The climate of the forest is oceanic, leading to frequent precipitation, high precipitation days, high moisture and low sunshine levels; temperature extremes are rare. The combination of moisture and low evaporation (low sunshine amounts) leads to high dampness levels.
Ninety percent[citation needed] of the Celtic forest habitat has been destroyed, generally over the last few thousand years, due to agriculture, fire-wood use and general deforestation. The outcome is an ecoregion which has not only lost most of its pristine cover, but which has been heavily degraded by fragmentation. The forests today are in a critical status, with the majority of the land having become the rolling pasture-hills typically associated with England.
Prehistory
This ecoregion is relatively young, having been buried under deep ice during the last glacial maximum. Human habitation began with Mesolithic peoples who were present shortly after the ice retreated, c. 9000–8000 years ago, scattered throughout the present-day English portion of the ecoregion, as well as in the Welsh, Irish, and eastern Scottish areas of the Celtic broadleaf forests.
Archeological evidence shows indigenous towns such as York had existed for a millennium prior to the Romans arriving, but the recorded history of the ecoregion begins with major Roman urban settlements established in the first century AD. Viking settlement in coastal areas of western Scotland, Wales, and eastern Ireland was widespread from at least the ninth century AD.