Restoring the Celtic Rainforests of Eryri

Simon Rogers, Countryside Manager, and Dave Smith, Lead Ranger, from the National Trust’s Eryri team first showed us around one of their finest examples of temperate rainforest, at the Dolmelyllyn Estate in Ganllwyd, which is designated as a National Nature Reserve (NNR).

The National Trust have owned the Dolmelynllyn estate for nearly 100 years and it has a long history of productive forestry. The National Trust continued this for some time, and even though it’s now managed for conservation, they still use any timber extracted. The estate is FSC-certified, ensuring the forest is managed responsibly. “We don’t sell much timber from here,” Simon explained  “But being FSC-certified means we can prove we manage our woods well and maybe inspire others to do the same.”

As you enter the estate, you are greeted by the Rhaeadr Ddu waterfall, cascading down the steep craggy hillside. The falls play a key role in supporting the rainforest, enshrouding the canopy in its mist. The woodland is dominated by sessile oak trees, though nearly all of the UK’s native deciduous species can be found thriving here. The whole forest looks like it’s covered in a green carpet festooned with life, with insects buzzing around, and the canopy a symphony of bird song, with redstarts, pied flycatchers and wood warblers flitting amongst the moss-clad branches. It’s also home to the elusive pine marten, a species which is critically endangered in Wales and England as much of its woodland habitat has been lost.

The long history of forest management on the estate has helped this Celtic rainforest to flourish, creating the perfect conditions for an array of rare lichens and bryophytes (mosses and liverworts). “It’s not just one or two rare species,” Simon explained. “It’s the assemblage, the sheer number of rare species together, that makes this place internationally important.” The rainforest is a patchwork of habitats, with open glades and denser stands, surrounding the waterfall. There is also a history of gold mining at the top of the estate. These areas of the forest remain more open, where trees were cleared for buildings, but are now naturally regenerating, reconnecting the patchwork.

It’s all about balance

Temperate rainforests need light, and without management, the forests would become choked with brambles and shrubs, which shade out lichens, wildflowers, and tree seedlings. Simon and Dave work closely with lichenologists (lichen experts) from Plantlife to look after the rare lichen species found here.  They have previously used techniques such as halo thinning, removing smaller trees around any larger trees, to let the light in to any areas that become too dense.  They have a new, much more photogenic, way of keeping the forest floor open these days. They have recruited a herd of hardy gardeners: Highland cows. These gentle grazers eat a wide range of plants. “They’re our best tool,” Dave explained. “They graze down the bramble and keep the understory open, which is vital.”

But managing this team of gardeners is a fine art. Too much grazing, and young trees can’t regenerate, and the wildflowers will be damaged. Too little, and the forest chokes. “We let the cattle in for a pulse,” Dave explained. “Then we move them out again. It’s all about balance.” They have clearly struck the right balance at Dolmelynllyn because natural regeneration is thriving, with oak seedlings covering the forest floor, thanks also in part to a lack of deer in the area. But even this success brings challenges. “The lichenologists say it’s getting too shady now,” Simon laughed. “It’s always a balancing act!”

A forest under threat

Despite the National Trust’s careful management, this rainforest is showing signs of the changing times. Tree lungwort is a rare leaf-like lichen, which grows on Ash trees, but the specimens we saw were yellow and shrivelled after yet another dry spring. “We’re in a rainforest in a drought,” Simon explained. “Some trees are losing their leaves early too. It’s a stress response.”

Wildfires, once unthinkable in these damp woods, are also becoming a concern. “They don’t usually happen in the woodlands,” Simon told us, “but they can burn the nearby heathland, where natural regeneration is happening, affecting woodland expansion.”

As we walked through the estate we saw more worrying signs, towering grey skeletons in the canopy. Ash, once a cornerstone of the rainforest, is being killed off by ash dieback, a fungal disease threatening forests all over the UK. It’s not just bad news for ash; it’s impacting the wildlife that depends on the trees. 

Simon and Dave are giving the rainforest a helping hand to adapt to these growing threats. They’re exploring the potential of planting drought-tolerant tree species, like hornbeam, and looking at sycamore to help offset the loss of ash trees. Though often seen as a nuisance by many forest managers, Simon and Dave are leaving sycamore to grow at Dolmelynllyn, because it can support many of the species that depend on ash. Working with Plantlife, they have begun a trial transplanting tree lungwort from dying ash onto sycamore, and so far, it’s working. Through their forward-thinking management approach, the team are steadily increasing the forest’s resilience, ensuring it can continue to thrive for generations to come.

To help restore and expand the Celtic rainforest of Eryri, the National Trust have another trick up their sleeve. We finished the day visiting their off-grid tree nursery, which they have created in heart of the National Park. The nursery began with a simple goal, to grow the trees that couldn’t be bought.  “We couldn’t buy enough big trees,” Simon explained. “We just couldn’t find anyone who was willing to sell us the amount of big trees we wanted. So, we started growing our own.” The team repurposed an old disused barn, replacing the roof with a clear one to help the seedlings grow.

They are growing many rare native species, like the black poplar, one of Britain’s most threatened timber trees, as well as under threat species like aspen and juniper. By collecting seeds locally and growing them on-site, they are ensuring that the trees are well-adapted to the climate, pests, and diseases of Eryri. This also helps to conserve genetic diversity, the diversity within each tree species. “I’m a strong believer that genetic diversity is as important as biodiversity,” said Simon, “maintaining those local genetics, keeping that variety... so we’re not bulk buying from the same supplier.” And while they can’t compete with commercial nurseries, that’s not the point. “It’s like the supermarket of the tree world,” Simon mused, “and I think we need more organic shops.” The team have also been registering their forests as seed stands, meaning that commercial tree nurseries can collect seeds from their sites, helping to boost the genetic diversity of trees available from other nurseries.

Dave admitted that they had a few teething troubles at the nursery, from parasites to a curious goat breaking in to snack on the saplings, but they keep adapting. With the support of dedicated weekly volunteers, they are now growing around 30,000 saplings each year. The trees are grown in different size containers in the barn before being planted outside, producing larger saplings than what can be purchased from commercial nurseries. These larger saplings are planted without protection from grazing animals, by hiding them on steep ground or in bracken and gorse. This enables woodland expansion without disruption to farming operations.