionable. 3. Current practices could be improved to address consistent hazard identification, encompass a hierarchy of spatio-temporal scales, incorporate uncertainty, generate realistic base-rates, and train risk assessors to limit cognitive biases. However, such refinements may still fail to predict weed risks any better than a knowledge of prior invasion history and quality of climate match. 4. Alternative approaches include scenario planning that seeks qualitative inputs regarding hypothetical events to facilitate long-range planning using multiple alternatives each explicit in their treatment of uncertainty. This represents a change from prevention towards adaptive management where the difficulty in prediction is acknowledged and investment targets early detection, mitigation and management. 5. Synthesis and applications. Scenario planning may be particularly suitable for weeds as they can be rapidly surveyed and have sufficiently long lag phases between naturalisation and invasion that early detection is often feasible. If integrated with assessments of ecosystem vulnerability to invasion and interventions to improve ecosystem resilience, it would deliver a robust post-border approach to invasive plant management. This approach would address threats from new introductions as well as 'sleeper weeds' already present in a region.

Abstract  There is growing interest in biofuel production, and energycane (Saccharum spp. x S. spontaneum L.) has been proposed as an important biofuel and biomass crop. However, little is known about the growth and ecology of this new crop, especially in the tropics. The present study evaluated the performance of 14 energycane clones, elephantgrass (Penniseium purpureum Schumach.), and two sugarcane (S. officinarum L.) varieties in the humid tropics of Costa Rica, and eight energycane clones in the subtropics of Florida. In the tropics, energycanes growth and biomass production were highly variable when comparing clones. However, the best performing clones US85-1006, US88-1006, and US78-1014 produced almost twice the dry biomass (>64 Mg ha(-1)) compared with sugarcane varieties Pindar and Q-132 (21-39 Mg ha(-1)). In the subtropics, energycane fresh (52-79 Mg ha(-1)) and dry (20-30 Mg ha(-1)) weights were less than half of those in the tropics. Fnergycane clones flowered in both environments, but pollen viability was three to four times higher (>40%) in the tropics than in the subtropics, although viable seeds were found only in the tropics. Weed risk assessment (WRA) scores were higher in the tropics than in the subtropics and varied among clones. The results confirmed that energycane is a promising feedstock for biomass production and could play an important role as a biocnergy crop when grown in the tropics and subtropics, but due to genotype x environment interactions, the tradeoff between biomass production and weedy and invasive risk must be assessed for each individual clone and environment.

Abstract  Genetic improvement through breeding is one of the key approaches to increasing biomass supply. This paper documents the breeding progress to date for four perennial biomass crops (PBCs) that have high output-input energy ratios: namely Panicum virgatum (switchgrass), species of the genera Miscanthus (miscanthus), Salix (willow) and Populus (poplar). For each crop, we report on the size of germplasm collections, the efforts to date to phenotype and genotype, the diversity available for breeding and on the scale of breeding work as indicated by number of attempted crosses. We also report on the development of faster and more precise breeding using molecular breeding techniques. Poplar is the model tree for genetic studies and is furthest ahead in terms of biological knowledge and genetic resources. Linkage maps, transgenesis and genome editing methods are now being used in commercially focused poplar breeding. These are in development in switchgrass, miscanthus and willow generating large genetic and phenotypic data sets requiring concomitant efforts in informatics to create summaries that can be accessed and used by practical breeders. Cultivars of switchgrass and miscanthus can be seed-based synthetic populations, semihybrids or clones. Willow and poplar cultivars are commercially deployed as clones. At local and regional level, the most advanced cultivars in each crop are at technology readiness levels which could be scaled to planting rates of thousands of hectares per year in about 5 years with existing commercial developers. Investment in further development of better cultivars is subject to current market failure and the long breeding cycles. We conclude that sustained public investment in breeding plays a key role in delivering future mass-scale deployment of PBCs.

Abstract  The rapid expansion of the plant bioeconomy is creating strong economic incentives to distribute novel plant material, including transgenic cultivars, exotic species, and species that were formerly constrained to small geographical areas, at large geographical scales. Such introductions carry with them the risk of invasive spread of the introduced species (Simberloff and Alexander 1998). Deployment of plant species for biofuel production offers a clear example of the benefits and risks associated with the new bioeconomy (Raghu et al. 2006). In a measure aimed at reducing U.S. dependence upon foreign petroleum reserves for energy production, President Bush announced the Advanced Energy Initiative (AEI) in his 2006 State of the Union address. This initiative provides federal funding and guidelines for the development of renewable energy sources, including plant biofuels. The objectives of the AEI, though admirable, have the potential to create a conflict with Executive Order 13112, which states that “[Federal agencies shall] not authorize, fund, or carry out actions that it believes are likely to cause or promote the introduction or spread of invasive species in the United States or elsewhere unless, pursuant to guidelines that it has prescribed, the agency has determined and made public its determination that the benefits of such actions clearly outweigh the potential harm caused by invasive species; and that all feasible and prudent measures to minimize risk of harm will be taken in conjunction with the actions.”

