Genetically Modified Herbicide-tolerant Crops Research Articles

Taxonomic and functional changes in wheat rhizosphere microbiome caused by imidazoline-based herbicide and genetic modification

Genetically modified (GM) crop cultivation has received a lot of attention in recent years due to the substantial public debate. Consequently, an in-depth investigation of excessively used GM herbicide-tolerant crops is a vital step for the biosafety of genetically modified plants. Several studies have been conducted to study the impact of transgenic GM crops on soil microbial composition; however, research into the effects of non-transgenic GM crops is inadequate. In the current work, high-throughput sequencing was used to evaluate the impact of the acetolactate synthase (ALS)-mutant (WK170B), its control (YN19B), and the imazamox (IM) herbicide on the wheat rhizobiome. Under normal growth conditions, our work revealed a minimal impact of ALS-mutant WK170B on the rhizosphere microbiome compared to the control YN10B, except for some cyanobacterial microorganisms that showed a significant increase in abundance. This suggests that the gene mutation could potentially have a beneficial impact on the bacterial communities present in the rhizosphere. Following IM exposure, taxonomic analysis revealed a significant reduction in the relative abundance of Ralstonia pickettii and an unidentified member of the genus Ancylothrix 8 PC. Analyses of both alpha and beta diversity revealed a statistically significant increase in both microbial richness and species diversity. IM-induced relative abundance modulation was also evident through Linear discriminant analysis Effect Size (LEfSe), MetaStat, and heatmap analyses. The SIMPER analysis revealed that the microbial taxa Massilia, Limnobacter, Hydrogenophaga, Ralstonia, Nitrospira, and Ramlibacter exhibited the highest vulnerability to IM exposure. The functional attributes analysis revealed that the relative abundance of genes associated with the extracellular matrix-receptor interaction, which is responsible for structural support and stress response, increased significantly following IM exposure. Collectively, our study identifies key microbial taxa in the wheat rhizobiome that are sensitive to IM herbicides and provides a foundation for assessing the environmental risks associated with IM herbicide use.

Impact assessment of genetically modified herbicide-tolerant cotton on arthropod communities

BackgroundCotton (Gossypium spp.) is one of the most important economic crops worldwide, and its production plays an important role in the economy of many countries. Genetically modified herbicide-tolerant (GMHT) crops, which were developed to minimize the losses caused by weeds, have gradually become the most widely adopted genetically modified crops in the world due to their economic and environmental benefits. However, the potential ecological and environmental risks of GMHT crops have attracted extensive attention and controversy. Arthropod communities form a prominent part of the biodiversity of agroecosystems and are important indicators of environmental health. Elucidating the effects of GMHT crops on the diversity of arthropod communities is necessary to ensure the safety of GMHT crops.ResultIn this 2-year study, we investigated the potential impact of GMHT crops on arthropod communities. The GMHT cotton variety GGK2 with glyphosate tolerance and its near-isogenic non-GMHT variety K312 were used for the experimental groups. The Shannon diversity index (H), Simpson diversity index (D), Pielou evenness index (J), and principal co-ordinates analysis (PCoA) of the Bray–Curtis distance were used to evaluate the population dynamics and biodiversity of arthropods in cotton fields. No significant differences were found between GGK2 and K312 in their total abundance of arthropod communities, and biodiversity indexes on most sampling dates. The arthropod composition in the GGK2 and K312 plots was similar. Sampling dates had a significant effect on biodiversity indexes, whereas no clear tendencies related to cotton variety or cotton variety × sampling dates interaction were recorded. In addition, PCoA revealed high similarity between the arthropod communities in the plots of the GMHT cotton variety GGK2 and its near-isogenic variety K312.ConclusionThere was no obvious difference in abundance, diversity indexes of arthropod communities between GMHT cotton variety GGK2 and its near-isogenic variety K312 under the small-scale planting regime.

