At the first stakeholder workshop we got a question about the name of the project, specifically on the use of the word evidence. Based on the discussion that followed, evidence and evidence-based are words that are understood in multiple ways. For a person evidence-based refers to someone who has been tested on his or her skills and has passed the exam. For another evidence refers to an experience that a certain management practice is working, and for third person, it refers to research results. In a way all these are evidence because fundamentally evidence is knowledge that we gather from different sources.
In evidence-based decision making, whether we talk about environmental sciences or medicine, evidence is often depicted through the evidence hierarchy (Figure 1). Evidence hierarchies vary somewhat but we use this one as it connects evidence with decision-making. At the bottom of the pyramid are primary research studies that provide the starting point for any evidence synthesis. Their quality may differ, for example regarding sample size, and hence, the evidence they have may have different weight.
At the next level are systematic maps that reveal what evidence exists but say nothing about the effectiveness of interventions. At the third level are systematic reviews that describe the effectiveness of interventions. At the top are reviews of reviews that synthesise the findings of systematic reviews conducted on a certain topic area.
The higher in the hierarchy we are regarding the evidence, the stronger the support for decision-making.
Lynn V. Dicks, Jessica C. Walsh, William J. Sutherland (2014) Organising evidence for environmental management decisions: a ‘4S’ hierarchy. Trends in Ecology & Evolution, 29:607-613.