By Paul Brannen, author of Timber! How Wood Can Help Save the World from Climate Breakdown (Agenda Publishing, 2024). This is the latest in our series exploring climate solutions.   

Chopping down trees to help solve climate breakdown appears to be counterintuitive, but the science backs this approach when sustainably grown mature trees are used in place of carbon-intensive building materials.

Let me explain.

There are different ways of classifying the carbon emissions responsible for the dire state of the climate. One classification identifies the built environment as the single biggest source of emissions, with 28% of emissions linked to building operations (i.e., heating and cooling of buildings) and 11% linked to the materials used. 

The 28% figure can primarily be addressed by retrofitting virtually the whole of the world’s building stock with significantly higher levels of insulation that can both keep buildings warmer in cold weather and cooler in hot weather. At the same time, all new buildings need to be highly insulated such that they require virtually no heating or cooling. These interventions would massively reduce energy use – energy which is still mainly generated from fossil fuels. 

Regarding the 11% figure, one construction material stands out as more problematic than all the rest combined – concrete, which is responsible for 8% of global carbon emissions, more than the whole of the EU. There are two reasons for this, both of which are linked to the manufacture of cement, a key component of concrete. Firstly, the chemical process of extracting lime from limestone generates emissions. Secondly, generating the high temperatures that the process needs involves the burning of fossil fuels. 

Steel manufacture, whether virgin or recycled, also needs high temperatures, hence it too has a large carbon footprint (i.e., a high level of embodied carbon).

With the world’s population continuing to grow exponentially, the demand for homes – a human right under the 1948 United Nations’ Declaration of Human Rights – will make it impossible to prevent runaway climate breakdown. Why? Because the majority of the rising global population, given current construction practices, will be housed in flats made from concrete and steel.  

The solution? Timber has very low levels of embodied carbon, and due to new applications, known as mass or engineered timber, it can now be used to build to over 20-storeys. The key point to note is that these engineered timbers can substitute for reinforced concrete and/or steel in the majority of large buildings. 

Professor Michael Ramage of the University of Cambridge calculated that erecting a 300-square-metre, four-storey student residence in wood generated only 126 tonnes of CO₂ emissions. If it had been made with concrete, the tally would have risen to 310 tonnes. If steel had been used, emissions would have topped 498 tonnes. Indeed, the wood building can be viewed as ‘carbon negative’ as there is the equivalent of 540 tonnes of CO₂ stored in the timber, resulting in a long-term removal of CO₂ from the atmosphere.

This additional ability of timber buildings to store carbon, as well as substitute for more carbon-intensive materials, is also significant in the battle against climate breakdown. A recent set of UK case studies produced by architects dRMM found that mass timber buildings averaged 1,000 tonnes of stored carbon. Combining these levels of carbon storage with the storage delivered by two storey family homes built with ‘ordinary’ timber could produce an impressively high level of national carbon storage, high enough to match the UK government’s proposed Carbon Capture and Storage scheme under the North Sea and Irish Sea (i.e. 8.5 million tonnes of carbon).  

Back in 2009, the world’s tallest timber apartment block at nine-storeys was built in Hackney, London. This record subsequently moved to Norway, then Canada, then Austria, and then back to Norway, who currently have the world’s tallest mixed use timber building at 18-storeys. Note, this building contains offices for Norway’s largest insurance company and I don’t think they would be there if they believed tall timber buildings weren’t as safe as concrete and/or steel! 

Meanwhile, the UK’s major house builders are shifting from brick and block structures to timber frames, in part because it’s a faster and more accurate way to build. This will significantly reduce the climate footprint of UK house building. It is also a shift that will bring England in line with Scotland where over 90% of family homes are already built with a timber frame, compared to less than 10% in England.

A switch to building more with wood rightly raises questions around the supply of sustainable timber. Reassurance here is provided by Sir David Attenborough speaking in a WWF video on forests in 2019, who said: 

“It is a fact that our growing global population will need to use more wood and that could be a good thing. Wood is an extraordinary renewable resource and taking it from well managed sources benefits forests and the planet. But on their own, natural forests can’t provide all the wood we need, so we also have to farm trees, just like we do other crops, and create a new generation of plantations.”

This, then, is why chopping down trees is necessary: to provide the timber to build more homes in the UK, across Europe and globally. But it has to be done in a sustainable way – hence when trees are felled, replanting must follow (i.e., the overall forest area should remain constant – or better still – expand). In the UK, it needs to expand as we have only 13.5% forest cover and we are the second biggest importer of timber in the world after China, with 80% of wood sourced from countries such as Sweden, Finland, Germany and the USA.

To conclude, more sustainable timber in more buildings could significantly reduce global carbon emissions via material substitution while simultaneously safely storing  vast amounts of carbon for decades.

Paul Brannen is former head of campaigns at Christian Aid and a former UK MEP. He now works for the Confederation of Timber Industries and is the author of Timber! How Wood Can Help Save the World from Climate Breakdown (Agenda Publishing, 2024).