Invertebrates and vegetation of field margins adjacent to crops subject to contrasting herbicide regimes in the Farm Scale Evaluations of genetically modified herbicide–tolerant crops

Abstract

The effects of management of genetically modified herbicide-tolerant (GMHT) crops on adjacent field margins were assessed for 59 maize, 66 beet and 67 spring oilseed rape sites. Fields were split into halves, one being sown with a GMHT crop and the other with the equivalent conventional non-GMHT crop. Margin vegetation was recorded in three components of the field margins. Most differences were in the tilled area, with fewer smaller effects mirroring them in the verge and boundary. In spring oilseed rape fields, the cover, flowering and seeding of plants were 25%, 44% and 39% lower, respectively, in the GMHT uncropped tilled margins. Similarly, for beet, flowering and seeding were 34% and 39% lower, respectively, in the GMHT margins. For maize, the effect was reversed, with plant cover and flowering 28% and 67% greater, respectively, in the GMHT half. Effects on butterflies mirrored these vegetation effects, with 24% fewer butterflies in margins of GMHT spring oilseed rape. The likely cause is the lower nectar supply in GMHT tilled margins and crop edges. Few large treatment differences were found for bees, gastropods or other invertebrates. Scorching of vegetation by herbicide-spray drift was on average 1.6% on verges beside conventional crops and 3.7% beside GMHT crops, the difference being significant for all three crops.

On the rationale and interpretation of the Farm Scale Evaluations of genetically modified herbicide-tolerant crops

“…Within each split-field, the study would concentrate on the plants and more-or-less sedentary herbivores and detritivores that react rapidly to any major change in field management (figure 3a). Protocols for measuring these organisms at defined sample points in each half-field were devised (Heard et al 2003a;Haughton et al 2003;Brooks et al 2003;Roy et al 2003). The split-field arrangement had to be repeated over a large number of sites-between 60 and 75 for each crop type-both to gain the statistical power to detect differences of ca.…”

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

“…Lond. B (2003) be observed in areas adjacent to the crop, as discussed by Roy et al (2003). This paper describes the indirect effects of the management of GMHT crops on within-field epigeal and aerially active arthropods, using sampling approaches that reflect the differences in behaviours and abundances of these groups.…”

Impact environnemental des cultures transgéniques

“…Réalisées sur une période de trois ans sur des dizaines de sites à l'échelle du pays, ces études ont démontré dans l'ensemble un effet significatif de la gestion des cultures associée aux lignées modifiées, comparativement aux impacts mesurés sur des parcelles témoins ensemencées de lignées conventionnelles traitées avec les herbicides de synthèse normalement utilisés (Bohan et al 2005;Brooks et al 2003;Champion et al 2003;Haughton et al 2003;Hawes et al 2003;Heard et al 2003a, b;Roy et al 2003). Ces impacts, indépendants du processus de transgénèse ou du caractère recombinant exprimé, étaient plutôt liés à l'efficacité du désherbage pour les différents types de gestion (Firbank 2003).…”