Landscape effects of transgenic cotton on non-target ants and beetles

Transgenic crops producing toxins from Bacillus thuringiensis (Bt) can be planted in the same field for many years, and many insects exploiting such crops must disperse to other habitats to persist. Accordingly, effects of transgenic crop farming could accumulate through time and affect insect populations across agricultural landscapes. We monitored the population density of seven ant genera and beetle families and of rare ants and beetles in 84 non-cultivated sites abutting agricultural fields in Central Arizona. We assessed the short-term (during planting year) and long-term (over 5-6 years) landscape effect of farming Cry1Ac cotton on ant and beetle density in non-cultivated sites in addition to several local and regional variables. Landscape variables unrelated to use of Bt cotton had greater influence on ant abundance in non-cultivated sites than local variables, but this was not the case for beetles. The farming of Bt cotton in neighboring fields frequently resulted in positive short- and long-term landscape effects on ants and beetles in non-cultivated sites, while Bt cotton planted farther away had less frequent negative short-term impacts.