- rapid, widespread loss of species across multiple taxa and habitats
- five major mass extinctions in Earth’s geological time:
- Ordovician-Silurian (~445 Ma): glaciation, sea level drop
- Late Devonian (~375 Ma): ocean anoxia, possible volcanism
- Permian-Triassic (~252 Ma): largest, ~96% marine species lost, Siberian Traps volcanism
- Triassic-Jurassic (~201 Ma): volcanic CO2, ocean acidification
- Cretaceous-Paleogene (~66 Ma): asteroid impact, end of dinosaurs
- each extinction was followed by adaptive radiation into vacated niches
- the sixth extinction is ongoing, driven by habitat loss, climate change, pollution
- entropy at the biosphere scale: loss of accumulated biological knowledge