Timber in construction - a climate change challenge

A recent report has claimed that Canada's forestry industry in general and industrial logging in particular, plays a far larger role in the nation's carbon emissions than had previously been acknowledged. This in turn has led to a renewed debate about the sustainability of timber use in construction and its true environmental impact, writes John Ridgeway.

The findings may shock many, as the use of timber in construction has long been considered a sustainable and environmentally friendly alternative to more carbon-intensive building materials such as concrete and steel. Timber is often celebrated for being a renewable resource that can sequester carbon throughout its growth cycle, thereby contributing to the reduction of greenhouse gas (GHG) emissions, however, the reality is more complex.

In some contexts, such as industrial logging in Canada, it can be shown that timber harvesting can contribute significantly to climate change due to unsustainable logging practices and the degradation of natural carbon sinks – and if it is happening in Canada, we can be reasonably sure that the same problem is occurring in forests across the globe.

Logging in Canada is a significant driver of climate change, contributing much more to the country’s GHG emissions than the government has historically reported. For many years, the Canadian government has employed an accounting system that has masked the full extent of the emissions associated with logging, classifying the forestry sector as either carbon-neutral or even as a net carbon sink. However, a closer examination reveals a much more troubling reality.

Logging’s true climate impact

According to the latest Greenhouse Gas Emissions: National Inventory Report (2024), human activities on managed forest lands were responsible for net emissions of between 24 and 85 megatonnes (Mt) of carbon dioxide equivalent (CO2e) annually from 2005 to 2022. Yet, this official estimate still underreports the true impact of logging on GHG emissions. Independent analysis suggests that logging emissions in 2022 were closer to 147 Mt, making logging the third-highest emitting sector in the Canadian economy, after oil, gas and transport.

This discrepancy arises from the way emissions are classified. For example, the government does not count emissions from natural disturbances such as wildfires, yet it credits the forestry industry with the carbon sequestration benefits of forests regrowing after these disturbances. This approach skews the overall carbon balance and significantly downplays the emissions caused by logging.

Timber has been lauded as a low-carbon alternative to steel and concrete in construction because of its ability to store carbon during its life cycle. When trees grow, they absorb carbon dioxide from the atmosphere through photosynthesis, locking it into the wood. This stored carbon is retained as long as the wood remains in use, whether in furniture, buildings, or other wooden products.

However, the environmental benefits of using timber in construction depend heavily on how the wood is sourced. Sustainable forestry practices, which include replanting harvested areas which minimise forest degradation, are crucial to ensuring that timber remains a viable, low-carbon building material. Unfortunately, large-scale industrial logging, particularly in regions such as Canada, often leads to deforestation, forest degradation and the release of stored carbon back into the atmosphere.

Timber as a Renewable Resource

In theory, timber is a renewable resource, meaning that forests can regrow after trees are harvested, continuing the carbon sequestration process. Sustainable logging practices involve carefully managing forest resources to ensure that trees are harvested at a rate that allows for regrowth. This process is often referred to as "harvest and regrow" or sustainable forestry.

However, timber’s renewability is compromised when forests are harvested at unsustainable rates, or when logging leads to long-term ecological damage. This is particularly problematic in boreal forests, like those found in Canada, where logging can disturb carbon-rich soils and slow the regrowth of trees, causing forests to become net emitters of carbon rather than carbon sinks. Furthermore, logging in these areas often replaces diverse, old-growth forests with monocultures or tree plantations, which have less biodiversity and store less carbon.

The recent recalculation of Canada’s logging-related emissions has shed light on the extent to which logging contributes to climate change. The key findings from this recalculation are striking. In 2022, for example, logging was responsible for 147 Mt of CO2e emissions, a figure that places it among the top three emitters in Canada, surpassing even agriculture and electricity generation. This demonstrates that logging is not a carbon-neutral activity.

The federal government’s official figures for forestry emissions in 2022 were just 24 Mt. The significant difference between this figure and the 147 Mt estimate for logging emissions suggests that the impact of industrial logging is being grossly underreported. Even worse, previously logged forests continue to emit more carbon than they sequester, even after reforestation efforts. This is due to the disturbance of carbon stored in soils and the slow regrowth of trees in certain forest types.

The logging sector’s significant carbon footprint raises important questions about how timber is sourced and used in construction. While timber can play a role in reducing the carbon footprint of buildings, it must be harvested and managed in a way that minimises its contribution to climate change.

Sustainable timber use in construction

Firstly, we need to ensure that timber contributes to climate change mitigation rather than exacerbating the problem. Using timber certified by reputable sustainability standards, such as the Forest Stewardship Council (FSC) or the Programme for the Endorsement of Forest Certification (PEFC), ensures that wood is sourced from forests that are managed responsibly. These certification schemes take into account factors such as biodiversity protection, carbon sequestration and forest regeneration.

It is also essential that builders and developers prioritise timber that comes from responsibly managed forests where logging is done in a way that allows forests to regenerate and continue sequestering carbon. This includes avoiding timber sourced from old-growth forests or regions where deforestation is rampant. In addition to sustainable logging practices, efforts should be made to restore degraded forests and plant new trees. Reforestation and afforestation projects can help offset the carbon emissions from logging and construction activities, contributing to global efforts to combat climate change.

Timber should also be used as efficiently as possible to minimise waste. This includes designing buildings that use timber in a way that maximises its carbon-storing potential and uses, where possible, engineered wood products like cross-laminated timber (CLT) that can reduce the amount of raw timber needed in construction.

That said, timber remains an important material for reducing the carbon footprint of the construction industry, but as we have shown, it is not without its challenges. Unsustainable logging practices, especially in regions like Canada, are contributing significantly to global greenhouse gas emissions. As the recent recalculations of Canada’s logging emissions have shown, industrial logging is far from being the carbon-neutral activity it has often been portrayed as – and this should be a wakeup call for us all.