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Treewilding; Six British tree species to boost your restoration project

Updated: Feb 16, 2021

Tree cover in Britain was once as high as 95%, declining to around 60% up until the Bronze and Iron Ages during which, deforestation became widespread[1]. Therefore, it’s natural that many people’s interpretation of a ‘rewilded’ British landscape often includes trees (with some important exceptions). With just 13% tree cover in the UK in today’s age, the government, charities and members of the public are committed to increasing tree cover in this country.

Increasing tree cover can come in many forms including reducing grazing pressure, allowing natural regeneration or planting trees. Each of these approaches are useful in different contexts and should be mindful to use best practice (watch this space for a future blog on that subject), but if you are committed to planting trees which species would work well?

Rowan or the mountain ash; the ultimate adapter. Credit; Flickr/Randi Hausken

For me it really depends on where you are in the country, the type of project you are planning and, of course, the ecology of your site. You should take all of these elements into account as well as the availability of local seed.

Before we start, it’s worth noting that the species listed below are those that appeal for me personally, but this list is not exhaustive or prescriptive, so you should interpret this blog in that light. Further, I am currently based in the south of England (and although I try and incorporate species representing the breadth of the mainland), the list does reflect that. You will notice that I have also included alternatives species where necessary.

All that said, there are some native tree species that really stand out to the ecologist in me as excellent candidates for British rewilding projects. And here they are;

The pioneer; white willow (Salix alba)

The white willow is at home on the riverside. Credit; Flickr/Andreas Rockstein

Growing at a rate of 40 centimetres per year, white willows are famously fast growing species so can work well as a ‘nurse tree’. White willow produces catkins in April which can be an invaluable early source of food for pollinators- especially for early emerging species in cold, wet springs. The species is also an important source of food for caterpillars which in turn will attract birds.

Projects incorporating freshwater conservation would do well to encourage willows as the weeping branches and roots will provide refuge for freshwater fish and invertebrates - as long as you don’t allow it to become over- shaded. Brown trout (Salmo trutta) for example, need complex habitats of light and shade as well as rough and slow water and are known to shelter among willow roots in chalk streams especially in autumn when they are young[2].

Brown trout utilise habitats created by willow. Credit; Flickr/Paul Asman and Jill Lenoble

In Essex, Spains Hall Beaver Project is trialling growing a variety of white willow within their beaver enclosure which used for making cricket bats. Although attractive to beavers, white willows grow well in wetlands too, so Spain’s Hall Estate are trialling various ‘beaver grazing’ mitigation measures to see if both species can live well side by side. These ‘bat willows’ are grown on rotation and could potentially provide an additional source of sustainable income for rewilders.

If your soils are more acidic you could also consider the osier willow (Salix viminalis), a species which doesn’t tolerate alkaline soils. The osier willow has the potential to grow one metre per year and has a bushier habit. A good alternative in Scotland and the north of England might be the bay willow (Salix pentandra).

The birdberry; rowan (Sorbus aucuparia)

Fieldfare alight on fruiting rowans in large flocks. Credit; Flickr/hedera.baltica

Rowan a similarly fast-growing tree to the willow but which has the added benefit in that it can be planted in a greater variety of habitats and, is a magnet for migratory birds. The species is heavily favoured by blackbirds but it also popular with other thrushes, tits and warblers to name a few. In fact, good fruiting years will also impact the movements of migrating fieldfares (Turdus pilaris) and waxwings (Bombycilla garrulus). Although rowan is closely linked to birds, it also features in the diets of a great variety of wildlife including pollinators, and is also consumed by a variety of species of interest to rewilders for example pine marten (Martes martes), deer (Cervus elaphus) and elk (Alces alces).

In northern Spain almost 10% of the pine marten's diet is fruits, particularly rowan berries (Raspé et al., 2001). Credit; Flickr/Mike Davison.

Otherwise known as the mountain ash, rowan is also a great option for upland areas as it thrives at higher elevations than most other British tree species. As you might expect, this makes it fairly resilient t windy areas and it is tolerant of most soil types, so it will do well in more open habitats, as long as it’s not excessively dry. You should however be cautious of planting rowan too extensively as although it is found in heathlands and uplands, the species is considered to be extremely flammable so may increase site vulnerability to fire if planted in high densities.

On the opposite end of the scale, while rowan will make itself at home in many environments, it does not cope well with flooding so won’t do so well in floodplains over time. Rewilders may also want to avoid this species in areas with high livestock browsing as rowan won’t tolerate heavy grazing from deer, sheep or cattle (the latter of which tend to debark them), so it’s best used in projects with lower stocking densities.

For habitat complexity; wych elm (Ulmus glabra)

The living dead? Credit; Flickr/Andreas Rockstein

I can hear you already; “they’ll just die from dutch elm disease”! Well, that’s exactly the point. For those areas where you’re starting from a pretty blank slate planting elm can be a great way to fast-track some habitat diversity into the site. Dead wood is a hugely important resource within ecosystems and as callous as it may sound, planting elm might be a great way of getting you there in 20 years instead of waiting 120. If you like this idea, you should make sure that you are using local seed and are not putting any other nearby trees at risk.

