The Case for Sustainable Timber
Can cutting down trees slow the effects of climate change?
The world is changing. This isn’t a metaphor for adaptive technology revolutionizing the workplace. The actual world is changing. Hundred-year floods are happening every five years. Hurricanes are lasting longer than ever. Heatwaves are ravaging Europe. These events show climate change (or crisis if you read The Guardian) having an impact on all of us.
This is a serious challenge facing the world of construction. It’s got a rep as one of the most wasteful industries on the planet. And manufacturing building supplies impacts climate change. We all know the cliché term for someone trying to save the planet is a tree-hugger. It’s a given that trees = good. So, would you believe that cutting down an old tree and building a timber structure with it was good for the environment? What if there was science to back it up?
Gassing the planet
While the cause of climate change is complex, one of the simpler explanations is this: over time, levels of greenhouse gasses in the atmosphere have increased. Carbon dioxide (CO2) traps heat and global temperatures rise. You can draw a line from CO2 in the atmosphere to the polar ice caps melting and raging forest fires in North America. That’s why organizations and governments are working hard to limit carbon production.
Timber frame buildings can help. There’s no denying that cutting down a tree for construction has a carbon footprint. Transport. Processing. Delivery. They’re all carbon intensive. But compare that to the alternative. Pulling iron ore and limestone from the earth to make steel and concrete burns a lot of energy. Then the raw materials must be heated above 2,700 degrees Fahrenheit before they can even become building materials. That’s just one reason why cement is the most energy-intensive of all manufacturing industries according to the U.S Energy Information Administration. Even steel, which in comparison is much easier on the planet, is still five time more energy intensive than wood.
If you look at the sustainability footprint in terms of embodied energy, there’s going to be a lot less carbon needed to create that end post-and-beam element. You look at the forestry-processing footprint versus everything that needs to go into a similar beam of steel. Steel doesn’t grow out of the ground. Trees do.
The carbon conundrum
Cutting down trees creates less carbon than mining iron ore. But trees are also excellent at taking CO2 out of the atmosphere. How can you reconcile that?
To really get into this, we need a little refresh on high school biology. Trees take the light of the sun, water from rain and CO2 from the atmosphere to make energy in the form of sugar. This is called photosynthesis. Trees take carbon out of the atmosphere and store it. This is carbon sequestration and it lets us breathe a little easier.
Holding on to carbon
In April 2019, CO2 levels in the atmosphere reached an all-time high. Cutting down trees to fix that doesn’t seem to track, but there is method to it. The trick is sustainable timber practices. Instead of cutting down the whole forest, only some of the trees in a particular area come down. That’s selective harvesting.
“Timber management is an important part,” says Kai Zhu, assistant professor in the department of environmental studies at the University California at Santa Cruz. He examined how different factors affected a forest’s ability to sequester carbon over time. “Simply removing the timber does not necessarily mean we are taking the ability of the forest to take out carbon. This is something about forest management: if you remove the timber, then the forest will regrow.”
Cutting through the science
Here’s how it works. A tree grows at different rates over the course of its life. When it’s younger it needs more energy for growth. It pulls more CO2 out of the air to get that energy. As the tree gets older, that process slows down. Old-growth trees are still taking carbon out of the air, but overall, the forest system isn’t using as much carbon.
“Old-growth forests have fewer trees,” says Kai. “In a young forest, you have more individuals and they grow faster as a system. The old-growth forests have fewer individuals and as a system they grow slower.” If a large old-growth tree is cut down and young fast-growing trees are replanted in the area, this forest system can take on more CO2.
Most of the carbon pulled out of the atmosphere is stored for the life of the tree. Once it dies and starts to decompose, it slowly releases carbon back into the atmosphere. If that tree is harvested and used in construction, the carbon remains locked in the wood. Score one for selective harvesting. It’s also good for forest health. It protects against erosion. And forest fires. When forests burn, they release large amounts of stored carbon back into the atmosphere quickly. That leads to increased global temperatures. Fewer fires will help keep climate change in check.
“If we can be smart enough to devise a management strategy that can capture the fast phase in the growth, we can do a better job in the carbon sequestration,” says Kai.
Europe is where we see this management strategy at work. The forest-management legislation is stricter in most European countries than it is throughout the rest of the world. This holds producers to higher environmental standards. Schilliger Holz is a Swiss timber company that subscribes to selective, sustainable harvesting practices. Under Swiss law, clear cutting forests is outlawed. Schilliger Holz will only remove 25% of the wood in a harvesting operation. These limits on harvesting ensure a healthy ecosystem. Clear cutting leads to nutrient removal from the soil. It also increases nitrogen levels in the ground water which impacts animal and forest health. Selective harvesting avoids this.
Schilliger Holz puts limits on how often they tap into the resources of a particular area. They cycle through their forests every five to 10 years, harvesting only the volume of trees that have grown during the interim. That time allows the forest to regenerate on its own, which means no artificial planting is necessary. And because 50% of forests are certified by the Forest Stewardship Council®, 10% of these spaces are set aside, remaining undisturbed by industry.
Trending towards timber
Studies show that using sustainably sourced wood building materials can reduce greenhouse gases. It’s something that has been embraced in Europe where timber structures date back almost 10,000 years. North Americans haven’t bought in as eagerly, but the tide is turning. Because it has to.
“[We] may not be building 18-story condo buildings out of wood, but you are going to be seeing that in the next five to 10 years, because we just don’t have the materials to create the buildings we need,” says Fahssi.
“As we get more and more people moving to urban environments, we’ve got to build more buildings. There’s housing crises everywhere. What material can we actually leverage to do that in the timeframe we need without putting more damage on the planet?”
“We have this great resource – trees. They can be regrown – planted at sustainable rates. That’s where I think the wood case comes from.”
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