Rethinking global carbon storage potential of trees. A comment on Bastin et al. (2019)

Authors: Taylor, Shawn; MARCONI, SERGIO - University Of Florida

Submitted to: Annals of Forest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2020
Publication Date: 3/20/2020
Citation: Taylor, S.D., Marconi, S. 2020. Rethinking global carbon storage potential of trees. A comment on Bastin et al. (2019). Annals of Forest Science. 77:23. https://doi.org/10.1101/730325.
DOI: https://doi.org/10.1101/730325

Interpretive Summary: Global estimates of ecosystem carbon sequestration potential are critical for long term allocation of resources. A recent article popularized the idea that restoring degraded forests worldwide could mitigate a large proportion of anthropogenic carbon emissions. Using empirical relationships of carbon storage in forests we showed how the original article vastly overestimated the forest carbon potential, thus placing too much importance on forest restoration as opposed to other carbon mitigation strategies. Forest restoration certainly plays an import role in mitigating climate change, but our contradictory results show that other large scale strategies, such as reductions in emissions, will likely have a more significant impact.

Technical Abstract: Bastin et al. 2019 use two flawed assumptions: 1) that the area suitable for restoration does not contain any carbon currently, and 2) that soil organic carbon (SOC) from increased canopy cover will accumulate quickly enough to mitigate anthropogenic carbon emissions. We re-evaluated the potential carbon storage worldwide using empirical relationships of tree cover and carbon. We use global datasets of tree cover, soil organic carbon, and above ground biomass to estimate the empirical relationships of tree cover and carbon stock storage. A more realistic range of global carbon storage potential is between 71.7 and 75.7 GtC globally, with a large uncertainty associated with SOC. This is less than half of the original 205 GtC estimate. The potential global carbon storage of restored forests is much less than that estimated by Bastin et al. 2019. While we agree on the value of assessing global reforestation potential, we suggest caution in considering it the most effective strategy to mitigate anthropogenic emissions.