Dead wood is critically important as it provides nesting sites for woodpeckers. Approximately 75%[3] of lesser-spotted woodpecker (Dryobates minor) - the rarest of the three British species- nesting sites are in dead or decaying trees. Woodpeckers are important ecosystem engineers which are critical in providing natural roosting and nesting sites for other birds, as well creating smaller holes suitable for boring insects. Woodpeckers therefore are an important species to attract to woodland sites in particular.

Lesser-spotted woodpecker depend on dead and decaying wood for breeding. Credit; Flickr/hedera.baltica

Wych elm is the hardiest of the three species in the UK which means it is suited to being planted across the UK. As a native tree, in the 20 years before it dies it will act as an important food plant for caterpillars and the birds which predate them. The species is particularly closely linked with the white-letter hairstreak (Satyrium w-album) butterfly which, along with many other butterfly species, declined heavily in the 1970’s in parallel with the rise of Dutch elm disease. Butterfly Conservation consider the white-letter hairstreak to be a high priority for conservation action and breeding success is greater on wych elm and appears to be able to find the the trees wherever they is growing!

For town and country; large-leaved lime (Tilia platyphyllos)

The regenerative power of the large-leaved lime. Credit; Flickr/Timo Scheurer.

One of my favourites; the large-leaved lime is the rarest of the limes found in the UK despite at one time being widespread across southern England which is why I think it’s a tree it’s is worth considering for planting and restoration projects . This tree, along with its more widespread relative, the small-leaved lime, have been traditionally used for urban tree planting so it’s a species that works well for urban and rural rewilding projects.

The large-leaved lime is particularly favoured by pollinators, particularly hoverflies, moths and bees. The high number of flowers producing nectar certainly appear to be a magnet for pollinators and while some limes will be debilitating (and even deadly) to bumblebees, the native varieties are considered safe. The oft-neglected night pollinators are provided for by lime trees too, as it is a food plant for many marvellous hawk moth caterpillars particularly the aptly-named lime hawk moth (Mimas tiliae).

Oyster mushrooms; an edible woodland delicacy. Credit; Flickr/Lukas.

Lime trees also play host a variety of fungi including oyster mushroom (Pleurotus ostreatus), shaggy scalp (Pholiota squarrosa) and giant polypore (Meripilus giganteus) to name a few. Aphids are famously associated with lime trees and produce copious amounts of honeydew, so much so as to make the ground (and anything else) beneath the tree sticky. The aphids do however draw in a whole ecosystem of insects (e.g. ladybirds and hoverflies) and thus, small birds. Based on anecdotal evidence, woodpeckers are thought to favour lime trees for ‘sap-sucking’ which has been observed in Wiltshire, Yorkshire, Somerset and Gloucestershire[4].

This tree works well for diversifying existing woodlands because lime saplings are tolerant of shade having evolved within dense woodland habitats. Once established, large-leaved limes grow into large trees and have a distinctive growth form which naturally fosters diversity; typically branches swoop and bend ground-wards and the limes will eagerly sprout from the trunk and its base. Shoots will also sprout from fallen trees so if left undisturbed lime trees will readily regenerate in the environment providing a variety of habitats over its life time. It’s sister species, works as a good alternatively as there is little difference between the two except that the small-leaved lime (Tilia cordata) is typically more geographically widespread and are considered to be smaller in stature.

Something a little different; black poplar (Populus nigra betulifolia)

The “disappearing tree of Europe”, the black poplar. Credit; Flickr/David Evans.

Described as the “disappearing tree species of Europe”, I include this tree as it really fascinates me. Not a lot is known about this tree – it’s actually Data Deficient on the IUCN Red List – although it’s fairly widespread in its global distribution it’s considered rare and declining in western Europe where the populations are recognised as a distinct subspecies.

The species nonetheless works well as a pioneer tree as it grows rapidly but as it regenerates vegetatively it could out-compete other species. This will however help if you’d like to reduce nutrient levels in the soil at your site or if your looking to reduce pollutants in the soil[5].

There may also be different forms of the tree in existence in the UK, as there are distinguishable differences between populations in the North, East Anglia and those in the Welsh borders/Wales. Although absent from Scotland, the species is best known as a floodplain tree and therefore thrives in lowland, riparian environments and is considered as one of Britain’s rarest trees (although not the rarest – this honour goes to the endemic whitebeams found in Scotland, Wales and northern England (Sorbus spp.), and arguably the Plymouth pear).

Support our native leopards. The leopard moth caterpillars feed on black poplars. Eat your heart out Hampshire Hyena Project. Credit; Flickr/Andy Phillips.

Widespread draining of the UK led to a massive decline in the black poplar’s floodplain habitat so the species has become highly fragmented. Not only this, because black poplars are dioecious (which means a given tree is either male or female) and the popularity of male specimens, it has low genetic diversity due to a lack of female plants in the wild as well as historic hybridisation with non-native poplars. Therefore, conservationists particularly recommend a landscape approach to the conservation of this species to ensure that cross-pollination between many individuals is possible. This means that - like the beaver - it particularly well-suited to large landscape scale management approaches.

