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.