Natural regeneration

How natural processes can complement tree planting to expand woodland cover

Credit: Avalon.red / Alamy Stock Photo
Credit: Avalon.red / Alamy Stock Photo

What is natural regeneration?

The UK needs more trees. We plant millions of native trees every year, but planting is just one way to help the UK's woodlands expand. Allowing nature to take its course is also an effective and efficient method of increasing tree cover.

Natural regeneration is the process by which trees and shrubs self-seed and spread. Given the right conditions, most trees and shrubs are very good at it! There are a number of reasons for this:

  • Trees are large and long-lived which means they produce a high volume of pollen and seeds every year, increasing their chances of reproducing.
  • Tree seeds can disperse great distances (either by wind, water or via birds or other animals).
  • Large population sizes mean that many offspring are produced, each with unique traits. This gives lots of opportunity for natural selection and the ‘survival of the fittest’.
  • In many cases, trees and shrubs readily colonise land if allowed to do so.
A tool to combat the effects of climate change

The Climate Change Committee have announced that woodland cover in the UK needs to increase from the current 13% to 19% by 2050 in order to reach our national carbon net zero commitment. Natural regeneration can aid rapid woodland creation, particularly when tree nurseries are unable to supply enough bio-secure tree planting stock to meet demand.

Is it a new concept?

Natural regeneration is as old as woodland itself. It is how trees have reproduced, unassisted by people, throughout their millions of years of evolution. Yet, when establishing woodland in the UK, planting is the cultural norm. This isn’t the case across mainland Europe. There, foresters define two types of tree establishment:

  • Artificial regeneration – planting seed or saplings
  • Natural regeneration – the renewal by natural seeding (self-sown seed), sprouting, suckering or layering.

In recent British history, natural regeneration has occurred in some places, but it has usually been a side-effect of land abandonment rather than an active decision to create naturally-regenerated woodland (for example due to the reduction in traditional grazing of heaths and commons).

In the past, natural regeneration of scrub and woodland has traditionally been viewed in a negative light, due to its association with neglect. However, the problems of biodiversity loss and climate change have now come to crisis point. We urgently need to start enacting the solutions, and we know that expanding tree cover will be a major one.

What are the benefits of natural regeneration?

Credit: Richard Becker / Alamy Stock Photo

Enhanced adaptation potential

Scientific evidence shows that the UK’s native tree species have a wide genetic diversity. Naturally regenerated trees show adaptation to locally prevalent environmental conditions, often surviving better than planted trees. New generations of trees are the offspring of those already thriving in the local area, making woodlands more resilient to a changing climate, pests and diseases.

Credit: Matt Berry / WTML

Diverse ecosystems

Natural regeneration can create more natural landscapes and species mixes, which can be far more beneficial for wildlife. Naturally regenerating trees also have more beneficial mycorrhizal (root) fungi, which help with water and soil nutrient uptake, and sharing resources between trees. 

Credit: Philip Formby / WTML

Benefits for people

Natural regeneration is often associated with continuous cover forest management systems (CCF), which create a patchwork structure of canopy gaps and mixed age stands of trees. These can deliver benefits such as improving water quality or reducing downstream flood risk.

Credit: Ben Lee / WTML

Low biosecurity risk

Importing tree planting stock from overseas carries with it the risk of introducing pests and diseases to the UK. To avoid this, we advocate for the planting of UK and Ireland Sourced and Grown trees, however there is not enough nursery stock to meet woodland expansion targets. Allowing trees to self-seed is another means of reaching these targets without resorting to importing from abroad.

Credit: Scotland: The Big Picture / naturepl.com

Cheap and sustainable

Natural regeneration can be cheaper and involve fewer plastic tree guards than planted trees. In many areas of the UK, trees will plant themselves in their millions over as large an area of land as we are willing to commit to reforestation. In some cases, the benefits of natural regeneration can be combined with planting to increase diversity when species have been lost from a site.

Credit: Papilio / Alamy Stock Photo

Hardiness

As naturally regenerated saplings grow in the same place their whole lives without being transplanted, this can confer hardiness to stressors such as drought through the establishment of better tap roots.

Where has natural regeneration been successful?

Large-scale and long-term studies on natural regeneration in the UK are lacking. But there are some examples where evidence has been collected.

Rothamstead

Two experimental plots near the Rothamstead Research Centre in Hertfordshire were abandoned to nature in the 1880s after being farmed for centuries. The progress of the sites has been monitored ever since, and they now both support woodland. Interestingly, the two woods are dominated by different tree species because the sites are on different types of soil – a perfect example of how the most suitable trees for a site will plant themselves.

Monks Wood Wilderness

In Cambridgeshire, an arable field next to an ancient woodland was experimentally abandoned in 1961. The adjacent woodland provided an ideal seed source, and within 30 years the field had transformed into a mixed woodland with oak, ash and many other species.

