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How much can forests fight climate change? (nature.com)
107 points by ramraj07 5 months ago | hide | past | web | favorite | 60 comments

Before jumping into detailed discussion of the points raised in the publication here, including "trees leak methane in the Amazon" -- is it possible that this article is getting promoted because it feeds into a "they dont know what they are talking about" meme of anti-science know-nothing'ness ?

There appear to be several sets of weasel-words candidates .. Such as "many scientists applaud X but some urge caution" without naming either side's strengths and weaknesses, notable refutation on either side, or any raw counts of how many "some" are...

Recently it was discovered that USA oil and gas industry self-reporting of methane emissions on extraction in the Permian Basin might be five times less than actual numbers, and might have doubled in the last two years. This was detected by satellite sensors and NGO analysis.


> is it possible that this article is getting promoted because it feeds into a "they dont know what they are talking about" meme of anti-science know-nothing'ness ?

I would go further and say it's not only possible, it's likely.....similar to how articles from the opposing viewpoint are promoted, also often full of weasel words to some varying degree depending on the specific topic. Much of science discussion in the mainstream is actually a bit of a meme war, but this has probably always been true.

Daniel Dennett: Memes 101 | How Cultural Evolution Works


Replace religion with "fundamentalism, of any kind":


Doesn't methane dissolve relatively quickly in the atmosphere so it's not a long term threat like CO2 so once you run the numbers amortize it all a tree that leaks methane but eats carbon is a net win so long as the carbon actually stays out of the atmosphere?

It turns into CO2. So all that happens is an initial spike of a more potent GHG turning into a baseline GHG.

And the half-life is a ~decade, with constant replenishment that's enough to have a significant effect that the same carbon emitted as CO2 would not have.

Methane oxidizes in the atmosphere with a half life of about 10 years. CO2's equivalent half life (due to ocean absorption) is 27 via a quick google.

So they're really not that different. Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades.

> Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades.

That only can be true if the resultant warming over those decades isn't significant enough to kick off other feedback loops or cause ecosystem collapse. For instance, the caps melting and lowering the planetary albedo, ocean acidification, etc. If these things happen too quickly, you're going to see a serious and nasty extinction event happen. Sure, not all life forms will die - archaea are pretty hearty after all, but it isn't going to be pretty for most complex lifeforms adapted to the climate of the current era.

Yeah. If the phytoplankton goes and stops renewing free oxygen; it becomes pretty hard to be a mammal in a relatively short time.

Could it also be possible that the current rate of emissions beefed up the planet's scrubbing capacity, and the climate return to pre-civ levels even faster?

The temperature impulse response of CO2 does not seem to have a half-life of 27 years if you look at page 711 of the IPCC report.


Yes, and on page 712:

> Figure 8.29 Development of AGWP-CO2, AGWP-CH4 and GWP-CH4 with time horizon. The yellow and blue curves show how the AGWPs changes with increasing time horizon. Because of the integrative nature the AGWP for CH4 (yellow curve) reaches a constant level after about five decades. The AGWP for CO2 continues to increase for centuries. Thus the ratio which is the GWP (black curve) falls with increasing time horizon.

That is, CO2 greenhouse forcing continues for centuries. Back when I worked on this stuff, we used an approximate half life of 250 years. But it's really more complicated. That IPCC report says this, on page 737:

> No single lifetime can be given [for CO2]. The impulse response function for CO2 from Joos et al. (2013) has been used. See also Supplementary Material Section 8.SM.11.

From Joos et al. (2013):[0]

> The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100 Gt-C emission pulse added to a constant CO2 concentration of 389 ppm, 25±9 % is still found in the atmosphere after 1000 yr; the ocean has absorbed 59±12 % and the land the remainder (16±14 %).

0) https://www.atmos-chem-phys.net/13/2793/2013/acp-13-2793-201...

That's pretty different from what I have heard elsewhere. Could you please provide some references so I could read further?

