Scotland's Atlantic Rainforest: A Habitat Rarer Than Tropical Forest

Each major claim carries one of three labels. established means supported by primary records, official bodies or several independent reliable sources. shared means the core fact is sound but sources disagree on details, dates or interpretation. traditional means widely repeated but not traceable to a primary or independent source.

Estimates of the habitat's extent vary depending on definitions. The claim that temperate rainforest is rarer than tropical rainforest is widely made by conservation bodies and reflects its small global extent; precise global figures depend on definitions.

What makes it a rainforest?

established Rainforests are not only tropical. Temperate rainforests occur where the climate is wet, mild and humid all year, mainly on western coasts at mid-latitudes, such as in Chile, the Pacific Northwest of North America, New Zealand, Norway and the British Isles. On Scotland's west coast, the Atlantic brings heavy rainfall and mild, steady temperatures, and native woodlands there support extraordinary communities of plants that need constant moisture.

Mosses, liverworts and lichens

established The trees of Scotland's rainforest are familiar species: oak, birch, hazel, ash, rowan and native pine. What makes these woods special is what grows on them. Trunks, branches, boulders and the ground are covered with mosses, liverworts, filmy ferns and lichens, many of them rare across Europe and the world. Some Atlantic hazel woods are thought to be among the oldest continuous woodlands in Scotland. Lichens such as the tree lungwort, which has its own card in this series, indicate clean air and long woodland continuity.

A fragmented habitat

established Centuries of clearance, grazing and management have reduced Scotland's rainforest to small, isolated fragments. Some estimates suggest as little as 30,000 hectares remain. Many woods were managed for oak bark (for tanning leather) and charcoal (for iron smelting), and others were felled or replanted with conifers.

Threats

established Grazing by deer and sheep is the most widespread threat, because it stops young trees growing and prevents the woods from regenerating. Rhododendron ponticum, an invasive shrub introduced to gardens, has invaded almost half of the remaining rainforest sites, shading out the mosses and lichens. About a fifth of the remnants have been planted with non-native conifers. Ash dieback, nitrogen pollution, development and climate change add further pressure.

Before it was called a rainforest

established Richard Mabey's Flora Britannica (1996), a plant-by-plant survey of Britain's wild flora, describes these places without the "rainforest" label that has become familiar since. He notes that sessile oak is commonest in the north and west, chiefly in semi-natural woodland, and that the western oakwoods were largely kept going by coppicing, with the wood used for iron-smelting and the bark for tanning. He describes polypody fern growing on the trunks and branches of trees as one of the plants that give "an ancient forest feel" to the wooded landscapes of the west and north, and Tunbridge filmy-fern as a plant of damp rock-faces and tree-trunks in shady western valleys. His photographs include an aspen wood on the shore of Loch Torridon, and he singles out the Taynish peninsula for one of Britain's longest-standing juniper populations.

established Mabey did reach for a rainforest comparison in one place. Writing of Britain's holly-woods, he called them a rare temperate equivalent of the evergreen cloud forests of South America and northern China. His examples were in England and Wales, but the idea of Britain's western woods as a temperate cousin of tropical forest was already there.

shared On rhododendron, Mabey adds a nuance. He agrees that Rhododendron ponticum is a menace in western Britain, where it has escaped from gardens and formed impenetrable thickets at the expense of almost everything else. But he points out that the species grew across much of Europe before the last glaciation, with pollen found in Ireland, so its spread is in a sense a return to old territory. That is a point of botanical history, not an argument against control: in today's climate and landscape it behaves as an invasive alien, and removing it is central to restoring the rainforest.

Saving the rainforest

established The Alliance for Scotland's Rainforest, a voluntary partnership of more than 25 organisations including NatureScot, Forestry and Land Scotland, the Woodland Trust and Plantlife, published The State of Scotland's Rainforest in 2019, setting out the risks. Restoration work includes clearing rhododendron, reducing deer numbers, removing planted conifers and connecting fragments. National Nature Reserves at Taynish, Glasdrum Wood, Ariundle Oakwood and Beinn Eighe are good places to see the habitat.

• Scotland has rainforest, on its west coast.
• Temperate rainforest is rarer worldwide than tropical rainforest.
• Its most important plants are mosses, liverworts and lichens.
• Invasive rhododendron has spread into almost half the remaining woods.
• Many Atlantic oakwoods were once managed for tanbark and charcoal.
• Rhododendron ponticum grew across much of Europe before the last Ice Age, but it now behaves as an invasive alien in Scotland's western woods.
• In 1996 Richard Mabey compared Britain's holly-woods to the evergreen cloud forests of South America and China.

• Disputed: How much rainforest is left. Some estimates suggest as little as 30,000 hectares, but the figure varies with how the habitat is defined.
• Disputed: That temperate rainforest is rarer than tropical rainforest. Conservation bodies widely make the claim, and it reflects the habitat's small global extent, but precise global figures depend on definitions.
• Myth: The rainforest is defined by its trees. The trees are familiar species such as oak, birch, hazel and ash. What makes the woods special is the mosses, liverworts, ferns and lichens growing on them.
• Myth: Rhododendron is a native plant that has simply come back. Rhododendron ponticum grew in Europe, including Ireland, before the last glaciation. But British plants are garden escapes that smother native woodland, and removing it is central to restoring the rainforest.