Also known as Atlantic or temperate rainforest, the habitat is home to many globally scarce plants - including some that are unique to Scotland.
These woodlands are just as significant and even less common than their better-known tropical counterparts.
They are found on Scotland’s west coast, in the ‘hyper-oceanic’ zone, where cool summers, mild winters, wet conditions and clean air provide ideal conditions for some of the world’s rarest mosses, liverworts, lichens, fungi and ferns.
Argyll is home to more than half of the remaining rainforest habitat in Scotland.
One woodland in the region supports a quarter of all mosses and liverworts found in the UK, with as many as 200 species inhabiting a single ravine near Knapdale.
But these rainforests are at risk, with forests under increasing threat from invasive alien species, fragmentation and poor management.
As little as 30,000 hectares remain – just two per cent of Scotland’s total woodland cover and only a fifth of the area with climatic conditions to support the habitat
Now conservationists have launched a new fundraising drive in a bid to safeguard this cornucopia of rare plant life.
The appeal has been launched through the Alliance for Scotland’s Rainforest, a voluntary partnership of 21 organisations.
Julie Stoneman, project manager for Saving Scotland’s Rainforest, said: “Only 30,000 hectares of Scotland’s rainforest remains.
“It is choked by rhododendron; unable to regenerate due to grazing pressure; crowded by conifer plantations; and exposed to ash dieback and nitrogen pollution.
“In short, we face the very real risk of losing this globally important habitat completely.”
Alistair Whyte, of partner organisation Plantlife Scotland, added: “The Alliance for Scotland’s Rainforest is a partnership of organisations with a shared vision to see this precious forest thrive once again.
“But we can’t do this alone. We need the support of funders and policymakers to save this valuable habitat that locks in carbon, provides local livelihoods and supports communities.
“We can protect and restore Scotland’s rainforest if we work together, but we must act now.”
A number of projects to help preserve the habitat are under way, but funding gaps have been identified.
Argyll and the Isles Coast and Countryside Trust (ACT), a social enterprise with a track record in conservation and development action, is urgently trying to raise £350,000 to allow the first phase of work in Argyll to get under way.
Meanwhile, Saving Morvern’s Rainforest aims to enhance and restore important areas of rainforest on the remote peninsula.
The project, led by RSPB Scotland, aims to clear out rhododendron and promote the rainforest as a visitor destination, but a shortfall of £500,000 will need to be filled.
The Alliance for Scotland’s Rainforest aims to establish landscape-scale projects to restore and expand rainforest sites and work collaboratively with landowners and managers in core areas.
The group has picked out 24 of the best places to experience Celtic rainforests at first hand, with sites ranging from Culag Woods in Sutherland down to Taynish national nature reserve in Argyll.