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Does the Amazon provide 20% of our oxygen?

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Re: Does the Amazon provide 20% of our oxygen?

#171

Post by abdullahkhalids »

DenisM wrote: post #100
crimsonalucard wrote: post #92

Earlier quoted context omitted.

https://wwf.panda.org/knowledge_hub/where_we_work/amazon/ama... it's just less accessible but I'm pretty sure like any forest on the face of the earth, portions of dead animal and plant matter is getting sequestered into the ground while another portion is getting exhaled by animals eating the leaves or other animals eating the animals. The stuff that's getting sequestered though is probably miniscule. At the timesca…

Even if a tiny amount was sequestered each year over the course of 55 million years there would be a huge pile of carbon there. But it isn’t there, is it?

There is. That's all the coal, oil and gas we burn.

Re: Does the Amazon provide 20% of our oxygen?

#172

Post by jefftk »

Merovius wrote: post #145
wcunning wrote: post #3

The basic gist of the article is found about 1/2 way in: "First, the phytoplankton in the oceans also photosynthesise [...] Therefore in terms of TOTAL global photosynthesis, photosynthesis in the Amazon contributes around 9%. [...] Second, a bigger point that is often missed is that the Amazon consumes about as much oxygen as it produces." This reminds me, as we should all be reminded on a regular basis, the bulk of…

> 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 FTR, this article is doing exactly that. Like, they a) divert your attention with the CO₂ O₂ conversion (which doesn't change relative num…

The article is making a much stronger claim:

> the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world's oxygen is effectively zero

If this is correct, then the entire Amazon could vanish without having any effect on CO₂ levels.

Re: Does the Amazon provide 20% of our oxygen?

#173

Post by chewbacha »

jefftk wrote: post #172
Merovius wrote: post #145

Earlier quoted context omitted.

> 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 FTR, this article is doing exactly that. Like, they a) divert your attention with the CO₂ O₂ conversion (which doesn't change relative num…

The article is making a much stronger claim: > the net contribution of the Amazon ECOSYSTEM (not just the plants alone) to the world's oxygen is effectively zero If this is correct, then the entire Amazon could vanish without having any effect on CO₂ levels.

It could be correct and still have an impact on CO2 levels as it is still a massive sequester of carbon. Burning it down removes the sequester and adds it to the atmosphere.

Also, just because it doesn’t produce the breathable O2 we need, that doesn’t mean it’s not part of a global system that produces and stabilizes our atmosphere. It actually is responsible for a massive silt run off that feeds the oceanic diatoms that in turn produce half of the worlds breathable O2 and fixes carbon right in the ocean.

This is a case where a literal point is incorrect but it does not decrease the importance of the rainforest to our globe.

Re: Does the Amazon provide 20% of our oxygen?

#174

Post by mirimir »

strainer wrote: post #166
mirimir wrote: post #161

Earlier quoted context omitted.

Sure. But long term, the Sahara may green, and "replace" the Amazon. At this point, I'd worry more about the oceans.

Burning the amazon down is something to worry about. Not afforesting widely and extracting timber from the amazon ecologically so it sequesters carbon and supplies materials replacing demand for carbon intense alternatives - is tragedy. The advice that amazons contribution is "zero", hedged under this safety-net word "effectively" is false to the understanding of geophysics and natural history. I hope the professor w…

I'm not arguing that it's not something to worry about. It certainly is something to be worrying about. But so are the tropical forests of Southeast Asia, which are arguably even more threatened.

But we should be worried about it because of the impact on global biodiversity. Not because we'll be running out of oxygen. Having ~20% oxygen in the atmosphere reflects a long-term equilibrium of biologic and non-biologic processes.

If advocates focus on the oxygen issue, adversaries can easily point to negligible changes, and argue that there's nothing to worry about.

And, as I said, to the extent that oxygen is an issue, we ought to worry even more about the oceans. They are by far the major oxygen source, and arguably more vulnerable to catastrophic collapse.

Re: Does the Amazon provide 20% of our oxygen?

#175

Post by [deleted] »

shkkmo wrote: post #170
EB66 wrote: post #164

Earlier quoted context omitted.

> 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 leve…

> 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 amou…

[deleted]

Re: Does the Amazon provide 20% of our oxygen?

#176

Post by Ericson2314 »

nearbuy wrote: post #151
EB66 wrote: post #142

Earlier quoted context omitted.

> 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.

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.

I assume the Amazon and it's tributaries wash most of it away.

Re: Does the Amazon provide 20% of our oxygen?

#177

Post by nearbuy »

baq wrote: post #169
nearbuy wrote: post #151

Earlier quoted context omitted.

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.

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.

Re: Does the Amazon provide 20% of our oxygen?

#178

Post by nearbuy »

Ericson2314 wrote: post #176
nearbuy wrote: post #151

Earlier quoted context omitted.

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.

I assume the Amazon and it's tributaries wash most of it away.

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.

Re: Does the Amazon provide 20% of our oxygen?

#179

Post by cmrdporcupine »

DenisM wrote: post #71

A few comments are saying that forests capture a lot of CO2. But how could that be? If a forest doesn't change over thousands of years it cannot be accumulating carbon in any significant quantity. Or else where would that material go? The Amazon trees are about as tall and wide today as they were 10,000 years ago, and only so many of them fit on a given area. If the amount of vegetation remains the same the only way…

Temperate forests sequester carbon over millions of years by leaving a layer of carbon rich top soil beneath them through leaf and other litter fall.

Soil can hold a _lot_ of carbon per square foot. Carbon that is partially lost to the atmosphere when it is plowed.

But my understanding is that tropical forests tend to have fairly carbon poor soils on the forest floor.

Re: Does the Amazon provide 20% of our oxygen?

#180

Post by gus_massa »

EGreg wrote: post #113

I have a question about trees: If trees sequester carbon in their trunks and release oxygen, what do they use the oxygen for at night, and how come they are oxygen-neutral, do they store it somehow? Also, if the Amazon is a carbon sink today, what about if there was dieback? It would turn into a carbon source, but how? Don’t the “unit economics” of trees remain the same?

Oversimplifiying: Some of the carbon goes to the wood and some goes to sugar. During the night the plant "burns" the sugar with oxygen produce energy. (If you keep a plant in hermetic place without oxygen and without light, it would die, exactly like an animal.)

(Notes about the oversimpliplification: Wood is made of cellulose that is a carbohydrate and sugar is algo a carbohydrate, they are quite similar chemically. Also, plants produce and "burn" other compounds.)

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