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Comment by antognini | Hacker News Reader

Trees are a temporary carbon store, but the issue is that they eventually die and rot, and then that carbon gets released right back into the atmosphere. A permanent solution would be to grow trees, chop them down, and then bury them.

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Alternately, let new trees grow to take the place of trees that die.

This is yet another stock/flow issue, where the sequestered carbon is a function of the stock of living trees, which itself grows with the delta of trees added - trees removed. You don't need to manually manage the lifecycle of each individual plant, just focus on the increasing the living stock, or rather, letting the living stock increase all on its own in response to more carbon in the air. So this is about land zoning and habitat protection, not building little coffins for individual trees. Let forests grow and protect their habitat, they will grow all on their own if allowed to.

FYI we've added 60 million hectares of forests since 2000. That process can be even expanded.

Yes, this is true. If you can create a stable forest then that becomes a carbon sink for the lifetime of the forest. It is still hard to see how this is going to make a big difference. The biomass of the Amazon rainforest is ~120 gigatons. Annual CO2 emissions are right now around 30-36 gigatons. Growing a new forest the size of the Amazon would make up for about four years of emissions.

Of course that doesn't mean that reforestation isn't valuable. It certainly is. But even enormous growth of forest wouldn't make a big dent in atmospheric CO2 levels. The carbon came from underground and almost all of it will have to return underground to get CO2 levels down.

Those are valid points. But you don't need to add the square footage of the Amazon, what also happens is that forests become more dense per square foot. But not only forests, grassland sequesters about 343 gigatons and that rate has been growing at half a gigaton/year as the grassland gets taller/denser due to increasing carbon in the air. Biomass in topsoil itself sequestors twice as much carbon as biomass in trees, but this covers only 3% of the earth's surface. This paper has a nice overview[1]

[1] https://innovate-eco.com/storing-carbon-in-plants-and-trees-...

“the issue is that they eventually die and rot, and then that carbon gets released right back into the atmosphere”

You make it sound like a rapid process. Univ of Arizona did a study that showed CO2 emissions of dead trees was lower than living ones due to the rotting process being very slow compared to a living trees normal respiration cycle

Well the timescale of climate change is on the order of a few decades to a century. The decomposition process is somewhat slow by human standards, but it's still fast compared to a century. In order to effectively remove CO2 from the atmosphere to prevent climate change, it needs to be removed on timescales longer than a century.

decomposition doesn’t evaporate the tree into the air, it can build the soil and become habitat for larger animals (which also count as biomass)

You can cut them down regularly and turn the wood to biochar and bury it. That is fairly stable in the soil. If you just bury them normally they'll decompose back to carbon dioxide much faster.

Bacterial rot is not the only thing that trees can turn into: their carbon can enrich the soil and be consumed by insects, fungus, lichens etc that goes onto feed higher species on the food chain. On top of that, rotting trees is fantastic habitat for animals, which are also made of carbon.

Grow trees, chop them down, and build houses. We still have a housing shortage.

So long as lifespan is on the order of 100 -- 1,000 years, the net gain is all but certainly worthwhile.

I still favour wetlands over trees as a first priority.

Mature forests are carbon neutral because new growth will take the place of growth that dies and decays.

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