Black swan theory is a metaphor that describes an event that comes as a surprise and has a major effect, based on the observed historical fact in Europe that black swans did not exist.

I guess we could call covid-19 a black swan event, although it was actually predicted that such an event would happen at some time, which was always ‘in the future’, until it wasn’t. Of course, globalised trade made this black swan event a worldwide phenomenon pretty rapidly.

Globalisation also means we can now see black swans in Europe without travelling to Australia. This one was at WWT Martin Mere, caught in the act of biting off chunks of reed.