They do it by splitting CO₂ molecules. The oxygen part (O₂) goes into the air, and the carbon (C) part becomes the plant.
So for the Amazon to continually produce surplus oxygen to the atmosphere, it must also continually produce an ever expanding amount of plant material ("wood") that would form an ever growing pile there.
This is not happening. Because forests don't produce surplus oxygen. Our atmosphere doesn't work that way.
> This is not happening. Because forests don't produce surplus oxygen. Our atmosphere doesn't work that way.
This is just plain wrong. The blogger is completely wrong on this point as well.
In normal atmosphere conditions, photosynthesis does result in net oxygen gain. Plants do require oxygen for respiration, but they require far less oxygen than what they produce during photosynthesis. Furthermore, at night when there's no light, plants do absorb oxygen and give off carbon dioxide in order to continue respiration -- but the amount of oxygen given off during the day is typically ten times greater than the quantity of oxygen consumed at night.
> This reminds me, as we should all be reminded on a regular basis, the bulk of the things you read in the popular press are at best skimming the surface and at worst outright misleading due to grabbing onto one obscuring factoid instead of the most important pieces of information.
Similarly, we should all be reminded that when skimming blogs and comments you're likely to come across misleading and inaccurate content. Scientifically inaccurate content like this gets posted on HN and blindly upvoted all the time.
> The blogger is completely wrong on this point as well.
I think you may not have read the article closely enough:
>> Plants produce oxygen through photosynthesis (green arrow). However, the the same plants consume the equivalent of over half the oxygen they produce in their own respiration ... my own team's research suggests this is more like 60%
>> The remaining 40% of the Amazon oxygen budget is consumed mainly by microbes breaking down the dead leaves and wood of the rainforest, a natural process called heterotrophic respiration
> Similarly, we should all be reminded that when skimming blogs and comments you're likely to come across misleading and inaccurate content
The "blogger" who wrote this article is "Professor of Ecosystem Science, University of Oxford" and "Founding Director, Oxford Centre for Tropical Forests" and probably knows more about this than you or I. This is not a peer reviewed paper, but it is probably more accurate than science journalism by a non-ecologist on this topic.
> my own team's research suggests this is more like 60%
My point was he hasn't cited that research - if it is concluded ? published? reviewed?
He seems to be just having a technical rant about a contextual phrase while giving the impression that forests in general, or at least the amazon or equatorial forests do not help maintain the atmospheres oxygen content. That would certainly be a maveric proposition at this stage in Earth sciences.
> My point was he hasn't cited that research - if it is concluded ? published? reviewed?
I am far more willing to take the word of an established and respected expert who understand the subject mater than a random internet person with a poorly contextualized citation. You can find the author's published papers on this and related subjects quite easily at the top of the article.
> He seems to be just having a technical rant about a contextual phrase while giving the impression that forests in general, or at least the amazon or equatorial forests do not help maintain the atmospheres oxygen content. That would certainly be a maverick proposition at this stage in Earth sciences.
He is a scientist clarifying a technical subject that has been being misconstrued. There has already been plenty of damage done by people throwing around fake facts and pictures.
The problem is I feel that he has confused understanding of the subject here rather than clarifying it, which is an easy thing for anybody to do in a conversational article.
Here is a recent work[1] which substantiates matters that Amazons practical involvement in the planets atmospheric oxygen/carbon levels is really not as the professor felt like putting it as "effectively zero".
> Abstract: The response of the Earth’s land surface to increasing levels of atmospheric CO2 and a changing climate provide important feedbacks on future greenhouse warming6,7. One of the largest ecosystem carbon pools on Earth is the Amazon forest, storing around 150–200 Pg C in living biomass and soils8. Earlier studies based on forest inventories in the Amazon Basin showed the tropical forest here to be acting as a strong carbon sink with an estimated annual uptake of 0.42–0.65 Pg C yr−1 for 1990–2007, around 25% of the residual terrestrial carbon sink3,4. There is, however, substantial uncertainty as to how the Amazon forest will respond to future climatic and atmospheric composition changes. .... Here we analyse the longest and largest spatially distributed time series of forest dynamics for tropical South America. .... Our data show that mature forests continued to act as a biomass sink from 1983 to 2011.5, but also reveal a long-term decline in the net rate of biomass increase throughout the census period. The decline in net biomass change is due to a strong long-term increase in mortality rates, and occurred despite a long-term increase in productivity. While mortality increased throughout the period, productivity increases have recently stalled showing no significant trend since 2000. ....
