Five lessons for avoiding failure when scaling in conservation.

Many attempts to scale conservation actions have failed to deliver their intended benefits, caused unintended harm or later been abandoned, hampering efforts to bend the curve on biodiversity loss. Here we encourage those calling for scaling to pause and reflect on past scaling efforts, which offer valuable lessons: the total impact of an action depends on both its effectiveness and scalability; effectiveness can change depending on scale for multiple reasons; feedback processes can change socio-ecological conditions influencing future adoption; and the drive to scale can incentivize bad practices that undermine long-term outcomes. Cutting across these themes is the recognition that monitoring scaling can enhance evidence-informed adaptive management, reporting and research. We draw on evidence and concepts from disparate fields, explore new linkages between often isolated concepts and suggest strategies for practitioners, policymakers and researchers. Reflecting on these five lessons may help in the scaling of effective conservation actions in responsible ways to meet the triple goals of reversing biodiversity loss, combating climate change and supporting human wellbeing.