The concept of Continuous Cover Forestry (CCF) has always made a lot of sense to me. Intuitively, forests need trees. The fungi, plants and animals that live in forests need trees. So we should manage our forests to maintain tree cover and not clear fell large areas. Natural processes have evolved over thousands of years to create forest ecosystems that are adapted to their local soils and climate. Surely we should be working with these, not fighting against or oversimplifying nature.
I am keen to learn more about CCF and how it works in practice to produce timber using a close-to-nature approach, so for two months in the autumn I took part on an online course ‘Forest MOOC For Change’ run by the European ‘Pro Silva’ movement https://mooc.forestmoocforchange.eu/. This has inspired me to share here (briefly) some of the many benefits of CCF, with the hope that more people will realise that this is a real alternative to the single-species, even-age clear-fell forestry that is often seen as the only option in Scotland. What I write below is information that I have learned from the MOOC, as well as ideas from a recent Soil Association report on regenerative forestry1, which aligns with the ideas of continuous cover forestry.
In recent history, forestry in Scotland has tended to be split into non-productive woodlands, typically broadleaf, managed for biodiversity or not managed at all, and productive forests, typically conifer2. Figures I can find suggest that the proportion of productive conifers is somewhere between 66 and 78 percent of total woodland cover.2 3 4 The ubiquitous conifer plantations typical of Scotland place a high emphasis on volume of timber production, with less concern about timber quality, little provision for biodiversity, and little consideration about landscape, amenity or recreation. Given the biodiversity losses we face, it is important that all land supports as much biodiversity as possible, even land that is managed productively. CCF provides a win-win solution to this issue because it can produce quality timber while also supporting a high level of biodiversity, as well as having a higher value for recreation and landscape.
Continuous Cover Forestry: principles and benefits
The principles of CCF are to manage forests that are functioning as closely as possible to natural forests, while also producing timber. This means that foresters maintain permanent tree cover and remove trees through selective felling of single trees or small groups. Continuous cover forests have a diverse mix of tree ages and species, using targeted interventions to favour trees of good timber quality by removing competing trees as appropriate. Continuous cover forests aim to produce timber of the highest possible quality through this approach and the emphasis tends to be on producing large diameter, high value timber.
In CCF forest renewal is primarily through natural regeneration, with supplementary planting used where necessary. It is therefore important to ensure that there are areas where light levels are sufficient for natural regeneration. This is achieved through successive thinning and removal of small groups of trees. The key with CCF management is to create a balance such that there is enough standing timber to allow ongoing harvesting of the largest trees once they reach a target diameter, whilst also thinning sufficiently to provide light for regenerating trees, which will maintain the timber harvest into the future.
Given that every forest is different, CCF management cannot be done using simple reductionist approaches, as is often used for mainstream clear-fell forestry. CCF management requires constant observation and adaptation, responding to how the forest develops. While management objectives are made at the scale of a stand or forest compartment, management interventions are made at the scale of a single tree or group of trees. The diverse mix of species found in continuous cover forests gives the forester options and provides resilience. For example, if one species begins to suffer from a disease or from drought impacts, other species can be favoured in management interventions.
Continuous cover forests have a diverse range of species and ages of trees and a complex structure with many different habitat niches. They also include retained deadwood, both standing and fallen, which is a very important habitat element of a natural forest and supports many fungi, invertebrate and bird species. The high level of biodiversity found in continuous cover forests helps to promote a healthy balance of insect pests and predators, meaning artificial pest control measures are not needed (in contrast to clear-fell systems, which can create imbalances and cause infestations of pests such as pine weevil that need to be chemically controlled).
The health and resilience of continuous cover forests is further promoted by the health of their soils. Management is carried out with minimal soil disturbance, by working from a fixed network of access routes. Continuous tree cover helps to protect the fungal mycorrhizal networks in the soil. These are the fungi that have symbiotic relationships with trees and help them obtain water, nutrients and minerals in exchange for sugars. They are critical to healthy growth of most trees and many other types of plant. They are thought to redistribute resources between trees, helping young trees to establish, and it has been found that large, old trees can act as hubs within the network. Therefore maintaining forest cover, including large trees, helps the fungal network remain intact, which promotes tree growth and provides greater resilience against stresses such as disease and drought. Clear-felling, in contrast, disrupts the fungal network, as well as causing greater soil disturbance and compaction, damaging this precious resource and making it more difficult for the next generation of trees to establish.
When compared over decadal timescales, timber outputs from continuous cover forests can be as high as forests managed through clear-felling and replanting. CCF has the added benefit of requiring lower inputs due to the reliance on natural regeneration and natural pest regulation. CCF also provides steady and regular revenues through ongoing harvesting of the incremental timber growth, whilst maintaining the forest ‘capital’, i.e. the remaining standing timber that will continue to grow and increase in value. In addition to this, and the biodiversity benefits, people value forests in the landscape and the diverse, mature forests that result from CCF have a higher amenity and recreation value than even-aged, single species plantations.
