Approaches towards the detection of critical biodiversity transitions

To understand biodiversity change in response to anthropogenic stressors, the idea of critical biodiversity transitions is a prevailing framework. It has been especially prominent in the literature of regime shifts, where a new regime is associated with a different biodiversity. A classical tipping point is defined as the threshold where a minor change in a driver or pressure level leads to an abrupt, disproportionate change in the response variable and the system transitions into a new regime. However, applying this framework to biodiversity presents a challenge: it remains unclear whether and how biodiversity ‘tips,’ and to what extent current detection methods are useful for capturing potential, multi-dimensional biodiversity state shifts. In this work, we conduct a systematic literature review to identify the most common approaches to detecting critical transitions in ecology. We specifically focus on studies analysing transitions in species and species assemblages. We review the current literature between 2020 and 2024 to assess the applied detection methods, their characteristics, advantages and limitations, and underlying concepts. Firstly, our analysis reveals conceptual confusion: terminology (e.g., 'tipping point,' 'regime shift,' 'threshold') is often used interchangeably, and many publications lack clear definitions of the terms and the specific ecological phenomenon under study. This conceptual ambiguity potentially impacts communication and comparison of results across studies. Analysing the characteristics of the different concepts, we show that most detection approaches are not sufficient to capture the complexity of biodiversity change, and they often rely on dimensionality reduction and analysis of subsystems. We argue that a clear definition of the phenomenon under study is urgently needed, and a cautious and critical interpretation of the results is necessary. We discuss methodological needs towards improved transition detection and call for a shift in perspective, with more focus on considering alternative hypotheses to understand biodiversity change rather than solely on threshold transgressions.