On the rationale and interpretation of the Farm Scale Evaluations of genetically modified herbicide-tolerant crops (original) (raw)
Related papers
2007
The Farm Scale Evaluations (FSE) investigated the effects of growing genetically modified herbicide-tolerant (GMHT) beet, maize, spring and winter oilseed rape on farmland biodiversity in the UK between 2000 and 2005. To date, this represents the largest field ecology experiment ever conducted. Results have been published in a range of publications. Here, we synthesise these results into one paper and summarise the findings of this work. In beet and spring oilseed rape, before post emergence herbicides were applied, there were more weeds in GMHT crops than in conventional crops. Following herbicide applications to these GMHT crops, however, weed counts, seed rain and biomass were substantially reduced in this treatment. In maize, the counts, biomass and seed rain of dicot weeds were larger throughout the season in GMHT crops. In winter oilseed rape dicot weeds were in greater abundance early in the season in GMHT crops, but after herbicides had been applied to this treatment, their counts, biomass and seed rain were larger in conventional crops. Monocot weeds, however, were more abundant in GMHT winter oilseed rape crops throughout the year. Across all crops, many of these effects were found to persist for up to two years in the seedbanks and rotations of following crops. Collembola were captured in greater numbers, particularly later in the season, from the GMHT treatments of all crops. Bees, butterflies and seed-feeding carabids often followed the trends for dicot weed resources reported for the treatments. Treatment effects on biota could be explained by differences in herbicide management and were remarkably consistent across years, regions and base-line biodiversity levels of trial sites. Using the taxa recorded in the FSE, food resources for a high proportion of farmland birds would be significantly reduced under GMHT beet, spring and winter oilseed rape cropping, but increased under GMHT maize cropping. If these trends were maintained under widespread commercial GMHT cropping it is likely that GMHT beet, spring and winter oilseed rape would exacerbate long-term declines of dicot weeds and the invertebrate and wildlife species which depend on them. Conversely, GMHT maize cropping may ameliorate such biodiversity declines. However, the magnitude of the effects of GMHT cropping need to be put in the context of changes in the wider landscape. It is likely, for example, that crop type can have a greater influence on biodiversity. Also, the effect of GMHT crops on the long-term population dynamics of biota will depend on the scale of their uptake, how their herbicide regimes are managed and the crop rotations and structure of the wider landscape in which they are grown.
Philosophical Transactions of The Royal Society B: Biological Sciences, 2003
The Farm Scale Evaluations of genetically modified herbicide-tolerant crops (GMHT) were conducted in the UK from 2000 to 2002 on beet (sugar and fodder), spring oilseed rape and forage maize. The management of the crops studied is described and compared with current conventional commercial practice. The distribution of field sites adequately represented the areas currently growing these crops, and the sample contained sites operated at a range of management intensities, including low intensity. Herbicide inputs were audited, and the active ingredients used and the rates and the timings of applications compared well with current practice for both GMHT and conventional crops. Inputs on sugar beet were lower than, and inputs on spring oilseed rape and forage maize were consistent with, national averages. Regression analysis of herbicide-application strategies and weed emergence showed that inputs applied by farmers increased with weed densities in beet and forage maize. GMHT crops generally received only one herbicide active ingredient per crop, later and fewer herbicide sprays and less active ingredient (for beet and maize) than the conventional treatments. The audit of inputs found no evidence of bias.
Environmental Science and Pollution Research, 2008
Background, aim and scope In a gradualist approach to the introduction of crop biotechnology, the findings of experimentation at one scale are used to predict the outcome of moving to a higher scale of deployment. Movement through scales had occurred for certain genetically modified herbicide-tolerant (GMHT) crops in the UK as far as large-scale field trials. However, the land area occupied by these trials was still <1% of the area occupied by the respective non-GM crops. Some means is needed to predict
Proceedings of the Royal Society B: Biological Sciences, 2006
Primary results from the Farm Scale Evaluations (FSEs) of spring-sown genetically modified herbicidetolerant crops were published in 2003. We provide a statistical assessment of the results for count data, addressing issues of sample size (n), efficiency, power, statistical significance, variability and model selection. Treatment effects were consistent between rare and abundant species. Coefficients of variation averaged 73% but varied widely. High variability in vegetation indicators was usually offset by large n and treatment effects, whilst invertebrate indicators often had smaller n and lower variability; overall, achieved power was broadly consistent across indicators. Inferences about treatment effects were robust to model misspecification, justifying the statistical model adopted. As expected, increases in n would improve detectability of effects whilst, for example, halving n would have resulted in a loss of significant results of about the same order. 40% of the 531 published analyses had greater than 80% power to detect a 1.5-fold effect; reducing n by one-third would most likely halve the number of analyses meeting this criterion. Overall, the data collected vindicated the initial statistical power analysis and the planned replication. The FSEs provide a valuable database of variability and estimates of power under various sample size scenarios to aid planning of more efficient future studies.