Split application of glyphosate in herbicide-tolerant maize provides efficient weed control and favors beneficial epigeic arthropods

Wide deployment of genetically modified herbicide-tolerant (GMHT) maize may affect the efficiency of weed control methods and impair ecosystem functioning. We examined these potential threats using glyphosate-tolerant maize NK603 (Monsanto Technology LLC, St. Louis, MO, USA) planted in 54 randomly distributed plots in 2013 and 2014. Maize was grown in three herbicide treatments combined with six tillage regimes. Conventional, single post-emergence application of a selective herbicide MaisTer (Bayer CropScience GmbH, Frankfurt am Main, Germany; hereafter as MT) was compared with two herbicide strategies used in the glyphosate-tolerant crops: split application of Roundup Rapid (Monsanto Europe S.A./N.V., Brussels, Belgium; hereafter as RRRR) and application of this herbicide mixed with the soil residual herbicide Guardian Extra (Monsanto Europe S.A./N.V.; hereafter as RRGE). MT proved unreliable, whereas RRRR and especially RRGE provided efficient weed control and affected weed performance during the season. RRRR permitted restoration of weed cover during the latter half of the cultivation season. Conventional, reduced, and conservation (mulching with Hordeum vulgare, Phacelia tanacetifolia, Sinapis alba, and Trifolium incarnatum) tillage had minor effect on the weed performance. Carabids, staphylinids, and spiders were monitored to assess environmental impact of tested weed management practices. Carabid communities were not affected by the type of tillage but responded to the herbicide treatments. The plots treated with MT harbored the highest carabid activity abundance and species richness, followed by RRRR, and then by RRGE. RRRR and RRGE treatments also reduced the rise of staphylinid abundance and species richness after harvest, while conventional tillage negatively affected staphylinids at the start of the cultivation season. Spider and carabid activity abundance was similar, but spider species richness was highest in the RRRR plots. Neither herbicides nor tillage strongly affected arthropod species evenness. Multivariate analysis showed that weed species richness was significantly correlated with the species activity abundance of all three arthropod groups; weed coverage had a similar but smaller effect but the effect of herbicides and tillage was negligible. We concluded that herbicide treatments curbed weed performance which consequently influenced associated arthropods.The RRRR herbicide treatment adequately regulates weeds and exerts restoration of weed cover later in growing season that is beneficial to the arthropods. Thus, GMHT crops have a potential to combine economic and environmental advantages for agroecosystem sustainability and can be recommended for implementation in European crop production systems.

What are the effects of the cultivation of GM herbicide tolerant crops on botanical diversity: a systematic review protocol?

BackgroundThere are concerns that the cultivation of genetically modified herbicide tolerant (GMHT) crops treated with broad spectrum herbicides will cause declines in botanical diversity and hence loss of biodiversity. Cultivation systems of these have different levels of inputs and management interventions and some incorporate the use of minimal/no tillage. Research results show a range of effects and the priority is to determine whether research studies show shifts in botanical diversity and/or declines in plant populations in GMHT compared with conventionally managed crops.MethodsWe will perform a rigorous review of studies of plant populations in fields and field margins of GMHT crops by complying with CEE requirements for Systematic Reviews (SR) and the EFSA Guidance on Systematic Reviewing. A Review Protocol (RP) is presented for the SR of data from field studies of GMHT crops, comparing the effects of GM crop, herbicide regimes and associated management applied to HT crops with conventional crops and their weed management for impacts on plant populations in fields and field margins as assessment end points or indicators of impacts on botanical diversity and associated food chain and ecosystem services effects. The literature search will include all the main GMHT crops including maize, soya, oilseed rape, sugar beet, cotton and rice. The keywords will be broad and the search strategy is developed to capture all literature relevant to the primary objective of the review. The range of data bases for the searches is described and all articles discovered in the searches will be collated by Endnote. The criteria against which studies will be included in the review and how they will be assessed are described. They include appropriate study designs, statistical power and comparators. The RP outlines the type of analyses that will be performed to assess bias of the selected studies and if covariables describing the heterogeneity of the studies introduce biases. Publications meeting the selection criteria will be filed separately and subjected to more detailed analysis and data on different plant species and types will be analysed separately, to determine outcomes.

Consequences of a coexistence policy on the adoption of GMHT crops in the European Union

This article examines the adoption of genetically modified herbicide tolerant (GMHT) crops in the European Union (EU) prior to its commercial release. A set of potential drivers including the implementation of coexistence measures by farmers, farmers’ own motivational factors (e.g. economic, environmental and technical factors) and perceived social pressure to accept or reject adoption may influence European Union farmers’ willingness to adopt GMHT oilseed rape and GMHT maize. The analysis includes economic and sociological factors. Results show that coexistence measures may hamper GMHT adoption in the EU.

