Disentangling biodiversity trends in the Anthropocene
The Anthropocene is a new geological era, proposed to reflect the extent to which Humans are currently modifying the planet. Humans have become a major driving force of the planet’s processes, changing the climate, biogeochemical cycles, and land cover, and in the process potentially causing a mass extinction. However, the relationships between change of different metrics of biodiversity are poorly understood. We analyzed 100 time series from biomes across Earth to compare how different metrics of α and β diversity are changing through time.
We did not detect systematic loss of α diversity across any of the metrics analyzed. The proportion of decreasing trends was similar to the proportion of increasing trends, and many time series had a slope of zero. In contrast, community composition changed systematically through time, with cumulative community similarity decreasing through time for most time series analyzed. Moreover, the rate of change observed in the data was several orders of magnitude in excess of predictions from null models. These findings can be reconciled with our understanding of the state of the planet by considering the loose coupling of biodiversity change at different scales. Specifically, spatial heterogeneity in rates of environmental change, species range shifts associated with climate change, and biotic homogenization may explain our results.