Ecologists are warning of an “extinction crisis” unfolding in Britain’s temperate rainforests, where some of the planet’s rarest mosses, lichens, and liverworts are disappearing at an alarming rate.

These forests, often referred to as Celtic rainforests, are primarily located along the western coasts of the UK. A 2024 survey of rainforests in Wales revealed that only 22% remain in good condition, with pollution, habitat fragmentation, and invasive species cited as major threats.

One illustrative loss occurred in December when a 500-year-old oak tree in Eryri National Park (formerly known as Snowdonia) was brought down by Storm Darragh.

“When this tree came down, in a flash we lost a species,” said ecologist Sabine Nouvet

The ancient tree supported one of the UK’s most notable populations of a rare lichen.

She said that the loss was “symbolic of the species crisis, the extinction crisis, that we are facing now”, said Ms Nouvet.

Its destruction, according to rainforest advisor Ms. Nouvet of the conservation group Plantlife, underscores the broader biodiversity crisis now underway.

That single tree once hosted over 60 different lichen species, including the extremely rare Rinodina isidioides, commonly known as “skeletal fingers” due to its finger-like structures visible under magnification. This lichen only survives on trees over 300 years old and in the moist, shaded conditions typical of the rain-soaked valleys of western Britain and Ireland.

Temperate rainforests cover less than 1% of the Earth’s surface, and Wales is home to internationally significant examples. These ecosystems—once widespread with their gnarled branches, filtered light, and lush, mossy floors—now survive only in fragmented patches. One such remnant is the Woodland Trust’s Coed Felenrhyd near Blaenau Ffestiniog in Gwynedd.

There is still hope for the skeletal finger lichen. Clippings from the fallen oak have been transplanted onto five other ancient trees nearby, with the goal that they will eventually colonise the bark—a process that could take up to ten years.

Wales retains around 33,024 hectares of rainforest, equivalent to 46,000 football pitches. However, these ancient woodlands, including Coed Felenrhyd, face numerous threats. The recent State of Wales Rainforest report found that just 4.3% of the landscape classified as rainforest is actually covered by this habitat. Many areas are isolated by farmland or plantations of non-native trees, reducing ecological connectivity. Others are degraded by overgrazing or invasive plants like rhododendron, which block sunlight and suppress native growth.

Farmer and retired forester Aled Thomas said the Celtic rainforest had been “grazed since the beginning of time”, leading to the formation of these woodlands.

However, past conservation approaches often involved fencing off forests entirely.

On his land at Coed y Gribin, near Dolgellau—a rainforest managed by the RSPB—he uses small Dexter cattle equipped with GPS collars and alarms to ensure they graze only in selected areas, protecting sensitive sites.

“They will provide a habitat for a much more diverse species range by their hooves marking the ground, driving in acorns, rolling on the ground and they’ll graze anything and everything,” he said.

“They eat brambles like they are having supper.”

Thomas believes that farms integrated with native woodlands hold the key to reconnecting fragmented rainforest habitats.

“The landscape has changed dramatically because the cows have been here for about three seasons and you notice there’s very little bracken and there are bluebells coming up.”

Mr Thomas said farms with more woodlands were the key to linking up isolated parts of the rainforest.

“You just don’t need a field for growing cows, you can grow food by grazing in woodland and the benefits from that are huge to the forest and the farm.”

Adam Thorogood of Plantlife emphasised that Wales bears an international duty to safeguard the Celtic rainforest for future generations.

“We’ve got a really unique situation here in Wales where we’ve got some vital areas of habitat, a type of rainforest we don’t really find anywhere else on Earth.

“People don’t even realise that we have temperate rainforest here… right on your doorstep.

“It’s there to be explored, there to be enjoyed, and there’s a huge diversity of species of plant but also other flora and fauna.”

He said interest from the public in the Celtic rainforest was coming at a time when it was under enormous pressure and significant investment was needed to secure its future.

Natural Resources Wales said it manages seven Celtic rainforest reserves in the Meirionnydd area that are “exceptionally important sites for species and communities of lichens bryophytes and breeding birds”.

“We strive to deliver favourable conservation management on these important sites and also work closely with partnership organisations and play a key role in the Celtic rainforest partnership to help deliver landscape scale management,” it said.

“The loss off the large mature tree with rinodina isidioides in Coed Felenrhyd was a real shame and a sign of this habitat’s fragility.

“It is vital the Celtic rainforest habitat in Wales is prioritised at both a local and landscape scale.”