> The problem is I feel that he has confused understanding of the subject here rather than clarifying it, which is an easy thing for anybody to do in a conversational article.
I couldn't agree more. A bunch of people are coming away from reading that article believing that forests have no impact on global carbon sequestration and oxygen production. In attempting to make a contrarian technical point and refute mass media figures, the author has done a disservice to furthering public understanding of the issue.
Sure, a mature forest can come into equilibrium with regard to carbon/oxygen production and consumption. A forest could even be a net contributor of atmospheric carbon by means of an insect or fungus overpopulation. However:
1. Studies show that's not true for the Amazon rainforest (annually it is still a carbon sink).
2. Over the lifetime of the forest the effect is clearly a massive gain in oxygen and massive sequestration of carbon as evidenced by all the biomass (e.g., trees) and dirt you find in forests.
> A bunch of people are coming away from reading that article believing that forests have no impact on global carbon sequestration and oxygen production.
If you were really concerned about people misunderstanding the article, you would not make up claims and attribute them to the author. Instead you would quote the relevant parts of the article to demonstrate what is actually being said.
The author in no way claims that the Amazon is in equilibrium, (probably because as one of the foremost global experts on rainforest carbon cycles, he knows it isn't.)
Edit:
The claims are quite specific:
1) The amazon provides ~9% of the global O2 production.
2) The amazon consumes most of the O2 it produces through tree metabolism and wood decomposition.
3) There is way, way more O2 in the atmosphere than CO2 so the effects all human activity (or ecosystems) on global O2 levels are miniscule compared to their effect on global CO2 levels.
Burning down the entire amazon rainforest would be a bad for a number of reasons (release of CO2, changes in global weather patterns, loss of bio-diversity, etc), but impact on global atmospheric O2 levels is NOT one of those reasons.
Fear mongering about a non-issue with made up facts only serves to provide ammunition to anti-science skeptics.
> If you were really concerned about people misunderstanding the article, you would not make up claims and attribute them to the author. Instead you would quote the relevant parts of the article to demonstrate what is actually being said.
What on Earth are you referring to?
> The author in no way claims that the Amazon is in equilibrium
Yes he does. As I already explained to you, the author asserts that the O2 produced by the Amazon rainforest ecosystem is equal to the amount of O2 consumed by the Amazon rainforest ecosystem -- that is a perfect example of what it means to be in equilibrium. He literally says it in big bold letters:
> the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world's oxygen is effectively zero.
Did he use the word equilibrium? No. Did he describe an equilibrium? Yes!
I am done arguing with you on this point -- it has truly devolved into semantics and has become unnecessarily inflammatory. At this point all I can do is refer you to a dictionary.
> Fear mongering about a non-issue with made up facts only serves to provide ammunition to anti-science skeptics.
Fear mongering? Now you've truly lost me. If asserting that forests net sequester carbon and produce O2 makes me a fear monger, then I'm guilty as charged...
> At this point all I can do is refer you to a dictionary.
The paper you cited as "disproving" the author's argument for "prefect equilibrium" was co-authored by the author.
Indeed, in the comments on the article, the author explains further:
>> [net carbon sequestration] is not related to the total amount of photosynthesis, but to where organic matter is being buried and removed from atmosphere and biosphere. This occurs in places like swamps, peat bogs and in particular deep ocean sediments. Material from the Amazon probably plays some role in this (e.g. organic material being swept out into the ocean and being buried in deep sediment), but this process is not strongly related to the amount of photosynthesis in any given area. I suspect the burial of a tiny fraction ocean plankton in deep sediments play a dominant role here.
> Fear mongering? Now you've truly lost me. If asserting that forests net sequester carbon and produce O2 makes me a fear monger, then I'm guilty as charged...