Attitudes of European farmers towards GM crop adoption

This article analyses European Union (EU) farmers' attitudes towards adoption of genetically modified crops by identifying and classifying groups of farmers. Cluster analysis provided two groups of farmers allowing us to classify farmers into potential adopters or rejecters of genetically modified herbicide-tolerant (GMHT) crops. Results showed that economic issues such as the guarantee of a higher income and the reduction of weed control costs are the most encouraging reasons for potential adopters and rejecters of GMHT crops. This article also examines how putting in place measures to ensure coexistence between GM and non-GM crops may influence farmers' attitudes towards GMHT crop adoption. Results show that the implementation of a coexistence policy would have a negative impact on farmers' attitudes on adoption and consequently may hamper GMHT adoption in the EU.

Environmental and agronomic monitoring of adverse effects due to cultivation of genetically modified herbicide tolerant crops

Herbicide tolerance allows a specific crop variety to survive a herbicide treatment without injury despite the fact that the herbicide cannot be used selectively in a common variety of the same crop. Widely adopted and used worldwide are genetically modified herbicide tolerant (GMHT) crops with tolerance to the non-selective herbicide active ingredients glyphosate and glufosinate. Development of GMHT crops has substantially changed weed control systems and sometimes crop rotations and soil tillage systems. Attention must be given to the environmental and agro-environmental aspects and sustainability of agro-ecosystems based on HT crops because some adverse effects with this technology can appear, especially if used without knowledge of the risks involved and their prevention. This paper identifies main areas that should be monitored and discusses such potential adverse effects as hybridization with related taxa, occurrence of feral crops, and evolved herbicide resistance within weed communities. If there is no principal difference between conventional and GM crop cultivation, we propose monitoring approaches shall be based mainly on existing methods and monitoring networks. Scientific approaches as basis, decentralization with site-specific focus, as well as reasonable extent of data collection and their effective utilization should be the main features of the monitoring.

Indirect effects of genetically modified herbicide tolerant crops on biodiversity and ecosystem services: the biological control example

Weeds can directly affect arthropods by providing favorable microclimates, food, shelter, mating sites and oviposition substrates. Indirect effects on herbivores and higher trophic level arthropods can occur if weed species interact with each other and with crop plants modifying plant physiology, chemical and visual cues and competing for resources. Hence, weed management can interfere in many different ways with arthropods. Evidence from literature is that our understanding of the mechanisms underlying the observed effects is still very limited. Higher plant diversity does not necessarily mean increased biological control. Genetically Modified Herbicide-Tolerant (GMHT) crops offer new possibilities for weed management with potential consequences for conservation biological control. For example, farmers have more flexibility in timing herbicide applications (early vs. late overall sprays), and band spraying in row crops have been shown to modify weed abundance and composition in favor of a number of predators and parasitoids. There is some evidence that maximum weed control with overall glyphosate spray of GMHT crops results in reduced weed biomass and lower arthropod abundance, including beneficial species. Conversely, many articles show that maintaining some weed enhances arthropod densities and natural biological control. GMHT crops may increase adoption of minimum and no tillage systems with possible effects on weeds and arthropods. Weed management systems with GMHT plants have a great potential to alter plant diversity in crops in favor of conservation biological control. However, careful consideration of other management options such as crop and herbicide rotation should be evaluated to make sustainable use of the benefits of GMHT crops.

Interplay between GMO regulation and pesticide regulation in the EU

Directive 2001/18/EC requires the assessment of “possible immediate and/or delayed, direct and indirect environmental impacts of the specific cultivation, management and harvesting techniques used for the genetically modified higher plant (GMHP) where these are different from those used for non-GMHPs.” For genetically modified herbicide tolerant (GMHT) plants this means that an assessment of the possible environmental impacts of the post-emergence use of the complementary herbicides compared to those of current weed control methods used in non-GM crops of the same species in the EU is required. On the other hand the post-emergence use of the complementary herbicide in a GMHT crop requires a new authorisation according to the EU pesticide Regulation because it is a new application of the herbicide. This raises the issue of interplay between genetically modified organism (GMO) and pesticide authorisation in the EU. An effective interplay would avoid a duplication of efforts, gaps in risk assessment and the possibility that conflicting decisions on pesticide usage could be made under the two systems. Principally, there are no scientific reasons for assessing the effects on the environment of the use of herbicides in GMHT-crops and in non-GM HT crops according to different standards. It also should be kept in mind that gene technology is only one method which can be used to generate crop plants which are tolerant towards broad-spectrum herbicides. The presentation identifies obstacles to an effective interplay between GMO regulation and pesticide regulation in the EU and discusses possible future developments.

