There's no reason not to plant trees in addition to everything else we'll need to do to fix this problem. The advantage of planting trees is that we know it works, it's cheap, and we can do it right now. So some people should be doing that, and others should be doing R&D on other means of carbon removal. No need to pit one against the other.

I totally agree and I'm sorry if I gave the impression that trees should not be part of a solution. Trees (and other nature based methods) should definitely not be neglected.

I merely wanted to try and raise some awareness to those who question the need for technological removal methods as there is a bit of a toxic "trees will save us" attitude when things like this get mentioned.

This kind of civil discourse is what makes HN such a gem on the internet.

Meta-warning;

I'm more into the juxtapositions of interactions between idiots vs experts, specialists vs generalists, startup-billionaire vs unemployed-drug-addict-hacker, and the level of insight that can be gained from these conversations.

I believe that the civility, and desire for unfettered conversation (avoiding ad-hominem, flame-wars. etc···) are more of an instrumental-goal of this process, than the true goal.

I don't really know why the comments on hn are the way they are, and I doubt anyone ever will. But that's what keeps me coming back here. It's the only place on the internet I can get this kind of thing, whatever it is.

I do have to say, there's something special and unique here. Like the userbases of wikipedia, stack overflow, 4chan, or twitter, there's something here that's impossible to recreate and worth preserving.

You're sure it's not comments like these? https://news.ycombinator.com/item?id=27826277

I thought it was funny to see similar sentiments back to back :)

> discourse

Hardly a discourse. Both gents above might have a negligible disagreement but they are sticking firmly to radical green agenda shadow-officially endorsed and promoted by Yahoo Combinator. Also, good for karma income. Just the same for praising comments.

> radical green agenda

What is this radical green agenda that you identify? I'm not disputing that exists, I'm certainly part of it, and I intend to continue leaning into it. I'm just curious how it looks from the outside.

Trees are nature's best solution after millions of years of evolution. The R&D cost is low as well as the complexity. The problem is that dead trees turn back into CO2 so there will need to be some kind of sequestration like burying lumber.

Trees did not evolve solely for the purposes of carbon sequestration. Similarly, it would be silly to say that mammals are nature's best solution at sequestering oxygen.

Even burying the lumber doesn't remove the coal from the cycle, just delays it by a few years. You'd need to get the carbon into a "not readily accessible to biological processes" form. Charcoal is probably an OK start, but something like calcium carbonate would be even more stable.

And you can (probably) do better than trees, in terms of carbon captured per time unit. But I guess you'd have to run comparative studies between birch and bamboo for biomass grown per time unit and area.

Hm, that means that a sensible unit for carbon capture would be "kg / (m * m * s)".

There's always some local maximum most efficient process. If you take into account process inputs trees would likely come out on top. A lot of carbon capture tech can capture lots of carbon but consumes a huge amount of power/energy intense resources. My unit would be kg / (W * m^2 * s)

IIRC, bamboo ends up as "less wasted" when you turn it into charcoal than most woods. And you'd need to do a lot more energy-intensive processing of the tree to get it into a for suitable for turning into coal. With bamboo, it's mostly "cut into suitable length". With wood, it's at least "cut into suitable length", but may also require splitting.

But, yes, my main reason for thinking bamboo is that it is pretty fast-growing under the right conditions.

And with a Watt actually being "kg * m^2 / s^3", your unit ends up being s^2 / m^4, which dimensionally looks less pleasant.

Intensive cropping of bamboo for carbon capture sounds like it would cause as many ecological problems as it solves.

Not necessarily. Well, not necessarily more than doing the same with trees instead of bamboo.

But, yes, it'd require some care.

Yes, the "magic bullet" mentality typical of media, politicians, and dumb Americans just isn't going to cut it. BEVs + wind + solar + storage. Tree planting. Efficiency. Insulation. Nuclear power. Synthetic fuels. Carbon taxes. Sequestration. Olivine. Seeding the ocean. Vegetarianism/cultured meat/fake meat.

We don't need to wait 100 years for maturation of the wood in forests, the nice thing about wood is that you can use it for paper and construction, and that effectively sequesters the carbon.

> The advantage of planting trees is that we know it works, it's cheap, and we can do it right now

Here in Sweden it is the law that if you cut down a forest you replant it. We have been doing it for a century. All forests here is basically in a constant plant-grow-cut cycle unless the land is claimed for new buildings (farm land has been steady declining every year).

