Mar 18 2021

Wales’ Celtic Rainforests



Moss covered forest floor, Phil Formby





Temperate rainforest, also known as Atlantic or Celtic rainforest, is an incredibly rare habitat, and even thought to be more threatened than tropical rainforest.


Temperate rainforest is also one of the most biodiverse habitats found in the UK. The high humidity and low temperature range create the perfect conditions for moisture-loving lichens and bryophytes (mosses and liverworts); a good example of this kind of habitat could contain over 200 different species of bryophytes, and 100-200 species of lichen.


Migrant birds such as pied flycatcher, wood warbler, redstart and tree pipit thrive in the insect-rich conditions temperate rainforests offer, flying to the UK to breed each summer.


Over 3,000mm of rain can fall annually in some parts of Welsh Celtic rainforest, and more than half of the world’s Western Atlantic sessile oak is found here in Wales alone.


Pied flycatcher and redstart, both Ben Andrew RSPB images.  Sessile Oak, Laurie Campbell WTML/



These special ecosystems have flourished for at least the last 400 years, but since the 20th century, Wales’ ancient oak rainforests are under threat thanks to invasive species and neglect.


Many of the tree species commonly found growing in and adjacent to our Celtic Rainforests are not considered native to these particular habitats. This includes commercial conifer species, in addition to some deciduous trees such as Red Oak (Querus Rubra), and Beech (Fagus sylvatica).


Essentially, this means that without the intervention of humans, it is unlikely these species would have been found naturally growing in these woodlands. Their presence will primarily have been as a result of deliberate introduction (i.e. for the purposes of timber production or for aesthetic purposes) but in some instances, they will have been introduced accidentally and are now spreading of their own accord.


Many non-native tree species have an important role to play in modern day forestry, particularly in the commercial forestry sector. However, in the context our Celtic Rainforests, they can have a detrimental effect on the ecology of these sensitive woodland habitats.


Non-native plants such as rhododendron can also smother an area and choke the forest floor – this is a substantial problem in Snowdonia where there have been extensive efforts to eradicate rhododendron plants and thin out conifer plantations so that native trees and wildlife can thrive.


The small and fragmented nature of our Celtic rainforests also reduces resilience against other threats, such as pests, diseases and climate change.


But evidence shows that even on sites where non-native tree species dominate, valuable fragments of ancient woodland flora and old broadleaved trees still survive, and therefore, it is crucial that we protect these from current and future threats.


Careful and gradual restoration management can secure and enhance the remnants of an original ancient woodland, moving it towards a revitalised, more natural state and slowly transforming it back into a thriving Celtic Rainforest habitat.


At the same time, these processes can often have added benefits for woodland owners, including the production of timber and wood fuel during the transformation stage, as well as a range of wider long-term benefits. These include the protection of soils, the provision of durable shelter for grazing animals, and improved water quality.


With careful management, it is possible to incorporate commercial aims (such as sustainable timber and wood fuel production) and deliver this in conjunction with an increase in biodiversity. Once a woodland site is free from threats (such as over-shading or over-grazing) it can then move towards a long-term sustainable management plan, gradually reflecting a more predominant Celtic Rainforest habitat.


The Celtic Rainforests Wales project is led by Snowdonia National Park Authority on behalf of a partnership consisting of RSPB Cymru, Coed Cadw (The Woodland Trust in Wales) Natural Resources Wales, Dŵr Cymru / Welsh Water, and Welsh Government.



Coed Cadw’s Celtic Rainforest


Coed Felenrhyd & Llennyrch is a rare, Atlantic oak woodland and one of our largest woods in Wales. It sits above the Vale of Ffestiniog and is fringed by the dramatic waterfalls of the Afon Prysor gorge in the Snowdonia National Park.

Fabulous view of Llennyrch


Y Felen Rhyd features in the famous 12th century collection of Welsh legends, the Mabinogion, as the last resting place of Pryderi, King of Dyfed. But the natural history of Coed Felenrhyd & Llennyrch goes back further still – having been many thousands of years in the making – truly reflected in the sheer diversity of the living things that make it their home.


During spring, swathes of bluebells cover the forest floor, especially in Llennyrch. Ravens nest on the gorge’s cliffs and you can see dippers in the river’s fast-flowing waters. Woodland species such as jay are joined in summer by migrant birds, including redstart and pied flycatcher.


Otters hunt along the river and badgers and foxes are active in the wood, as are a number of bat species. The oak woods of Meirionnydd are important for the rare lesser horseshoe bat, providing good conditions for foraging and breeding and cool, safe places to hibernate.


Lichens, mosses and liverworts thrive here in the humid air along the wood’s streams and rocky gullies. The gorge is home to 25 species of nationally scarce mosses and liverworts and at least 42 nationally scarce species of lichens. A recent survey showed the wood is among the best lichen sites in Wales.


These include rainforest specialists like the barnacle lichen (Thelotrema petractoides), and acid-bark specialists like Parmelinopsis horrescens. Rare rainforest mosses like the prostrate signal-moss (Sematophyllum demissum) cling to rocks in the ravine. In the British Isles, this species is only found in North Wales and parts of south west Ireland.


A multitude of mosses, Lorne Gill


Written by Jane Chicco Mendes on behalf of Coed Cadw.

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