Genetic diversity of a microbial community will inevitably be affected by environmental stress. However, our understanding of the implications of these effects is limited. Genetic exchange between natural microbial communities appears to be a common phenomenon, mediated by a number of microbial processes (conjugation, transformation, and transduction). These mechanisms of change are presumably adaptations to natural environmental perturbation, e.g., the low levels of antibiotics produced by other organisms. However, anthropogenic influences on the environment may be accelerating genetic change within microbiologic ecosystems, beyond these natural adaptation rates. This article highlights some of the perceived risks to ecosystem health and research questions that need to be addressed.