Snowdonia is an area of northern Wales with a very rich history. It is unique in that it has one of the most detailed and closely studied pollen records in the British Isles. Preserved pollen in the area has allowed for the identification of all of the main types of vegetation that have grown in the area since the most recent ice age. The record goes back approximately 12,000 years.
The beginning of the pollen record shows the very early plants of the area that were struggling to eke out a living on the barren landscape after the glaciers receded and exposed the soil once more. Since that time, the landscape of Snowdonia has changed numerous times. Sometimes it has changed through the hands of nature and sometimes through the hands of mankind. The newly exposed, barren land right after the ice age gave way to dense forests, then lighter woodlands, and finally to sparely populated plains.
Many of the original plants of post-ice age Snowdonia are no longer found in the area. These include Iceland purslane, wild azalea, and dwarf birch. A handful of the earliest plants of Snowdonia have managed to survive at higher altitudes in the area. These include alpine saxifrage and dwarf willow. Other founding plants have survived to this day at lower altitudes, such as black bindweed, plantains, and nettle. Some plants like hoary plantain, Jacob’s ladder, meadow saxifrage, and rock-rose are no longer found in Snowdonia. However, the pollen record shows they were once abundant in the region. Because these plants grow in loamy soil, this shows that the soil in Snowdonia was a lot less acidic right after the ice age than it is today.
The landscape of Snowdonia was devoid of animals or people at first. It took some time for fauna to make its way into the area after the ice age ended. Gradually, though, animals and them people arrived and made changes to the flora of Snowdonia. Animals grazed the plants and people cut down the trees for timber. The timber provides fuel and construction materials for houses. Cutting down trees was also eventually used to clear land to make room for grazing for domestic livestock. The forests of Snowdonia slowly became more sparse. The flora changed along with the forests.
The forests remained relatively thick in all but a few populated places until the Romans came. The Romans cleared vast swaths of forest for roads. Anglo-Saxons continued this after the Romans left Britain. The clearing was done strategically but sporadically until the 12th century. It was at this time that the pollen record shows a large decline in all trees and shrubbery in Snowdonia. It looks like forest clearing became a more regular activity around this time as more farmers settled in the area. The larger clearing of the forest in the 12th century also corresponds with the first appearance of hemp in the area.
Hemp is an easily grown and quickly replenished plant and farmers living off the land probably found it to be useful in making textiles. The pollen record suggests that Snowdonia was the most significant site in Wales for the production of domestic hemp. Some of the hemp may have been used for pleasure and recreation, much as tobacco was among the inhabitants of North America at the same time. However, this was probably only a small portion of its use, as the THC that gives hemp its mind-altering properties is not produced in large quantities in cold climates like Snowdonia. Hemp plants are however very adaptive and in current times it is possible to grow plants from a variety of cannabis seeds of whichautoflowers are a lot more cold resistant.
You can read a more extensive report of the Field Study by Peter Rhind and Barbara Jones in PDF here:THE VEGETATION HISTORY OF SNOWDONIA SINCE THE LATE GLACIAL PERIOD