Here is a link that argues the opposite side: https://www.skepticalscience.com/co2-residence-time.htm


"What really governs the warming potential is how long the extra CO2 remains in the atmosphere. CO2 is essentially chemically inert in the atmosphere and is only removed by biological uptake and by dissolving into the ocean. Biological uptake (with the exception of fossil fuel formation) is carbon neutral: Every tree that grows will eventually die and decompose, thereby releasing CO2."

Thanks for your perspective.

> if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades.

Do you have any links to research which backs up this quote? Because I would love to believe it.

OP here. No climate scientist, just someone who's been following climate change for a couple decades. Not a climate change denier by a long shot, if anything I've actually already made a bunch of large life decisions under the assumption that climate change is going to change this world quite a bit in the next few decades.

The main accusation you make, that I (and other who are promoting this article) are suggesting that the scientists don't know what they are talking about, I actually plead guilty for that. I really do think we don't know what we're talking about anythign other than the primary assertion that we are warming this planet through our actions. I don't believe we actually have a real handle on the rate (we could be drastically under or overestimating) of climate change, and I definitely don't think we have an inkling on whether geoengineering efforts would work the way we expect it to.

The main light bulb for me from this article is it has made me consider even planting trees as a geoengineering effort, as vicarious as other proposals like dumping iron in the ocean or particles into the stratosphere. Right now I would consider any effort at controlling global warming other than actually just reducing emissions as geoengineering.

The most apt analogy I have found for geoengineering efforts like this was given by the comedian Bill Burr in a podcast, where he shits on a Ted talk about genetically engineering malaria mosquitos (https://youtu.be/vEZ0z0WSrUA ).

I have seen similar over-confidence among my fellow scientitsts in biology, in complicated subjects like cancer, immunology and metabolism. Time and again, people will assert they have understood a system, make a drug, and it won't work, and then they will blame the failure on the same complexity they said they had conquered.

We have made tremendous progress on all these scientific fronts (biology, climate science, etc) but the systems under study have become so complex, I would consider it a criminal offense if any scientist makes a claim that they really have figured out all the ramifications of their geoengineering plans. Criminal because I am worried that any major geoengineering effort if it goes wrong might be irreversible. Orders of magnitude more studies are needed IMO to make sure we understand these systems, and I don't think we are going to invest that effort until things get far, far worse. Until then I would prefer we err on the side of caution.

Btw it's not just methane, they actually talk about a bunch of other potential issues (like VOCs) in that article. Also, this is nature mag, if you think nature mag is anti-science or climate change denying I'm not sure who else you think is your ally.

Hey ramraj07, I just wanted to say thanks for submitting this article!

A couple weeks ago I read a different article on Nature that claimed that "Restoring natural forests is the best way to remove atmospheric carbon" (https://www.nature.com/articles/d41586-019-01026-8).

I added it then to some notes I've been taking, listing evidence for and against claims, which I was able to update quite a bit today using information from the article you posted: https://www.wikiclaim.org/index.php?title=Increasing_foreste...

FUD tactics are certainly an issue to keep in mind, but I do like to be able to consider all the available evidence when assessing claims. Thanks!

> we could be drastically overestimating

Would you mind explaining this bit? Besides [1], which hardly changes the big picture and came out literally last month, what evidence have you seen in the last couple decades of following climate change that suggest to you that the likelihood that we have been "drastically overestimating" the rate is anything comparable to the likelihood that we have been correct (if not underestimating)? From as far back as I can remember, the predictions have only stayed about the same or gotten more dire. They used to say weather patterns would get more intense, with more storms etc., and they indeed have. They say sea levels would rise and I really have no reason to believe they cannot calculate the rise correctly. I would think that if climate scientists had no idea what they're talking about, we could point to their erroneous predictions and prove them wrong?

[1] https://www.nationalgeographic.com/environment/2019/03/one-p...

I definitely am not refuting the estimates by climate scientists about our worsening climate rates; I will totally assume that the rate they suggest is the expected value until proven otherwise.

