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