AK Lilley et al. Trends in Biotechnology (2006) Vol.24#1 p 10 – 14
“Life in earth: the impact of GM plants on soil ecology?”
Studies of microbes in the soil cannot (yet) provide general commercially valuable information. Macroscopic variables, such as water retention, are recorded routinely but linking them and any changes in them with GM agriculture remains speculative.
Some changes would be described as contamination, some as changes in biodiversity (both would be of interest to the regulator in charge of remediation).