Aliens!

Across the world, the damage of alien species invasions is said to treble every decade (https://www.theguardian.com/environment/2021/mar/31/damage-from-alien-species-invasions-trebling-every-decade). The alien animals, plants and fungi either 'hitch a ride' or are deliberately transported by people. Aliens cause damage to crops, buildings and public health. They also often have profound destructive effects on the ecologies of the locations they reach. It is worrying that the UK is currently skipping any attempt at phytosecurity because of customs difficulties. Prior to this, my home town of Swansea, became Japanese knotweed central. This alien was brought in (minus, as usual, any species to keep it in check) by gardeners, in Victorian times. Japanese knotweed is now everywhere. It is difficult (it has rhisomes) and expensive to eradicate. This is a plant that can crack the foundations of buildings and roads.