Extinctions: Living and Dying in the Margin of Error

Hannah, professor in the school of geography, environment, and earth sciences Victoria University of Wellington, explores the nature of mass extinction events in his passionate debut. Better understanding the patterns and causes of previous mass extinctions, Hannah argues, will offer insight into the impact humans are currently having on the world’s ecosystems. He presents a nuanced analysis of the major mass extinction events, covering the “big five” extinctions from the end of the Permian (which wiped 96% of marine species) to now, and impressively breaks down paleontological data, as when he discusses global marine biodiversity estimates over time. Biodiversity is key—Hannah contends that “the complex network of reservoirs and fluxes that maintains planetary conditions at a climatic equilibrium” for life on Earth is dependent upon a robust level of biodiversity that is currently under threat. Nonetheless, he’s optimistic that there’s time to avert true environmental catastrophe, and even if not, “Life will get through a mass extinction: it always has.” Hannah’s warning is clear, but his solutions are scant—he urges that “we must act to avoid” extinction, but dedicates little time to exploring what that means. While his discussion of extinctions is thorough, readers are likely to be left wanting. (Oct.)