Clarification on the applicability of systematic reviews

In their recent article, Dafforn et al. (Front Ecol Environ 2015; 13[2]: 82–90) reviewed the literature on marine urbanization to produce a conceptual framework for the design of multifunctional marine artificial structures. Their review highlighted the rapid increase in marine urbanization and the well-documented ecological impacts of marine infrastructure. The authors stated that “a systematic review was not possible given that much of the relevant literature crosses scholarly disciplines and is located in books, conference proceedings, and gray literature that would not have appeared in searches”. While we fully agree that such a topic poses challenges in terms of searching across subject domains and incorporating the substantial utility of gray literature, we felt compelled to draw attention to common misconceptions regarding systematic reviews.