However, I will also not be surprised if things get far worse extremely fast, or if they actually suddenly start getting better (or slowing down). My only rationale for this belief is that as we go into warmer and warmer climate, we are also going into a territory that the scientists themselves have no real data for - literally uncharted territory. I'm sure they have run models to extrapolate their predictions but the actual fact that we are already experiencing climate that has not been seen for however amount of time means any prediction has to be taken with a slight grain of salt.

Practically speaking, we always hear of the finding that global warming might release methane bodies or it's turning into a runaway chain reaction. We don't even know how many other chain reaction scenarios exist that have not even been considered. Similarly (though with orders of magnitude less likelihood even for me), there exists possibilities that excessive warming into uncharted temperatures might trigger some feedback that might slow this warming too. I'm not counting on it but I am not ready to % exclude it yet either.

> there exists possibilities that excessive warming into uncharted temperatures might trigger some feedback that might slow this warming too.

I very much doubt this is the case.

What is happening to the world can be explained by science and using scientific principles the changes can be predicted by modelling.

The hard part is creating the model, only because the problem domain is very complex. But what we have seen, is over time that modelling has been getting better.

Now if there was some possibilities that excessive warming into uncharted temperatures might trigger some sort of cooling effect then surely that would have come out in the modelling.

You're right we're not sure, but splitting the difference like this sounds like you're equivocating the two possibilities. "Oh, it could get worse, it could get better, we just don't know." When the reality might be a 90:10 relative likelihood in a particular direction.

It's a sad state of affairs when we dismiss everything we don't agree with as some conspiratorial piece of fake news. Yes, that type of content absolutely exists, but we should not let that excuse intellectual dishonesty.


For the sake of argument, even if what you say is 100% applicable, and every single person expressing concern about overpopulation is just focused on their own lifestyle, it shouldn't make any difference.

Overpopulation is something that, if real, will have an impact regardless of the motivation for people's concern. It's not purely a social construct like say the wearing of tattoos.

It's lazy to dismiss such serious concerns with appeals to hypocrisy. Even if 100% of the people making such claims now are actually hypocrites, your voice could improve the ratio to only 99.9999%

If you were really trying to engage in a thought experiment with me honestly, I don't think starting with a mischaracterization and inventing a fallacy ("appeal to hypocrisy") to tear it down is a good place to start. That also seems, to me, lazy.

> Overpopulation is something that, if real, will have an impact regardless of the motivation for people's concern

"If real", that is the key, and I am glad you pointed it out. For the sake of argument, we would first have to define why overpopulation real. It seems to me most people start off with the assumption that it is real.

Who is defining overpopulation? What is the criteria? Not enough food? Well that's not true at all, we know that the US for example wastes more food daily that could feed the entire continent of Africa with 1/3rd of a pound of food. Not enough land for people to expand to? Well even a 5 year old knows that one is false. Is it not enough natural resources? Despite the fearmongering about water and energy resources drying up, we seem to be doing just fine. Capitalists reaping the country to sell to a nation of consumers? This is the most insidious form of the argument, but again, very wrong. Plus it assumes greedy capitalists somehow wouldn't exist with 5 billion people, or 3, or 2, or even 1, that wouldn't cause some kind of destruction to natural resources. The final one is one made more by hard left academics in favor of socialism. They need an easy explanation for why socialism always sounds so great in theory and never works in practice, so they point to overpopulation. If we simply had less people, then socialism would work!. Except, as we now know, this was in part one of the rationales behind the gulags and gas chambers.

So what is the criteria? Not comfortable enough for you and me -- that seems to be the essence of the arguments left after eliminating the ones above.

Plus, even if the above were remotely true, why rule out technological solutions? Seems to me pretty crazy people on a technology focused board would rule this one out (not singling you out, "overpopulation is a problem" is an opinion expressed here often, unfortunately), especially since it was technology that has allowed us to easily achieve our current population levels at the exploding standard of living the globe is currently undergoing.

