The Non-Native Species Secretariat (NNSS) for Britain doesn’t list apple snails (Pomacea canaliculata and P. maculata) as invasive species, but perhaps it should.
Apple snails are aquatic. They spread when there’s flooding, when they cling onto larger animals or onto vegetation and when people move them. Some people farm them as food and keep them as pets. I’ll say ‘heliculture’ although that word usually means farming land snails.
Aquatic heliculture has gone sour in several Asian and American countries, and in South Africa, where apple snails have become invasive. They eat plants including rice (Oryza sativa) and they spread parasitic roundworms (nematodes). Here’s some of the science.
The Centre for Agriculture and Biosciences International (CABI) shows us a map of where P. canaliculata is invasive. You can click on that map to see that the snails have been reported in the countries I’ve mentioned and also in parts of Southern Europe.
How far will apple snails spread in Europe? Here’s a report from the European Food Safety Authority (EFSA) about where apple snails might invade and how that might affect rice farmers. ‘The area of potential establishment of the apple snails comprises only part of southern Europe including the rice production areas in Europe and most of the wetlands of southern Europe and the Balkans up to the latitude of the Danube River.’
Economic times are hard in Southern Europe just now. The last thing those countries need is an invasion of crop-eating snails.