NOTE: Below is the abstract of an important new study that concludes that the planting of Bt maize in some areas of Europe would cause increased mortality in the larvae of the protected peacock butterfly (Inachis io).

Interestingly the authors note that their study contradicts the findings of a previous study by Joe Perry and colleagues. Perry is the current chair and a long-time member of the EFSA GMO Panel, which assesses the risks posed by GMOs submitted for approval in the EU. Perry concluded there was negligible risk from Bt maize to the peacock butterfly and the two other species examined.

The authors of the new paper say they used more empirical data in their study than Perry and colleagues - in other words, hard data based on what actually happens to the butterfly and Bt maize pollen in nature, rather than assumptions.

The authors conclude that "a more comprehensive assessment is warranted of the risk implied to butterflies when and where Bt maize is grown." They add, "We contend that such an assessment is best carried out using empirical data, which invites scientific review and integration of knowledge, rather than on expert opinion, on which a qualified assessment is not possible."

This is a clear criticism of the lack of empirical data currently used in GMO risk assessments by EFSA, which are based heavily on flawed assumptions. It is also a criticism of the system of expert opinion that EFSA currently relies upon. This system is being replaced in some areas, such as evidence-based medicine, by more progressive risk assessment methods based on a systematic and replicable search and evaluation of all available data using pre-set transparent criteria. While far from perfect, these methods are increasingly being viewed as more reliable than expert opinion. 
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Increased mortality is predicted of Inachis io larvae caused by Bt-maize pollen in European farmland
Niels Holst, Andreas Lang, Gabor Lövei, Mathias Otto
Ecological Modelling 250 (2013) 126–133
 http://www.sciencedirect.com/science/article/pii/S0304380012005315

Abstract
A potential environmental risk of the field cultivation of insect-resistant (Bt-toxin expressing) transgenic maize (Zea mays) is the consumption of Bt-containing pollen by herbivorous larvae of butterflies (Lepidoptera). Maize is wind-pollinated, and at flowering time large amounts of pollen can be deposited on various plants growing in the landscape, leading to inadvertent ingestion of toxic pollen with plant biomass consumed by these butterfly larvae. To examine the possible effect of this coincidence, we focused our study on the protected butterfly Inachis io and two regions of Europe. Using climatic records, maize and butterfly phenology data, we built a simulation model of the butterfly’s annual life cycle, over- laid with the phenology of maize pollen deposition on the leaves of the food plant Urtica dioica, and linked these with the dose–response curve of I. io larvae to Bt-maize pollen (event MON810). The simulations indicated that in Northern Europe, where I. io is univoltine, Bt-maize pollen would not be present on the food plant at the same time as the I. io larvae. However, in Central and Southern Europe, where I. io is bivoltine, Bt-maize pollen and the second generation I. io larvae would coincide, and an increased mortality of the larvae was predicted. This prediction differs from earlier studies which predicted negligible effect of field-grown Bt-maize on I. io larvae. Our model is an improvement over previous efforts since it is based on more detailed, empirical data, includes more biological detail, and provides explicit estimation of all model parameters. The model is open-source software and is available for re-use and for modelling the effects on other species or regions.