Abstract  The selection of herbicide-resistant weed populations began with the introduction of synthetic herbicides in the late 1940s. For the first 20 years after introduction, there were limited reported cases of herbicide-resistant weeds. This changed in 1968 with the discovery of triazine-resistant common groundsel. Over the next 15 yr, the cases of herbicide-resistant weeds increased, primarily to triazine herbicides. Although triazine resistance was widespread, the resistant biotypes were highly unfit and were easily controlled with specific alternative herbicides. Weed scientists presumed that this would be the case for future herbicide-resistant cases and thus there was not much concern, although the companies affected by triazine resistance were somewhat active in trying to detect and manage resistance. It was not until the late 1980s with the discovery of resistance to Acetyl Co-A carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors that herbicide resistance attracted much more attention, particularly from industry. The rapid evolution of resistance to these classes of herbicides affected many companies, who responded by first establishing working groups to address resistance to specific classes of herbicides, and then by formation of the Herbicide Resistance Action Committee (HRAC). The goal of these groups, in cooperation with academia and governmental agencies, was to act as a forum for the exchange of information on herbicide-resistance selection and to develop guidelines for managing resistance. Despite these efforts, herbicide resistance continued to increase. The introduction of glyphosate-resistant crops in the 1995 provided a brief respite from herbicide resistance, and farmers rapidly adopted this relatively simple and reliable weed management system based on glyphosate. There were many warnings from academia and some companies that the glyphosate-resistant crop system was not sustainable, but this advice was not heeded. The selection of glyphosate resistant weeds dramatically changed weed management and renewed emphasis on herbicide resistance management. To date, the lesson learned from our experience with herbicide resistance is that no herbicide is invulnerable to selecting for resistant biotypes, and that over-reliance on a weed management system based solely on herbicides is not sustainable. Hopefully we have learned that a diverse weed management program that combines multiple methods is the only system that will work for the long term.

Abstract  This article presents comparative perspectives from Australia, the European Union, and the United States from a plenary session, "Herbicide resistance: Challenges for Farmers and Implications for the Environment" at the 19th Annual Conference of the International Consortium on Applied Bioeconomy Research. Herbicide-resistant (HR) weeds threaten the sustainability of herbicide-tolerant (HT) crops, pose environmental risks from alternative weed control methods, and are altering public and private research and development programs. Institutional responses to HR weeds across the three regions, while confronting similar problems (in some respects, but not others), are taking different forms. The article discusses public policies and private-sector strategies to address weed resistance problems. Considerations of HR weeds are already transforming regulatory approval processes for new HR crop varieties. We conclude by discussing over-arching public policy and agricultural research challenges.

Abstract  Biological invasions are responsible for substantial biodiversity declines as well as high economic losses to society and monetary expenditures associated with the management of these invasions1,2. The InvaCost database has enabled the generation of a reliable, comprehensive, standardized and easily updatable synthesis of the monetary costs of biological invasions worldwide3. Here we found that the total reported costs of invasions reached a minimum of US$1.288 trillion (2017 US dollars) over the past few decades (1970-2017), with an annual mean cost of US$26.8 billion. Moreover, we estimate that the annual mean cost could reach US$162.7 billion in 2017. These costs remain strongly underestimated and do not show any sign of slowing down, exhibiting a consistent threefold increase per decade. We show that the documented costs are widely distributed and have strong gaps at regional and taxonomic scales, with damage costs being an order of magnitude higher than management expenditures. Research approaches that document the costs of biological invasions need to be further improved. Nonetheless, our findings call for the implementation of consistent management actions and international policy agreements that aim to reduce the burden of invasive alien species.

Abstract  Conservation tillage in American soybean production has become increasingly common, improving soil health while reducing soil erosion and fuel consumption. This trend has been reinforced by the widespread adoption of glyphosate-based weed control systems. Many weed species have since evolved to resist glyphosate, reducing its effectiveness. We provide evidence that the spread of glyphosate-resistant weeds is responsible for significant reductions in the use of conservation tillage in soybean production. We estimate reduced-form and structural probit models of tillage choice, using a large panel of field-level soybean management decisions from across the United States spanning 1998-2016. We find that the first emergence of glyphosate-resistant weed species has little initial effect on tillage practices, though by the time that eight glyphosate-resistant weed species are identified, conservation tillage and no-till use fall by 3.9 percentage points and 7.6 percentage points, respectively. We further find that when ten glyphosate-resistant species are present, the predicted adoption rate of non-glyphosate herbicides rises 50 percentage points, and that the availability of non-glyphosate herbicides facilitates continued use of conservation tillage as glyphosate-resistant weeds proliferate. Using a simple benefits transfer model, we conservatively estimate that between 2008 and 2016 farmers' tillage responses to the spread of glyphosate-resistant weeds have caused water quality and climate damages via fuel emissions valued at nearly $245 million. This value does not account for climate damages due to carbon released during soil disruptions and is likely to grow as glyphosate resistance becomes more widespread and more farmers turn to tillage for supplemental weed control.