It is debatable if the practice is carbon negative or carbon neutral. Most of wood product do get burned sooner or later, or turned into bio gas which then get burned. Almost nothing remain as stable carbon sink. A planted forest is an future investment to be cut, processed and burned. The only exception is forest reservations and those are much more expensive to make than planting trees.

The advocacy behind replanting might be better invested into a political action of bringing similar replanting laws to other countries. Sweden mostly did it because it looked ugly to have wast areas cut down without regrowth, and because it hurt biodiversity. It also make sense economically in the long run.

>There's no reason not to plant trees in addition to everything else we'll need to do to fix this problem.

Yes, there is. Trees take a up valuable real estate. As long as people can do something even remotely profitable with land they own, this can not work.

Trees are valuable too. The problem is we don't understand and/or appreciate that value.

For instance, trees essentially power the entire terrestrial water cycle. Without trees all the water rains out within a few hundred km of the coast. Trees (far moreso than simple evaporation) are responsible for pushing that water back into the air-stream. Isotopic analysis confirms that 80% of the rainfall on land is caused by transpiration, and most of that is trees. https://www.nature.com/articles/nature11983

This explains why deforestation causes desertification. Cut down the trees and you get a continent-wide desert.

These dynamics aren't well-captured by the present economic system, which only sees "valuable real estate" being "taken up" by trees.

>> Anyone still think it's a good idea to utilize all that "valuable real estate" being "taken up" by trees?

As long as plantation owners and/or illegal loggers do, then all your argumentation is moot.

Correct, thanks. Incidentally before seeing your post I just edited that part for clarity. Since I already made the edit, I'll leave it as-is.

Just up the ante for illegal logging and equate it to terrorism. Life sentence for anyone involved. I am sure it will make anyone think twice before doing illegal logging with such punishment.

With carbon credits, planting trees can be a profitable land use.

Stop subsidizing industry by socializing the cost of carbon and planting trees will be profitable.

Yes, tree planting for carbon binding absolutely need to be profitable to get real traction!

The US government already pays many farmers to plant things other than commodity crops.

A few other problems - 1) trees take a lot of water to grow, and 2) all the carbon they sequester can go right back into the atmosphere in a forest fire. Some very scrupulous carbon-offset companies (like YC co terraformation!) are careful to plant diverse, native species in a way that rebuilds habitat and fits local water supplies. But there are a huge number of irresponsible tree-planting orgs that plant monoculture trees in places they don’t belong. For instance, eucalyptus trees in California - an invasive species that sucks water out of the ground, then burns up like an oil rag

Trees take a lot of water to grow but they also hold water and share it through the air and ground with other plants and with other creatures in the form of transpired water vapor.

Definitely true! I am a huge fan of trees. But the wrong tree in the wrong place is a bad thing. I try to advocate for responsible and thoughtful reforestation - which is, unfortunately, a lot more expensive than people want it to be.

Where can I learn more about the costs and challenges of thoughtful reforestation, and the key differences between the responsible and irresponsible sort? (Just popping in to ask because it seems like you might know). I'm interested in doing some work in this space but don't have any background.

Hmm… can’t point to one specific book, but there are lots of links. You can google “reforestation monoculture” and “reforestation native species.” This article is a great place to start: https://e360.yale.edu/features/why-green-pledges-will-not-cr... It doesn’t get into the granularity of the costs, but highlights that the basic issue is countries are still hoping to make a profit off these “carbon sinks” by planting easily usable timber - aka monoculture - which greatly diminishes the benefits of forests and leaves them vulnerable to blights and other disasters.

Thank you very much!

Trees rarely burn to the ground in a wildfire. Their foliage burns quickly and the bark chars, but it takes years for even trees in the hottest spots to finally fall and then, many more years to decompose back into the soil.

This depends on the health of the tree. The bark beetle has decimated many pine trees in the sierra nevadas, leaving many trees standing but actually sick or dead, and unable to resist a forest fire.

Also, planting trees sequesters co2 into the biosphere. That is not good enough, we need to be sequestering co2 into the geosphere if we want to remove it from the equation

I'm sure it's been mentioned elsewhere here already by someone, but I've always thought that converting felled 'sequestration stock' to bio-char and making terra preta out of it would be win-win-win, as it could then be used to improve desertified land.

As much as CO2 emissions befear me, so too does increasingly poor topsoil, globally.

