Initiatives to manage landscapes for both biodiversity protection and sustainable development commonly employ participatory methods to exploit the knowledge of citizens. We review five examples of citizen groups engaging with landscape scale conservation initiatives to contribute their knowledge, collect data for monitoring programs, study systems to detect patterns, and test hypotheses on aspects of landscape dynamics. Three are from landscape interventions that deliberately target biodiversity conservation and aim to have sustainable development as a collateral outcome. The other two are driven primarily by concerns for agricultural sustainability with biodiversity conservation as a collateral outcome. All five include programs in which, management agencies support data collection by citizen groups to monitor landscape changes. Situations where citizen groups self-organise to collect data and interpret data to aid in landscape scale decision making are less common and are restricted to landscapes where the inhabitants have a high level of scientific literacy. Given the complexity of landscape processes and the multiple decision makers who influence landscape outcomes we argue that citizen science broadly defined should be an essential element of landscape scale initiatives. Conservation managers should create space for citizen engagement in science and should empower citizen groups to experiment, learn, and adapt their decision-making to improve landscape scale outcomes.