By Ed Bradbury, Forest Canopy Foundation, 2022

Can man afford to stand back and let nature fix the problem? A mini study comparing carbon sequestration in artificial and natural regeneration.


Establishing new trees and woodlands is an effective way to sequester atmospheric carbon. In the UK, even slower-growing native species such as oak (Quercus robur) can sequester ~2.68 tonnes of CO2e in a single tree over 100 years (Cannell, 1999). Because of this, man is now turning to various forms of tree establishment as nature-based solutions to mitigate climate change.

Foresters define two types of tree establishment: artificial regeneration and natural regeneration. Artificial regeneration involves deliberate planting of seed or saplings. Natural regeneration refers to the process by which plants and woodlands are allowed to establish from seeds dispersed naturally from local sources. This study takes a practical look at how carbon outcomes of these contrasting approaches compare and the inherent costs and implications of sequestering carbon through each method.

It is important to look at this in the context of the climate emergency we are currently tackling as well as existing policy and funding frameworks. The IPCC have concluded that to avoid catastrophic warming in excess of 1.5oC above pre-industrial levels countries must aim to meet net zero by 2050 (Masson-Delmotte et al., 2018). Therefore, carbon outcomes of the next 25 years are focussed on in this study. We explore this in a lowland context where potential for tree establishment is high in the UK.

Rates of Carbon Sequestration:

In a recent global study by Bernal et al. (2018), planted forests and woodlots were found to have the highest CO2 removal rates of any method of forest landscape restoration. The study estimated that these artificial regeneration projects sequester 40.7tCO2 per ha during the first 20 years of growth. On average, atmospheric CO2 removal rates for natural regeneration projects lower and reach a maximum of just 18.8tCO2 per ha during the first 20 years of growth. This shows that on average, carbon sequestration is ~116% higher in artificial regeneration when compared to natural regeneration.

The Woodland Carbon Code (WCC), the quality assurance standard for woodland creation projects in the UK, can also be used to model carbon sequestration for both natural and artificial regeneration. The WCC models are based on inventory data from Forest Research and modelling methods of Morison et al. (2012). For a model natural regeneration project, the WCC models predict the scheme will sequester 80.3 tonnes of CO2 per ha by year 25. In contrast, a model artificial woodland creation project is predicted to sequester 194.8 tonnes of CO2 over the same period *. This supports the findings of Bernal et al. (2018) and shows that carbon sequestration rates in artificial regeneration projects can be significantly greater (~144% in this case) than natural regeneration projects in the first 20-25 years. Maximising sequestration in the next 25 years is crucial meet net zero by 2050.

*The criteria/inputs used for this comparison are provided in Appendix 1.

Natural Regeneration

Artificial Regeneration

Cost of Sequestration:

Financial viability is key to ensure projects are implemented at scale. To compare the costs of artificial regeneration to natural regeneration, a budget for each approach has been produced for a model 10ha scheme, managed for 25 years. Consistent rates for project management, planting and protection, and aftercare were used in each case. Income estimates are based on the Forestry Commissions England Woodland Creation Offer (EWCO) scheme.

Full costings are shown in Appendix 2.

The net cost of the natural regeneration project is estimated to be £139,767 whereas the cost of artificial regeneration is significantly higher at an estimated £200,867. However, when comparing this on a cost per tonne of CO2 basis (based on WCC modelled rates -see previous section), it costs and estimated £174 per tonne through the natural regeneration approach but just £103 through artificial woodland regeneration. Therefore, it is more economical to sequester carbon through artificial regeneration than through natural regeneration.

Natural regeneration at Knepp

Other Considerations:

There are several other factors to consider when comparing these practises for carbon sequestration.

  • Establishment of woodlands via natural regeneration can also be unreliable with patchy tree cover at much lower densities than artificial regeneration projects. For example, a successful UK natural regeneration project established closed-canopy oak, ash and field maple with densities of up to 390 trees per hectare. Artificial regeneration projects in lowland England typically plant between 1800 and 2500 trees per hectare. In the initial stages of natural regeneration projects, it is common for only shrubland to develop by year 15 (e.g. UKCEH, 2021). Because of this, areas eligible for natural regeneration are highly constrained. Funding (EWCO) for these projects requires land to be within 75m of a seed source and may require remedial planting, ground preparation (scarification) and respacing to ensure outcomes are achieved.
  • Active management of pests such as the grey squirrel is key to achieve desired carbon outcomes from woodland in the England and Wales (RFS, 2021). At present, the reduction in carbon sequestration from grey squirrel damage is estimated to be £9 million per year in the UK (RFS, 2021). If squirrels are not controlled in unmanaged rewilding schemes where natural regeneration is occurring, there may be a significant reduction in carbon sequestration.
  • Species established is dependent on the local seed source for natural regeneration projects. This means trees that establish successfully are likely to be well matched to the current site conditions and eliminates biosecurity risks (Forestry Commission, 2021). These factors can be met to an extent in artificial regeneration projects through intelligent species choice and following established biosecurity protocols (e.g. Plant Healthy). Artificial regeneration allows foresters to choose species that may be best suited to growth under future climates which may benefits carbon sequestration long term.
  • Timber is also a key consideration when exploring which form of woodland creation. Timber outcomes are closely linked to carbon sequestration as production is highly dependent on growth rates. If woodlands are harvested for timber this may compromise some of the carbon sequestered in the later stages of tree growth. However, there is a significant carbon substitution effect when timber is used instead of concrete or steel in construction (Weatherall, 2019). It is estimated that the carbon footprint of a timber frame building is 75% lower than steel buildings (IDEAL, 2020).
  • Income from sales of carbon credits and timber is key to persuade landowners to pursue these projects.
  • Minimal intervention in rewilding/natural regeneration projects and inherent connectivity with existing woodlands means natural regeneration projects have high biodiversity value. Biodiversity benefit in artificial woodland creation is dependent on species choice and therefore highly variable.


In summary, whilst both natural regeneration and artificial woodland creation are effective methods of sequestering carbon, artificial woodland creation is much more effective over 25 years than natural regeneration. It is critical that we drive maximal carbon sequestration ahead of 2050 to best ensure net-zero is met.


Cannell, M.G.R. (1999) Growing trees to sequester carbon in the UK: answers to some common questions. Forestry72(3), pp.237-247.

IDEAL (2020) Why timber and not steel?. Available at: (accessed 10/12/21)

Forestry Commission (2021) Using natural colonisation for the creation of new woodland. Available at: . (accessed 21.12.21)

Masson-Delmotte, V., Zhai, P., Pörtner, H.O., Roberts, D., Skea, J., Shukla, P.R., Pirani, A., Moufouma-Okia, W., Péan, C., Pidcock, R. and Connors, S., (2018) Global warming of 1.5 C. An IPCC Special Report on the impacts of global warming of1(5).

Morison, J.I.L., Matthews, R., Miller, G., Perks, M., Randle, T., Vanguelova, E., White, M. and Yamulki, S. (2012) Understanding the carbon and greenhouse gas balance of UK forests. Report for Forestry Commission. Forest Research.

RFS (2021) The cost of grey squirrel damage to woodland in England and Wales. Available at: (accessed 10/12/21)

UKCEH (2021). Passive rewilding can rapidly expand UK woodland at no cost. Available at: (accessed 10/12/21)

Weatherall, A. (2019) What ‘rewilding’ really means for forestry. The Guardian . 24th May 2019.

Appendix 1: