The Ancient Atlantic Oakwoods

24th April 2022

The Atlantic Oakwoods of Scotland range from Sutherland in the North to Loch Lomond in the South, but fragments remain all the way down the Atlantic Coast of the Western Highlands, South-West Scotland, Cumbria and the Lake District, the West coast of Ireland, and through Brittany in France, Galicia in Spain and the West coast of Portugal. The Atlantic Oakwoods of Scotland are part of the once great Caledonian Forest, which in turn would have been part of the vast Wildwood or Greenwood that once covered most of Britain. Even at its peak, this woodland would have probably been a patchwork of open woodlands, interspersed with areas of heath, moor and meadows, rather than a continuous canopy of trees.

The Oaks of the Atlantic Oakwoods

Although classified as an ‘oakwood’ there are actually more other trees such as Birch, Ash, Elm, Beech and Scots Pine in many parts of the Atlantic Oakwoods in Scotland. The oaks in the Atlantic Oakwoods are predominantly Sessile Oaks in the Highlands where the soil tends to be more thin and acidic, and Pedunculate Oaks in the richer soils of the lowlands, although there is increasing hybridisation between the two.

The Celtic Rainforest

People are often surprised when we talk about rainforests in Scotland, but the Atlantic Oakwoods are recognised as a temperate rainforest with sufficient rainfall - the average for here in Strontian, on the edge of the Ariundle Oakwoods is 2197 mm or 86.5 inches of rain a year. The climate in the West coast of Scotland is affected by its proximity to the Gulf Stream that results in a combination of high humidity, frequent rain and cloud cover and a mild climate which means that mosses and lichen grow very well. The carpet of mosses in theses temperate rainforests absorb a large amount of the frequent rainfall, and this slowly evaporates during the dryer spells and maintains the levels of humidity and supports the growth of liverworts and ferns. Many of these ferns can be seen growing in where the branches and the trunks of the trees join, all the way up to the tops of the trees, another indication that these are temperate rainforests.

Mosses, Liverwort and Lichens

There are a number of mosses, liverworts and lichens that thrive in the Atlantic Oakwoods. There is one lichen that is only found in one location outside Central and South America, Resipole in Sunart, that is called Parmentaria chilensis and said to look like ‘blackberries floating in custard’.

The Ecosystem of the Oakwoods

The ecosystem of an Oakwoods usually consists of three layers. The main storey comprises large Oak and Birch trees, sometimes interspersed with Elm and Ash, providing a canopy of branches and leaves. The understory comprises smaller trees, such as Hazel, Holly, Rowan, Hawthorn and sometimes Juniper, with the ground layer comprising brackens and other ferns, grasses, heather, mosses and an abundance of wild flowers. Shade is important for this lower layer as it stifles the growth of new trees, although the natural death and consequent falling of older trees then allows light into and allow seedlings to flourish.

Historic Damage and Future Change

In the 1970s the Forestry Commission (as it was then) planted vast tracts of the West coast of Scotland with fast growing species of conifers such as Sitka Spruce. These were often planted under the mature Oaks and Birches that initially provided shelter for the growing saplings, but these would eventually overtake them and crowd them out. Since this time, the Atlantic Oakwoods have been identified as a threatened habitat and steps have been, and continue to be made to save and restore these native woodlands. This has included removal of non-nature species such as Sitka Space and Lodgepole Pine and attempts to return many areas to native broadleaf trees. However this new planting, bolstered by natural regeneration, is still a very slow process. This is very important though in protecting the rare and endangered species of plants and animals that live within the Atlantic Oakwood ecosystem and large parts of the remaining Atlantic Oakwoods are designated as Special Areas of Conservation (SAC).