Sorry, I am talking about making claims like "the amazon produces 20% of our oxygen." and I was doing so to justify what you called "nitpicking"
The point I was trying to make (and clearly did a poor job with) is summarized by the author in one of his responses to attacks like yours and strainers:
>> No ecosystem scientist I have spoken disagrees with the science in this post: it simply highlights a long-established scientific understanding that oxygen angle is a myth. Just like no serious climate scientist denies the seriousness and importance of human-caused made climate change. If you choose to be selective about which science to choose to hear you fall into the same trap as the climate deniers, construct your own alternative facts universe and you betray your scientific training. The also open yourself the other, more accurate arguments being discredited as a package when the scientific truth emerges
That should be obvious. Any evidence of amazon sequestering carbon is evidence of amazon liberating oxygen. If you cant bear that in mind you have been distracted by the artificial separation proposed here, between "a strong carbon sink" sinking carbon and the respiring of O2, they are very effectively both expressions of the same process.
> one of that authors of that paper, is the same "YADVINDER MALHI" who wrote this blog post
Correct and it puts into stark contrast the co-authors private blog advice that "the net contribution of the Amazon ECOSYSTEM (authors emphasis) to the world's oxygen is effectively zero". That misjudged statement which is even highlighted in the article now, is in plain contradiction to that paper he took part in, which is also about the Amazon ECOSYSTEM and the Amazon can not physically be "a strong carbon sink" and at the same time have zero contribution to the worlds atmospheric oxygen system.
The claim is wrong, and hangs only on the ambiguities of what "effectively zero" could be argued to mean that is in reality documented to be very far from zero indeed.
The Amazon has been known for decades as great "lung" of the planet, SINKING Carbon and RELEASING O2. Malhi has himself taken part in work which describes it "greatly" doing so. If its personal credentials you put faith in you could regard Sir David Attenboroughs describing it the same, for many years, in finished and award winning works, as opposed to a professors conversational web article.
Malhi's advisory 9% figure (that is then subsequently reduced to zero?!) is not even necessarily more final or uncontestable as the supposedly terrible global media outbreak of 20% reports. And since (even that work Mahli took part in reveals) that the amazon is recently in serious flux, such figures are technically speaking conditional.
The point of publicity figure is to be defensible and educate the fact that the Amazon has had and can have major effects on the atmospheres important constituents. That whether it is currently in equilibrium or a great carbon sink or grave carbon emitter - is a very grave matter because by its size and history it is capable of all those things.
> they are very effectively both expressions of the same process.
But the effects on global atmospheric composition are not equivalent as has already been explained to you. The fact that you seem to choose to deliberately not understand this does not speak well of you.
> The claim is wrong, and hangs only on the ambiguities of what "effectively zero" could be argued to mean that is in reality documented to be very far from zero indeed.
There are no ambiguities, the caveats of that statement are quite clearly stated in the article.
> Malhi's advisory 9% figure (that is then subsequently reduced to zero?!) is not even necessarily more final or uncontestable as the supposedly terrible global media outbreak of 20% reports.
Nobody ever said it was final or uncontestable (that's not how science works). It is a fairly rough estimation, but even as such it is FAR more accurate and its precision is sufficient for popular discussion.
> The point of publicity figure is to be defensible and educate the fact that the Amazon has had and can have major effects on the atmospheres important constituents. That whether it is currently in equilibrium or a great carbon sink or grave carbon emitter - is a very grave matter because by its size and history it is capable of all those things.
Neither I nor the author dispute the importance of the amazon. What is disputed is the bad science that is being spread by the well-intentioned but misinformed.
Atmospheric O2 levels are not a problem, atmospheric CO2 levels are.
What do you think you are accomplishing by attacking environmental scientists and spreading misinformation? Are you really trying to help spread accurate knowledge about climate change? How does this help with that?
Please I have not attacked the professor at all. I have "attacked" an article which has you calling a statement which in all likelihood originates from the advice of an earth scientist > "bad science" and "mis-information" and has you defending the claim that the amazon ecosystems contribution to atmospheric oxygen "effectively zero" And that practically extends to co2 - any caveats are in fact in contradiction to the professors advice that fires and organisms use up all the produced oxygen. But we've already gone through that and are talking past each other now.
