[lazide]

Forests are not long term carbon sinks. They flatline rather quickly.

This is obvious to anyone who has spent much time in a forest, because if this wasn’t the case, forests would be sitting on thousands of feet of sequestered carbon. Instead of a few feet (typically) of non-mineral soil.

Forests also (typically) go through cycles of burning.

The highest rate of carbon sequestration is when a forest is in the 3-25 year old range, because that is when the bulk of the actual growth is occurring.

Renewable doesn’t mean ‘indefinite carbon sink’. Renewable means ‘renews’.

This entire discussion is incredibly ridiculous.

[knappe]

Look dude, read the papers or read the book. I don't have much more to offer you. This isn't just about the forest itself but about the land used to grow the forest.

"In the Carbon Costs of Global Wood Harvests, published in Nature in 2023, WRI researchers using a biophysical model estimated that annual wood harvests over the next few decades will emit 3.5-4.2 billion tons of carbon dioxide (CO2) per year. That is more than 3 times the world’s current annual average aviation emissions. These wood-harvest emissions occur because the great majority of carbon stored in trees is released to the atmosphere after harvest when roots and slash decompose; as most wood is burned directly for heat or electricity or for energy at sawmills or paper mills; and when discarded paper products, furniture and other wood products decompose or burn. Another recent paper in Nature found that the word’s remaining forests have lost even more carbon, primarily due to harvesting wood, than was lost historically by converting forests to agriculture (other studies have found similar results1). Based on these analyses, a natural climate solution would involve harvesting less wood and letting more forests regrow. This would store more carbon as well as enhance forest biodiversity."[0]

[0]https://www.wri.org/technical-perspectives/wood-harvest-emis...

And the original paper that introduced the idea of land use https://www.science.org/doi/abs/10.1126/science.1151861

[MOARDONGZPLZ]

So I see what you’re saying. You’re talking about the whole system. Take land and then plant trees, the trees sequester carbon as they grow, some of them fall to the forest floor continuing to sequester carbon. But, I think the issue with your argument is, this process isn’t indefinite. The natural cycle is that these trees will decay, fall, rot (releasing carbon naturally) or natural forest fires will burn them anyways (releasing carbon naturally). Then more trees will take their places and sequester carbon, ad infinitum in the cycle that has taken place for the last 2 billion years since the Paleoproterozoic era.

But I see no difference between humans speeding this cycle by planting quick growth trees, cutting them down, releasing their stored carbon, planting more. It’s the same thing being sequestered and released continuously.

[wizzwizz4]

The planet isn't infinite: by running the cycle more quickly, you knock the "baseline" atmospheric carbon up a few more ppm. This has knock-on effects.

[lazide]

Even if we converted all arable land in the United States to forest, best case we would take many years to sequester even a single years fossil carbon emissions. And we’d all starve to death in the process.

Any co2 released by harvesting a forest, is very shortly taken back up again by the forest regrowing. Within a lifetime for sure.

Trees are nice, I get it. But this is all in the noise.

[wizzwizz4]

Where do these numbers come from?

[lazide]

USFS studies, and US data on overall arable land. I broke it out in a prior thread exhaustively, but it’s been covered in other areas too. Here is one [https://www.nrs.fs.usda.gov/pubs/gtr/gtr_wo059.pdf]

The US emits a truly massive amount of fossil carbon. [https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emis...], “Total emissions in 2022 are 6,343.2 Million Metric Tons of CO₂ equivalent”. Yes, that is 6 billion metric tons of co2 equivalent a year. 6 trillion kg. Or about 20,000 kg per person in the US, every year.

Currently (since ~ 1990), US forested land is estimated to offset ~ 13% of fossil co2 emissions. Forests cover 36% (!) of US land area, and have been slowly increasing since ~ 2000.

Farmland covers another 39% of US land [https://www.nass.usda.gov/Publications/Highlights/2024/Censu...].

Pretty much all the rest is either 1) waterways, 2) cities, 3) non-arable land like steep mountains and deserts with no ready source of water.

So even with a back of the envelope, easy math, if we changed all our farmland to grow forests, we’d roughly double the amount of carbon we could sequester - which would still be ~ 25% of the amount of fossil carbon we’re emitting, every year.

And then we would still need to DO something with all that wood, because burning it or letting it rot just releases all it’s co2 back into the atmosphere.

And we’d all starve to death in the meantime.

[dmbche]

Go look at the article about the effects of the introduction of wolves back in yellowstone that was frontpage yesterday.

That f'ing with one species.

Now imagine the impact of f'ing with the forest itself.

