Assessing the sensitivity and robustness of the Living Planet Index through simulated population dynamics: strengths, stability, and challenges

Cristian A. Cruz-Rodríguez, Gaëlle Mével, Janaína de Andrade Serrano, Shuaishuai Li, Jessica Currie, Maria Isabel Arce-Plata, Sarah Ravoth, Timothée Poisot , Louise McRae , Robin Freeman, Valentina Marconi, Sandra Emry, David AGA Hunt

Understanding population change through time is crucial for effective conservation of biodiversity. The Living Planet Index (LPI) is a key indicator for tracking global species abundance trends under the Kunming-Montreal Global Biodiversity Framework, offering a picture of population change over time. However, the sensitivity of the index to zero values or to the number of missing values in time series has not been fully explored. Using simulations, we assessed how missing data and zero values influence the index and associated trends. We found that the LPI method is informative with complete datasets, as missing data raises variation but only results in minor deviations from baseline trends. In contrast, the presence and distribution of zeros within the underlying data substantially influence the results and produce significantly lower trends. These findings highlight the need to develop complementary approaches for evaluating how data heterogeneity influences LPI trends, towards a comprehensive understanding and better-informed decisions on biodiversity change