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The blogged claim that Amazon "consumes about as much oxygen as it produces" is not sourced and the piece seems to fly in the face of professional work on the s

The blogged claim that Amazon "consumes about as much oxygen as it produces" is not sourced and the piece seems to fly in the face of professional work on the subject. eg: "The global oxygen budget and its future projection" [1] > Fig. 4 summarizes the annual averaged global O2 budget from year 1990 to 2005, with the mass of O2 in gigatonnes (Gt) listed in each sink and for each process mentioned above (see Section 2.5). The inputs of O2 to the atmosphere by land and outgassing from oceans are quantified as 16.01 and 1.74 Gt/a, respectively. .... [1] https://www.sciencedirect.com/science/article/pii/S209592731830375X#f0020 https://www.sciencedirect.com/science/article/pii/S209592731...

BurningFrog 7y ago
Let's demystify how plants "produce oxygen". 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 https://en.wikipedia.org/wiki/Photosynthesis
- EB66 7y ago
  > 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.
  - nearbuy 7y ago
    Then where is the carbon going?
    - EB66 7y ago
      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.
      - nearbuy 7y ago
        > 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?
        EB66 7y ago
        > That means some significant fraction of the 20 billion tonnes of carbon the Amazon photosynthesizes each year is turning in to soil. Correct. That fraction is obviously reduced when the forest is burned.
        nearbuy 7y ago
        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.
        7y ago
- strainer 7y ago
  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.
james_s_tayler 7y ago
One Strange Rock documentary on Netflix makes the same claim.
mirimir 7y ago
The paper that you cite is talking about small changes. > Under the Representative Concentration Pathways (RCPs) RCP8.5 scenario, approximately 100Gt (gigatonnes) of O2 would be removed from the atmosphere per year until 2100, and the O2 concentration will decrease from its current level of 20.946% to 20.825%. 2018 209460 ppm 2100 208250 ppm That's 15 ppm per year. From Stolper et al. (2016) A Pleistocene ice core record of atmospheric O2 concentrations:[0] > We present a record of Po2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that Po2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. That's 7000 ppm decrease over 800000 years, or 0.009 ppm per year. And so yes, atmospheric oxygen concentration is dropping lots faster now. But TFA's point that it's slow, and regulated by long-term processes, is still valid. 0) https://science.sciencemag.org/content/353/6306/1427 https://science.sciencemag.org/content/353/6306/1427
- strainer 7y ago
  So that's where he is getting the context for his rant >> "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." Practically, the reason why we have oxygen in the atmosphere is plant photosynthesis over long terms. We can quibble over the net annual product of every forest and ecosystem as he has - but over geological timeframes, the plant life they contain is the reason we have any oxygen to breath. And if the amazon currently amounts to about 20% of the plant life on earth now, its not wrong to teach that it is doing 20% of the oxygen maintaining. The fact that long term maintenance is obscured by shorter term dynamics including our modern industrial activity, does not make a lie of the understanding and respect that forests are lungs of the planet.
  - eveningcoffee 7y ago
    I am lately thinking that we are assigning too less value to this fact. We all need oxygen and we should have enough forests to produce it and this means that we should globally subsidize forest keeping. It is not a single country problem. It is a global problem.
shkkmo 7y ago
> the piece seems to fly in the face of professional work on the subject. The blogger does professional work on the subject. The article makes it pretty clear that the net positive production of oxygen the the Amazon is so close to zero that it is only relevant on the time scale of millions of years.

BurningFrog 7y ago

Let's demystify how plants "produce oxygen". 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 https://en.wikipedia.org/wiki/Photosynthesis

EB66 7y ago
> 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.
- nearbuy 7y ago
  Then where is the carbon going?
  - EB66 7y ago
    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.
    - nearbuy 7y ago
      > 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?
      - EB66 7y ago
        > That means some significant fraction of the 20 billion tonnes of carbon the Amazon photosynthesizes each year is turning in to soil. Correct. That fraction is obviously reduced when the forest is burned.
        nearbuy 7y ago
        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.
        7y ago
strainer 7y ago
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.

james_s_tayler 7y ago

One Strange Rock documentary on Netflix makes the same claim.

mirimir 7y ago

The paper that you cite is talking about small changes. > Under the Representative Concentration Pathways (RCPs) RCP8.5 scenario, approximately 100Gt (gigatonnes) of O2 would be removed from the atmosphere per year until 2100, and the O2 concentration will decrease from its current level of 20.946% to 20.825%. 2018 209460 ppm 2100 208250 ppm That's 15 ppm per year. From Stolper et al. (2016) A Pleistocene ice core record of atmospheric O2 concentrations:[0] > We present a record of Po2 reconstructed using O2/N2 ratios from ancient air trapped in ice. This record indicates that Po2 declined by 7 per mil (0.7%) over the past 800,000 years, requiring that O2 sinks were ~2% larger than sources. That's 7000 ppm decrease over 800000 years, or 0.009 ppm per year. And so yes, atmospheric oxygen concentration is dropping lots faster now. But TFA's point that it's slow, and regulated by long-term processes, is still valid. 0) https://science.sciencemag.org/content/353/6306/1427 https://science.sciencemag.org/content/353/6306/1427

strainer 7y ago
So that's where he is getting the context for his rant >> "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." Practically, the reason why we have oxygen in the atmosphere is plant photosynthesis over long terms. We can quibble over the net annual product of every forest and ecosystem as he has - but over geological timeframes, the plant life they contain is the reason we have any oxygen to breath. And if the amazon currently amounts to about 20% of the plant life on earth now, its not wrong to teach that it is doing 20% of the oxygen maintaining. The fact that long term maintenance is obscured by shorter term dynamics including our modern industrial activity, does not make a lie of the understanding and respect that forests are lungs of the planet.
- eveningcoffee 7y ago
  I am lately thinking that we are assigning too less value to this fact. We all need oxygen and we should have enough forests to produce it and this means that we should globally subsidize forest keeping. It is not a single country problem. It is a global problem.

shkkmo 7y ago

> the piece seems to fly in the face of professional work on the subject. The blogger does professional work on the subject. The article makes it pretty clear that the net positive production of oxygen the the Amazon is so close to zero that it is only relevant on the time scale of millions of years.