All observations will be based on a single season. Thus differences in a parameter represent within-season differences and are not cumulative changes over years. Data from different years will be treated as different observations.
If data for one Bt line and multiple control lines are available, data of the near-isoline or closest related line to the Bt line will be used. If data for multiple Bt lines and one control line are available, the values of the control line will be used several times for comparisons with the Bt lines. If data for one Bt treatment and multiple control insecticide treatments are available, the values of the Bt line will be used several times.
It will be noted in the database if one treatment is used for different comparisons. The following comparisons will be made: Bt untreated — Conventional untreated; Bt untreated — Conventional insecticide treated; Bt insecticide treated — Conventional insecticide treated. In a first step, the data collected by Naranjo [ 12 ] will be checked to make sure the data were all recorded accurately. All identified datasets will be presented by means of a narrative summary of the extracted outcomes. All studies will be coded with keywords for certain categories.
Tables and figures illustrating all existing evidence will be produced. Examples of how the data will be grouped and presented are: number of years covered, study year, first year and long-term cultivation with Bt-maize, crop and field margin, continent of study, country of study, spatial scale of experiment, experimental design, taxonomic group, functional group, parameter measured, Cry-proteins studied, and studies comparing Bt maize to insecticide treated or untreated conventional maize.
Statistical meta-analyses will be conducted for frequently studied taxonomic groups and measured parameters. Based on the knowledge gained from previous meta-analyses, a sufficient number of datasets is available for arthropods and the parameter abundance. Untreated Bt maize is compared to untreated or insecticide-treated conventional maize or insecticide-treated Bt maize is compared to treated conventional maize.
Insecticide treatments include sprays, soil granules or seed coating, depending on the target pest s. Original data are available from the publication tables, figures or from the authors upon request. The response variable will be abundance of non-target animals [ 12 ]. If enough data are available, other response variables might be used e. Bt and control maize fields will be compared for different ecological functional groups, main taxonomic groups, geographical regions continents , different Bt proteins Lepidoptera and Coleoptera specific , commercialized and non-commercialized events.
Separate analyses will be performed for insecticide treated or untreated Bt and conventional maize. We will assess if the unit of intervention Bt maize cultivation, insecticide treatment is the same as the unit of analysis plots or fields analysed in a study.
For field experiments with Bt maize, clustering issues in the experimental design are not likely to occur. A data issue that is likely to occur, however, is the multiple use of the same dataset for different comparisons. For data extraction, we defined the rule that if multiple Bt lines are compared to one control line, the values of the control line are used several times and if one Bt treatment and multiple control insecticide treatments are present, the values of the Bt line are used several times.
Furthermore, data on higher taxonomic levels may include data on individual genera or species and might result in a multiple use of the same data. Those datasets will be flagged see Table 2 , variable replicate data issues in the database during the data extraction process.
The proportion of datasets reused several times in one analysis will be given and discussed. Analyses with and without the multiple use of datasets might be conducted within the sensitivity analyses described below.
Studies in which relevant data were recorded but not reported in the publication will be identified and the authors will be contacted and asked if they were able to provide the missing information. If the relevant data as specified in the inclusion criteria cannot be obtained or calculated from the given data, the dataset will not be included in the meta-analyses.
Any estimates and calculations will be documented in the database. The results of the meta-analyses will be presented with the help of figures and tables. Effect sizes significantly different from 0 as well as the total number of observations will be indicated.
Effect sizes will be calculated such that negative effect sizes are associated with lower abundance or another response parameter on Bt crops compared with non-Bt controls [ 12 ]. A narrative discussion of the findings will be provided. The outcome of the study quality assessment will be discussed. We will test for heterogeneity across studies using adequate statistical approaches. The influence of variation caused by studying different taxa, environmental conditions countries, regions, continents , crop managements tillage, irrigation, pesticide application, rotation , spatial scales, and experimental designs will be explored.
The influence of different parameters causing heterogeneity will be investigated. For parameters causing high heterogeneity, separated meta-analysis of subgroups may be conducted to isolate and help identify the causes of the heterogeneity.
Influence of studies where peak-days were measured in comparison to studies where seasonal means were measured. Influence of different transformation events discussion of differences in Bt protein concentration in different plant parts. Effect sizes will be compared for publications with different funding types see sensitivity analyses described above.
Systematic differences would indicate a publication bias depending on funding source of a study. Missing data around effect size 0 might indicate that studies showing any kind of effect positive or negative are more likely to get published than no effect studies file drawer problem. Geographic distribution of global agricultural lands in the year Glob Biogeochem Cycles , GB Pest Manag Sci , — Transgenic Res , 1— Sci Total Environ , 31— Environ Sci Pol , 82— Article Google Scholar.
