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Steel, plaster, concrete: In the 1920s, the Bauhaus art school in Weimar used these materials to establish an architectural style that soon became the flagship for modern living – in Germany and around the world. The designers disparaged the building material wood, it only disturbed the chic industrial look.

Today, around 100 years later in the midst of the climate crisis, a new study by the Potsdam Institute for Climate Impact Research (PIK) comes to the following conclusion: More living in new buildings made of wood instead of steel and concrete could avoid more than 100 gigatonnes of CO2 by the year 2100.

For this, 90 percent of the new urban population would have to be accommodated in such newly built wooden houses. The avoided greenhouse gases correspond to an amount that mankind currently causes in two years.

Abhijeet Mishra is a scientist at PIK and lead author of the study, which was published in the journal Nature Communications. In a Tuesday press release, Mishra says, “More than half of the world’s population currently lives in cities, and by the year 2100 that number will increase significantly.”

According to the researcher, this means that more houses will be built from steel and concrete, which usually have a large carbon footprint. “But we have an alternative: We can accommodate the new urban population in multi-storey buildings – we are talking about four to twelve floors – made of wood.”

For a sufficient supply of timber, tree plantations would have to grow by 149 million hectares worldwide by the end of the century – this corresponds to an area four times larger than the whole of Germany. “Our results show that the expansion of tree plantations for wooden buildings is possible without major impacts on agricultural production,” the authors write in their analysis.

Misha explains: “The production of wooden building materials releases much less CO2 than steel and cement. In addition, wooden building materials store carbon and make wooden cities a unique long-term carbon sink.”

In 2020 alone, the production of materials for new buildings using conventional construction was responsible for about ten percent of the world’s annual greenhouse gases. The cement required for the concrete accounted for around 1.5 gigatonnes of CO2, while the production of iron and steel caused around 3.5 gigatonnes of CO2.

Alexander Popp, also a scientist at PIK and co-author of the study, remarked: “In our computer simulations we have set a clear limit for logging and establishing new tree plantations: Nothing may be cut down in pristine forests and protected areas for biological diversity.” The explicit Protection of these areas is extremely important.

But Christine Fürst is skeptical when it comes to the scarce space. She is Professor of Sustainable Landscape Development at the Institute for Geosciences and Geography at the Martin Luther University Halle-Wittenberg and was not involved in the study.

“In general, the scenarios that are very much in the direction of an expansion of ‘timber plantations’ would come very strongly into conflict with the food supply,” explains Fürst in an assessment for the Science Media Center (SMC). She didn’t completely see through where the areas should actually come from. In addition, the authors did not include how available, productive and usable the areas would be in the face of progressive climate change in the future.

The researcher also points to a problem in Europe: “Due to the heat waves, many of our forest stands have died back and the quality of the wood has also been affected by pests. This results in a large amount of damaged wood on the market, which is sold off at extremely low prices.” It would take at least 30 to 50 years for new wood from renewable stocks to be available here.

In this period of time, however, we can expect cities to grow rapidly and the need for new living space to increase as a result. Jürgen Bauhus, professor of silviculture at the Albert-Ludwigs-Universität Freiburg, is more confident about the scarce areas.

At first glance, the additional 149 million hectares seemed a lot. At second glance, however, this is quite realistic. “For example, about 420 million hectares of forest have been converted to other land uses since 1990,” Bauhus tells the SMC. “The required areas thus represent a moderate reconversion into forest areas.” Reduced meat consumption could contribute to converting agriculturally used areas into tree plantations.

The need for new living space and thus also for building materials is expected to remain high: According to a report by the United Nations, 6.7 billion people could live in cities by 2050. That would be around 2.5 billion more than in 2018.