A scale of greatness and causal classification of mass extinctions: Implications for mechanisms

Abstract

A quantitative scale for measuring greatness, G, of mass extinctions is proposed on the basis of rate of biodiversity diminution expressed as the product of the loss of biodiversity, called magnitude (M), and the inverse of time in which that loss occurs, designated as intensity (I). On this scale, the catastrophic Cretaceous-Tertiary (K-T) extinction appears as the greatest since the Ordovician and the only one with a probable extraterrestrial cause. The end-Permian extinction was less great but with a large magnitude (M) and smaller intensity (I); only some of its individual episodes involved some semblance of catastrophe. Other extinctions during the Phanerozoic, with the possible exception of the end-Silurian diversity plunge, were parts of a forced oscillatory phenomenon and seem caused by marine-and landhabitat destruction during continental assemblies that led to elimination of shelves and (after the Devonian) rain forests and enlargement of deserts. Glaciations and orogenies that shortened and thickened the continental crust only exacerbated these effects. During the Mesozoic and Cainozoic, the evolution of life was linearly progressive, interrupted catastrophically only at the K-T boundary. The end-Triassic extinction was more like the Paleozoic extinctions in nature and probably also in its cause. By contrast, the current extinction resembles none of the earlier ones and may end up being the greatest of all. greatness scale ͉ intensity ͉ magnitude ͉ mass dying ͉ shelf destruction

Where are the survivors? Tracking relictual populations of endangered frogs in Costa Rica

“…Our planet is presently experiencing its sixth mass extinction, but in contrast to previous extinction events, this one is being driven by a single species, Homo sapiens (Brooks & McLennan, 2002; Sengör et al. , 2008; Wake & Vredenburg, 2008).…”

The effect of singletons and interval length on interpreting diversity trends from the palaeobotanical

“…The study of the evolutionary rates and the reevaluation of the previous evolutionary patterns have been conducted using the methodological principles indicated by Foote (2000aFoote ( , 2000b. The use of these per-capita rates rates has increased in recent years (Peters, 2006;Kiessling et al, 2007;Fröbisch, 2008;Liow et al, 2008;Sengor et al, 2008;Simpson and Harnik, 2009), and today these algorithms, which do not consider singleton taxa, are reference rates in modern palaeobiology. These type of rates based on boundary crossed taxa, as it was commented by Foote (2000aFoote ( , 2000b, present a relative insensitivity to the preservation problems and, therefore, they can potentially diminish the biases related to the incompleteness of the record in comparison with the classic diversity measures.…”