Environmental and Health Impacts of GM crops – the science 
Greenpeace, September 2011
http://www.greenpeace.org/eu-unit/en/Publications/2011/impacts-the-science/

This [carefully referenced] briefing gives an overview of the scientific evidence regarding the environmental and health risks of GM crops.

Extract:

A decade of research fails to acquit GM crops

Contrary to GM industry spin, the publication "A decade of EU-funded research" prepared by the Directorate-General for Research of the European Commission, does not provide scientific evidence on the environmental safety of GM plants. The vast majority of research referred to under the chapter Environmental Impact of GMOs is mostly about the development of GM crops with plant protection traits and has very little to do with assessing the environmental impacts (for example on soil health or on butterflies and moths) of the pesticide-producing and herbicide-tolerant GM crops awaiting an EU authorisation. The few projects that do examine environmental safety raise concerns.