People who think overpopulation is an issue by just pointing to some things "drying up" or some places "crowding" is by definition engaging in a lazy form of argument. So to me, until there some hard facts and figures on what overpopulation means, please excuse me if I take it for a hypocritical statement, as the great Carlin said, made by bourgeois liberals that have never experienced actual hardships and live in such an advanced society they have nothing better to do than ponder the scenarios where their cushy lifestyles could be threatened.

When you don't have any actual enemies to fight, you have to invent some in your head to keep you busy.

'notable refutation on either side, or any raw counts of how many "some" are...' - Why does it matter to dig into why one side is right or wrong? Earth atmosphere is complex beyond imagination of any person/society and you should expect science (or anyone else)to be wrong most of this time at what they have to say about this topic.

Don't be hell-bent on trying to comprehend mechanics of Earth atmosphere and finding 'scientific' solution to climate change. If you are aware of what has worked well until now for earth's climate then why not just follow it?

The math doesn't work out. Since the beginning of the Industrial revolution humankind has emitted about 550 GtC (gigatons of carbon) into the atmosphere. All plant life on earth contains about 450 GtC. Assuming all of it is forests (which isn't the case, a lot of it is algae, plankton and weeds) and assuming 100% capture rate (which also isn't the case due to forest fires, rotting and reduced albedo), earth's tree cover would more than double to capture all carbon emitted so far.

Clearly, that is not realistic. A more realistic (but still implausibly ambitious) goal would be increasing the earth's forests by 10%, storing 45 GtC for us. Well, it is better than nothing but at the current (increasing!) rate of 10 GtC emissions added per year that nets us another 4.5 years.

https://www.vox.com/science-and-health/2018/5/29/17386112/al... https://www.co2.earth/global-co2-emissions

I've come to terms with the fact that nothing is going to stop anthropogenic climate change and we'll just have to adapt to it. It's not a technical problem but a political game-theoretic problem.

Major CO2 cuts would require a global all-cooperate (in a game theory sense) scenario and that's unlikely given that the payoff is very high for defecting. This is because global cuts in fossil fuel use would make fossil fuels incredibly cheap, increasing the economic advantage for nations that use them. This is going to be hugely appealing to developing nations with large populations. We already see this with China and India and pretty soon you're going to see it in Africa.

The only way I can see CO2 emission growth halting or reversing is a huge breakthrough in energy generation that results in something dramatically cheaper and easier to deploy and scale than fossil fuel. It would take Mr. Fusion (Back to the Future reference), solar and batteries that are just absolutely dirt cheap, or something equivalently awesome. I don't see anything like this arriving before CO2 hits 800-1000ppm.

We are pretty adaptable. A bio professor of mine was fond of saying that humans are like cockroaches and that this was a compliment coming from a biologist. We should be preparing to move Miami.

> that's unlikely given that the payoff is very high for defecting.

Trade policy (e.g. through the WTO) can be designed in a way that allows countries to internalise the damage caused by greenhouse gas emissions by imposing higher tariffs on countries that do not cooperate.

But you still need everyone else to cooperate. And in a multipolar world (or at least a world with some viable political blocs outside of the US led order) that will be difficult to say the least.

What makes you think the US is not the defector?

Most of the world is defecting at the moment. Few are truly serious about cutting emissions dramatically.

The US is relatively high (but by no means the highest) in per capita CO2 while China is the #1 emitter in total and also per dollar GDP (last I checked). The per dollar GDP number would make China the largest emitter in terms of carbon intensity of its economic activity.

I’m too tired to respond in detail but this underestimates the scale of the problem. There is no “adapting” to the scenario if we don’t stop kicking out CO2. We’re talking billions dead and most large species extinct, over the course of decades at most, depending on how quickly the planet flips from one steady state to the next.

Sea level rise would be no problem. Storms would be no problem. But it's hard to imagine how we could possibly adapt to the worst case scenario, which would be if runaway feedbacks triggered conditions similar to early mass extinctions...

