A new European Union (EU) regulation aiming to control invasive alien species comes into force on 1 January 2015 (see go.nature.com/ajiwtd). It could inadvertently promote — rather than deter — the release of exotic animals into the wild.
The regulation prohibits the keeping, breeding, sale, movement and release of listed invasive alien species. The EU has set September 2015 as the deadline for the preliminary list: after this, member states will be required to consider eradication of listed species from within national borders.
Many species that are now among the worst invaders in Europe originated from private collections, which are at present governed only by piecemeal legislation. It is likely that several animals, which include the North American bullfrog (Lithobates catesbeianus), the ruddy duck (Oxyura jamaicensis), northern raccoon (Procyon lotor) and Pallas's squirrel (Callosciurus erythraeus), will be added to the list under the new ruling.
There is a risk, therefore, that this could prompt owners to release their newly illegal holdings into the wild, as happened after the 1997 EU trade ban on red-eared slider turtles (Trachemys scripta elegans).
A carefully managed interim process to prevent deliberate releases by pet owners should therefore be an EU-wide priority.