- ed

I'm not even sure we'd need to wait for trees to mature either - we just need work with whatever plant absorbs the most CO2. Perhaps algae, even?

This is definitely a thing: https://en.wikipedia.org/wiki/Bioenergy_with_carbon_capture_...

In theory it's energy positive: burning the crop can produce energy.

So I’m thinking the same. Soil + Terra preta(charcoal + food waste) is the best way. There needs to be some kind of inverse Bitcoin - something where we incentivize large number of people to claim areas of land and terra Preta it up. The reward is some kind of token that can be exchanged for value. We can maybe use satellite imagery to identify which land has been converted. Someone has to be forming a team on this for the prize.

Naturally (without human influence) a combination of biosphere (decades) and geosphere (millenia) would keep CO₂ levels in check.

We (humans) have accelerated emissions (by burning, thus reversing, geosphere capture via oil) and destroyed the biosphere through deforestation. This has also been accelerated as raising temperatures thaw permafrost & destroy ocean life (among others).

Anything we can do to reverse this is beneficial.

Has anyone checked if earths total biomass has increased as co2 increases?

There is more greenery/forestation, and likely more biomass downstream, but I would expect other effects to cancel those effects beyond certain thresholds. For example, even though plankton and algae might benefit from additional carbon and heat, acidification of the ocean might lead to a net decrease in both.

I guess it would be impossible to actually measure.

Heat could also increase biomass since there would be a longer growing season and higher latitudes opening up.

But like you say, it’s a trade off so hard to predict.

We’ve pumped a lot of nitrogen into the biosphere. I wonder how much that’s increased the total biomass.

That assumes a lot about the world in 50-100 years when trees planned today are full grown!

We need technology, but more important is business and government. We have all the data on what is causing the problem, but we are not making value judgements, and taking action based on those judgements.

Until our technology catches up and provides net carbon-neutral energy, we have to pollute less. And that may be and doing less, and "consuming" less. And that will require force. Public pressure, social pressure, and regulation. No business will do it voluntarily, and no government will make itself unpopular voluntarily.

Long term we need green energy technology. Short term, we need technology is to help force change in our habits.

Do all the other stuff too, sure, but it seems like most of the pollution currently comes from Industry, Agriculture and transport. Things that enhance human quality of life. We need to decide which enhancements are most essential, and cut back.

https://www.epa.gov/ghgemissions/global-greenhouse-gas-emiss...

Depends on the tree.

Empress seems to be the ideal candidate.

https://www.bloomberg.com/news/features/2019-08-02/we-alread...

Planting a monoculture would be a disaster, as we've seen when a billion poplars died in china's green wall.

It’s not just about carbon equations. Appropriately selected, well planted trees reduce local environment temperatures, regulate rainfall and soak up excess water in a positive feedback loop. The urban heat island effect will make lived experience even more challenging than it already does as the planet warms; turning cities into agro-forestry reserves would counteract this.

Planting more trees in cities makes a lot of sense, but it doesn't do much for CO2 levels in the air.

I've heard that planting trees in the Sahara would be worse because since they're darker they would absorb way more heat.

Actually yes, planting trees (especially the wrong trees) is not always a good thing. Darker leaves will attract more heat (imagine if it was possible to turn the polar regions into trees - this would have a very negative effect).

Also mono cultures and replacing natural vegetation with man-made forestation can actually be more limited to the amount of carbon they can capture long term.

Source: https://spiral.imperial.ac.uk:8443/bitstream/10044/1/80271/6...

It does seem unlikely that we'd be able to control temperatures without resorting to sulfur dioxide.

It'll probably start a war, but once natural resources start getting scarce I fully expect the affected nation to deploy SO2.

I don’t think you should be downvoted. People really don’t like it because it is clearly not the optimal way to solve the problem, but we should take the possibility seriously instead of down voting anyone who brings it up as something that might happen.

We are letting anthropogenic global warming happen because it’s cheaper in the very near term. But climate change is a real thing and will have real, life-threatening effects especially for some geographic regions.

If we accept the reality that: 1) humans often just do what is cheapest and easiest even if the long-term consequences are bad AND 2) global warming will start killing massive numbers of people from things like heat stroke, putting enormous political pressure on governments to do something,

…then The logical conclusion (combined with how insanely cheap SO2 is to deploy, we’re talking maybe $50 billion a year, maybe less) is that there is an extremely high probability that some nation will just unilaterally do sulfur dioxide. Think of a Nation like India, with a large population that will be vulnerable to heat stroke and a big enough budget and military to just unilaterally do something like this to stop the political unrest of hundreds of thousands of heat stroke deaths per yearz

And on top of that I don't think it'd even be possible to know who deployed the SO2.