Could the capacity to sequester carbon be affected by second or third order effects?

[lazide]

Modeling a forest like a spring is a better model than a petrochemical reservoir. (Though a water reservoir is not a terrible analogy if forest fires == a dam breaking! And overflows or evaporation == rotting.)

The (very common) thinking that forests are ‘sinks’ (aka it goes in one way and stays) or like a petrochemical reservoir (we can put it in, or take it out - but it stays there once in, or out) are a big part of the confusion.

On a geological timescale, carbon being stored in a forest is a temporary and rather rare circumstance. Some global percentage will always be in vegetation (see carbon cycle), but any given atom will move around a lot.

Harvesting forests and burning them, takes carbon that was in the atmosphere, then in wood, then puts it back in the atmosphere. Total carbon in the atmosphere was only temporarily out of it in this situation.

If we wanted to permanently take it out of the atmosphere, we’d need to bury all those trees (deep enough where they won’t decompose and/or the decomposition products won’t make it into the atmosphere!). Turning it into furniture or building products is a more useful, but shorter term solution.

One idea-logically most pure solution would be to puree them and inject them into old depleted oil fields, eh?

Because otherwise those trees will just burn, die and decompose, etc. - it’s inevitable.

Ideally they would be replaced in a shortish timeframe by new trees or growth, roughly locking up the same amount of carbon. But that doesn’t always happen.

And people aren’t allowed to clear cut forests in the US (generally) anymore. Most (all?) US timberland is multi-generational new growth now at this point, and is harvested using as realistically healthy a process as possible. If we had battery powered industrial equipment, it would be even better.

I’ve read the papers, and I’ve done the math many times.

The amount of carbon being released by burning the trees, is roughly the same amount as was taken out by them growing. That’s the nature of it. When they regrow,they’ll take more out.

That is the nature of being renewable. Unlike fossil fuels, where chances are no more will replace it naturally.

Complaining about someone cutting down the trees, specifically from a ‘renewable’/‘total carbon’ perspective is silly in this context. The carbon released isn’t even fossil carbon, and will be back in the trees soon enough - less than a lifetime!

And I’ve done the math - even if we turned all of the arable land in North America into forests, based on the USDA data from National Forests, it would take 4-10ish years worth of growth to temporary store 1 years worth of fossil carbon being released just by the US right now.

Every year.

And to even try that, we’d all starve, because we turned all our crop land into forests too.

Worry about the massive quantities of fossil carbon still getting sucked out of the ground. That is what is feeding the impending disaster.

Unless people are salting the earth and stopping further growth (which generally is already forbidden in the US!), cutting down and burning a forest is a temporary nudge in the accounting that will self correct.

Generally most of it will get used in lumber though, which means it should net decrease atmospheric carbon until it rots or burns in a fire. If landfilled, it could go thousands of years.

In summary - the math doesn’t actually check out when you look at it over realistic timescales, and this is more an ideological thing than an actual real thing. I love trees. But they aren’t going to save us from this mess, no matter how hard core we go.

[vintermann]

Sinks is about flows. The question is about reservoirs. Forests are a long term carbon reservoir. Yes, it's possible to regrow it and let it stay that way. But we don't do that if we regularly chop it down for wood pellets. If we regularly do that, then the carbon in it will spend more of its time in the atmosphere and cause trouble, even if it wasn't pumped from a fossil reservoir.

This is why you can't ignore land use changes in carbon budgets. It's a sound argument, it's not ridiculous at all.

[rrobukef]

I disagree, wood pellets are more expensive than oil for energy, especially if only counting the production cost of oil w/o the tax. So even the first time an old forest is cut, when the land changes, it already displaces oil use. At greater expense even, so demand would be reduce the amount energy produced further.

Furthermore Europe can also choose to replant non-forest land or replant permanently afterwards.

[fodkodrasz]

The soil they create, if they stay alive and are able to retain the soil layer, is gradually washed away (and locally replenished) and is fertilizing the lowlands.

[littlexsparkee]

Even fast growing trees need 10-20 years to start storing significant amounts of carbon and old-growth forests can sequester it for hundreds of years.

[lazide]

The challenge is that old growth forests, while retaining carbon, don’t pull much net carbon from the atmosphere. Their ‘spring’ is nearly fully compressed.

They are really beautiful and important, but they aren’t doing much when it comes to reducing atmospheric carbon anymore.

As ugly as it is, chopping them down (as long as we can stop the wood from rotting/burning/etc) and then having new trees grow in their place does more actual atmospheric carbon reduction.