Comment by yobbo
4 days ago
> Too bad that we are currently doing the exact opposite (cutting down more forest than is regrown)...
Carbon is captured when trees grow. Lumber binds carbon into buildings and constructions.
4 days ago
> Too bad that we are currently doing the exact opposite (cutting down more forest than is regrown)...
Carbon is captured when trees grow. Lumber binds carbon into buildings and constructions.
Old forests sequester more carbon than new ones. When you cut down a tree, you leave half of it under ground, and when the roots break down all that carbon is released to the atmosphere.
It is far from straightforward whether it is better to leave the forests standing or cut down and replant. The forestry industry is of course claiming that a cultivated forest is better for the climate. The environmentalists are claiming that old forests that are left alone are better for the climate and in addition better for ecological diversity.
I tend to believe the side whose income doesn’t depend on their claim.
Sounds dubious. Most trees are not nearly 50% roots by biomass. The roots that remain will get broken down, but not into gases exclusively. A new tree that’s growing is actively capturing new carbon. Cutting down a tree won’t help much, but if a new tree grows where the old one was, it’s hard to find reasoning to suggest a net loss.
What happens to the parts that are cut down and used is what matters. If you build long-lasting houses from them, then it's probably good for the climate, as long as new tree is planted in its place. If you use the wood to make toilet paper, then it's not so good for climate since that carbon will return to the atmosphere faster.
>and when the roots break down all that carbon is released to the atmosphere.
How do you figure, exactly?
Bacteria and other organisms “eat” the wood, and then “breath” out CO2 (and sometimes methane).
https://en.wikipedia.org/wiki/Soil_respiration?wprov=sfti1#
It’s a net negative over time if the square footage that was housing a tree is replaced with grassland or a neighborhood. You trade a one-time, one-tree-sized fixing event against all fixing by all future generations of trees on that spot.
The climate math of lumber works if you’re talking about “productive forests” where trees are allowed to grow to replace trees cut down. It doesn’t work for situations when a forest is cleared and not replaced, which is mostly what is happening where rainforest is being cleared.
In the USA, at least, most the lumber for home construction is farmed. We don't rely on "old growth" for much anymore.
Meaning the forests are kept forests and new trees are planted to replace the ones that are cut down. The land the trees are farmed from is kept forested because it provides a income source for the owners. Also the trees tend to grow much faster then they do in natural forests because things like spacing out trees is optimized.
This is a big complaint for wood working folks, ironically. Because natural grown trees grow slower the wood grain is much tighter and ends up being generally higher quality. Where as modern farmed wood has huge rings.
Although it isn't too bad because you don't use soft woods much for things like furniture making. Where as construction lumber is almost all soft wood.
So at least in the USA the ratio of grown-to-cut wood is about 1.92. So we plant trees nearly 2 to 1 versus what we cut down.
I guess a tree farm (if the trees are used for construction and not burning) would be significantly net negative for atmospheric carbon, especially if the operation was entirely powered by solar and electric?
Most (all?) of the carbon sequestered by a tree that dies and rots on the forest floor goes back into the atmosphere. So the "fixing by all future generations" is just the same carbon sink as the current 1 alive standing tree for that spot of real estate.
Regardless, the net carbon sink of a healthy forest is higher than the net carbon sink of a few houses that were built in its place.
Simply think of the number of tons of wood in an acre of forest, compared with the number of tons of wood in a housing development.
It doesn't matter that some trees die and release their carbon, other trees grow. Instead of thinking of individual trees, simply think of the entire biomass of the forest.
A tiny amount is turned to coal (often via forest fires) which then isn't returned to the cycle. We are talking about -0.1C over thousands of years though, if we otherwise went carbon neutral - which seems unlikely for the long tail of small users but if we get the major uses of fossil fuels to something carbon neutral that would get us very close to stopping global warming at least.
I’m talking specifically about when trees are used for lumber.
I think the subsistence farmers cutting down the Amazon are doing more burning than construction.
Much less than half of the tree mass is used that way. (But of course also the part in buildings is there only temporarily, for the lifespan of the building)