101-14 Major extinctions and macroevolutionary stress linked to Phanerozoic mega-climate states

Abstract:

The role of abiotic environmental factors on Phanerozoic diversity and extinction is difficult to disentangle given the complexity of Earth-life systems involved. Yet as we barrel towards increasingly rapid environmental changes today, progress towards understanding these complexities is as imperative ever. Here we derived an index of global macroevolutionary stress to summarize large extinction vulnerability based on generic-level biodiversity records across the Phanerozoic. We link macroevolutionary stress to the environmental context of large time-scale global climate changes via a combination of recurrence-based analyses of empirical data and dynamical systems models. Five recurring and long-lived mega-climate states were identified using joint recurrence analysis of Phanerozoic stable isotope and atmospheric CO₂ records. The fidelity of these states were supported by a climate-carbon cycle dynamical model, which combines an excitable carbon cycle, temperature dependent weathering, and impulsive inputs (such as carbon injection from large igneous province emplacement) with a simple energy-balance model that incorporates ice-albedo feedbacks and logarithmic greenhouse gas forcing.

Results suggest that Phanerozoic biodiversity and its relationship with global climate is, unsurprisingly, hierarchical: we observe an overall positive trend between extinction vulnerability and global temperature records across the Phanerozoic as a whole, however, within individual mega-climate states the relationship is more variable and subject to noise. Notably, macroevolutionary stress appears higher overall near mega-climate transitions than within a given regime. Macroevolutionary stress is also markedly higher during early Paleozoic hothouse conditions versus the Cenozoic icehouse. This evokes a more optimistic view of the potential biospheric response to current and projected future environmental changes linked to extinction vulnerability. In sum, our findings suggest that mega-climate states may be setting a baseline macroevolutionary stress landscape within which short-timescale and event-specific environmental perturbations are more or less likely to result in extreme biospheric vulnerability to extinction.

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