By Brent Sohngen (sohngen.1@osu.edu)
A recent study argued that tree harvesting all over the world – including fuelwood harvesting in the world’s poorest places – cause large unaccounted carbon emissions (see Peng et al., 2023). Many people have taken issue with the approach used in Peng et al. because the calculations ignore history, the future, and markets, among other things (see this blog post). The question of whether wood harvesting creates a net carbon emission, and thus whether wood products are “sustainable”, has been well-studied, with hundreds of analyses. Much of this analysis seems to focus on the life cycle of wood harvested in rotational forestry operations in developed places like the United States, Canada, and Europe.
What about the substantially less intensive harvesting that happens all over the tropics where relatively few stems per hectare are removed in each operation? There is lots of worry that this wood harvesting can lead to considerable emissions because of the damage done to nearby forests when large, old trees are removed or when roads are built to skid trees out of the forest (Ellis et al., 2019; Matricardi et al., 2020). Do these types of harvests lead to net carbon emissions for the earth?
This question came to the forefront a few years ago when a group proposed that the pedestrian promenade on the Brooklyn Bridge be restored with wooden planks from a tropical forest in northern Guatemala (see https://www.brooklynbridgeforest.com/about). The tropical forest where harvesting would happen wasn’t just any tropical forest, it was a forest managed by the community of Uaxactun. Most people have never heard of this small and isolated community in the northern reaches of Guatemala. More than a hundred years ago, however, community members there helped the Wrigley Company become a household name in the United States by providing the essential ingredient for Juicy Fruit – chicle latex from a local tree species. Tapping trees to provide latex was (and is) a sustainable operation, much like harvesting maple syrup in North America. By the second half of the twentieth century harvests were waning as easier to obtain substitutes displaced chicle. Fortunately, the roots of sustainably managing forests in the region were well established.
The question facing New Yorkers today worried about the sustainability of their future promenade is not as straightforward as harvesting sap from trees. Instead, the question of sustainability revolves around whether removing trees from this ecosystem can be done sustainably at all. Studies like Peng et al. are declarative, stating bluntly that any harvesting creates massive carbon emissions equaling 1 ton CO2 per m3 of wood removed. To put this in context for the average American homeowner with a 2500 square foot (230 m2) house, your abode probably contains around 35 m3 of timber. The standard claim is that you are storing 32 tons of CO2 in that wood, all while the same forest used to grow those trees is, with near 100% certainty, removing those and more tons from the atmosphere every year.
In contrast, the claim by Peng et al. is that the 2500 ft2 wood-framed house created an unabated emission of 35 tons of CO2 when built. Under the social cost of carbon estimates used by the Biden administration, the Peng et al. result means that every homeowner today should pay a one-time tax of about $2 per ft2 for their wooden homes to make up for the extensive damage they have apparently done to the atmosphere. I bet you, like me, never thought you were living with such a large climate liability?
Harvesting is much different in Guatemala than the typical operation in the United States where these calculations are based. In Uaxactun, the typical wood harvesting operation results in removing only a few really valuable stems per hectare every 30 years or so. Such harvesting operations undoubtedly lead to carbon emissions, even if some of the stem wood ultimately makes its way into wood planks fastened to the Brooklyn Bridge. These emissions happen when cut wood is left in the forest to decompose slowly over time. Sawdust and small bits will litter the floor of the local mill, perhaps making their way into bedding for animals or other uses. In the forest, it will take some time for the gap in the canopy to be closed by growth of new trees and for the carbon in the forest stock to be regenerated.
Emissions definitely happen when wood is harvested in Uaxactun. The question is whether those emissions are replaced by re-growth in the forest. If you cut 1 ton CO2 of trees out of the forest, put 0.3 tons in long-lived wood products, and emit the other 0.7 tons that looks like a lot of emissions. However, if 1 ton regrows over the next decade or two, society has 1 ton in the forest, and 0.3 tons of CO2 stored in wood products for a total of 1.3 tons stored.
