If you go down to the WOODS today

...you're sure of a big surprise, as the children's song goes. Except, this is no picnic. A recent report has rung alarm bells about the damage being done by species that are thriving where they don’t belong. Fish that contribute to flooding; corals that destroy coral. Meet the villains of our making

- Sukanya Datta

As they quietly expand their kingdoms, we can look in the mirror and ruefully shake our heads.

Over the past two centuries, amid growing trade and amid colonisation, plants, trees, fish and mammals have been transported from their home territories to new regions, for a range of reasons. Some shrubs were pretty, so they were planted as hedges (see the story alongside, on the lantana, for a bit on how much damage this has done).

Some trees grew fast and seemed intriguing; now, it turns out there are few ways to stop them.

Fish, ants and other insects were moved along sea routes, both intentionally and unintentionally, and now suck oxygen and nutrients out of distant water bodies.

Invasive alien species crowd out natives, alter habitats, can change water and soil composition; they contribute to the ravaging of crops, destruction of houses, damage to streets, pavements and building foundations.

Over 3,500 of the most harmful such species were recognised in a first-of-its-kind 2023 global assessment report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).

The cost of controlling their spread can be so high that, in the UK, lawsuits have been won and damages paid after a particularly virulent Japanese weed was not reported by a seller to a home buyer.