Thinning: the missing dimension of biodiversity loss

Ecological communities worldwide have experienced profound changes over the last several decades, including the loss of overall abundance driven by simultaneous population declines in formerly common taxa. Although multi-species abundance decline has been observed in nearly all ecosystems, its effects on ecosystem function and biodiversity remain largely unaddressed in ecological theory. Here we formally define multi-species abundance decline, i.e. “thinning”, for the first time, as an ecological process that occurs before local extinction and separate from patterns of community turnover. We examine the causes and consequences of thinning, and propose hypothetical thinning trajectories that a community might follow. Using simulations, we show that many commonly-used biodiversity metrics are insensitive to patterns of thinning, suggesting that thinning is an overlooked aspect of community change. Finally, we provide recommendations for the consideration of thinning in biodiversity studies to facilitate a more thorough characterization of global ecological change. Contents: ThinSim.R: R code to generate a community matrix (sites as rows, species as columns) and simulate thinning by sequentially removing each individual, calculating diversity metrics after each removal/death ThinSim_Parameters.csv: A table with different parameters for the abundance and occupancy distributions of each simulation run. MetricPlots.zip: zip file containing the plots of diversity vs. abundance for all 48 iterations of the simulation . ZetaPlots.zip: .zip file containing the plots of zeta-diversity vs. abundance for all 48 iterations of the simulation. FrequencyDistributions.zip: .zip file containing plots showing 1) the abundance frequency distribution, 2) the occupancy frequency distribution, and 3) the occupancy-abundance relationship for all 48 iterations of the simulation.