A case for occupancy as a state variable for wild bee monitoring

Abstract

Reports of widespread pollinator declines, data deficiencies, and inabilities to assess status and trends underscore the need for wild bee monitoring. Chief among the challenges with wild bee monitoring is identifying monitoring objectives and state variables. Here we make the case for considering occupancy, the proportion of area occupied, as a primary state variable of interest for monitoring wild bee populations. A focus on occupancy can help to resolve some of the current complications arising from population monitoring of bees. We highlight the strengths of occupancy specifically in the context of wild bee monitoring, drawing from achievements of current monitoring programs of other taxa. We provide guidance for incorporating occupancy models into the design of current and future wild bee monitoring efforts and address important sampling biases to consider when monitoring bee populations. We also stress the importance of developing bee monitoring objectives that result in actionable conservation or improved scientific understanding. Our viewpoint provides a framework for kickstarting monitoring efforts that will better lead to effective conservation actions for wild bees.