> I think you may not have read the article closely enough
I did read the article closely :)
>> Plants produce oxygen through photosynthesis (green arrow). However, the the same plants consume the equivalent of over half the oxygen they produce in their own respiration ... my own team's research suggests this is more like 60%
>> The remaining 40% of the Amazon oxygen budget is consumed mainly by microbes breaking down the dead leaves and wood of the rainforest, a natural process called heterotrophic respiration
The author is stating that the Amazon rainforest is in perfect equilibrium without citing any studies or evidence. There are plenty of studies that indicate otherwise, such as this 30 year survey involving 100 researchers: https://www.nature.com/articles/nature14283
> While this analysis confirms that Amazon forests have acted as a long-term net biomass sink, we find a long-term decreasing trend of carbon accumulation.
But even if we accept the author's argument that today the Amazon is in perfect equilibrium -- I think it was misleading of the author not to clarify that in order for any forest to grow, it must be a net carbon sink and net oxygen producer up to that point in the forest's lifetime.
Now the comment that I originally replied to said something different. That comment argued that forests cannot be net producers of oxygen because there aren't "ever growing [piles of wood]" and then he provided the Wikipedia article for photosynthesis as evidence supporting that. That's wrong as I explained above.
You can have forests that are net carbon sinks and net producers of oxygen and you don't need "ever growing [piles of wood]" in order for that to happen.
> The author is arguing that the Amazon rainforest is in perfect equilibrium without citing any studies or evidence
The author argued no such thing, You are making up claims adn attributing them to the author, so perhaps an even closer reading of the blog post would be beneficial.
>> So, in all practical terms, the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world's oxygen is effectively zero. The same is pretty much true of any ecosystem on Earth, at least on the timescales that are relevant to humans (less than millions of years).
The paper you cited is talking about carbon dioxide, not oxygen. The net effect on global O2 levels of carbon sequestration is minimal and not significant on human time scales. That same carbon sequestration has a significant impact on global CO2 because there is much less CO2 in the atmosphere.
> The author argued no such thing, You are making up claims adn attributing them to the author, so perhaps an even closer reading of the blog post would be beneficial.
Please go read the article again. That's exactly what he's saying. He is saying that Amazon rainforest O2 production and consumption are in equilibrium.
> The paper you cited is talking about carbon dioxide, not oxygen. The net effect on global O2 levels of carbon sequestration is minimal and not significant on human time scales. That same carbon sequestration has a significant impact on global CO2 because there is much less CO2 in the atmosphere.
For heaven's sake, please read the study. If you'd rather not read the study, then just Google until you find a satisfactory source that explains that net O2 production and net CO2 sequestration strongly correlate with one another.
> He is saying that Amazon rainforest O2 production and consumption are in equilibrium.
where?
> net O2 production and net CO2 sequestration strongly correlate with one another.
yes, but we have ~500 times more O2 than CO2 in the atmosphere so the effects on atmospheric composition are not anywhere close to equivalent.
edit: Let me put it another way. We have so much oxygen that if we were to use any significant amount (say 1%) of that oxygen burning sequestered carbon (rainforests, oil, etc) we would have increased the carbon dioxide in the atmosphere by something like ~2000% (and would already be totally screwed in many, many ways)
> The author is stating that the Amazon rainforest is in perfect equilibrium without citing any studies or evidence. There are plenty of studies that indicate otherwise, such as this 30 year survey involving 100 researchers: https://www.nature.com/articles/nature14283
Y. Malhi, one of the authors of that paper, is also the author of this blog post. That makes sense since he a preeminent rainforest ecologist who publishes lots of papers on the carbon cycle.
Yes, you also pointed out this fact up above in the comment chain as well. And as @strainer pointed out, it leaves us with more questions than answers. Specifically: how could he have participated in the study but publish a blog post that contradicts the primary conclusions of the study?
> how could he have participated in the study but publish a blog post that contradicts the primary conclusions of the study?
Short answer: Because the article doesn't contradict the study at all.
