<scp>RCTs</scp> in the wild: Designing and implementing conservation programs as randomized control trials

Abstract Experimental evaluation of environmental programs, including those aiming to conserve biodiversity, is rarer than those of social programs. However, there is growing interest in conducting such evaluations in conservation. Randomized control trials (RCTs), in which units are randomly assigned to receive one of two or more treatments, can avoid biases associated with observational designs and provide reliable estimation of program effectiveness. We present a typology of conservation RCTs, which differentiates between interventions that have a direct impact on biodiversity and those where the impact is mediated through changes in human behavior. With a focus on RCTs in behaviorally mediated conservation programs, which have received limited attention, we examine: (1) technical challenges (selection of randomization unit, avoiding interference between units, ensuring excludability and external validity) and solutions, (2) ethical and practical challenges, and (3) incentives that conservation organizations have to run RCTs. We end by summarizing the steps needed for good design and transparent reporting of RCTs. RCTs are not always appropriate, but we believe conservation science and practice would benefit from their wider application. By demystifying RCTs of conservation programs, we hope that this article will serve as a practical, grounded guide to foster broader adoption.