Upland oak woodland known as temperate rainforests may provide nature-based solutions to climate change (Credit - Lloyd Russell, University of Plymouth)
When we talk about the conservation of rainforests, our minds often drift to the Amazon rainforest of South America, or the tropics of central Africa or Southeast Asia. Yet, closer to home, temperate rainforests are equally deserving of our attention and protection. 
These internationally rare habitats are increasingly recognised as important ecosystems which might aid us in conservation of biodiversity and attempts to mitigate climate change. How and where we restore these rainforests should concern us all.

What are temperate rainforests?

Temperate rainforests are woodlands which support humid environments in temperate zones, allowing plants to grow on substrates with no or minimal amounts of existing soil (e.g. epiphytes) such as the bark of trees and other surfaces (e.g. rocks). 
Temperate rainforests are consequently characterised by verdant growth of specialist arboreal lichens, bryophytes (mosses and liverworts) and ferns, communities which thrive in moist and mild environments. 
Temperate rainforests, although less studied than their tropical counterparts – are known to be key hotspots for biodiversity, important habitats for long term carbon storage, and ecosystems which might help us mitigate the worst effects associated with climate induced river drought and flooding.
Rainforest conditions have previously been characterised as requiring:
  • greater than 1,400 mm annual precipitation, with 10% or more occurring during the summer months
  • cool frequently overcast summers with July isotherm < 16oC
  • minimal temperature fluctuations with year-round mild temperatures.
Understanding of where temperate rainforest sites can be found and how quickly they might develop are still developing with differences in character across their range. For example, within UK it is thought that mean temperature of the coldest month being no lower than 2oC is an important additional defining criteria for their potential extent (Averis 2023).
Atlantic oak woodland at Piles Copse on Dartmoor, UK, was studied to better understand oak regeneration into upland pastures (Credit - Lloyd Russell, University of Plymouth)
Fenced livestock exclosures at the edge of oak woodland at Piles Copse where efforts are ongoing to encourage woodland expansion (Credit - Thomas Murphy, University of Plymouth)
Wistman's Wood

Where are temperate rainforests located?

These rainforests typically occur between 40-60 degrees north and south of the equator along coastal and upland windward slopes where high humidity and low temperature fluctuations keep conditions amenable for the growth of epiphytic mosses, lichens and ferns. Despite their global distribution these temperate rainforest habitats are rare – comprising just 2% of the Earth’s surface.
Temperate rainforest sites include: 
  • Valdivian temperate rainforests of South America
  • temperate rainforests of the pacific north west coast of North America
  • the Knysna-Amatole coastal rainforests along the south coast of Africa
  • the Taiheiyo (Pacific) rainforests of Japan and western Asia
  • the Westland temperate rainforests of New Zealand
  • and closer to the UK – the Atlantic oak rainforests of Western Europe. 
Temperate rainforest wildlife includes the giant Pacific salamander (Dicamptodon tenebrosus), Pacific tree frog (Pseudacris regilla), banana slugs (Ariolimax spp), Roosevelt elk (Cervus elaphus roosevelti), Arboreal marsupials (Dromiciops gliroides) and many more rainforest specialists.

The temperate rainforests of the UK

The rainforest of Northwestern Europe and UK are often characterised by the gnarled, wind battered limbs of oak, hazel and rowan – shaped by a combination of frequent Atlantic storms, low nutrients and thin soils.
The temperate rainforest zone of the UK is estimated to covers 20.8% of UK land surface (Ellis et al 2016) mostly located in the north and western areas such as western Scotland, north-west England, Wales, and south-west England. 
Rainfall in these locations is high, positioned on the windward side of the north-east Atlantic Ocean and enhanced by a generally hilly terrain (resulting in orographic rainfall). air temperatures in these regions are heavily moderated by the effect of the Atlantic ocean and warming ocean currents (e.g. the ‘gulf stream’) meaning temperatures never get too hot in summer or very cold in winter. 
However, in the UK these woodlands have been progressively cleared by humans largely since the late Neolithic (6000 before present), and now only cover a fragment of their former extent (Fyfe et al., 2014).
Piles copse short video
Pasture and native woodland sit side by side at Colly Brook on Dartmoor (Credit Paul Lunt, University of Plymouth)

Why are temperate rainforests important?

Temperate rainforests support a unique array of species which are specialists at taking advantage of the wet and warm climate. Many of the species of moss and bryophytes are ‘endemic’ only found in these habitats. 
The UK has over 1,000 species of moss and liverwort (estimated 1/20th of the world population), and the UK's temperate rainforests support moss and lichen diversity matching almost anywhere else on the planet with the greatest concentration of oceanic lichens and mosses in Europe. 
Examples of rare and specialist UK temperate rainforests species include:
  • mosses – greater pincushion moss (Ptychomitrium polyphyllum)
  • liverworts – prickly featherwort (Plagiochila spinulosa)
  • lichens –  ‘horsehair lichen’ (Bryoria smithii)
  • tree lungwort (Lobaria pulmonaria) and ferns – Wilson's filmy-fern (Hymenophyllum wilsonii). 
Temperate rainforests are also key habitats for a range of other important rare and distinctive communities including:
  • a range of species of fungi – hazel gloves fungi (Hypocreopsis rhododendri)
  • birds – pied flycatcher (Ficedula hypoleuca), wood warbler (Phylloscopus sibilatrix), redstart (Phoenicurus phoenicurus)
  • mammals – pine marten (Martes martes)
  • invertebrates – blue ground beetle (Carabus intricatus) and the world's largest land-based slug ‘Ash-black Slug’ (Limax cinereoniger)

