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[Solved] Trees supposedly take 30 years before they absorb CO₂. Why? (feddit.de)

submitted 11 months ago* (last edited 11 months ago) by [email protected] to c/[email protected]

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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.

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[–] [email protected] 14 points 11 months ago* (last edited 11 months ago)

I highly question this. A Dougie at 30 is about a foot across. I just took 7 Dougie's down on my lot, the largest was 24in at chest height. I can see Puget sound from my place. In fact, I actually counted the rings on one of them and it was 101 years old. Shit. Now I'm gonna go look and measure the 30. I dyed every fifth ring when I counted it initially.

K, so at 30y/o the only stump I left in the ground was only 8.5 inches across and 20in in diameter at 101, so that's an easy 24in with the bark. The tree was 120ft tall when I felled it in July. A real shame too, I wanted to keep all of them but fire damage. The next day beetles had already hit all of them. I dropped the trees a week after the fire and debarked them to help protect the wood before i could mill them, and there were hundreds of beetle tracks under the burned bark. Pine beetles live under the bark, in the cambium, no bark=no beetle. But the California wood wasps showed up the day I dropped the bark. Those things are terrifying, jet black, 2.5 inches long with an inch long stinger on top of that, so about the width of your palm. Adult pine beetles are about 3inches long when they emerge too. Wicked little fuckers, the both of them