(14d) Wooden cities the solution to reduce climate change?

An article published in The Guardian describes how mass timber projects in Portland, Oregon and New York City are believed to offer eco-friendly dwellings while the article questions whether ‘plywood on steroids’ can actually catch on in the industry.


According to the article, building mid-to-high rise wooden buildings may be a good alternative to building concrete buildings. It mentions that concrete needs to be transported and as it is heavy and fossil fuels are used, the transport results in the release of large quantities of green house gasses while wood is lighter and thus less of these gasses are released. The article also mentioned it 'will be New York City’s first to use mass timber systems'.

According to Amir Shahrokhi, one of the benefits of wooden houses is that the use of plenty of wood has demonstrated
"... to have considerable psychological benefits for the inhabitants, from reduced hearts rates and stress levels to improved productivity."
I can accept this argument as indeed natural material give a kind of comfort. Still, over the past few years replacements of wood were invented as building materials such as lamination that uses fewer if any wood but even sustainable plastic wood alternatives that resemble well the appearance of wood but isn't wood itself and thus these materials should also have some of the psychological benefits, certainly when houses are heated with underfloor heating so the lamination feels warm.

Figure 1: How many trees were needed to build those few small wooden houses?

It has always puzzled me how cutting trees to use the wood in the building industry can be eco-friendly and sustainable. I can accept that cutting some trees to use wood for some decorations while replacing the trees with new ones can be called sustainable. But cutting large areas of trees to build large or many wooden buildings (cutting only a few trees will be insufficient), can that be called sustainable? Indeed, we all know that forests disappear to build new cities and those forests never recover while additional areas disappear as people use wood for different purposes, including to make furniture that is sold abroad. And thus I posted following comment under the article:
I don't understand how cutting forests to build large buildings is environmental friendly. OK, when a few trees are cut to build a small house I can understand. But history has shown how whole regions are now without forests because we used the wood for building.

In addition, trees remove CO2 from the air and thus cutting them will reduce the amount taken from the air while, if we replant the forests, it takes trees years to become large. But the experts probably have studied all these questions.
I received three responses to my comment about how building large wooden buildings can be sustainable as I show below:

Reply 1
Seriously please research the topic of sustainable forestry...
Young tress remove carbon faster, better than older trees

Reply 2
Depends where the wood comes from. Like paper some of it comes from forests where they manage the land. This would usually mean plant in X trees for each one removed.
Wood also locks in carbon as it grows so you end up locking carbon in to your building for its lifespan until that wood is destroyed. (Much like charcoal under the ground)

Reply 3
" don't understand how cutting forests to build large buildings is environmental friendly"
OK, which forests do you think will be cut?
Although the first person seems to be bored to respond, he gives an explanation that seems plausible.

Also the second response gives an explanation while the same commentator explains it even better as a response to a comment from another reader:
... Unless you destroy the first tree you cut down (you won't since its ending up as construction material) your going to end up with two trees. Just one of them will now be planks and plugboard making up the walls/floors of a house. So your first tree with its X amount of carbon trapped in it still exists and your second freshly planted tree is growing locking in even more carbon. ...
Indeed, as long as the first tree that has been cut isn't burned, no CO2 will be released and thus CO2 from the sky was captured by the original tree while the new tree that replaces the first one further reduces CO2 from the air and thus the timber industry seems to be carbon negative. Nevertheless, I still have doubts because knowing humans, if they replant any trees, they will probably use the cheapest and quickest solution which isn't always the best. Indeed, another article in the Guardian seems to suggest that large biodiversity is needed both in trees but also in animals to capture CO2 while replacing hardwood trees in forests with softwood trees has less impact on the reduction of this gas.

