The world has all the fibre it needs to build future cities out of timber; however, to do so, it needs to better utilise waste, improve the circularity of products and turn hardwoods destined for wood fuel into higher-value mass timber products. That is according to a new study, “Global wood harvest is sufficient for climate-friendly transitions to timber cities,” published in Nature, which reveals that shifting wood fuel to industrial use and maximising the circular use of wood can make large-scale wood transitions possible without increasing harvest volumes.
“Our results reveal that these pathways have better environmental performance than increased harvesting, reducing total CO2 equivalent emissions by 2100 by 40.8 Gt compared to business as usual,” according to research led by Alperen Yayla from Imperial College London. “To achieve the wood transition, regional and cross-sectoral governance and planning are needed, addressing national-level pathways and inter-regional wood transport. The most critical actions are reducing the use of virgin wood as fuel by promoting cleaner alternatives and using wood waste more effectively globally, rather than expanding plantation forests.”
Timber cities where 90% of residential and commercial buildings use engineered timber and/or wood-based envelopes are considered critical for policymarkers to tackle embodied carbon in buildings to meet climate targets: “However, it is poorly understood how the supply of wood from natural forests and anthropogenic sources (for example, plantations, circular use) can meet the anticipated increase in demand required to achieve the wood transition, globally or regionally.”
Forestland does not need to
The problem, the researchers said, is that in many of the countries with the highest demand for engineered timber – India, Nigeria, the Congo and Ethiopia – the lack of secondary forests (suitable for sustainable harvest) and plantation forests means that any increase in wood production also leads to a substantial risk of deforestation: “Therefore, it is crucial to explore alternative ways, other than further harvesting, to meet the wood demand of timber cities.” As it stands, the vast majority of wood transition studies have focused on increasing harvesting and expanding plantation forests (from 131 million hectares to 425 million hectares over the next 80 years), to meet demand for engineered timber – a figure that conflicts with the 2.5% reduction in global forest area between 2000 and 2021:
“Past research has proposed shifting wood fuel harvesting to industrial use could fulfil the requirement for engineered timber in 50% of new residential and commercial buildings globally,” the researchers said, “(but) large-scale wood fuel replacement may result in increased demand for carbon-intensive alternative energy sources such as oil and coal, particularly in Africa and Latin America, due to the population’s dependence on bioenergy. These facts show the substantial potential for supply–demand imbalances in, and unintended environmental impacts such as an increase in fossil fuel use, and loss of natural forest ecosystems and biodiversity of the wood transition.”
And whilst engineered structural timber currently plays a tiny role in the global wood cycle (just 0.26% of total end-use wood) and 2.7% of all timber used in construction projects – representing just 2.9% of the worldwide demand for residential and commercial projects: “Hardwood use in construction may be the key to meeting engineered timber demand in wood transition,” they said. “Common hardwoods such as Quercus species (that is, oak) and Fagus sylvatica species (that is, beech) are naturally very durable…As such, it is more attractive to increase hardwood use in construction through the development of suitable machinery, and more importantly, reducing the dependence of bioenergy on hardwood.”
Then, there is also substantial potential to reduce the dependency on increased harvesting by increasing material efficiency, including through functional recovery and recycling in the wood cycle: “Total unrecovered waste and total waste used for energy recovery consisted of 28% of the total harvest in 2021. Increased engineered timber production in the wood transition will lead to increased production of wood waste (for example, wood chips, residues) generation in the global wood cycle, creating more circular use potential.”
“Our results show that either high circular wood use, wood fuel shifting to industrial use, or a mix of these pathways can fulfil the engineered timber demand for the global wood transition to timber cities without further harvesting,” they said. “We reveal (for example) that shifting 40% of annual wood fuel harvesting to industrial roundwood can satisfy this transition for 90% of the new urban populations.” Whilst upcycling timber from demolition sites also shows excellent potential for future mass timber projects: “Increasing circular use requires better management of the life cycle of products from production to end use, and creating markets for waste-derived products. For example, the design and installation of timber components in a building requires special planning so that it can be disassembled without any damage to use in a new project.”
For further information: Yayla, A., Mason, A.R., Wang, J. et al. Global wood harvest is sufficient for climate-friendly transitions to timber cities. Nat Sustain (2025). https://doi.org/10.1038/s41893-025-01605-w
