Measuring and Comparing Extinction Events: Reconsidering Diversity Crises and Concepts.

Area of Science:

• Paleontology
• Ecology
• Conservation Biology

Background:

• The current biodiversity crisis presents unique challenges compared to past "Big Five" mass extinctions.
• Past analyses often prioritized marine data, potentially obscuring terrestrial extinction patterns and causes.
• The distinction between anthropogenic and natural extinctions, especially from the Pleistocene, remains unclear.

Purpose of the Study:

• To re-evaluate the concept of "mass extinction" in light of the unique characteristics of the current biodiversity crisis.
• To propose a revised framework for analyzing diversity crises that accounts for terrestrial and marine environments distinctly.
• To emphasize the importance of considering both extinction and origination rates in diversity analyses.

Main Methods:

• Critically analyzing the limitations of traditional "mass extinction" definitions.
• Comparing patterns of terrestrial vertebrate faunal changes with marine-dominated mass extinction events.
• Advocating for situationally defined and statistically normalized analyses of diversity crises.

Main Results:

• The "Big Five" mass extinctions were primarily marine, while the current crisis is largely terrestrial and anthropogenic.
• Terrestrial vertebrate faunas show patterns of steady turnover rather than sudden catastrophic loss during past extinction events.
• Existing analyses of diversity crises have often overlooked origination rates and the interplay between origination and extinction.

Conclusions:

• The term "mass extinction" is ill-defined and may not accurately capture the nuances of all diversity crises.
• A new concept, "diversity crises," is proposed, requiring operational and situational definitions.
• Future analyses must incorporate both origination and extinction rates, normalized across taxa and environments, for a comprehensive understanding of biodiversity changes.