Abstract  The first study which has quantified the invasiveness of bioenergy crops, researchers compared the risks of invasion for 40 bioenergy crops proposed for introduction to Hawaii, to a random sample of 40 non-bioenergy crops, using an established methodology known as 'Weed Risk Assessment'. The results showed that the bioenergy crops were two to four times more likely to establish wild populations and become invasive. 70% of the bioenergy species were high risk, compared to 25% of the random sample. Bioenergy crops are more likely to be invasive as they are selected for the same traits as belong to many successful invasive species: pest resistance; high biomass or reproductive capacity; tolerance to harsh conditions; ability to thrive as a monoculture. Some of these risks could be managed so that the benefits of planting the crops outweigh the costs. The researchers encourage governments to consider the invasiveness of bioenergy crops when granting funds or approval for these.

Abstract  A virtually intact subtropical reef community (14 phyla, 40 families and 62 non-native taxa) was associated with a rig under tow from Brazil that became stranded on the remote island of Tristan da Cunha. This exposes rigs as a significant vector spreading alien marine organisms, and includes the first records of free-swimming marine finfish populations becoming established after unintentional movement. With relatively trivial effort, a pre-tow clean would have obviated the need to salvage and dispose of the rig (undertaken largely to address concerns about invasive species), at a cost of similar to US$20 million. Our findings show that towing biofouled structures across biogeographic boundaries present unexcelled opportunities for invasion to a wide diversity of marine species. Better control and management of this vector is required urgently. Simultaneous, unintentional introductions of viable populations of multiple marine organisms are rare events, and we develop a basic framework for rapid assessment of invasion risks.

Abstract  1. Biofuel production has the potential of reducing CO2 emissions while decreasing global dependence on fossil fuels. However, concerns have been raised on the invasiveness of biofuel feedstocks. Estimating invasion potential remains a challenge because of inconsistencies and inherent limitations of using first-tier qualitative weed risk assessment (WRA) protocols singularly.

2. We evaluated the usefulness of second-tier quantitative WRA methods using a recently introduced oilseed crop, Camelina sativa, as a model species. First, we subjected C. sativa to the qualitative Australian WRA and found that it should not be allowed entry. We then used demographic models fit with field-estimated parameters as a second-tier approach to quantitatively evaluate its invasion potential. Data on disturbance (two herbicides, mechanical, none) and seeding season (autumn, spring) relative to C. sativa demography were obtained over 2 years in two rangeland ecosystems in Montana, USA. Population growth (lambda) was forecast by developing population dynamics models using field data.

3. Emergence rates were greatest when C. sativa was spring-seeded; all survivors to maturity occurred only in mechanically disturbed plots. Population growth rate never exceeded 0.03, and the maximum time to extinction was 6 years. Perturbation analyses indicated that consistent propagule pressure and biologically improbable rates of seed survival are necessary to sustain C. sativa populations, indicating that the risk of invasion by this species in the studied ecosystems is low.

4. Synthesis and applications. Although more site-years of demographic data would strengthen our conclusions about the invasion potential of C. sativa, we contend that the methods developed provide a useful contribution to WRA. If applied to proposed plant biofuel species, our second-tier quantitative refinements will elucidate important population dynamics often overlooked by qualitative WRAs and, in turn, may reduce the frequency of invasions or rejection of potentially useful species.

Abstract  The widespread adoption of genetically engineered (GE) crops has clearly led to changes in pesticide use, but the nature and extent of these impacts remain open questions. We study this issue with a unique, large, and representative sample of plot-level choices made by U.S. maize and soybean farmers from 1998 to 2011. On average, adopters of GE glyphosate-tolerant (GT) soybeans used 28% (0.30 kg/ha) more herbicide than nonadopters, adopters of GT maize used 1.2% (0.03 kg/ha) less herbicide than nonadopters, and adopters of GE insect-resistant (IR) maize used 11.2% (0.013 kg/ha) less insecticide than nonadopters. When pesticides are weighted by the environmental impact quotient, however, we find that (relative to nonadopters) GE adopters used about the same amount of soybean herbicides, 9.8% less of maize herbicides, and 10.4% less of maize insecticides. In addition, the results indicate that the difference in pesticide use between GE and non-GE adopters has changed significantly over time. For both soybean and maize, GT adopters used increasingly more herbicides relative to nonadopters, whereas adopters of IR maize used increasingly less insecticides. The estimated pattern of change in herbicide use over time is consistent with the emergence of glyphosate weed resistance.