title: Recent shifts in the occurrence, cause, and magnitude of animal mass mortality events.
abstract: Mass mortality events (MMEs) are rapidly occurring catastrophic demographic events that punctuate background mortality levels. Individual MMEs are staggering in their observed magnitude: removing more than 90% of a population, resulting in the death of more than a billion individuals, or producing 700 million tons of dead biomass in a single event. Despite extensive documentation of individual MMEs, we have no understanding of the major features characterizing the occurrence and magnitude of MMEs, their causes, or trends through time. Thus, no framework exists for contextualizing MMEs in the wake of ongoing global and regional perturbations to natural systems. Here we present an analysis of 727 published MMEs from across the globe, affecting 2,407 animal populations. We show that the magnitude of MMEs has been intensifying for birds, fishes, and marine invertebrates; invariant for mammals; and decreasing for reptiles and amphibians. These shifts in magnitude proved robust when we accounted for an increase in the occurrence of MMEs since 1940. However, it remains unclear whether the increase in the occurrence of MMEs represents a true pattern or simply a perceived increase. Regardless, the increase in MMEs appears to be associated with a rise in disease emergence, biotoxicity, and events produced by multiple interacting stressors, yet temporal trends in MME causes varied among taxa and may be associated with increased detectability. In addition, MMEs with the largest magnitudes were those that resulted from multiple stressors, starvation, and disease. These results advance our understanding of rare demographic processes and their relationship to global and regional perturbations to natural systems.
authors.affiliation: Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520; Department of Biological Sciences, Dartmouth College, Hanover, NH 03755; samuel.fey@yale.edu.
authors.forename: Samuel B
authors.initials: SB
authors.lastname: Fey
authors.affiliation: Department of Biology, University of San Diego, San Diego, CA 92110;
authors.forename: Adam M
authors.initials: AM
authors.lastname: Siepielski
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; and.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Nusslé
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; and.
authors.forename: Kristina
authors.initials: K
authors.lastname: Cervantes-Yoshida
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; and.
authors.forename: Jason L
authors.initials: JL
authors.lastname: Hwan
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; and.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Huber
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, NH 03755;
authors.forename: Maxfield J
authors.initials: MJ
authors.lastname: Fey
authors.affiliation: Department of Zoology, Southern Illinois University, Carbondale, IL 62901.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Catenazzi
authors.affiliation: Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA 94720; and.
authors.forename: Stephanie M
authors.initials: SM
authors.lastname: Carlson
mesh_terms: D000818:Animals; D018533:Biomass; D053476:Extinction, Biological; D008954:Models, Biological
keywords: catastrophes; death; defaunation; rare demographic events