This old article from ScientificAmerican still keeps me up at night.


Exactly this.

It scares the life out of me that even on HN, a community of generally scientifically-engaged people, the scale of the problem is often not understood.

We are literally looking at the end of civilisation as currently constituted, and billions dead, and we are not doing anything close to enough.

You're ignoring the gun about to go off: https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis

We already see ocean acidification and warming - if that triggers the release of methane deposits stored under the ocean, that's a potential extinction-level event (or at least a civilization reset back to the stone ages).

I don't disagree that there are huge risks. I just don't think anyone is taking those potential massive risks seriously, and that includes a substantial number of environmentalists and the leaders of most of the world.

Another thing that might cause change to actually happen is if we're "lucky" enough to get a "minor" catastrophe that totally changes global opinion but isn't anywhere near as massive as the stuff you're talking about.

Considerable academic studies and literature on this subject exists. Recent capture rate from current global forestation is estimated to be approximately 2.5 GtC/year. Current global carbon stock of forests is estimated to about 861 GtC [1] ( virtually twice that hastily sourced figure for total plant life even without those assumptions about algae etc )

Sequestration of current forests, despite the fact they are currently being depleted rather than maintained or increased is estimated by studies to be equal to about 5% of current overall anthropogenic emissions. [2]

For in-depth advice see Chapter 11 of IPCC AR5 [3]

" Reducing emissions from deforestation; reducing emissions from forest degradation; conservation of forest carbon stocks; sustainable management of forests; and enhancement of forest carbon stocks (REDD) consists of forest-related activities implemented voluntarily by developing countries that may, in isolation or jointly lead to significant climate change mitigation. REDD was introduced in the agenda of the UNFCCC in 2005, and has since evolved to an improved understanding of the potential positive and negative impacts, methodological issues, safeguards, and financial aspects associated with REDD implementation. "

[1] https://www.globalcarbonproject.org/global/pdf/pep/Pan.etal....

[2] https://forestsnews.cifor.org/12135/clocking-the-worlds-fore...

[3] https://www.ipcc.ch/site/assets/uploads/2018/02/ipcc_wg3_ar5...

Did you take into account that trees have died since the start of the industrial revolution, taking their carbon with them, and that new trees grew and are sequestering more carbon? I.e. if there were 200 GtC of trees and the average tree lived 100 years that is 400 GtC sequesters in 200 years. (I don't know exact figures.)

That's not the case. When a tree dies it will be broken down by microbes, animals, fungi, etc and as that happens, all of the co2 it sequestered will be released back into the atmosphere.

The only time this was not true was during the carboniferous period.. before those microbes existed.. that's how we got coal. But that will never happen again.

I can't tell if I'm missing something or if this number is missing, but how much of that 550 GtC has actually stayed in the atmosphere until now?

I don't have the figures, but I believe most of that went in to the oceans, causing other problems there.

> earth's tree cover would more than double to capture all carbon emitted so far.

> Clearly, that is not realistic.

It's perfectly realistic in terms of what the trees can do; it's happened before.

The question is whether we want to cede so much space to trees, which I agree that we don't.

I read The Hidden Life Of Trees a while back. I believe the author suggests that old growth forests are bigger carbon sinks because they have deeper humus [1]. I don’t know the merits of that idea but it helped me realize that when people talked about forests, I was only thinking about the trees themselves, not taking the soil into consideration, too. If that idea has merit and the research does eventually conclude that forests are a carbon sink strategy, then it suggests that preserving old growth forests might be more effective than planting new ones.

[1] https://en.wikipedia.org/wiki/Humus

It's not just the humus, an aged forest also has at least 7 layers of carbon sequestration.


Forest are much more than store carbon. Them affect the local climate, and maybe(??) the global(??). Help the local fauna. Clean the air of more than just pollutants, make the soil more fertile, combat erosion, help the river flow to not get so dry, and that is from the top of my head with my limited understanding of the subject.

