How sustainable timber buildings can help fight the climate crisis

Samy Porteron

Global wood consumption is overshooting what forests can sustainably provide by up to 67% – and this overconsumption is likely to continue growing. In the EU alone, member state climate plans forecast 40-100% more demand for forest and agricultural products for energy and materials than will be sustainably available.

This situation is untenable: global strategies must be developed setting out the role sustainable wood consumption can play as part of our built environment.

A cascading use of wood resources should take place across sectors that use wood (construction, energy, packaging, paper, furniture, textiles, chemicals…) to conserve forests and address the twin climate and biodiversity crises that are linked to forest harvests.

Forest resources are slow-growing and cannot match the rapid consumption from sectors such as large-scale bioenergy and single-use packaging, which are better met with zero-carbon feedstocks and reusable solutions.

The strategy should therefore be to ensure that the use of finite wood resources is prioritised between sectors, with use in construction valued over other uses where alternatives exist, while moving away from burning wood for energy and protecting and restoring particularly primary and old growth forests.

Even within the construction sector, the demand for timber should be controlled by implementing a sufficiency approach to only use the necessary amount of wood products, at the same time implementing circularity principles to ensure the demand is met with reused and recycled wood whenever possible. Lastly, harvested wood used should come from ecologically managed forests.

While forests and wood products can certainly contribute to carbon neutrality objectives thanks to their carbon storage properties, they are not always carbon neutral or carbon negative. In fact, the increasing demand for forest wood products is a driver in the decrease in forests’ carbon sink capacity, for example in Europe, even if the forest cover is growing. This means that human pressure on forests is harming their ability to naturally sequester carbon when climate targets require this carbon sink to largely increase. As forest management can either impair or improve biodiversity and ecosystem functions, a shift towards ecological forestry is urgently needed. Within the building sector, where climate impacts are huge and growing, a circular and long-lasting use of wood can be beneficial to replace conventional materials such as steel and concrete.

Timber buildings offer a typically lower embodied carbon and long-lasting carbon storage (see box below)6. If combined with high energy efficiency, timber buildings can present better whole life carbon performance than typical concrete and steel-structured buildings.

Embodied carbon is estimated to be responsible for 10-20% of EU buildings’ whole life carbon footprint, alongside operational carbon emissions, and up to 50% in countries with low-carbon energy. Greenhouse gases emitted from material extraction, manufacturing of construction products, as well as construction and renovation of buildings in the EU are on average estimated
at 5-12% of total national GHG emissions.

While a timber-based transformation of the building sector is desirable, timber demand for construction must remain within planetary boundaries. Sustainable use of timber in buildings and a transition to ecological forestry must be linked and addressed jointly in policies and standards.

At a time when climate and environmental policy is being shaped, policymakers face a unique and pressing opportunity to create a coherent framework for timber used in construction, and forestry.

A concerted switch towards mass-timber construction, if conducted without creating significant additional pressure on forest ecosystems and with systematic cascading of wood resources, can increase carbon storage in buildings globally by at least an order of magnitude. Research shows that if such construction were to become the norm by 2050, annual carbon storage could be as high as 700 million tonnes of carbon (MtC) instead of just 10 MtC in a business as-usual scenario. However, this requires optimised use of wood to prevent forest degradation and loss.

Our understanding of forests, wood uses and the climate, and biodiversity impacts of buildings are still in development, while industry standards lack precision. This is particularly the case for data and methods for assessing forest management impacts; the duration of carbon storage in products and buildings; and the overall balance of lifecycle impacts from forest to buildings. Policy should therefore support their improvement, but it should not rely on them to allocate incentives to industry until methodology
and data robustness are ensured systematically.

Even in the absence of quantitative methodologies, policy frameworks can already boost timber buildings’ lifetime and circularity (for example, with renovations). Policy can ensure that the cascading use principle applies to timber as a construction material and in other sectors to enhance the duration of its carbon storage effect and to moderate demand for primary wood resources.
Forest policies and standards must preserve forest carbon stocks (including organic carbon found above and below the soil) and the various ecological functions of forests.
It is important that policy makes use of certification requirements for ecological forest management (e.g. close to-nature forestry) and sustainable timber sourcing.

Policies and standards should also create more transparency regarding forestry and construction impacts and support the reporting of environmental information until it becomes mandatory. Finally, it is crucial that climate mitigation goals — including ambitions to increase carbon removals — do not eclipse other environmental policy priorities, such as circularity, biodiversity, and climate adaptation.


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