The stuff isn't uranium and not much is needed. Any nation with an airplane should be able to get away with it.

You need quite a bit, and it needs to be continually deployed. It wouldn’t be hard to tell who is launching like 25,000 tons of sulfur dioxide into the stratosphere every year. It would leave effects clearly visible by satellite: https://earthdata.nasa.gov/esds/competitive-programs/measure...

But I said $50 billion per year. That’s what probably way too high. Other estimates mention $18 billion per year, I found one that mentioned $2 billion per year, and just doing the calculation by hand based on fuel and per hour operating costs, I get only like $100 million, although that depends on altitude (I think 20km is usually ideal, although most cargo jets can’t go much above 13km).

I even wonder what the effect would be of just using sulfur-rich jet fuel on regular commercial long-haul flights. The cost would be minimal or even negative (as sulfur-rich crude is cheaper). I guess in this way any nation could just decide to do sulfur-rich fuel in their long haul fleet and few would immediately notice.

It’s such a crappy solution to the problem, though, and will doubtless cause a bunch more problems. But it’d be insanely cheap to do.

Because I think you’d be the person to ask: what is the feasibility of putting up a space sunshade to block some incoming solar radiation, using starship/super heavy?

Let’s say you need to reflect 1% of the light reaching the earth’s disc. If you’re using solar sail like devices with an average areal density of 10 g/m² and you have launch cost of $10 per kilogram (using LEO figures because devices made really lightweight can actually move themselves around with pressure from sunlight)… about $150 billion in launch costs. Material/spacecraft costs are a big question mark and can vary by 5-6 orders of magnitude, so let’s say it’s $10/kg, for a total of $300 billion.

Still sub optimal compared to other solutions but it’s possible we may need to try something like that.

Thanks for the breakdown. I like the idea of something we can remove more easily down the line, even if it’s more expensive. I suppose we probably won’t have the luxury, though.

Calcium carbonate is a better fit - see Gates’s experiments. Likely to still be disastrous, but better than sulfur dioxide

Grammar tip, if someone name ends in s, you can just write Gates’ experiment.

Interesting thanks.

Why disasterous?

Particulate matter in the air causes precipitation. Spraying large amounts of particulate matter into the sky is likely to drastically change global rainfall patterns - so you might get a ton of rain in the Sahara, where it’s useless, and none at all in the American Midwest. The result could be drastic food shortages and famines. Major volcanic eruptions have been associated with droughts and famines. I think geoengineering on this scale may be necessary, but it is a terrible option and an absolute last resort

When you say rain in the Sahara would be useless, are you saying it's already a carbon sink or something? After all it seems that rain in the Sahara would eventually cause forests to grow, given a few years.

Top soil takes a long time to form. I imagine most of the water would go into the aquifer.

Isn't the upside of this kind of geoengineering the reversibility? If we inject SO2, and we don't like the effect, we stop. IIRC it doesn't hang around that long.

There's likely a decade+ tail after the end of active particulate injection. If there is too much to begin with, you piss off all the electorates with years of chaotic weather, threatening food production, financial markets, and ecologies all over the world. Get it just right, you wreak less havoc, piss off fewer electorates, and lower global average temperatures. Get too small an effect, you risk overcorrection or the project failing before it has a chance to really work.

There's also the fact that you're altering a chaotic system, with fundamentally unpredictable side effects, some of which could last longer than a human lifespan. Wanna make California get monthly hurricanes? How about weekly tornados in Colorado? Bury New York city in ice?

It's not that any of those things are probable just that they're possible, and chaotic systems can drastically, catastrophically, and exponentially change configuration, and no matter how good your supercomputer simulations are, you fundamentally cannot predict the consequences.

All of human civilization teeters on the current climate configuration - geoengineering has terrifying potential. Humans have a horrible track record in attempts to predictably alter chaotic systems and ecologies. We damn well better know what we're doing before we use globally acting tools.

What is country A likes it but B does not? Seems like a source of conflict.

Similar to the GERD but in the sky.

Can somebody please explain the SO2 thing? Im googling to no avail...

>Our use of technology threw nature out of balance and we need to use technology to get the balance back again.

