Underlying mechanisms shaping wild bee decline

Abstract Within the Drivers–Pressures–States–Impacts–Responses (DPSIR) framework, anthropogenic activities such as environmental pollution and climate change have consistently been identified as major pressures contributing to the alarming decline of bee populations. While the DPSIR framework provides a valuable structure for assessing the broader context of bee decline, it lacks the resolution to capture the underlying mechanisms that mediate the link between anthropogenic pressures and changes in bee population states. In particular, it does not consider how these pressures disrupt key biological processes that ultimately compromise bee reproductive fitness. This substantial knowledge gap currently limits our ability to pinpoint the causal pathways linking anthropogenic pressures to population declines. To address this limitation, we propose an extension of the DPSIR framework by incorporating a missing yet central component, namely mechanisms, which delineates the biological processes mediating the relationship between pressures and the observed bee population states. We identify and discuss five key mechanisms intrinsically linked to critical phases of the life cycle of bees, each directly affecting reproductive fitness. The delineation of these mechanisms offers a structured and experimentally testable approach for hypothesis-driven research, facilitates the understanding of causal relationships, and fosters more effective communication within the scientific community working on bee conservation.