In Europe, the major diversity is found in the Mediterranean, with large numbers of species in the following biogeographical regions: Alpine, Continental, Macaronesian, Mediterranean and Pannonian. Species richness is relatively poor in the remaining areas north of the Alps. All of the Atlantic islands and the Mediterranean islands also hold a significant proportion of narrow-range endemic species, some of which are already listed as threatened species either at the national or global level.
However, for the families considered in this project, the top five EU countries in terms of terrestrial snail species richness (in descending order) are: Spain, Greece, Italy, France and Portugal. Austria and Slovenia can be highlighted has holding an important number of species within a small area.
Similar to the increase of species and subspecies numbers from north to south, there is a clinal increase of narrow-range endemism towards the Mediterranean countries. Several hot spots can be identified here: (1) the Macaronesian Islands comprising the Canary Islands, the Azores, and Madeira; (2) Italy with a particular focus on Sicily; (3) the Balkan radiation culminating in mainland Greece with a considerable contribution from Crete; and (4) the Alpine arc ranging from the Pyrenees to the Carpathian Mountains.
The bulk of threatened terrestrial snails in Europe occur in Western Europe, particularly on the Macaronesian Islands, i.e. the Canary Islands and Madeira, which are showing a trend up to tenfold the numbers of threatened species if compared with the continent. Other countries, such as Spain, France, Greece and Italy are also areas of high threats.