The flora of Iceland: ancient or recent?

Iceland is situated in the North Atlantic between the continents of Europe and North America.  Greenland is the nearest country, the nearest point being 300 km away.  While, the coasts of Norway 1000km, Scotland 800 m, and Ireland are considerably further away. Opinions differ on the origin of the flora and how the plants arrived here.  Some species of plants were likely carried across the ocean by birds while others drifted by ocean currents or were carried here by high winds. There is some controversy over how many plants species re-established from ice-free mountain peaks, nunataks, after the ice age.  However, plants are also thought to have colonized Iceland after the ice age, some perhaps with the settlers of Iceland and transport to the country during the last millennium.

The composition of the Icelandic flora is similar to the Scandinavian flora.  However, there are fewer species here and some plants here originate in North America.  In the future more plant species are predicted to colonize Iceland and to be carried here by humans and natural forces.