Nature-based solution
Temperate rainforests support long-lived ‘mega flora’, including dominant species such as oak (Quercus spp) and redwoods (Sequoia sempervirens) in the Pacific Northwest. These persist for thousands of years and support organic rich soils, giving significant potential for enhanced carbon storage. 
Temperate rainforest expansion in the UK is on steep, upland pasture slopes which are currently diminished in carbon and therefore could significantly complement nature-based carbon sequestration strategies alongside peatland restoration, and other nature-based carbon initiatives. 
University of Plymouth research has showed how temperate rainforests expansion can significantly improve the hydrological functioning of soil within short timescales (10-15 years) (Murphy et al 2020) and could go a significant way to help mitigate increases in flood risk associated with elevated winter rainfall elevated winter rainfall and over-compacted soils (Murphy et al 2019; 2020).
Tom on Dartmoor
Oak seedling
Tree planting

Threats and challenges

Whilst the potential extent of the rainforest zone in the UK is estimated at 20.8% of land area, the actual fragments remaining are vanishingly small – despite their global rarity and importance temperate rainforests face a number of emerging threats and challenges:
  • Climate change – projected increases in air temperature and growing uncertainties and variabilities in precipitation place considerable risk for the future viability of these habitats and their conservation. Their current fragmented status in northwest Europe leaves these woodlands even more vulnerable to climate induced deterioration. 
  • Invasive species – the spread of invasive non-native ground flora such as rhododendron (Rhododendron ponticum), cherry laurel (Prunus serotina) are damaging temperate rainforest habitats by swamping existing plant communities in so doing diminishing the diversity of these distinctive habitats.
  • Inappropriate management – Both overgrazing and under-grazing by deer, sheep and cattle can simultaneously restrict the conditions needed to conserve and protect existing epiphytic indicators and restrict opportunities for restoring and connecting existing rainforest fragments by diminishing the capacity of new trees to colonise at the edges of these woodlands.
  • Ash dieback – The fungal pathogen Hymenoscyphus fraxineus have diminished the extent and condition of ash trees (Fraxinus excelsior) across their range. These trees are key components of many temperate rainforest sites and support distinct lichen communities. The diminished frequency of ash trees represents a considerable challenge for temperate rainforest conservation. 
  • Air pollution – Many of the distinct lichen flora which characterise temperate rainforests are vulnerable to increases in air pollution such as ammonia emissions from farm manures and fertilisers, or nitrogen oxide emissions from fossil fuels.

Taking local action to conserve rainforests

Recent University of Plymouth research working with the UK Environment Agency on Dartmoor highlights how expansion of these temperate rainforest habitats will require careful management and changes in conservation practice and policy to support establishment of young oak trees (Murphy et al 2022).
Better understanding of how natural colonisation and tree planting interventions is needed to better support temperate rainforest expansion, their future resilience, and the benefits they might provide. Such approaches will help us better direct conservation of these temperate rainforests locally but also coordinate wider restoration efforts for this ecosystem type globally.
Whilst recent best-selling books such as ‘The Lost Rainforests of Britain’ written by Guy Shrubsole have brought the UK’s temperate rainforests to the attention of the wider public – there remains an action gap. 
For example, whilst it is good news the first temperate rainforest strategy for England has been published – still too many of these rainforests are unrecognised and in need of strengthened protections, and active and informed conservation approaches. 
The dire state of temperate rainforests along the UK’s Atlantic coast has spurred into creation the ‘Rainforest Alliances’ in Scotland, Wales, and now Southwest England. How these local efforts can best be best co-ordinated to facilitate global conservation of this widely distributed ecosystem remains however an open question.
What is clear however is that individuals and groups can influence the fate of this habitat through the choices they make. For example, people can volunteer with organisations actively involved in temperate rainforest education, restoration and expansion initiatives. Organisations including Moor Trees, Woodland Trust, Wildlife Trust’s, Plantlife, and recently established Thousand Year Trust all aim to bring these key habitats back into health with ongoing national and local restoration initiatives. 
Whilst the ever-present biodiversity and climate-crisis can make individuals feel powerless, people can make a tangible difference in restoring and conserving a rare, globally significant rainforest habitat – one which is located on their doorstep not far from home.
Nature-based Solutions (NbS) are increasingly advocated as an effective means to tackle climate change and its impacts, alongside a suite of environmental problems from pollution to biodiversity loss
NbS also offer considerable potential to improve societal and economic outcomes through nature-based actions often involving restoration of damaged ecosystems or the integration of nature into human development.
This group welcomes researchers and practitioners from across disciplinary boundaries and study systems who are working or interested in NbS to explore how they can best be implemented to ensure successful and applied NbS.
Oak woodland. A group of trees on a hill.

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