I often hear science-adjacent folks stating that a tree needs to be 30 years old before it starts absorbing CO₂, usually paired with the statement that it’s therefore pointless to start planting tons of trees now for slowing climate change.
Now, as far as my understanding goes, the former statement is very obviously nonsense. As soon as a tree does photosynthesis, it takes carbon out of the air, which it uses to construct cellulose, which is what wood is made of.
Really, it seems like it would absorb most CO₂ during its initial growth.
I understand that it needs to not be hacked down + burnt, for it to actually store the carbon. But that would still mean, we can plant trees now and not-hack-them-down later.
I also understand that some CO₂ invest may be necessary for actually planting the trees, but it would surprise me, if this takes 30 years to reclaim.
So, where does this number come from and is it being interpreted correctly? Or am I missing something?
Edit: People here seem to be entirely unfamiliar with the number. It might be that I’ve always heard it from the same person over the years (e.g. in this German video).
That person is a scientist and they definitely should know the fundamentals of trees, but it was usually an offhand comment, so maybe they oversimplified.
Volume of a cylinder is πr^2Height
Assuming the height of the tree stays the same, let’s say 100’.
Radius is 2’ and then we have a 500 year old with a radius of 5’
2’ x 100’ tree has a volume of 1256’
5’ x 100’ tree has a volume of 7852’
Trees are made of carbon. Older trees sequester more carbon
Young trees of many species also grow faster, though, and if the old tree dies and decays all that carbon returns to circulation. Forestry, done right, actually is carbon negative. However, it’s also incompatible with the critters that need old-growth forests (and old growth itself soaks up carbon fairly slowly). Environmentalism needs to get better at appreciating tradeoffs IMO.