Combined to NOT deforest so hard, and is a win.

Forest are a force multiplier.

Trees are batteries that store carbon. The carbon is restored into the atmosphere when a tree dies and decays, or is burnt.

A long time ago trees didn't decay because the Earth didn't have "fungus" that made them rot and decay. So they just piled on top of each other and turned into coal.

Plant more trees. https://onetreeplanted.org/

> Trees are batteries that store carbon. The carbon is restored into the atmosphere when a tree dies and decays, or is burnt.

By extension, wooden building materials are carbon batteries as well. Plant more trees and build more things out of wood.

Beside the reasonable point that building out of wood allows "sequestrating" carbon long(er?) term, are there studies working the maths out and confirming that?

It seems the intuitively clear solutions often can be deceiving since there are hidden aspects balancing things out and I'm wondering if it's the case here.

A study is not really required to confirm that wooden constructions contain and retain their carbon. Even over many hundreds of years the wood in Tudor houses is chemically stable (without preservatives - as long as it has correct ventilation)

Studies may look into possible mistakes or optimizations that could be made, but the basic material reality is evidenced in plain sight.

Right, and I asked (or tried to, at least!) about that latter question: stuff like transport, isolation, etc that could make wood less interesting than other construction materials, environmentally.

I rarely, if ever, see people talking about ~bidirectional benefits (think two variables, or force moment).

Having people planting and caring more about forest will not only help absorb a bit of CO2 but also make these people do less emitting.

Is it useless on a large scale ?

So in that case, rather than seeing forest planting as a complete all-in-one solution to climate change, should we instead see it as just one component of a greater solution? Use trees to solve the carbon sequester problem, look to other technologies for solutions to the albedo and heat absorption problems?

I think from long time scientists are studying the topic of Ocean Seeding and Iron Fertilization.

Video on Ocean Seeding - https://www.youtube.com/watch?v=xofhzc1NZ8s


You have to cut down the trees at maturity and preserve them and re plant in order to actually reduce carbon in the atmosphere. We should probably be doing this (as long as we're careful not release more co2 than we capture doing all this)... But we should also be putting government money behind scaling climeworks and other direct carbon capture tech... We should also be seriously studying other more drastic measures.

Increasing the total biomass of trees also reduces atmospheric CO2, even if you just let the natural cycle of life go on.

If the albedo effect is so big can't we just paint the oceans white? How many ping-pong balls would it take to stop global warming? Or maybe empty water battles connected into rafts and painted white?

How much can climate change help forests?

> Unger says she received death threats, and that some colleagues stopped speaking to her.

That is totally fucked up. I don't recall hearing about death threats against scientists pre Internet. Maybe against some research on primates, but I'm not sure. Yet another consequence of Eternal September :(

> “I have heard scientists say that if we found forest loss cooled the planet, we wouldn’t publish it.”

That is also totally fucked up. But I guess that it's not that surprising. I mean, Kuhn and all.

> I don't recall hearing about death threats against scientists pre Internet.

Galileo? I imagine Darwin had his fair share. And those are obviously just the most famous examples.

It was the Catholic Church that went after Galileo, not individual haters. And based on some searching, I find nothing about threats against Darwin. Indeed, it seems that he was quite the popular figure, at least in the UK. Even after he declared agnosticism.

Recently, of course, Christian and Muslim haters have threatened people who support evolution.

I haven't heard of any threats directed against Darwin personally. If this is so, one possible reason is that he was extremely circumspect in the timing of publication, since he was well aware of its likely social and theological impact.

Darwin's personal preference to not be an asshole, was one reason On the Origin took twenty years to reach publication.

After publication, Darwin was fortunate to acquire celebrity bull-dogs such as Huxley, who would take up the cause and allow Darwin to continue his gentlemanly pursuits, out of the direct firing line.

Maybe he didn't get death threats because the sorts of idiots who make death threats didn't read his stuff. And maybe because pastors were too civilized to encourage their flocks to make death threats.

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