Post Market Monitoring of GM Herbicide-Tolerant Crops

AbstractAs soon as humans adopted agriculture as the principle means of feeding themselves, they have had an effect on the environment, and by implication, also on biodiversity. It is not possible to grow crops in an intensive manner without doing so, but it is necessary to do so to feed the population. In this respect, the use of herbicides or other weed control practices (e.g. hand-hoeing) inevitably will have an effect on biodiversity, whether those methods are used in conventional, organic or genetically modified herbicide-tolerant (GMHT) crops. Recent literature from the UK following the Farm Scale Evaluations (FSE) of the environmental impact of GMHT oilseed rape, maize and sugar beet suggests that the recommended weed management techniques applied in the cultivation of GMHT crops caused indirect effects on non-target organisms by affecting the biodiversity of plants within a field and the creatures which depend on them. Reductions in the number of weeds in glufosinate-treated HT-oilseed rape, and glyphosate-treated HTsugar beet compared to conventionally managed crops resulted in significant reductions in weed biomass (as might be expected from a superior treatment) and subsequent weed seed production later in the season and in following crops. In contrast, weed biomass and seeds were increased in glufosinate-treated HT-maize crops, leading to higher numbers of some invertebrates that fed on or were associated with the greater mass of decaying plant matter present. These effects were entirely related to the efficacy of weed control by the different herbicide regimes, and were not a feature of the HT crops themselves. They would occur with any herbicide/crop combination that changed the spectrum and density of weeds present. A much greater effect on biodiversity was seen between crops than between herbicide regimes, with non-GM maize having the greatest adverse effect on biodiversity compared to oilseed rape and sugar beet. Thus it is the growing of crops in the first place that is likely to have the greatest impact on the environment not whether it is GM or not. In this context, how is it possible to devise methods of post-market monitoring of GMHT crops? What should be the baseline against which environmental impact is measured? How can this be done simply without incurring the huge costs of studies such as the FSE in the UK? This presentation will present a personal view of the FSE and other research results that could provide guidelines for future introductions of GMHT crops in Europe.

Post Market Monitoring of GM Herbicide-Tolerant Crops

As soon as humans adopted agriculture as the principle means of feeding themselves, they have had an effect on the environment, and by implication, also on biodiversity. It is not possible to grow crops in an intensive manner without doing so, but it is necessary to do so to feed the population. In this respect, the use of herbicides or other weed control practices (e.g. hand-hoeing) inevitably will have an effect on biodiversity, whether those methods are used in conventional, organic or genetically modified herbicide-tolerant (GMHT) crops. Recent literature from the UK following the Farm Scale Evaluations (FSE) of the environmental impact of GMHT oilseed rape, maize and sugar beet suggests that the recommended weed management techniques applied in the cultivation of GMHT crops caused indirect effects on non-target organisms by affecting the biodiversity of plants within a field and the creatures which depend on them. Reductions in the number of weeds in glufosinate-treated HT-oilseed rape, and glyphosate-treated HTsugar beet compared to conventionally managed crops resulted in significant reductions in weed biomass (as might be expected from a superior treatment) and subsequent weed seed production later in the season and in following crops. In contrast, weed biomass and seeds were increased in glufosinate-treated HT-maize crops, leading to higher numbers of some invertebrates that fed on or were associated with the greater mass of decaying plant matter present. These effects were entirely related to the efficacy of weed control by the different herbicide regimes, and were not a feature of the HT crops themselves. They would occur with any herbicide/crop combination that changed the spectrum and density of weeds present. A much greater effect on biodiversity was seen between crops than between herbicide regimes, with non-GM maize having the greatest adverse effect on biodiversity compared to oilseed rape and sugar beet. Thus it is the growing of crops in the first place that is likely to have the greatest impact on the environment not whether it is GM or not. In this context, how is it possible to devise methods of post-market monitoring of GMHT crops? What should be the baseline against which environmental impact is measured? How can this be done simply without incurring the huge costs of studies such as the FSE in the UK? This presentation will present a personal view of the FSE and other research results that could provide guidelines for future introductions of GMHT crops in Europe.