Needless to say the tree is of value to a variety of wildlife. Like the elm, black poplars are linked to many rare butterfly species including the extirpated large tortoiseshell (Nymphalis polychloros). Many species are associated with poplars on general, including the poplar hawk moth (Laothoe populi) and a variety of birds who feed on the seeds and resident caterpillars. Poplar plantations are known to harbour quite an impressive number of birds including rarer species (although nowhere near as many as riparian habitats[6]).

The large tortoiseshell; a species no longer found in the UK. Credit; Flickr/Dennis Kallmer.

In the UK for example, the golden oriole (Oriolus oriolus) is most reliably found among the poplars near Lakenheath Reserve. I can imagine this species many years ago, with nesting storks in its crown, butterflies gliding about its branches and ducks dabbling below.

An alternative option if you’re looking to enrich soils, or are in Scotland, the “swamp-dwelling” alder (Alnus glutinosa) is a good alternative to black poplars as it has similar habitat requirements and also grows fairly quickly - at a rate of approximately 60cm per year.

To attract mammals; beech (Fagus sylvatica)

Beechnuts pack more protein than acorns. Credit; Flickr/Blondinrikard Fröberg.

Like many of the trees featured above, for the purposes of this blog I’m assuming you’re starting more or less from scratch so here’s another fast growing species; the beech tree. The beech tree is a long-lived species and is an important food resource for wildlife. Beech trees particularly appeal to coal tits (Periparus ater), marsh tits (Poecile palustris) and nuthatches (Sitta europaea), which store beechnuts throughout the woodlands where they are found.

This is important because birds are dispersers of tree seeds, especially nuts, so attracting them is useful in promoting sustainable forest spread and regeneration. Amusingly, naturalist T Richards (1958) describes birds as having a greater influence than squirrels upon the reproduction and dispersal of forest trees because “squirrels appear to be too efficient to allow many of their planted seeds to germinate”[7].

Marsh tits are particularly fond of beechnuts. Credit; Flickr/Airwolfhound.

Like oaks, beech trees famously have bumper years (known as mast years) where the trees produce a huge amount on beechnuts across the continent. Such mast years have a huge impact on wildlife and trigger population booms in many other species, including wild boar (Sus scrofa)[8]. Small rodents, squirrels (and even pine martens) would also likely benefit from masting years, along with the former’s predators. Interestingly black bears (Ursus americanus) in America are known to depend heavily on beechnuts and annual fruiting patterns can determine breeding probability in female bears[9].

Wild boar populations increase rapidly in mast years. Their populations are expected to boom as the climate warms. Credit; Flickr/Tomasz Przechlewski.

Beech are a good source of food for humans too, hosting mushrooms such as beefsteak fungus (Fistulina hepatica), oyster mushrooms (Pleurotus ostreatus) and two types of native truffle grow in beech woodlands. Truffles are a wild crop that have the potential to yield 100kg in a good year from just four hectares and - at the other end of the supply chain – are worth £150/kg to restaurateurs.

An imposing and impressive tree, the common beech is a wise addition in most landscapes and will do well across the UK, as long as it’s a well-drained site. English oak (Quercus robur) is likely to be a good alternative in colder, wetter climes as they have many similar benefits and the will also do well in open woodland pasture (thus grazed sites).

So concludes my not so short list of trees for rewilding and restoration projects in the UK. There are so many more and a great variety of native trees to choose from so remember to check what suits your site and its ecology, and ensure you make informed decisions (or seek advice) on which species work where as well as how you should go about sourcing seed (if needed!). Good luck!

Quick references;

[1] Woodbridge, J. et al. (2014) The impact of the Neolithic agricultural transition in Britain: a comparison of pollen-based land-cover and archaeological 14C date-inferred population change [2] Riley, W. et al. (2006) Seasonal variation in habitat use by salmon, Salmo salar, trout, Salmo trutta and grayling, Thymallus thymallus, in a chalk stream [3] Glue, D. & Boswell, T. (1994) Comparative nesting ecology of the three British breeding woodpeckers [4] Gibbs, J. (1983) 'Sap-sucking’ by woodpeckers in Britain British Birds [5] Michalak, M. et al. (2014) Desiccation tolerance and cryopreservation of seeds of black poplar (Populus nigra L.), a disappearing tree species in Europe [6] Martín-García er al (2013) Contribution of poplar plantations to bird conservation in riparian landscapes [7] Richards, T. (1958) Concealment and recovery of food by birds, with some relevant observations on squirrels British Birds [8] Beiber, C. & Ruff, T. (2005) Population dynamics in wild boar Sus scrofa: ecology, elasticity of growth rate and implications for the management of pulsed resource consumers [9] Perkins, D,. (2017) Beechnuts – superfood for bears and other wildlife (blog)

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