The carbon costs of global wood harvests

Abstract

After agriculture, wood harvest is the human activity that has most reduced the storage of carbon in vegetation and soils1,2. Although felled wood releases carbon to the atmosphere in various steps, the fact that growing trees absorb carbon has led to different carbon-accounting approaches for wood use, producing widely varying estimates of carbon costs. Many approaches give the impression of low, zero or even negative greenhouse gas emissions from wood harvests because, in different ways, they offset carbon losses from new harvests with carbon sequestration from growth of broad forest areas3,4. Attributing this sequestration to new harvests is inappropriate because this other forest growth would occur regardless of new harvests and typically results from agricultural abandonment, recovery from previous harvests and climate change itself. Nevertheless some papers count gross emissions annually, which assigns no value to the capacity of newly harvested forests to regrow and approach the carbon stocks of unharvested forests. Here we present results of a new model that uses time discounting to estimate the present and future carbon costs of global wood harvests under different scenarios. We find that forest harvests between 2010 and 2050 will probably have annualized carbon costs of 3.5–4.2 Gt CO2e yr−1, which approach common estimates of annual emissions from land-use change due to agricultural expansion. Our study suggests an underappreciated option to address climate change by reducing these costs.

Stand age diversity and climate change affects forests’ resilience and stability, although unevenly

“…Consequently, the ability of aging forests to act as carbon sinks and mitigate the effects of climate change may be compromised (Collalti et al, 2019; Zhu et al, 2019). Another recent study (Peng et al, 2023) suggested that reducing the forest harvesting rate could become an effective mitigation option based on the claims that forest harvesting has annualized carbon costs comparable to the annual emissions from land-use change due to agricultural expansion. Such conclusions were drawn based on strong assumptions that are not necessarily verifiable or will occur, such as the “higher value” of short-term mitigation actions or the eventuality that we do not shift toward other emission sources.…”

Society’s material stocks as carbon pool: an economy-wide quantification of global carbon stocks from 1900–2015

“…Incorporating more wood into socioeconomic C stocks however requires either large-scale expansion of tree plantations or intensification of forest use. The effect of such options is under debate, with some scholars arguing that increased wood demand might enhance more effective forest management [65], while others warn that increasing harvest could undermine the ecological integrity of forests and their capacity to act as C sinks [66,67]. Either way, the climate-change mitigation effect of C accumulation in socioeconomic timber stocks is constrained by biological capacities of ecosystems, because harvesting more than the annual woody increment reduces ecosystem C pools and thus does not contribute to keeping C from the atmosphere.…”

Conflicts and opportunities for commercial tree plantation expansion and biodiversity restoration across Brazil

“…Tree plantations grown to provide wood products are a rapidly expanding component of tropical landscapes, growing by 32.2 million hectares (Mha) between 2000 and 2012 and occupying 131 Mha of lands worldwide in 2020 (FAO, 2020). New markets for construction and bioenergy (Mishra et al, 2022;Peng et al, 2023) and the inability of natural production forests to support growing timber demand (Piponiot et al, 2019;Shearman et al, 2012;Sist et al, 2021) are forecasted to promote substantial additional tropical plantation expansion in the near future (Edwards, Cerullo, et al, 2021;Lewis et al, 2019;Peng et al, 2023). Meanwhile, ambitious restoration commitments, including under the UN Decade on Ecosystem Restoration and the Bonn Challenge to restore 350 Mha of degraded lands by 2030, may also drive substantial plantation cover increases if these are counted towards national restoration targets (Lewis et al, 2019).…”

“…Nevertheless, the substantially higher yields generated within tree plantations means that they may deliver significant environmental benefits if they spare natural forests from wood harvesting, or reduce harvest intensity within ecosystems earmarked for production (Betts et al., 2021; Cerullo, Barlow et al., 2023, Cerullo, França et al., 2023; Harris & Betts, 2023). Although evidence of such passive sparing effects is inconclusive (Pirard et al., 2016; Warman & Nelson, 2016), plantations clearly have a critical role in fulfilling timber production needs at least cost to native habitats (Harris & Betts, 2023), particularly in light of a 54% predicted increase in wood demand between 2010 and 2050 (Peng et al., 2023). This has spurred the design of alternative tree plantation models which attempt to increase resilience against climate change and maximise environmental and conservation benefits (Brancalion et al., 2020; Messier et al., 2021), including by targeting plantations to replace agropastoral land uses, especially degraded pastures.…”