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 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.
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 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.
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.
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.
> 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!
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.
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.
