The Role of Secondary Forests in Reducing Atmospheric Carbon

Mark Altaweel

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Carbon capture solutions will likely be some of the most important ways in which countries attempt to reduce overall climate change emissions. Within this, using natural methods, particularly growing forest cover, is important in the overall scheme of mitigating climate change because secondary forests provide natural and ecological benefits in addition to capturing carbon.

Researchers have argued that enabling natural forest regrowth should be part of carbon credit programs. In other words, the carbon market should incentivize secondary forest growth rather than conversion of land to other forms of production. In addition, secondary growth forests need long-term monitoring and management that ensures biodiversity.

Carbon capture with secondary forests

Secondary forest growth, that is natural growth of new forests in areas that were deforested previously, could be one of the best options to enable carbon capture as part of a global strategy to reducing atmospheric carbon. However, this presents challenges given that secondary growth forests often face various threats.

Protecting secondary growth forests

Several solutions may need to be in place if secondary forests have the best chance in helping carbon capture solutions. For instance, there needs to be a reduction in the pressure to periodically clear recovering forests, particularly in marginally productive lands for agriculture. This is the case in rain forests around the world. This likely means we need to better integrate food production policies with forest regrowth policies.

Land that is not very productive should be left out of agricultural production all together and incentives should be created to enable this. This may also mean more efficiency in how agricultural products are grown so that existing productive land and resources are better utilized even across boundaries.

Second, carbon markets could potentially encourage large-scale forest restoration, but proposed or existing methods do not enable this. Young secondary growth forests are not properly accounted for in carbon credits or have little importance relative to more pristine forested lands.

Incentivizing secondary forests as a carbon storage strategy

Protecting young second-growth forests should be highly incentivize in carbon markets. The level of importance should be between avoiding deforestation in the first place, which should be the top priority, and non-secondary forest growth.

Finally, carbon markets generally favor plantation-style forest regrowth rather than natural regrowth. Raising additional finance for second-growth forests based on ecosystem services, and not just carbon capture, would put greater motivation for natural forest regrowth. In other words, the carbon markets need to capture the range of ecological benefits and not just focus on carbon capture, particularly in areas such as rainforests.

Overall, carbon market systems need to evolve such that methods of regrowth and types of forest regrowth are placed as high priorities for carbon storage. This would enable much more land potentially to be put under protection and create the incentive structures needed to sustain them.[1]

Secondary forests and biodiversity challenges

One problem that is evident in carbon capture programs and carbon markets is that biodiversity is a constant challenge. Even if secondary growth is enabled, forests are often invaded by invasive species and biodiversity becomes a significant challenge.

Research has found in Brazil that carbon stock recovery in non-invaded forests was three times lower than in invaded forests. Non-invaded forests recovered three to six times higher in taxonomic and phylogenetic representation than invaded forest. Therefore, restoration planning needs to consider the overall health of forests and the species representation within them. Planning and management need to be sustained to ensure that as early secondary growth forests develop then invasive species are kept out to enable local species to take hold and thrive.

Once invasive species set in, then it increases the challenges to manage overall species diversity in secondary growth forests. Overall, forests may grow but their productive value for ecosystems may be undeserved. Incentive structures, therefore, need to enable a sustained effort for species and biodiversity in secondary growth forests. This means carbon capture markets may also need to reflect long-term management of forests and not just immediate carbon capture in calculations.[2]

Secondary forests play an important role in global carbon capture

Secondary growth forests represent some of the best long-term solutions for capturing carbon as we attempt to mitigate climate change and, hopefully, in the long-term, reverse damage already in place. However, to successfully do this, biodiversity and the types of forests we are growing need a closer look. This means incentive structures, such as carbon capture markets that are created, need to carefully consider overall health of forests and prioritize this not only in the short-term but also long-term.

Careful long-term monitoring of secondary growth lands, using imagery, will be needed to ensure that important incentive structures are followed and are getting through to forest regrowth areas.

References

[1]    An article that argues for changes to carbon credit programs to better reflect secondary growth forests and their benefits is found here:  Brancalion, P.H.S., Balmford, A., Wheeler, C.E. et al. A call to develop carbon credits for second-growth forests. Nat Ecol Evol (2024). https://doi.org/10.1038/s41559-023-02288-2.

[2]    For more on the challenges and benefits in enabling forest to have non-invasive species, see:  Matos, F.A.R., Edwards, D.P., S. Magnago, L.F., Heringer, G., Viana Neri, A., Buttschardt, T., Dudeque Zenni, R., Tavares De Menezes, L.F., Zamborlini Saiter, F., Reynaud Schaefer, C.E.G., Vieira Hissa Safar, N., Pacheco Da Silva, M., Simonelli, M., Martins, S.V., Brancalion, P.H.S., A. Meira-Neto, J.A., 2023. Invasive alien acacias rapidly stock carbon, but threaten biodiversity recovery in young second-growth forests. Phil. Trans. R. Soc. B 378, 20210072. https://doi.org/10.1098/rstb.2021.0072.

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About the author
Mark Altaweel
Mark Altaweel is a Reader in Near Eastern Archaeology at the Institute of Archaeology, University College London, having held previous appointments and joint appointments at the University of Chicago, University of Alaska, and Argonne National Laboratory. Mark has an undergraduate degree in Anthropology and Masters and PhD degrees from the University of Chicago’s Department of Near Eastern Languages and Civilizations.

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