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You can also search for this author in PubMed Google Scholar. Bacillus thuringiensis , or Bt, is a common soil bacterium whose genome contains genes for several proteins toxic to insects.
For decades, Bt has been sprayed on fields as an organic pesticide; several major pests of corn that are difficult and expensive to control with chemical insecticides are susceptible to Bt.
When sprayed on the surface of crops, however, Bt toxins break down quickly when exposed to ultraviolet light, and they also wash off in a strong rain. Some strains of Bt produce proteins that are selectively toxic to caterpillars, such as the southwestern corn borer, while others target mosquitoes, root worms, or beetles. This left a famine-stricken population without food aid. In December , the Zambian government changed its mind in the face of further famine and allowed the importation of GM maize Anonymous b, In January , the Hungarian government announced a ban on importing and planting of GM maize seeds, which was subsequently authorized by the European Union James In , the Minister of Agriculture in Egypt announced a ban on the cultivation of Bt cotton and maize after a debate on a TV program concerning the possibilities of hazards of Bt crops unpublished.
In Hawaii, growing Bt cotton has been prohibited since James Burkina Faso, Africa top cotton producer, banned Bt cotton in because of economic and quality concerns James Romania decided not to plant GM crops in due to onerous requirement by the government James Although repeated scientific assessments have concluded that GM crops are as safe for humans and environment as the conventional crops, a majority of Governments, parliamentarians, and European people oppose cultivation of such GM crops James The European countries that banned cultivation of GM crops made their decision because they prefer producing the organic food.
These countries import over 30 million tons per year of Bt corn and GM soybeans as animal feed and livestock industry. However, Russia issued a ban on both cultivation and importing Bt crops James A review of 19 studies announced that consumption of GM corn or soybeans lead to significant organ disruptions in rats and mice, particularly in the liver and kidney Gucciardi Cry toxins had a good run and will hang on for a while longer, but the era of the Cry toxins seems to be ending. They suggested that Bt crops should contain two or three different toxins to delay resistance.
If an insect had an allele to survive on toxin 1, it probably does not have different alleles to survive on toxins 2 and 3 Anonymous The report also claimed that the newest Vip Vegetative insecticidal protein toxins for caterpillars does a good job of controlling many species.
Once again, the insects will have adapted, or partially adapted, to the old toxins, so selection for resistance will be on Vip and again the era of the Cry toxins seems to be ending Anonymous A declaration of European scientists indicated that amoratorium on the cultivation of GM Bt maize approved by the European Union EU is not scientifically justified. Such a decision could be based only on imaginary or false uncertainties concerning environmental or food safety. It would bring no new knowledge that could reduce the hypothetical risks that could be generated by the cultivation and the consumption of GM Bt maize.
Such a moratorium would be in contradiction with the precautionary principle Naud et al. Plant varieties obtained either by classical breeding or by gene transfer share a similar level of risk, which is low in both cases.
Maize has been cultivated and eaten by humans for thousands of years without any negative effect for animal or human health despite the numerous genetic modifications undertaken during classical genetic selection. The insecticidal active toxin presents in Bt maize has been exploited for decades within the applied commercial compounds of Bacillus thuringiensis without any observed toxicity or allergic response Naud et al.
This review shows that some researchers support the cultivation of Bt crops depending upon the results of their laboratory and field studies on the safety of such crops to environment and mammals. Others are against Bt crops as they may cause risk to human. A review of 19 studies announced that consumption of GM corn or soybeans may lead to significant organ-disruption in rats and mice particularly in the liver and kidneys. This declaration relies, as mentioned, on the following: 1 Any plant variety obtained either by classical breeding or by gene transfer has a similar level of risk which is little in both cases.
Finally, and from my point of view, it seems that this controversy could be attributed, in part, to a competition between the companies producing chemical insecticides and those producing bio-control agents.
In addition, there are still scientists as well as crops producers worldwide that do not trust in the biological control of insects. Environ Entomol 32 5 — Article Google Scholar. Transgenic Res — Toxicol Int 17 2 — Anonymous Bt cotton. Google Scholar. Anonymous Genetically modified food. Anonymous Genetically modified maize.
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McGraw-Hill, p Springer, New York, pp 27— Chapter Google Scholar. Nat Biotechnol 21 9 — J Appl Toxicol:1—5. Dis Milner RJ History of Bacillus thuringiensis. Agric Ecosyst Environ — In , GM crops were grown in 28 countries and on There are currently no GM crops being grown commercially in the UK although scientists are carrying out controlled trials.
GM crops were first introduced in the USA in with the Flavr Savr tomato, which had been genetically modified to slow its ripening process, delaying softening and rotting.
The farming of GM crops has massively increased since the mid s.
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