Functional approaches for assessing plant and invertebrate abundance patterns in arable systems

A functional group approach was developed for plant and invertebrate assemblages from UK arable fields to assess the variation in functional composition of these highly disturbed, managed systems. Data were taken from the Farm-Scale Evaluations (FSE) of genetically modified herbicide-tolerant (GMHT) crops where the impact of management of the GMHT crop has been assessed for winter and spring sown oilseed rape, beet and maize. Twenty plant and 36 invertebrate functional groups were defined according to trophic behaviour and traits that affect resource capture, quality and availability. The functional composition of the plant community was significantly affected by season of sowing, the type of crop sown and, to a lesser extent, herbicide management. The invertebrate community composition was also affected by crop type and sowing season, but not by management. Resource and consumer groups were positively related, and data provide strong evidence for top-down control of herbivore populations. Two main interaction groups were identified within the arable food web: one between omnivores, generalist predators and detritivores, which are positively associated with monocots, and one between omnivores, parasitoids, sap feeders and leaf chewers, which have a stronger association with dicots. Although management has an impact on within-field arable biodiversity, crop type and sowing season have an overriding effect on the functional composition of plant and invertebrate assemblages in arable systems. Für Pflanzen- und Invertebratengesellschaften auf Kulturflächen in Großbritannien wurde ein Ansatz über funktionelle Gruppen entwickelt, um die Variation in der funktionalen Zusammensetzung dieser hochgradig gestörten, bewirtschafteten Systeme zu bestimmen. Die Daten stammen aus der “Farm-Scale-Evaluation” von genetisch modifizierten herbizidtoleranten Feldfrüchten (GMHT), bei der der Einfluss der Bewirtschaftung der GHMT-Feldfrüchte für Winter- und Sommerraps, Rüben und Mais abgeschätzt wurde. Es wurden 20 funktionelle Gruppen von Pflanzen und 36 von Invertebraten unter Berücksichtigung der trophischen Stellung und Eigenschaften definiert, welche die Ressourcennutzung, Qualität und Verfügbarkeit beeinflussen. Die funktionelle Zusammensetzung der Pflanzengemeinschaften wurde signifikant durch die Aussaatsaison, durch den ausgesäten Nutzpflanzentyp und in geringerem Maße durch das Herbizidmanagement beeinflusst. Die Zusammensetzung der Invertebratengemeinschaften wurde ebenfalls durch den Nutzpflanzentyp und die Aussaatsaison beeinflusst, aber nicht durch das Management. Die Ressourcen- und Konsumentengruppen standen in einer positiven Beziehung zueinander und die Daten liefern starke Hinweise auf eine top-down Kontrolle der Herbivorenpopulationen. Es wurden zwei wesentliche Interaktionsgruppen innerhalb des Kulturnahrungsnetzes gefunden: Eine zwischen den Omnivoren, unspezialisierten Prädatoren und Detritivoren, die positiv mit Monokotylen assoziiert sind, und eine zwischen Omnivoren, Parasitoiden, Saftsaugern und Blattfressern, die eine stärkere Assoziation mit Dikotylen zeigen. Obwohl die Bewirtschaftung einen Einfluss auf die Biodiversität innerhalb der Kulturfelder hat, zeigen Kulturpflanzentyp und Aussaatsaison eine überwältigenden Einfluss auf die funktionale Zusammensetzung der Pflanzen- und Invertebratengemeinschaften in Kultursystemen.