1) The rainforest is a carbon sink: It holds carbon that would otherwise be present in the atmosphere as CO2.
2) The rainforest is currently a net carbon sink: As an ecosystem it takes in more CO2 than it releases.
3) The rainforest (like most ecosystems) operates fairly close to equilibrium: The amounts of CO2/O2 consumed and produced tend to be pretty close.
4) Major ecological net carbon sinks depend less on the amount of photosynthesis in the ecosystem than they do on the sequestration of bio-matter into the ground.
5) There is ~500x more O2 than CO2 in the atmosphere. This means that the effects of the carbon cycle on atmospheric O2 are far less pronounced than on CO2.
6) net oxygen production of the amazon is effectively 0 (millions of years before a significant impact) because of 5) and 3)
In what way do any of these points contradict eachother?
The major reason (carbon cycle related, excluding biodiversity & global weather patterns & cooling etc) to care about about the amazon is to avoid releasing the CO2 already there. Purely in terms of net carbon sinking ecosystems, we should be paying more attention to our oceans as they do a much better job of sequestering that carbon into the ground.
Oxygen in the atmosphere is simply not an issue because we have so much of it.
A single plant does produce oxygen while it's alive, and the carbon is bound in its growing body.
But that carbon is all released back as it decomposes after its death.
On a "whole forest/whole year" perspective, there is normally an equal mass of plants growing and being decomposed, and thus the net oxygen effect is zero.
> But that carbon is all released back as it decomposes after its death.
> On a "whole forest/whole year" perspective, there is normally an equal mass of plants growing and being decomposed, and thus the net oxygen effect is zero.
Sure, if you're talking about a timespan of one hour, one month, one year, etc then it's definitely possible for biological processes in a forest to expel carbon in the form of CO2 in equal volumes that were sequestered by plants. You could even have an overpopulation of some kind of insect or fungus cause a forest to temporarily become a net contributor of atmospheric carbon.
But over the lifetime over the forest, the net effect is obviously massive CO2 sequestration and massive O2 production. If the net carbon impact was zero over the lifetime of a forest, then forests would have no soil. But we know that not to be the case. Forests grow, they accumulate soil, etc.
Despite constant heavy rains and erosion, soil in the Amazon rainforest is often several meters deep and spans an area of over 2 million square miles. That's a lot of carbon sequestration!
> I assume it reaches an equilibrium after some time
Yep definitely and in part because CO2 only makes up ~0.04% of our atmosphere. Photosynthesis processes slow when CO2 levels fall and increase when CO2 levels rise. But as well as know atmospheric CO2 levels are rapidly on the rise and is outstripping the ability of large forests to sequester it.
We're talking about oxygen production. Not carbon sequestration.
Regarding sequestration: the carbon goes into the trunk, branches, roots and leaves of the tree. Leaves fall off the tree, rot and become soil. The tree eventually dies, rots and becomes soil.
Some carbon will be given off by various decomposition processes, but the overall net effect is by far a carbon sink.
> We're talking about oxygen production. Not carbon sequestration.
BurningFrog said the carbon from CO2 goes into plants. Since plant matter isn't accumulating, carbon can't be accumulating, and therefore oxygen can't either. You replied, "This is just plain wrong".
So you're saying the part that is sequestered goes into the soil. That means some significant fraction of the 20 billion tonnes of carbon the Amazon photosynthesizes each year is turning in to soil. You're claiming the amount of soil increases by this amount each year, correct?
Then why is the soil layer in the Amazon only about a meter deep after millions of years of carbon sequestration? The rainforest photosynthesizes about 3 kg of carbon per square meter per year.
The soil is not only a meter deep. In most places it's several meters deep and it's that deep despite constant heavy rains and erosion.
The soil does not need to be millions of meters deep in order for the forest to be both a net carbon sink and net positive oxygen producer -- it can slowly acrue over time.
And even if biological respiration processes in the forest began to equal carbon sequestration processes -- the forest would still be a massive carbon sink over its lifetime given the massive quantites of plant matter and soil present.
It's about a meter deep on average, but it's such a moot point to quibble over because it's too low by a factor of about 100,000. If it were 100 meters deep, we'd still have to answer the same question.
