Mass extinctions decimate the planet’s biodiversity, and in doing so, they can change the composition of the planet’s biota.The biota that goes into a mass extinction is not the same as the one that emerges. The actual extinctions are over very quickly – 20,000 years in the case of the end-Permian. But the recovery takes much longer. It takes time for new species to evolve and the biosphere to recover – and the Earth System will not operate properly until both processes are complete. Detailed analysis of the fossil content of sediments deposited following the end-Cretaceous extinction event reveal a long-term ecological recovery that parallels the short-term ecological succession that follows modern environmental disasters such as fires and floods. But the succession that follows a mass extinction occurs on a global scale and over a much longer time frame – often millions of years. This new post-mass-extinction recovery phase has been dubbed the Earth System succession.

The first chapter introduces a new geological period – the Anthropocene – and explains its origins its timing and importance in emphasizing the current biotic crisis. The current idea that we are in the sixth extinction is criticized because (1) the current level of extinction isn’t high enough to justify it and (2) it limits today’s biotic crisis to just those species that have gone extinct and does not include those under threat. The term defaunation is used in preference because it provides a clearer picture of the situation we find ourselves in. It does this by including both species that have gone extinct and those under threat of extinction. The important concept of the Earth System is outlined and its role in maintaining planetary conditions explained. The link between sudden shifts in Earth System due to climatic forcings and mass extinctions is explained.