101-12 Is There an Objective Definition for a Mass Extinction (and Should There be One)?

Abstract:

Paleontologists have considered the concept of mass extinction events for more than 70 years, with the topic blossoming into a multidisciplinary research area encompassing paleobiology, sedimentology, geochemistry, and other fields. If asked to define what makes an event a mass extinction, most would note attributes such as the severity of taxonomic loss, disappearances of lineages across the tree of life, a widespread-to-global scope both on land and in the oceans, and a short temporal duration. Indeed, qualitative definitions of the mass extinction concept have consistently included these descriptors since the earliest publications. However, there remains debate about how many events can be called a mass extinction, and whether the modern biodiversity crisis is or will be joining the group. Does this matter, and would it improve mass extinction research to have a more objective definition of a mass extinction, distinguishing it from other types of events and the background? I will review whether and how mass extinctions differ from or are similar to other events in terms of severity, taxonomic and geographic scope, temporal duration, and ecological consequences. Are there objective criteria that distinguish mass extinctions, and what can this tell us about the modern biodiversity crisis?

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