The Roughs

In Northamptonshire an old wartime airfield was abandoned and allowed to return to nature in 1948. After 56 years it had not developed into closed canopy woodland; it had extensive scrub with patches of trees alongside areas of thick grassland. Rigorous ecological surveys showed it was home to a higher number of different wildlife species than any of the surrounding land including woodland, arable and set-aside.

Knepp Estate

Perhaps the most famous example of natural regeneration in action has taken place relatively recently at the Knepp Estate in Sussex. In 2001 the previously conventional arable and dairy farm was taken out of intensive farming and grazing animals were introduced. Some of the most dramatic wildlife conservation success stories ensued. The natural regeneration of scrubland led to the return of turtle doves, nightingales and purple emperor butterflies – species which are on the brink of vanishing from the rest of our countryside. This site is large, and demonstrates what can be achieved when natural regeneration is employed at scale.

Landowners need support

There is currently no grant support to help landowners utilise natural regeneration.

What are the barriers to natural regeneration?

Natural regeneration is prevented by physical and ecological barriers. These can include:

  • Ploughing of arable land
  • Mowing of lawns, road verges and parks
  • Intensive livestock grazing
  • High abundance of native and non-native deer
  • Thick grass sward preventing seeds reaching the soil
  • Lack of nearby trees to provide a source of seed.

These barriers can be emotionally, politically and financially driven. Humans like to exert control over the landscape, as our ancestors have done for millennia. The land has always provided for our needs, and the idea of allowing land out of food production can at first feel like an unacceptable waste. The traditional view of scrub as ‘wasteland’ reflects those values.

But our land does so much more for us than just producing food. Scrub and woodland are simply a different form of land use, providing the vital services of storing carbon and supporting biodiversity. Natural regeneration also requires patience – it is tempting to get stuck in with planting to speed things up.

While naturally regenerated trees plant themselves for free, the land being converted will be coming out of production, reducing the landowner’s income. This would be the same for a landowner creating woodland by planting trees, but unlike for tree planting, there is currently no grant support to help landowners utilise natural regeneration. This highlights the need for funding schemes to deliver both planting and natural regeneration across the UK. At present there are no set targets for woodland  to be created specifically by natural regeneration, so there is no special incentive for landowners to choose this method.

Is there still a place for tree planting?

Natural regeneration versus planting doesn’t need to be a binary choice. Tree planting has its own advantages and will remain an important part of what we do here at the Woodland Trust. If we are to meet the Government’s target for net zero emissions by 2050 and the amount of woodland expansion required, we will have to draw on every method and tool available to us. This will include both a massive increase in tree planting efforts, and an unprecedented upsurge in the use of natural regeneration.

There are circumstances when tree planting really comes into its own. For example, where the seed source for the desired tree species is absent, and is unlikely to arrive on site naturally. Tree planting can help with bringing back tree species that are known to be lost from a site. Planting can be used to complement natural regeneration or to enhance the species mix if a single type of tree is dominating.

Planting tree saplings can help to make sure that trees establish quickly and reliably, so that the trees can get to work on carbon sequestration sooner. It reduces the risk that trees might not manage to regenerate if the conditions for natural seed set and survival are not quite right.

See natural regeneration at work in our woods

Glen Finglas, Brig o'Turk

Glen Finglas estate is the largest site in our care and demonstrates how natural regeneration can be used at scale in vast landscapes. It already boasts a mosaic of woodland, open-grown trees and open ground – a habitat type known as wood pasture. Our long-term vision is to allow woodland cover and open ground to expand and contract over time in response to natural processes, by balancing natural regeneration with just the right intensity of grazing. 

Heartwood Forest, St Albans

At Heartwood, natural regeneration has been used to create wooded buffer zones around patches of ancient woodland, to expand the woodland habitat and protect the precious ancient core from outside impacts. This means the new trees are benefitting from hundreds, if not thousands of years of local adaptation to that site, since they are the offspring of the ancient woods themselves. In addition, tree planting with tens of thousands of volunteers has led Heartwood Forest to become England’s largest area of uninterrupted woodland, and wildlife is now booming here.

Hucking Estate, Kent

Hucking Estate is a mixture of 75ha of ancient woodland and 140ha of secondary woodland including both planted and naturally regenerated areas. The aim for this site is to create secondary woodland using natural regeneration at a scale rarely seen in southern England. This will provide opportunities for nature to express itself and assist greater species movement through the landscape.

Delve deeper into our work

Journal

Wood Wise - woods in waiting

PDF  (5.28 MB)

Read the autumn 2020 issue of Wood Wise, our tree and woodland conservation magazine, which discusses the importance of natural regeneration for expanding tree and woodland cover in the UK.