Mitigation of indirect environmental effects of GM crops

Currently, the UK has no procedure for the approval of novel agricultural practices that is based on environmental risk management principles. Here, we make a first application of the 'bow-tie' risk management approach in agriculture, for assessment of land use changes, in a case study of the introduction of genetically modified herbicide tolerant (GMHT) sugar beet. There are agronomic and economic benefits, but indirect environmental harm from increased weed control is a hazard. The Farm Scale Evaluation (FSE) trials demonstrated reduced broad-leaved weed biomass and seed production at the field scale. The simplest mitigation measure is to leave a proportion of rows unsprayed in each GMHT crop field. Our calculations, based on FSE data, show that a maximum of 2% of field area left unsprayed is required to mitigate weed seed production and 4% to mitigate weed biomass production. Tilled margin effects could simply be mitigated by increasing the margin width from 0.5 to 1.5 m. Such changes are cheap and simple to implement in farming practices. This case study demonstrates the usefulness of the bow-tie risk management approach and the transparency with which hazards can be addressed. If adopted generally, it would help to enable agriculture to adopt new practices with due environmental precaution.

Effects of successive seasons of genetically modified herbicide-tolerant maize cropping on weeds and invertebrates

The use of genetically modified herbicide-tolerant (GMHT) crops influences the abundance of weeds and some invertebrate groups because the associated herbicide regime contrasts with that of conventional systems. However, it is not clear to what extent these effects might be cumulative; should GMHT crops be grown continuously. In northern Europe, in the near future, this situation is most likely to apply to maize crops. Here, we consider the effects of continuous GMHT maize cropping on plant and invertebrate taxa using a split-field experiment. Half of each field was managed using GMHT and the other half with a conventional variety, with the treatments retained for two seasons. The treatment effects were broadly consistent with those found in the larger sample of non-continuous maize sites within the Farm Scale Evaluations. There was little evidence of effects being significantly more pronounced in the second year; any cumulative differences in above-ground biodiversity between GMHT and conventional cropping were too variable to be readily detected.

The effects of GMHT crops on bird abundance in arable fields in the UK

Abstract Bird surveys were carried out in summer 2000 and winter 2000/2001 on 24 sugar beet fields, 11 maize fields, 10 spring rape fields and (for winter-only) 23 winter rape fields divided into conventional and genetically modified herbicide tolerant (GMHT) treatments. These fields were a sub-sample of those used in the farm scale evaluation (FSE [Firbank, L.G, Heard, M.S., Woiwod, I.P., Hawes, C., Haughton, A.J., Champion, G.T., Scott, R.J., Hill, M.O., Dewar, A.M., Squire, G.R., May, M.J., Brooks, D.R., Bohan, D.A., Daniels, R.E., Osborne, J.L., Roy, D.B., Black, H.I.J., Rothery, P., Perry, J.N., 2003. An introduction to the farm-scale evaluations of genetically modified herbicide tolerant crops. J. Appl. Ecol. 40, 2–16.]). The study aimed to compare bird abundance between GMHT and conventional crop treatments. In the summer, the abundance of yellowhammers Emberiza citrinella and of granivores collectively was significantly greater on conventional than GMHT sugar beet. Abundance of granivores and species richness was significantly greater on conventional than GMHT maize, but only after the application of herbicides to the GMHT treatment. No significant differences were detected in spring oilseed rape. No significant differences were detected prior to herbicide application in any crop. In winter, granivores were more abundant on bare plough following conventional sugar beet treatment than following GMHT treatment. Woodpigeon Columba palumbus , blackbird Turdus merula and corvids were more abundant on maize stubbles following GMHT treatment. These differences were in accord with likely differences in food availability ascertained from previous research carried out under the FSE.

Effects of genetically modified herbicide-tolerant cropping systems on weed seedbanks in two years of following crops

The Farm Scale Evaluations (FSEs) showed that genetically modified herbicide-tolerant (GMHT) cropping systems could influence farmland biodiversity because of their effects on weed biomass and seed production. Recently published results for winter oilseed rape showed that a switch to GMHT crops significantly affected weed seedbanks for at least 2 years after the crops were sown, potentially causing longer-term effects on other taxa. Here, we seek evidence for similar medium-term effects on weed seedbanks following spring-sown GMHT crops, using newly available data from the FSEs. Weed seedbanks following GMHT maize were significantly higher than following conventional varieties for both the first and second years, while by contrast, seedbanks following GMHT spring oilseed rape were significantly lower over this period. Seedbanks following GMHT beet were smaller than following conventional crops in the first year after the crops had been sown, but this difference was much reduced by the second year for reasons that are not clear. These new data provide important empirical evidence for longer-term effects of GMHT cropping on farmland biodiversity.

