THE CAUSES OF MASS EXTINCTIONS: HOW CAN WE BETTER UNDERSTAND HOW, WHY AND WHEN ECOSYSTEMS COLLAPSE?

Major advances in our understanding of mass extinctions have resulted from greater resolution in the fossil record, better dating, and improved proxies for paleoenvironmental change. Despite these, consensus is far from reached on the drivers of extinction. In recent years the realization that Earth is once again facing some of the stresses implicated in its past crises (global warming, anoxia, ocean acidification) has intensified debate over the ultimate cause(s) of mass extinctions (e.g. large igneous provinces vs. bolide impacts). There is growing evidence that large igneous province eruptions might be the driver of proximal kill mechanisms, but the link between those phenomena is still not well understood. Likewise, the temporal relationship between bolide impact and the end-Cretaceous extinction implies a causal relationship, but the mechanics of the biotic losses remain unclear. This talk will review and evaluate the environmental factors implicated in major episodes of species extinctions through time, and further explore the mechanisms that link these proximal killers to their ultimate drivers. Alongside our improved understanding of mass extinction events, developments in experimental biology have yielded important knowledge of the responses of species to environmental change. Reduced pH, for instance alters the efficacy of fishes’ chemical receptors, leaving them less equipped to detect prey, predators and mates – raising the possibility of a powerful “death-by-celibacy” extinction mechanism. This talk will explore ways to link experimental geobiology with Earth Science as a means to unravel the causes of past extinctions, and better inform our understanding of modern extinctions.