Yes, the rainforest has been a massive carbon sink over its 30+ million year lifetime - because of the carbon it sequestered while it was first growing and expanding.
Yes, it could be producing very, very tiny amounts amounts of oxygen each year so that the rise in soil level isn't noticeable. If the rainforest was still slowly sequestering carbon in soil at a rate of about 1 meter of soil depth per 30 million years, then you're talking about it sequestering about 0.00005% of the carbon it captures through photosynthesis. If you're calling the article "completely wrong" over that, I'm not sure what to say.
And it's not just the yearly rate of oxygen production that must be negligible. The total oxygen produced over the Amazon's lifetime is negligible. As the article points out, if you burned the entire Amazon rainforest, releasing all the sequestered carbon, it would only decrease atmospheric oxygen from about 20.95% to 20.93%.
Bacteria and fungus eat the rest? Consider the Azolla event where dead plant material sank into very salty and oxygen poor water, which left several meters of carbon on the bottom of the polar ocean after 800k years.
If fungus or aerobic bacteria eat it, then the Amazon doesn't produce surplus oxygen from it. Eating involves recombining the carbon with oxygen into CO2.
The biomass of the Amazon is not, for the most part, sinking into very salty water.
Most of the soil is kilometers away from the nearest tributary. And it wouldn't explain why it washes away everything except for the last 1 meter of soil. Or why the organic matter wouldn't re-enter the food chain once it reached the ocean, thereby recapturing the oxygen.
If 3kg of carbon sequestration per year per square meter were accumulating as soil, and the rainforest has existed at least 30 million years, the soil would be over 2,000,000 meters deep (with rich organic soil being about 9% carbon). If even 1% of the carbon captured through photosynthesis was sequestered in soil, we should still have much, much deeper soil.
Exactly, it goes into the plant, and is then released as the plant decomposes - so in a stable rainforest, where the total plant mass isn't increasing, the new plants growing (creating O2 and absorbing CO2) is fully balanced by old plants decomposing or burning (absorbing O2 and creating CO2); so there's no net creation of O2.
That would be true only if you always burn 100% of biomass, which doesn't happen. Carbon gets sequestered into soil, and partly consumed by insects and animals up the food chain.
All carbon in your body was once sequestered by plants.
The point is that in a stable rainforest the amount of biomass isn't growing, so you obviously do burn/decompose 100% of the newly created biomass - otherwise the amount of biomass would have grown. Carbon gets sequestered into the soil in cases where soil is being enriched and is "growing in size" (for example, when a previously barren place gets forested) but in a stable, centuries-old rainforest the soil amount really isn't increasing - so as much as gets sequestered, gets released by decomposition.
As the total biomass of insects isn't growing, the carbon they consume is balanced by the carbon released by decomposition of (otherwise) unconsumed insects; the same applies for animals up the food chain - if at the end of 2019 the total weight of insects and animals in the Amazon is not larger than at the end of 1919, then zero carbon has been sequestered in these insects and animals over a hundred years.
If forests did not then some other body of plant mass would have to - erosion and weathering of rocks takes a lot of oxygen out of the atmosphere, and this needs replaced by biology by photosynthesis. In the long term this is the reason the Earth needs to "breathe", and plants are how it has done so.
Plants die and are eaten by ranging animals, dispersing their material, creating soils and eventually sediments. This is a long cycle through which carbon is returned to ground, sometimes to metamorphic rock.
It takes place at a lower intensity than our burning of fossil material and forests in recent history. Regrowing forest, usefully captures carbon and releases oxygen more rapidly than mature forest, but of course not rapidly enough to make up for burning them down.
They do it by splitting CO₂ molecules. The oxygen part (O₂) goes into the air, and the carbon (C) part becomes the plant.
So for the Amazon to continually produce surplus oxygen to the atmosphere, it must also continually produce an ever expanding amount of plant material ("wood") that would form an ever growing pile there.
This is not happening. Because forests don't produce surplus oxygen. Our atmosphere doesn't work that way.
https://en.wikipedia.org/wiki/Photosynthesis