Studies like Peng et al. use a no-harvesting counterfactual and discounting to calculate that this time when the forest has less carbon after harvesting creates a carbon deficit for the atmosphere. By ignoring economics, and focusing entirely on physical calculations, this approach conveniently ignores the likelihood that if Uaxactun’s forests are no managed for timber, they are likely to be converted to agriculture – a far worse counterfactual than the old growth forest Peng et al. assume. In this part of the world, harvesting wood provides economic opportunity for families and communities, which helps the groups who manage forests repel the forces of land conversion. This benefit of timber harvesting is not an idle promise in the Peten. It’s the result of really good planning and incredibly hard work over the last 30+ years.
During Guatemala’s long civil war, which ended in 1996, the Peten, as the region in northern Guatemala is known, served as a relief valve of sorts for people displaced by violence. As population grew in the 1980s and 1990s, worry that rampant agricultural conversion would imperil biodiversity and cultural artifacts from previous Maya civilization grew.
In the 1990s, Guatemala and its international partners set about on a bold plan to create the Maya Biosphere Reserve, an area that would be managed partly as a park, but more importantly as a practical place where land and its forests could be used for the betterment of people and the planet. Some of the forests were indeed devoted to national parks and protected areas. But large tracts were also devolved communities where timber and non-timber forest product harvesting could benefit residents. Other parts of the forest were left to their fate in a buffer zone.
Over time, forests in national parks and protected areas have fared poorly throughout large swaths of the Maya Biosphere Reserve (Blackman, 2015) as drug lords and others have used land as they wish. These forests are owned by government, which doesn’t do a lot to ward off the interlopers. So too, forests have been lost in the buffer zone where ordinary people have converted them to farms. The forests in the community concessions, however, have fared pretty well, especially in communities like Uaxactun, which have a long-established connection to the region (Bocci et al., 2018; Fortmann et al., 2017).
It turns out that when local residents are given access to land they can call their own, and make money from the products the land provides, they will protect it. There is a good bit of tourism in the area with Guatemalans and foreigners alike showing considerable interest in Maya history, but tourism has not yet developed at a scale anything like that in Costa Rica. Perhaps if tourism achieved such a level of remuneration, timber harvesting would not be necessary, but today, timber harvesting in places like Uaxactun provide much needed income that generates carbon benefits timber harvesting and by avoiding deforestation.
Among other problems (see earlier blog post), studies like Peng et al. miss this important function of tree harvesting. There are absolutely poorly planned and executed tree harvests all over the world. Tree harvesting in many old growth situations undoubtedly does lead to net emissions that may not be recovered by forest regrowth and wood product storage. Yet in some of those tropical forests in places like Uaxactun, tree cutting is an economic activity that keeps carbon in forests rather than the atmosphere, all while providing benefits to the communities and owners who cut trees, giving them a livelihood that will encourage them to protect the very forests they manage.
Blackman, A., 2015. Strict versus mixed-use protected areas: Guatemala’s Maya Biosphere Reserve. Ecol. Econ. 112, 14–24.
Bocci, C., Fortmann, L., Sohngen, B., Milian, B., 2018. The impact of community forest concessions on income: an analysis of communities in the Maya Biosphere Reserve. World Dev. 107, 10–21.
Ellis, E.A., Montero, S.A., Gómez, I.U.H., Montero, J.A.R., Ellis, P.W., Rodríguez-Ward, D., Reyes, P.B., Putz, F.E., 2019. Reduced-impact logging practices reduce forest disturbance and carbon emissions in community managed forests on the Yucatán Peninsula, Mexico. For. Ecol. Manag. 437, 396–410.
Fortmann, L., Sohngen, B., Southgate, D., 2017. Assessing the role of group heterogeneity in community forest concessions in Guatemala’s Maya Biosphere Reserve. Land Econ. 93, 503–526.
Matricardi, E.A.T., Skole, D.L., Costa, O.B., Pedlowski, M.A., Samek, J.H., Miguel, E.P., 2020. Long-term forest degradation surpasses deforestation in the Brazilian Amazon. Science 369, 1378–1382.
Peng, L., Searchinger, T.D., Zionts, J., Waite, R., 2023. The carbon costs of global wood harvests. Nature 1–6.