Biology Letters, 2006
Genetically modified (GM), herbicide-tolerant crops have been adopted extensively worldwide, resulting in increased homogenization of agricultural practices. However, several countries still view GM crops with trepidation, citing potential risks to human health and the environment. We currently know little about how non-target biota responds to cultivation of GM crops under field conditions. 2. This study describes a series of microcosm and field experiments in Ontario, Canada, that estimated the effects of transgenic, glyphosate-tolerant (GT) crops and their management on the abundances of detritivorous soil biota and crop litter decomposition. 3. Absolute abundance of few of the measured biotic groups were affected by either the herbicide or variety treatments and, where significant effects were observed, the responses were not consistent across all years or for all sample dates within a year. More frequently, but not consistently, the GT herbicide system was associated with increased fungal : bacterial biomass ratios, suggesting a state of reduced enrichment. 4. Although the conventional and GT varieties studied differed in composition, we observed few effects of the modification for glyphosate-tolerance on maize Zea mays and soybean Glycine max litter decomposition. Overall, the herbicide system associated with GT crops reduced soybean-and corn-litter decomposition, but responses were inconsistent across Ontario, with many trials demonstrating no effect. Effects were probably underrepresented in this study as average daily precipitation was positively correlated with the magnitude of this system effect and many sites received well-below average levels of precipitation. 5. Synthesis and applications . Most concerns regarding the potential impacts of GM crops on non-target biota have targeted traits associated with the biotechnology itself. However, shifts in management practices associated with biotechnology are also widespread and have the same, if not greater, potential to alter the structure and functioning of agroecosystem biodiversity. The lack of observed permanent negative effects on soil biota in this study is heartening; however, more research is required to determine the functional consequences of observed transient effects and effects on other biota, as well as how altered crop litter decomposition affects agroecosystem nutrient cycling and carbon sequestration.
Journal of Applied Ecology, 2003
The effects on British farmland wildlife of the management of four genetically modified herbicide-tolerant crops are currently being studied in a 5-year trial termed the Farm-Scale Evaluations (FSE), the first 4 years of which are completed. The FSE is controversial and extensive. There has been intense scrutiny of the experimental design and proposed analysis, and of the estimated statistical power to detect effects of a given magnitude, should any exist. 2. For each crop, the FSE is a form of on-farm trial with a single composite null hypothesis and a simple randomized block experimental design. This has statistical implications for the imposition of treatments by growers and the need for proper randomization. The choice of a half-field experimental unit was based on field availability, the focus on herbicide management, the need to reduce variability and efficiency gains in sampling effort. Farms and fields were selected to represent the range of variability of geography and intensiveness across Britain for each crop. 3. Results of a power analysis suggested that the planned replication of the FSE of about 60 fields per crop over 3 years would be sufficient to provide useful information, from which valid statistical inferences could be drawn. The achieved replication for spring crops in the FSE exceeded, by more than threefold, that in any of 82 comparable terrestrial manipulative ecological experiments undertaken previously. 4. Here, we exemplify a range of analyses including covariates, interactions between various factors including years and treatments, diagnostic procedures to aid selection of the most efficient statistical model, the estimation of power from coefficients of variation, a novel and apparently robust test statistic and the calculation of overall variance from within-and between-unit variability. Preliminary results indicated that a simple log-normal model appeared adequate for most analyses. 5. Synthesis and applications. Statistical challenges created by the scope of the FSE were resolved from a sound knowledge of good experimental design. There is an urgent need for further statistical studies to develop experimental designs or modelling approaches that allow similar studies of genetically modified (GM) crops, at reduced cost. However, this power analysis has shown that this cannot be achieved at the expense of adequate replication, essential for all risk assessment studies.