Predicting longer‐term changes in weed populations under GMHT crop management

SummaryThe UK Farm Scale Evaluations (FSE) compared the effects on biodiversity of management of genetically modified herbicide‐tolerant (GMHT) crops and conventional crops over the shorter term. We simulated population changes over seven 4‐year rotations (28 years) for weeds in crop rotations that included cereals and spring‐sown GMHT and conventional oilseed rape and beet, using FSE data and assuming the continuation of the weed management systems practised in the FSE. The weed density dependence that was modelled integrated change caused by population dynamics and farmers’ responses to changes in weed density. Predicted weed seed populations decreased under conventional management and at a greater rate under GMHT. Total seed densities were lower for GMHT cropping by a factor of 0.7–0.8. The predicted distributions of weeds had more fields with lower weed densities under GMHT cropping. Such changes could affect animal populations on farmland, depending on the scale of uptake of GMHT crop cultivars.

Invertebrate responses to the management of genetically modified herbicide–tolerant and conventional spring crops. II. Within-field epigeal and aerial arthropods

The effects of the management of genetically modified herbicide-tolerant (GMHT) crops on the abundances of aerial and epigeal arthropods were assessed in 66 beet, 68 maize and 67 spring oilseed rape sites as part of the Farm Scale Evaluations of GMHT crops. Most higher taxa were insensitive to differences between GMHT and conventional weed management, but significant effects were found on the abundance of at least one group within each taxon studied. Numbers of butterflies in beet and spring oilseed rape and of Heteroptera and bees in beet were smaller under the relevant GMHT crop management, whereas the abundance of Collembola was consistently greater in all GMHT crops. Generally, these effects were specific to each crop type, reflected the phenology and ecology of the arthropod taxa, were indirect and related to herbicide management. These results apply generally to agriculture across Britain, and could be used in mathematical models to predict the possible long-term effects of the widespread adoption of GMHT technology. The results for bees and butterflies relate to foraging preferences and might or might not translate into effects on population densities, depending on whether adoption leads to forage reductions over large areas. These species, and the detritivore Collembola, may be useful indicator species for future studies of GMHT management.

Weeds in fields with contrasting conventional and genetically modified herbicide–tolerant crops. II. Effects on individual species

We compared the effects of the management of genetically modified herbicide-tolerant (GMHT) and conventional beet, maize and spring oilseed rape on 12 weed species. We sampled the seedbank before and after cropping. During the season we counted plants and measured seed rain and biomass. Ratios of densities were used to calculate emergence, survival, reproduction and seedbank change. Treatments significantly affected the biomass of six species in beet, eight in maize and five in spring oilseed rape. The effects were generally consistent, with biomass lower in GMHT beet and spring oilseed rape and higher in GMHT maize. With few exceptions, emergence was higher in GMHT crops. Subsequent survival was significantly lowered for eight species in beet and six in spring oilseed rape in the GMHT treatments. It was increased for five species in maize and one in spring oilseed rape. Significant effects on seedbank change were found for four species. However, for many species in beet and spring oilseed rape (19 out of 24 cases), seed densities were lower in the seedbank after GMHT cropping. These differences compounded over time would result in large decreases in population densities of arable weeds. In maize, populations may increase.

Design of the farm‐scale evaluations of genetically modified herbicide‐tolerant crops

AbstractThe Farm‐Scale Evaluations (FSE) is a three‐year experiment to study the effects on farmland wildlife of the commercial management of four genetically modified herbicide‐tolerant (GMHT) crops—beet, maize, spring oil‐seed rape and winter oil‐seed rape. The experiment records abundance of a wide range of weed and invertebrates in the arable system. The FSE is a paired comparison arranged as a randomized block design with two treatments (GMHT and conventional crop management) and fields as blocks. The choice of the half‐field as the experimental unit is based on field availability, the primary focus on the vegetation, the need to reduce variability and gains in sampling effort. Farms and fields are selected to reflect the range of geographical variation and farming intensity for each crop. A power analysis shows that using about 60 fields per crop over the three years will be sufficient to detect differences of ecological significance. Copyright © 2003 John Wiley & Sons, Ltd.