New findings accentuate value of old growth forest in addressing climate change

A UK study published in December 2022 suggests carbon volume in larger trees is likely to be much higher than previously estimated. 

This potentially has huge implications for the value of forests, old growth in particular, for mitigating climate change – and underlines a correspondingly much greater cost of their destruction.

The indepth study is based on 3D terrestrial laser scanning (TLS), a remote sensing technique that accurately captures the volume and mass of carbon from pulse emissions. This methodology supplants more sketchy estimates currently based on allometric models from calculation of tree diameter, which assume size and mass grow at a steady rate; these are deemed more suitable for trees less than 50 cm diameter.

The TLS shows Above Ground Biomass (AGB), used to calculate carbon storage, are nearly 80% higher than previously thought – at 410 tonnes per hectare as against 232, across a sample of over 800 trees at Witham Wood in Oxfordshire. 

Whilst not part of the study, adding below-ground biomass will of course add very significantly to storage, and underline the need for non-intervention in the most carbon absorbent forests, otherwise rapidly degraded by emissions from felling and soil disturbance.

These findings are the work of an international team that comprises University College London, together with the universities of Ghent, Tampere, Sylvera, Oxford and the UK National Centre for Earth Observation (NCEO).

Professor Mat Disney (UCL and NCEO) co-author of the study declared: “Forests currently act as a carbon sink in the UK. However, whilst our finding that the carbon storage capacity of typical UK woodland could be nearly double what we previously thought might seem like a purely positive outcome, in practice this means that for every ha of woodland lost, we’re potentially losing almost twice the carbon sink capacity we thought”.

Whilst wider geographic replication can only add to the weight of evidence, this study provides the clearest backing for IUCN Resolution 127 from the Marseille 2021 Congress collated by Daniel Vallauri of WWF France, calling for cessation of logging and improved support for protection and restoration of all European primary & old growth forests – and based on Wild Europe’s Old Growth Forest Protection Strategy.

It also underlines the need to ensure strict protection for old growth/primary forests, as cited in the EU Biodiversity Strategy, is based on non-intervention.

Further reading: 

Mat Disney et al, Laser scanning reveals potential underestimation of biomass carbon in temperate forest, Ecological Solutions and Evidence (2022). DOI: 10.1002/2688-8319.12197

Kim Calders et al, Terrestrial laser scanning data Wytham Woods: individual trees and quantitative structure models (QSMs), Zenodo (2022). DOI: 10.5281/zenodo.7307956 provided by University College London