The notion being that nature or even the climate is balanced/stable ?

I think the focus should be on increasing resiliency not hoping everything is going to be alright "if we just undo this one thing".

Having said that I'm all for reverting CO2 emissions, just dislike this implicit notion that nature is harmonious by default and humans fucked it up - there's speculation about weather related disasters pre industrial era, so even very recently in human context. Or the disruptions we have with relatively minor volcanic activity. So many natural thing could screw us way worse than global warming and for the first time in history we're getting technologically advanced enough to protect against it.

I'm working on agri-forestry and biochar reactors on a hobby farm.

Hybrid poplars mature within a decade, and a biochar reactor is a net-energy producing reaction that produces soil improving char as a byproduct.

It won't save the world on it's own, but trees can be leveraged in powerful ways.

Can you think of anyway we could measure individuals doing this? I’m thinking reverse Bitcoin - provide a kit for people to start generating terra preta and deploying it and then give them coins for the amount of carbon they store.

Hang on. That sounds carbon-neutral at best.

Great for replacing fossil fuels, but not a carbon sequestration technique.

You can bury the char or plow it into fields as a soil ameliorant.

Or if you wanted you could literally just bury it. Then it becomes a coal plant in reverse

A decade sounds like a pretty good start. If we could combine that with transitioning away from lawns and towards gardens / orchards (like even on highway medians!), imagine the savings in terms of shipping food.

Highway medians are lawn for safety reasons. Planting an orchard between two lanes of traffic going 75 mph would result in a ton of fatalities

Seems like you'd intentionally plant many small/short trees that will act as nice crash barriers, not large strong trees that act like brick walls. Orchards tend to be short trees anyway.

Hitting the tree equivalent of those sand-filled barrels sounds a lot better than dissipating that same energy by either A) flipping, or B) colliding with oncoming traffic.

It would be interesting to see the videos of "crash testing" various types of orchards!

Sure, but small trees contain little carbon.

Grass contains even less carbon, and it doesn't produce anything of economic value.

As I wrote elsewhere in the thread, it's all about maximizing the total carbon stored per hectare. That means more trees in the median, more trees in our suburbs, more trees in the city, and (most importantly) more trees in agriculture.

There's a small set of "farmer's trees" (eg black locust) that coexist with crops right up to the trunk, drop copious mulch, have deep tap roots that bring up minerals, and make nutritious pods that are good fodder for animals. Planting 15-20 of these trees per hectare will actually increase the crop yield beneath.

Tons more carbon stored, better crop yield, cuts down wind erosion, and free fodder too. The cost is that the farmer has to drive around the trees. It's a non-zero cost yes, but it's a much easier switch than transitioning to full-on agroforestry.

Not a solution, but still - check "Oxytree". It's a tree "farmed" in Europe, that was created in Spain. Within 6 years it grows to 16 meters. You can cut it almost completely, and it will regrow. You cut it then every 4 years. It will regrow multiple times. The tree as far as I know cannot re-plant itself (so its not invasive), and it absorbs up to 10 times more CO2 than regular trees. It's still young project, but more and more countries create plantations of it (also as a way of CO2 recapture).

Do trees actually help? AFAIK once a forest reaches equilibrium it puts out as much CO2 as it takes in through various decomposition processes.

Using more wood as construction material helps to tie the CO2 for longer period.

This. Early trees sequestered a whole bunch of carbon in their structure (and there wasn’t efficient methods of breaking down lignin at the time, so the carbon stayed in the ground instead of rotting and returning to the sky). If we build long-lived structures out of wood or other carbon bearing materials whose carbon source is the atmosphere, we’ll be doing the same thing as trees but with human civilization as the organism.

Sounds like the real question is, how does 1 hectare of stick frame buildings compare to 1 hectare of mature forest? What stores more carbon-per-hectare, and how many years does the building actually lock up that carbon?

While a hectare of forest may be "only" CO2-neutral, a hectare of buildings are typically net CO2 emitters.

Yep, but reaching equilibrium once we've removed enough from the atmosphere is fine.

Of course this strategy does have to go hand-in-hand with drastic emission reductions to prevent use getting back to the same point and having nowhere else to put trees.

Yes, but that takes 50 years at least.

In the 2070s things will be very different.

We already have all the pieces needed, they just need to be connected in a better way.

