Temporal instability of evidence base: A threat to policy making?

A shift towards evidence-based conservation and environmental managementover the last two decades has resulted in an increased use of systematic reviewsand meta-analyses as tools to combine existing scientific evidence. However, toguide policy making decisions in conservation and management, the conclu-sions 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 overrelatively short time periods. We argue that such rapid temporal changes incumulative evidence represent a real threat to policy making in conservationand environmental management and call for systematic monitoring of temporalchanges in evidence and exploration of their causes.