Systematic mapping (SM) is used to describe the state of knowledge on a focussed or broad topic/question. SM follows the same methodology for systematic review to gather and collate evidence (published and unpublished literature from multiple sources). However, as SM do not set out to answer a question the evidence is not synthesised. One of the key outputs of a SM is a searchable database of included studies and their meta-data (information describing the study and its methods), study location and availability. This database is used to create a narrative report to describe the evidence base, highlight areas of sufficient evidence (evidence clusters) to permit secondary research (eg. systematic review) and subjects not frequently studied (knowledge gaps) that would benefit from primary research. Implications for research, policy and practice are provided. For an example of a systematic map conducted by the CEBA click here. Guidelines for systematic mapping can be found on the Collaboration for Environmental Evidence website.