Only a small number of the listed species are globally extinct (most famously the Irish elk, great auk and woolly mammoth).
Insularity first occurred around 125,000 BP, during the Ipswichian interglacial,[1] when a warming climate raised sea levels and flooded Doggerland.
With the cooling climate, the sea level fell and by 60,000 BP a land bridge reformed so new or returning species could repopulate Britain.
[2] By around 20,000 BP the climate was so cold, with much of Britain under ice and the rest a polar desert, that little life could survive, and the glacial fauna also went extinct.
Many of the former species had gone extinct during the interval, but the majority of the surviving European temperate fauna, and some new immigrants, including modern humans (Homo sapiens), were able to reach Britain until the rising sea level once again isolated the islands.
Great Britain was cut off from mainland Europe in around 8,200 BP by the Storegga Slide tsunami flooding Doggerland.
[71] Ongoing projects involve both these species: the corn crake into parts of England and Scotland, and the great bustard on Salisbury Plain.
[72] A few hundred beavers live wild in the Tay river basin, as a result of escapes from a wildlife park.
[82] The northern clade of the pool frog was reintroduced from Swedish stock in 2005, to a single site in Norfolk, England, following detailed research to prove that it had been native before its extinction around 1993.
Smaller species, mainly reptiles, such as the green lizard and Aesculapian snake, have formed colonies probably due to a result of release from captivity.
There have been calls for the reintroduction of the Eurasian lynx, brown bear and grey wolf to the UK, because no large predators are living in viable populations in Great Britain.