Constructing new houses from timber, rather than steel and concrete, could prevent more than 100 billion tonnes of CO₂ emissions over the next 80 years and help avoid a climate catastrophe, scientists claim.
Experts warned that providing the wood for construction will require more tree plantations, which could threaten biodiversity “if not managed carefully”, but timber’s carbon dioxide emission level is significantly lower than that of steel and concrete.
Scientists at the Potsdam Institute for Climate Impact Research (PIK) indicated that the emissions savings generated by the widespread use of timber as a building material in cities would account for approximately 10% of the world’s remaining carbon budget. This study is the first to analyse the impact of a large-scale transition to timber cities on land use, land-use change emissions, and long-term carbon storage in harvested wood products.
“Currently, more than half of the world’s population lives in cities, and by 2100 this number will increase significantly,” said PIK scientist and lead author of the study Abhijeet Mishra.
“This means that more and more houses will be built from steel and concrete, which largely generates serious carbon dioxide emissions,” the author continued. “But we have an alternative: we can accommodate new urban residents in mid-rise buildings, which are four to 12 storeys high, built from timber.”
The research team pointed out that timber has the lowest carbon footprint of any comparable building material because trees absorb CO₂ from the atmosphere as they grow, which is then stored in the building, making timber buildings long-term carbon sinks.
Engineered wood products include laminated veneer lumber, engineered timber beams, glued laminated timber, and cross-laminated timber, as well as widely used wood products such as MDF and oriented strand board (OSB).
Products such as cross-laminated timber and glued laminated timber gain enormous strength and versatility by using many layers of glued wooden boards and are typically made from cheaply grown plantation wood that would not be suitable for construction purposes if cut as standard lumber.
To assess the potential benefits of shifting to timber construction, the scientists looked at four different scenarios: one based on conventional building materials such as cement and steel, and three based on additional demand for timber on top of what already exists.
The scientists analysed how the high demand for timber building materials could be met, where they could be sourced from, and what the consequences might be in terms of direct and indirect carbon emissions from land use.
“Our modelling shows that a sufficient amount of timber for new mid-rise urban buildings can be provided without a significant impact on food production,” said study co-author Florian Humpenöder (Florian Humpenöder), who is also a PIK scientist.
“Timber is obtained from both tree plantations and natural forests. The majority of the required additional tree plantations – we are talking about approximately 140 million hectares – are established on harvested forest areas, thus not at the expense of agricultural land.” He added: “We need agricultural land to grow food for people – using it to grow trees could potentially create competition for limited land resources.”
However, the scientists suggest that by simultaneously changing human diets and reducing reliance on livestock farming, more than enough land could be freed up to establish new plantations.
Head of the land-use management group at PIK and co-author of the study Alexander Popp (Alexander Popp) believes: “The question of how and where to source timber for timber city construction is very important. In our computer simulations, we have set a clear limit for timber extraction and the establishment of new tree plantations: Nothing should be harvested in intact forests and protected areas of biodiversity.”
He added: “The clear preservation of these protected areas is vital; however, if tree plantations were created at the expense of other unprotected natural areas, this could further increase biodiversity loss in the future.”