Forests need to be managed to optimize for sequestration; log the right parts at the right time, replant. Also need to invest more in controlling forest fires (hell, use the military if that's the only way to get the budget).

At the other end we need to reduce burning wood for fuel through other renewables and put more lumber into building.

> we can only undo a decades worth of emissions

Sounds like dramatic progress to me. It uses a technology we already have against a problem that is only getting worse by the second. The side effect of fostering sustainable natural resources would be an unquestionable good as well.

A lot can happen in decades.

Trees do much more than remove carbon from the air. Carbon removal machine could potentially create c02 deficit regions, creating hostile environments for trees.

We can't possibly build a machine for every function a tree does.

> Carbon removal machine could potentially create c02 deficit regions, creating hostile environments for trees.

If we could remove so much CO2 from the air that it prevented plants from growing (even if the effect were highly localized, which is pretty much a certainty), then we might actually have a shot at being able to remove CO2 in a reasonable amount of time. So this definitely sounds like a good problem to have. Personally I think that's pretty unlikely though.

CO2 is pretty well-mixed and it takes a lot of energy to pull CO2 out so it is unlikely to be the primary method of address Climate change. Also at this point we are substantially above the pre-industrial level of CO2 so there’s essentially no chance of having CO2 poor regions.

I think the point GP was making was that just planting trees is not enough, not that we shouldn't be doing it. If all we do is plant trees, we're still running full bore up shit creek.

Yes thank you - trees are part of the solution, not _the_ solution.

Are there any sources of this?

As I understand it the air carrying the CO₂ is constantly moving and will not create any deficit regions?

Besides, with the large over concentration of carbon dioxide we have at the moment I think increasing temperatures have a higher chance of creating hostile environments.

>For some context, if we planted trees wherever we could around the world we can only undo a decades worth of emissions[0].

Not even, say you could transform the Sahara to rain forest, awesome right? I mean it would be an incredible feat, but it would give you exactly 0 with reducing carbon. Contrary to popular belief the Amazon rain forest aren't the "lungs" of the planet, the Amazon rain forest is basically net 0. Why? Because the rain forest also has a tremendous amount of life/animals, those animals use the oxygen and produce carbon. The real "lungs" of the planet are in the ocean.

The Amazon rain forest is not net zero because of animals. It's net zero (actually net negative last I heard) because humans are burning it to make way for agriculture.

Trees sequester carbon. They also return that carbon to the atmosphere eventually, but as long as they're replaced by new trees, that's fine. That's not what's happening in the Amazon.

From a carbon perspective forests for timber are even better because then we keep several generations of trees worth of carbon locked up in our structures. It's also an easier sell because that has real economic value.

From a biodiversity perspective it's not as good to have monoculture crops of any kind, including trees.

> The Amazon rain forest is not net zero because of animals. It's net zero (actually net negative last I heard) because humans are burning it to make way for agriculture.

According to the documentary "One Strange Rock", which I admit I have not fact checked, your statement is absolutely false. The documentary claims 100% of the oxygen produced by the Amazon rain forest is used up by the animals that live in it.

EDIT:

Also this PBS article backups the claim. https://www.pbs.org/newshour/science/no-the-amazon-fires-won...

"Forest plants produce lots of oxygen, and forest microbes consume a lot of oxygen. As a result, net production of oxygen by forests – and indeed, all land plants – is very close to zero."

I find that believable, but we're talking about carbon, not oxygen.

Forests do sequester carbon for a period, although most of it is released again in fires and decomposition (chemically just a slow fire.)

But the point is that a forest locks up a lot of carbon compared to cleared grazing or cropland.

Wait a minute. Are you saying that the animals in the Amazonian rain forest produce more CO2 than the plants within it consume? Do you have any data that shows this?

This is cited in the documentary "One Strange Rock". That is the only data I have. I am trusting that the documentary is accurate, I have not fact checked the documentary.

EDIT: You might find this PBS article interesting as well, https://www.pbs.org/newshour/science/no-the-amazon-fires-won...

"Forest plants produce lots of oxygen, and forest microbes consume a lot of oxygen. As a result, net production of oxygen by forests – and indeed, all land plants – is very close to zero."

Saying net production of oxygen is zero is not identical to saying net sequestration of carbon dioxide is zero.

Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2

You can see here that there's glucose (a carbohydrate) being produced in addition to oxygen.

When people talk about adding new forests, they're mostly talking about the carbon used to make up the trees and animals. That all comes out of the air.