And thus, as mentioned at the start but also in my comment, I can accept that using some wood in the building industry can be beneficial. Indeed, cutting some trees can even be good for the forest on condition we allow the forest to recover, first by allowing many plants to compete for light in the space that became available (and when they die they provide some new organic materials to prevent the soil exhausts) while finally one or a few smaller trees will fill the space, resulting in shadow so the smaller plants will disappear. But as I also mentioned, I think that for those big "sustainable" building projects, trees will not be collected from many different places but the easier solution will be used, i.e. many trees at one area will be cut and thus deforestation may accelerate. Indeed, the Amazon but also Indonesia's forest are examples where trees are cut to use locally and worldwide in the building industry and as a result large areas of forest disappear each year although they can be replaced with often monoculture (e.g. palm trees); this happens also elsewhere. Not only is this bad for climate change as less trees are available to remove CO2 from the air, it can also have devastation consequences such as landslides after heavy rainfall while tourism is affected because people want to visit what can only be seen at certain places in the world: large areas of forests. And thus when the forest is gone, why should people pay to visit those countries unless the eroded places are beautiful in themselves? Finally, monocultures are more vulnerable to diseases.

And although growing trees need CO2 to grow, I do not believe they capture as much C02 as adult trees of which some are centuries old. Compare with humans: although children grow and in comparison to their size eat more than adults, quantitatively they eat less than adults, even when adults at older age start to eat less than when they were in their twenties. Indeed, only the oldest humans start eating less than children and in general, this means they are close to the end of their lives. Similarly, large trees will probably also capture more CO2 and other gasses they need to survive than much smaller still growing trees. In addition, old trees provide housing and protection for many animals and even memories as animals will know that a certain tree provides food in a certain period of the year while trees also contribute to rainfall and thus the local and wider climate. Remove them and climate can change with unforeseen consequences.

Therefore, use of wood in the building industry can be useful if only small amounts are needed and when the tree population is kept healthy; this also provides work for loggers when trees are cut sensible and replaced with new ones. Still, experience informs us that mostly more trees disappear while if they are replaced, biodiversity in general decreases.

But trees should not only be living in forests, also plenty of living trees should be present in towns and cities as I think they provide even more psychological benefits for the inhabitants than wood that is used in buildings because people can enjoy walking under them, watching animals living in them while they refresh the air. And if these trees are cut, it is more likely they are replaced with new ones or the inhabitants will notice the reduction in greenery.

The third person who responded to my comments asks a question that I can answer: building large wooden skyscrapers requires huge amounts of wood and thus a few trees will be insufficient. Also hardwood may be used and thus tropical forests may be cut to provide the wood. Today people already complain that the West alone uses so much hardwood that forests are cut to provide sufficient amounts while new hardwood trees of different species are not planted because it takes too long for them to grow. And thus building large wooden buildings will require even more trees from forests that can't be replaced quickly enough.


And thus I still think that, instead of wood, concrete is the way forward. Indeed, concrete is beautiful if maintained well but also extremely strong as the Roman Emperor Hadrian's Pantheon demonstrates that still stands after almost 2000 years. In addition, it is much safer than wood of which few buildings survive the centuries because they can burn. Further, concrete walls can be painted or light can be projected on them to enliven the place. During the construction, all sorts of decorations can be plastered into the walls such as a resemblance of wood as is done in the National Theatre in London (see arrow in Figure 2B). Of course, the walls need to be cleaned sometimes but this is similar for all buildings. And if people are bored with the building, it can be broken down, the stone can be ground and reused. As a consequence, less new material than expected needs to be imported from far away and thus concrete is more eco-friendly than people think. Already, in modern cities concrete is used for many buildings, including (metro) stations.

Figure 2: A) View from river Thames of the Royal Festival Hall and National Theatre. B) and C) Details of the beauty of the concrete building - in B) the red arrow points to the "year rings" added as decoration in the concrete while C) shows other manners of decorations. During the night, the theatre is illuminated in different colours as D) shows. E) Saint-Paul's Cathedral that is built in limestone although to me, it is difficult to notice the difference with the concrete.


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