Native Tree Species:
The UK Native trees definition is given by The Woodland trust (woodlandtrust.org.uk). The term native is used for any species that has made its way to the UK naturally, not intentionally or accidentally introduced by humans. In terms of trees and plants, these are species that recolonised the land when the glaciers melted after the last ice age and before the UK was disconnected from mainland Europe.
During the ice age itself, areas of the UK were completely covered by a huge ice sheet. This prevented many trees and plants from growing and many species retreated south to survive the freeze. The ice sheets that covered large areas of the planet locked up lots of water from the Earth’s system. This made sea levels much lower than today and exposed a strip of land (now submerged beneath the Channel Sea) that connected the UK to mainland Europe.
As the Earth warmed and ice began to melt and retreat (over 10,000 years ago), species began to recolonise the once frozen land from the warmer south. However, trapped water released back into the system from the melting ice caused sea levels to rise again. Gradually the rising sea flooded the land bridge from the UK to Europe and prevented any more species (unless they could fly) from colonising the UK.
Non-native Tree Species:
Any species that has been brought to the UK by humans is non-native. This means species which were not naturalised here if it were not for humans intentionally or accidentally bringing them to UK.
About 8,000 years ago, Neolithic man first arrived in Britain and brought new species, such as plant crops and livestock, and a few stowaways like the house mouse.There are many non-native species living in the UK. Some, like Douglas fir and Sitka spruce, are used in forestry; and others, such as copper beech and London plane, were brought here for their beauty.
British tree pages feature some of the most common non-native trees that have naturalised in the the landscape.