Temporal Instability of Evidence Base: A Threat to Policy Making?

A shift towards evidence-based conservation and environmental management over the last two decades has resulted in an increased use of systematic reviews and meta-analyses as tools to combine existing scientific evidence. However, to guide policy making decisions in conservation and management, the conclusions of meta-analyses need to remain stable for at least some years. Alarmingly, numerous recent studies indicate that the magnitude, statistical significance, and even the sign of the effects reported in the literature might change over relatively short time periods. We argue that such rapid temporal changes in cumulative evidence represent a real threat to policy making in conservation and environmental management and call for systematic monitoring of temporal changes in evidence and exploration of their causes.