Continuous Cover in Comar Wood
My management plan for Comar Wood was already based around the idea of CCF because I did not like the idea of clear-felling the spruce and wanted to retain forest cover whilst transforming the plantation to a more diverse woodland. However, the MOOC has made me think slightly differently about some aspects of the plan.
The CCF approach is a reactive one that lets nature guide. The examples from the course highlighted to me the long-term nature of forest development and encouraged me not to rush to completely remove the spruce. Comar Wood currently contains considerable areas of even-aged, dense spruce that are detrimental to the ancient woodland, so management is required to open up the stand through thinning and group felling. However, I have already come to appreciate some of the positive qualities of the spruce within the woodland (see Sitka spruce: the ugly, the bad and the good) and I have now realised that while some spruce trees are still providing a benefit to the woodland, either as a quality timber asset, or for habitat, there is no need to completely remove the spruce.
CCF places high importance and value on large trees. The course has encouraged me to think more about retaining higher quality spruce (i.e. straight stem and a good, healthy crown) through thinning and letting these trees grow on to reach their potential. They are an asset and helping concentrate growth on these trees will increase yield in the medium term, more than felling sooner and restocking.
The course has made me realise the extent to which I should be able to use natural regeneration to restock felled areas. While I will need to use supplementary planting of certain species, I should be able to rely on natural regen more than I was originally planning. A further idea taken from the course was the possibility of progressive thinning of spruce to the point where natural regeneration will occur within the stand. I had discounted this idea previously, thinking that I would eventually clear groups to allow regeneration. However, some areas in the wood may lend themselves to being thinned repeatedly to the point where there is enough light for a range of species of tree to regenerate beneath (although this may result in a very high proportion of spruce regen, then requiring management). It is something to consider further.
More Continuous Cover needed
Given the multiple and integrated benefits that CCF provides, you might wonder why it is not practised more widely in Scotland. Clear-fell and replant has been the prevalent system in the many plantations that were established in the 20th century, in the rush to grow more timber following the World Wars. According to the Soil Association report1, the tax system pre-1988 favoured clear-fell forestry systems due to favouring separate periods of revenues and costs, and this has remained the dominant forestry model. Given the prevalence of the even-aged Sitka plantation, the wood processing sector has been set up to deal with the standard-size softwood logs that harvesters churn out from clear-fell sites. Plantations are established or re-stocked to meet the demand from this processing sector, perpetuating the same forestry model.
Transforming an even-aged plantation to CCF requires an input of time and resources and the current grant system does not do enough to incentivise or support this. Most sawmills are not currently able to handle the larger diameters and longer lengths that can be produced from CCF and markets for premium quality timber are niche so, again, there is little incentive to convert plantations to CCF. Continuous cover is not mainstream and most foresters are not trained in this type of management. Sites where productive CCF is practised are relatively rare, meaning foresters and the general public have few opportunities to see CCF and the types of woodlands and timber outputs that result. This all leads to the perception that CCF is too difficult or complex and that the prevalent practice of even-aged clear-fell forestry is the way to do productive forestry.
With its numerous advantages (much more to say about them than I can fit in here) and the current pressures on land, biodiversity and resources, surely CCF needs to be adopted much more widely. There needs to be a push to incentivise foresters and forest owners to move towards this regenerative approach. Forestry courses should teach CCF and regenerative approaches as standard. The grant system must encourage the transformation of existing forests to CCF management and to ensure that there is support for newly planted woodlands to be managed through continuous cover, to realise the potential for the many benefits of this approach. In their report the Soil Association call for their vision of regenerative forestry (i.e. CCF) to be applied across all publicly owned forests, not just a few exemplar sites.
As CCF becomes adopted more widely, momentum will build as people start to see the many advantages of this approach. Although CCF is complex, when viewed holistically it makes much more sense than mainstream forestry. This complexity is to be embraced, not bemoaned, because many of the advantages of CCF stem from its very complexity. Nature is complex and continuous cover forestry is forestry that respects nature.
- Regenerative forestry. Forestry and forests for the future, Soil Association, 2022. https://www.soilassociation.org/causes-campaigns/regenerative-forestry/
- A Forest for the Future, Jim Knight/Reforesting Scotland, 2019 https://reforestingscotland.org/a-forest-for-the-future/
- https://www.gov.scot/publications/scotlands-forestry-strategy-20192029/documents/
- https://www.nature.scot/professional-advice/land-and-sea-management/managing-land/forests-and-woodlands/history-scotlands-woodlands
Interesting as always. I understand that there’s been work recently on the complex relationship between the micorrizal fungal network and how it works with both established and establishing trees. This is fascinating.
With regard to natural regeneration, even in our own little wood, (predominantly sitka but with native hardwood boundaries) there has been significant early regeneration following a first fell about 7 years ago. I’ve noticed oaks and some beech, and oddly, many young holly!
Thank you once again for a thought provoking article.