What are the main causes of extinction?

Geologists have identified at least 5 major extinction events that wiped out more than 50% of species - humans may be instigating a 6th species extinction event.

Large volcanic eruption are now seen as a major cause of many of these 5 extinctions. These are no ordinary eruptions - they are sustained eruptions that emit millions of tonnes of magma for up to 1 million years! They also emit huge amounts of CO2 which then often set off a massive global warming event.

Asteroid impacts are another cause of extinctions, in particular, the one that killed off the dinosaurs 65 million years ago. The impact would have set off a number of other catastrophic events including massive global fires and soot that would have cooled the planet and temporarily shutdown photosynthesis and the extra CO2 from fires that then set off a global warming event. Tsunamis may have flooded the land and acid rain may have also poured down.

Glaciations tend to cool the planet and can cause species to go extinct and they also lower sea level so that coastal shelf regions are exposed, which then kill off marine animals that live on the shelf.

Human actives including destroying habitats, over fishing and hunting & logging, agriculture, climate change, air and sea pollution, human population growth, are all contributing to the 6th great extinction event going on right now!

The primary factors leading to extinction are pollution, overhunting, invasive species introduction, habitat degradation, and climate change.