Using evidence mapping to display and categorize environmental studies cannot replace 'evidence synthesis' in guiding decision-making (M. C. McKinnon et al. Nature 528, 185–187; 2015). There are no shortcuts to evidence-based practice.
The results of investigations need to be synthesized to allow conclusions to be drawn from contradicting data (L. V. Dicks et al. Trends Ecol. Evol. 29, 607–613; 2014). Studies can be assigned a 'level of evidence' indicator of design and quality, which is derived from evidence hierarchies (see, for example, A.-C. Mupepele et al. Ecol. Appl. http://dx.doi.org/10.1890/15-0595.1; 2016). This indicator reflects the confidence with which the reported outcome can be causally attributed to the investigated driver.
Practitioners' questions are rarely answered directly by an existing set of studies. Evidence-based medicine tackles this problem by developing clinical guidelines on the basis of collated scientific results and clinical experience, and by using systematic reviews of research results and evidence assessments that are supported by hierarchies.